Vehicle tracking system using gps and gsm techniques


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  • A Major Project Report On Vehicle Tracking System using GSM and GPS Submitted in partial fulfillment of the requirement for the degree of BACHELOR OF TECHNOLOGY In ELECTRONICS & COMMUNICATION ENGINEERING Submitted by CH. Bharath. 107B1A0435 P. Vijay Kumar. 107B1A0437 P. Anil Reddy. 107B1A0449 B. Abhishek. 107B1A0468 Under the Esteemed Guidance of Mr. B. SRINIVAS M. Tech, MISTE, AMIE, (Ph.D) A s s i s t an t P ro f es so r DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING SAGAR INSTITUTE OF TECHNOLOGY (SITECH) SAGAR GROUP OF INSTITUTIONS (Affiliated to JNTU Hyderabad and Approved by AICTE, New Delhi) Flame of Forest, Urella-Chevella Road, Chevella, RR District (2010-2014)
  • Certificate This is to certify that this dissertation work entitled “Vehicle Tracking System using GSM and GPS” is a bonafide work carried out by CH. Bharath (107B1A0435), P. Vijay Kumar (107B1A0437), P. Anil Reddy (107B1A0449) and B. Abhishek (107B1A0468) in partial fulfillment of the requirements for the award of the degree of Bachelor of Technology in Electronics and Communication Engineering, from “Sagar Institute of Technology”, during the period 2013 under the guidance and supervision. Head of the Department Prof. V. Bhagya Raju M. Tech, (Ph.D.) Professor & HOD of ECE. Internal Guide Mr. B. SRINIVAS M. Tech, MISTE, AMIE, (Ph.D.) A s s i s t an t P ro f es so r D ep ar tmen t o f E CE External Examiner SAGAR GROUP OF INSTITUTINS SAGAR INSTITUTE OF TECHNOLOGY (Affiliated to JNTU Hyderabad and Approved by AICTE, New Delhi) Flame of Forest, Urella- Chevella Road, Chevella, RR Dist.
  • DECLARATION We hereby declare that the project “Vehicle Tracking System using GSM and GPS” submitted in the partial fulfilment of that requirements for the award of the degree of bachelor of technology in electronics and communication engineering from Sagar Institute Of Engineering and Technology, Chevella, affiliated to JNTU, Hyderabad is an authentic work and has not been submitted to any other university/institute for award of degree. CH. Bharath (107B1A0435) P. Vijay Kumar (107B1A0437) P. Anil Reddy (107B1A0449) B. Abhishek (107B1A0468) i
  • ACKNOWLEDGEMENT With great pleasure we want to take this opportunity to express our heartfelt gratitude to all the people who helped in making this Major Project work a grand success. We are grateful to Prof.V.Bhagya Raju, Professor & Head of Electronics and Communication Engineering department, Mr. B. Srinivas, Asst. Prof. Dept of ECE and P. Tejaswi Project Assistant at ECIL for their valuable suggestions and guidance during the execution of this project and also for giving us moral support throughout the period of our study in SITECH. We are also highly indebted to our principal Dr. V.V. Satyanarayana, for giving us the permission to carry out this Major Project. We would like to thank the teaching and non-teaching staff of ECE Department for sharing their knowledge with us. Last but not the least we express our sincere thanks to Dr.W.R.Reddy and all the founders of Sagar Institute of Technology for their continuous care towards our achievements. ii
  • Index Declaration i Acknowledgement ii Index iii List of Figures viii List of Tables ix Abbreviations x Chapter 1: Introduction To VTS 1 1.1 Introduction 1 1.2 Vehicle Security using VTS 2 1.3 Active versus Passive Tracking 4 1.4 Types of GPS Vehicle Tracking 5 1.5 Typical Architecture 6 1.6 History of Vehicle Tracking 7 1.6.1 Early Technology 8 1.6.2 New development in technology 9 1.7 Vehicle Tracking System Features 9 1.7.1 Vehicle Tracking Benefits 10 1.8 Vehicle Tracing in India 10 Chapter 2: Block Diagram of VTS 12 2.1 Block Diagram of Vehicle Tracing Using GSM and GPS Modem 2.2 Hardware Components 2.2.1 GPS 13 iii
  • Working of GPS 13 Triangulation 14 Augmentation 14 2.2.2 GSM 15 2.2.3 RS232 Interface 16 The scope of the standard 16 History of RS 232 17 Limitation of Standard 18 Standard details 19 Connectors 21 Cables 24 Conventions 24 RTS/CTS handshaking 25 3-wire and 5-wire RS-232 26 Seldom used features 26 Timing Signals 27 Other Serial interfaces similar to RS-232 27 2.2.4 MAX232 IC 28 Voltage Levels 29 Pin Diagram 30 Pin Description 31 2.2.5 Relay 31 History of a Relay 32 Basic Design and Operation of a Relay 33 iv
  • Pole and Throw 34 Uses of Relays 35 2.2.6 LCD 35 Advantages and Disadvantages 36 Chapter 3: Working of VTS 37 3.1 Schematic Diagram of VTS 37 3.2 Circuit Description 37 3.3 Circuit Operation 38 3.3.1 Power 38 3.3.2 Serial Ports 38 3.4 Operating procedure 38 Chapter 4: Microcontroller AT 89S52 40 4.1 Features 40 4.2 The Pin Configuration 41 4.2.1 Special Function Registers (SFR) 42 4.3 Memory Organization 43 4.4 Watch Dog Timer 43 4.4.1 Watchdog Timer for both modes of operation 44 Chapter 5: GSM Module 46 5.1 GSM History 46 5.2 Services Provided by GSM 47 5.3 Mobile Station 48 5.4 Base Station Subsystem 50 5.4.1 Base Station Controller 51 v
  • 5.5 Architecture of the GSM Network 52 5.6 Radio Link Aspects 53 5.7 Multiple Access and Channel Structure 54 5.8 Frequency Hopping 54 5.9 Discontinuous Reception 55 5.10 Power Control 55 5.11 Network Aspects 56 5.12 Radio Resources Management 57 5.13 Handover 57 5.14 Mobility Management 59 5.15 Location Updating 59 5.16 Authentication and Security 60 5.17 Communication Management 61 5.18 Call Routing 61 Chapter 6: GPS Receiver 63 6.1 GPS History 63 6.1.1 Working and Operation 64 6.2 GPS Data Decoding 65 Chapter 7: KEIL Software 67 7.1 Introduction 67 7.2 KEIL uVision2 66 7.3 KEIL Software Programing Procedure 67 7.3.1 Procedure Steps 67 7.4 Applications of KEIL Software 69 vi
  • Chapter 8: Applications 70 8.1 Applications 71 8.2 Limitations 72 Chapter 9: Result Analysis 73 Chapter 10: Conclusion and Future Scope 75 References 76 vii
  • List of Figures Figure 1.1 Vehicle tracking system 2 Figure 2.1 Block diagram 12 Figure 2.2 A 25 pin connector as described in the RS-232 standard 16 Figure 2.3 Trace of voltage levels for uppercase ASCII "K" character 19 Figure 2.4 Upper Picture: RS232 signaling as seen when probed by an actual oscilloscope 20 Figure 2.5 MAX232 chip 28 Figure 2.6 Pin diagram of MAX232 30 Figure 2.7 UK Q-style signaling relay and base. 32 Figure 2.8 Automotive-style miniature relay, dust cover is taken off 32 Figure 2.9 Circuit symbols of relays. 34 Figure 2.10 A general purpose alphanumeric LCD, with two lines of 16 characters. 35 Figure 3.1 Schematic diagram of vehicle tracing using GSM and GPS 37 Figure 5.1 Mobile station SIM port 49 Figure 5.2 Baste Station Subsystem. 50 Figure 5.3 Siemens BSC 51 Figure 5.4 Siemens’ TRAU 52 Figure 5.5 General architecture of a GSM network 53 Figure 5.6 Signaling protocol structure in GSM 57 Figure 5.7 Call routing for a mobile terminating call 61 Figure 6.1 G.P.S receiver communicating with the satellite 65 Figure 9.1 Picture of final VTS kit 73 Figure 9.2 Message received from the VTS kit 74 viii
  • List of Tables Table 2.1 Commonly used RS-232 signals and pin assignments 22 Table 2.2 Pin assignments 23 Table 2.3 RS-232 Voltage Levels 29 Table 2.4 TX and RX pin connection 30 Table 2.5 Pins assignment of MAX232 30 ix
  • Abbreviations VTS Vehicle Tracking System GSM Global System for Mobile Communication GPS Global Positioning System RI Ring Indicator Tx Transmitter Rx Receiver SFR Special Function Register LCD Liquid Crystal Display RAM Random Access Memory ROM Read Only Memory RS-232 Recommended Standard TTL Transistor Transistor Logic CMOS Complementary Metal Oxide Semi-Conductor UART Universal Asynchronous Receiver Transmitter RST Reset ALE Address Latch Enable PSEN Program Store Enable WDT Watch Dog Timer x
  • Chapter 1 Introduction to VTS 1.1 Introduction Vehicle Tracking System (VTS) is the technology used to determine the location of a vehicle using different methods like GPS and other radio navigation systems operating through satellites and ground based stations. By following triangulation or trilateration methods the tracking system enables to calculate easy and accurate location of the vehicle. Vehicle information like location details, speed, distance traveled etc. can be viewed on a digital mapping with the help of a software via Internet. Even data can be stored and downloaded to a computer from the GPS unit at a base station and that can later be used for analysis. This system is an important tool for tracking each vehicle at a given period of time and now it is becoming increasingly popular for people having expensive cars and hence as a theft prevention and retrieval device. i. The system consists of modern hardware and software components enabling one to track their vehicle online or offline. Any vehicle tracking system consists of mainly three parts mobile vehicle unit, fixed based station and, database and software system. ii. Vehicle Unit: It is the hardware component attached to the vehicle having either a GPS/GSM modem. The unit is configured around a primary modem that functions with the tracking software by receiving signals from GPS satellites or radio station points with the help of antenna. The controller modem converts the data and sends the vehicle location data to the server. iii. Fixed Based Station: Consists of a wireless network to receive and forward the data to the data center. Base stations are equipped with tracking software and geographic map useful for determining the vehicle location. Maps of every city and landmarks are available in the based station that has an in-built Web Server. iv. Database and Software: The position information or the coordinates of each visiting points are stored in a database, which later can be viewed in a display screen using digital maps. However, the users have to connect themselves to the web server with the respective vehicle ID stored in the database and only then s/he can view the location of vehicle traveled. 1
  • 1.2 Vehicle Security using VTS Vehicle Security is a primary concern for all vehicle owners. Owners as well as researchers are always on the lookout for new and improved security systems for their vehicles. One has to be thankful for the upcoming technologies, like GPS systems, which enables the owner to closely monitor and track his vehicle in real-time and also check the history of vehicles movements. This new technology, popularly called Vehicle Tracking Systems has done wonders in maintaining the security of the vehicle tracking system is one of the biggest technological advancements to track the activities of the vehicle. The security system uses Global Positioning System GPS, to find the location of the monitored or tracked vehicle and then uses satellite or radio systems to send to send the coordinates and the location data to the monitoring center. At monitoring center various software’s are used to plot the Vehicle on a map. In this way the Vehicle owners are able to track their vehicle on a real-time basis. Due to real-time tracking facility, vehicle tracking systems are becoming increasingly popular among owners of expensive vehicles. Figure 1.1 Vehicle tracking system The vehicle tracking hardware is fitted on to the vehicle. It is fitted in such a manner that it is not visible to anyone who is outside the vehicle. Thus it operates as a covert unit which continuously sends the location data to the monitoring unit. When the vehicle is stolen, the location data sent by tracking unit can be used to find the location and coordinates can be sent to police for further action. Some Vehicle tracking System can even detect unauthorized movements of the vehicle and then alert the owner. This gives an edge over other pieces of technology for the same purpose Monitoring center Software helps the vehicle owner with a view of the location at which the vehicle stands. Browsing is easy and the owners can make use of any browser and connect to the monitoring center software, to find and track his vehicle. This 2
  • in turn saves a lot of effort to find the vehicle's position by replacing the manual call to the driver. As we have seen the vehicle tracking system is an exciting piece of technology for vehicle security. It enables the owner to virtually keep an eye on his vehicle any time and from anywhere in the world. A vehicle tracking system combines the installation of an electronic device in a vehicle, or fleet of vehicles, with purpose-designed computer software at least at one operational base to enable the owner or a third party to track the vehicle's location, collecting data in the process from the field and deliver it to the base of operation. Modern vehicle tracking systems commonly use GPS or GLONASS technology for locating the vehicle, but other types of automatic vehicle location technology can also be used. Vehicle information can be viewed on electronic maps via the Internet or specialized software. Urban public transit authorities are an increasingly common user of vehicle tracking systems, particularly in large cities. Vehicle tracking systems are commonly used by fleet operators for fleet management functions such as fleet tracking, routing, dispatch, on-board information and security. Along with commercial fleet operators, urban transit agencies use the technology for a number of purposes, including monitoring schedule adherence of buses in service, triggering changes of buses' destination sign displays at the end of the line (or other set location along a bus route), and triggering pre-recorded announcements for passengers. The American Public Transportation Association estimated that, at the beginning of 2009, around half of all transit buses in the United States were already using a GPS-based vehicle tracking system to trigger automated stop announcements. This can refer to external announcements (triggered by the opening of the bus's door) at a bus stop, announcing the vehicle's route number and destination, primarily for the benefit of visually impaired customers, or to internal announcements (to passengers already on board) identifying the next stop, as the bus (or tram) approaches a stop, or both. Data collected as a transit vehicle follows its route is often continuously fed into a computer program which compares the vehicle's actual location and time with its schedule, and in turn produces a frequently updating display for the driver, telling him/her how early or late he/she is at any given time, potentially making it easier to adhere more closely to the published schedule. Such programs are also used to provide customers with real-time information as to the waiting time until arrival of the next bus or tram/streetcar at a given stop, based on the nearest vehicles' actual progress at the time, rather than merely giving 3
  • information as to the scheduled time of the next arrival. Transit systems providing this kind of information assign a unique number to each stop, and waiting passengers can obtain information by entering the stop number into an automated telephone system or an application on the transit system's website. Some transit agencies provide a virtual map on their website, with icons depicting the current locations of buses in service on each route, for customers' information, while others provide such information only to dispatchers or other employees. Other applications include monitoring driving behavior, such as an employer of an employee, or a parent with a teen driver. Vehicle tracking systems are also popular in consumer vehicles as a theft prevention and retrieval device. Police can simply follow the signal emitted by the tracking system and locate the stolen vehicle. When used as a security system, a Vehicle Tracking System may serve as either an addition to or replacement for a traditional car alarm. Some vehicle tracking systems make it possible to control vehicle remotely, including block doors or engine in case of emergency. The existence of vehicle tracking device then can be used to reduce the insurance cost, because the loss-risk of the vehicle drops significantly. Vehicle tracking systems are an integrated part of the "layered approach" to vehicle protection, recommended by the National Insurance Crime Bureau (NICB) to prevent motor vehicle theft. This approach recommends four layers of security based on the risk factors pertaining to a specific vehicle. Vehicle Tracking Systems are one such layer, and are described by the NICB as “very effective” in helping police recover stolen vehicles. Some vehicle tracking systems integrate several security systems, for example by sending an automatic alert to a phone or email if an alarm is triggered or the vehicle is moved without authorization, or when it leaves or enters a geofence. 1.3 Active versus Passive Tracking Several types of vehicle tracking devices exist. Typically they are classified as "passive" and "active". "Passive" devices store GPS location, speed, heading and sometimes a trigger event such as key on/off, door open/closed. Once the vehicle returns to a predetermined point, the device is removed and the data downloaded to a computer for evaluation. Passive systems include auto download type that transfer data via wireless download. "Active" devices also collect the same information but usually transmit the 4
  • data in real-time via cellular or satellite networks to a computer or data center for evaluation. Many modern vehicle tracking devices combine both active and passive tracking abilities: when a cellular network is available and a tracking device is connected it transmits data to a server; when a network is not available the device stores data in internal memory and will transmit stored data to the server later when the network becomes available again. Historically vehicle tracking has been accomplished by installing a box into the vehicle, either self-powered with a battery or wired into the vehicle's power system. For detailed vehicle locating and tracking this is still the predominant method; however, many companies are increasingly interested in the emerging cell phone technologies that provide tracking of multiple entities, such as both a salesperson and their vehicle. These systems also offer tracking of calls, texts, and Web use and generally provide a wider range of options. 1.4 Types of GPS Vehicle Tracking There are three main types of GPS vehicle tracking, tracking based mobile, wireless passive tracking and satellite in real-time GPS tracking. This article discusses the advantages and disadvantages to all three types of GPS vehicle tracking circumference. i) Mobile phone based tracking The initial cost for the construction of the system is slightly lower than the other two options. With a mobile phone-based tracking average price is about $ 500. A cell- based monitoring system sends information about when a vehicle is every five minutes during a rural network. The average monthly cost is about thirty-five dollars for airtime. ii) Wireless Passive Tracking A big advantage that this type of tracking system is that there is no monthly fee, so that when the system was introduced, there will be other costs associated with it. But setting the scheme is a bit 'expensive. The average is about $ 700 for hardware and $ 800 for software and databases. With this type of system, most say that the disadvantage is that information about where the vehicle is not only can exist when the vehicle is returned to the base business. This is a great disadvantage, particularly for companies that are looking for a monitoring system that tells them where their vehicle will be in case of theft or an accident. However, many systems are now introducing wireless modems into their 5
  • devices so that tracking information can be without memory of the vehicle to be seen. With a wireless modem that is wireless passive tracking systems are also able to gather information on how fast the vehicle was traveling, stopping, and made other detailed information. With this new addition, many companies believe that this system is perfect, because there is no monthly bill. iii) Via satellite in real time This type of system provides less detailed information, but work at the national level, making it a good choice for shipping and trucking companies. Spending on construction of the system on average about $ 700. The monthly fees for this system vary from five dollars for a hundred dollars, depending on how the implementation of a reporting entity would be. Technology Over the next few years, GPS tracking will be able to provide businesses with a number of other benefits. Some companies have already introduced a way for a customer has signed the credit card and managed at local level through the device. Others are creating ways for dispatcher to send the information re-routing, the GPS device directly to a manager. Not a new requirement for GPS systems is that they will have access to the Internet and store information about the vehicle as a driver or mechanic GPS device to see the diagrams used to assist with the vehicle you want to leave. Beyond that all the information be saved and stored in its database. 1.5 Typical Architecture Major constituents of the GPS based tracking are i. GPS tracking device The device fits into the vehicle and captures the GPS location information apart from other vehicle information at regular intervals to a central server. The other vehicle information can include fuel amount, engine temperature, altitude, reverse geocoding, door open/close, tire pressure, cut off fuel, turn off ignition, turn on headlight, turn on taillight, battery status, GSM area code/cell code decoded, number of GPS satellites in view, glass open/close, fuel amount, emergency button status, cumulative idling, computed odometer, engine RPM, throttle position, and a lot more. Capability of these devices actually decides the final capability of the whole tracking system. 6
  • ii. GPS tracking server The tracking server has three responsibilities: receiving data from the GPS tracking unit, securely storing it, and serving this information on demand to the user. iii. User interface The UI determines how one will be able to access information, view vehicle data, and elicit important details from it. 1.6 History of Vehicle Tracking GPS or Global Positioning Systems were designed by the United States Government and military, which the design was intended to be used as surveillance. After several years went by the government signed a treaty to allow civilians to buy GPS units also only the civilians would get precise downgraded ratings. Years after the Global Positioning Systems were developed the military controlled the systems despite that civilians could still purchase them in stores. In addition, despite that Europe has designed its own systems called the Galileo the US military still has complete control. GPS units are also called tracking devices that are quite costly still. As more of these devices develop however the more affordable the GPS can be purchased. Despite of the innovative technology and designs of the GPS today the devices has seen some notable changes or reductions in pricing. Companies now have more access to these devices and many of the companies can find benefits. These days you can pay-as-you go or lease a GPS system for your company. This means you do not have to worry about spending upfront money, which once stopped companies from installing the Global positioning systems at one time. Today’s GPS applications have vastly developed as well. It is possible to use the Global Positioning Systems to design expense reports, create time sheets, or reduce the costs of fuel consumption. You can also use the tracking devices to increase efficiency of employee driving. The GPS unit allows you to create Geo-Fences about a designated location, which gives you alerts once your driver(s) passes through. This means you have added security combined with more powerful customer support for your workers. Today’s GPS units are great tracking devices that help fleet managers stay in control of their business. The applications in today’s GPS units make it possible to take full 7
  • control of your company. It is clear that the tracking devices offer many benefits to companies, since you can build automated expense reports anytime. GPS units do more than just allow companies to create reports. These devices also help to put an end to thieves. According to recent reports, crime is at a high, which means that car theft is increasing. If you have the right GPS unit, you can put an end to car thefts because you can lock and unlock your car anytime you choose. GPS are small tracking devices that are installed in your car and it will supply you with feedback data from tracking software that loads from a satellite. This gives you more control over your vehicles. The chief reason for companies to install tracking devices is to monitor their mobile workforce. A preventive measure device allows companies to monitor their employees’ activities. Company workers can no longer take your vehicles to unassigned locations. They will not be able to get away with unauthorized activities at any time because you can monitor their every action on a digital screen. The phantom pixel is another thing some webmasters do to get better rankings. Unfortunately it will backfire on you since the search engines do not want this to occur. You see, the phantom pixel is when you might have a 1 pixel image or an image so small it cannot be seen by the regular eye. They use the pixel to stuff it with keywords. The search engine can view it in the code, which is how they know it is there and can give you better rank for the keywords in theory. Of course since the search engines don’t like this phantom pixel you are instead not getting anything for the extra keywords except sent to the bottomless pit. 1.6.1 Early Technology In the initial period of tracking only two radios were used to exchange the information. One radio was attached to the vehicle while another at base station by which drivers were enabled to talk to their masters. Fleet operator could identify the progress through their routes. The technology was not without its limits. It was restricted by the distance which became a hurdle in accuracy and better connectivity between driver and fleet operators. Base station was dependent on the driver for the information and a huge size fleet could not have been managed depending on man-power only. The scene of vehicle tracking underwent a change with the arrival of GPS technology. This reduced the dependence on man-power. Most of the work of tracking 8
  • became electronic. Computers proved a great help in managing a large fleet of vehicle. This also made the information authentic. As this technology was available at affordable cost all whether small or big fleet could take benefit of this technology Because of the cheap accessibility of the device computer tracking facilities has come to stay and associated with enhanced management. Today each vehicle carries tracking unit which is monitored from the base station. Base station receives the data from the unit. All these facilities require a heavy investment of capital for the installation of the infrastructure of tracking system for monitoring and dispatching 1.6.2 New development in technology New system costs less with increased efficiency. Presently it is small tracking unit in the vehicle with web-based interface, connected through a mobile phone. This device avoids unnecessary investment in infrastructure with the facility of monitoring from anywhere for the fleet managers. This provides more efficient route plan to fleet operators of all sizes and compositions saving money and time. Vehicle tracking system heralded a new era of convenience and affordability in fleet management. Thus due to its easy availability it is going to stay for long. 1.7 Vehicle Tracking System Features Monitoring and managing the mobile assets are very important for any company dealing with the services, delivery or transport vehicles. Information technologies help in supporting these functionalities from remote locations and update the managers with the latest information of their mobile assets. Tracking the mobile assets locations data and analyzing the information is necessary for optimal utilization of the assets. Vehicle Tracking System is a software & hardware system enabling the vehicle owner to track the position of their vehicle. A vehicle tracking system uses either GPS or radio technology to automatically track and record a fleet's field activities. Activity is recorded by modules attached to each vehicle. And then the data is transmitted to a central, internet-connected computer where it is stored. Once the data is transmitted to the computer, it can be analyzed and reports can be downloaded in real-time to your computer using either web browser based tools or customized software. 9
  • 1.7.1 Vehicle Tracking Benefits An enterprise-level vehicle tracking system should offer customizable reporting tools, for example to provide a summary of the any day activities. It should have the ability to produce and print detailed maps and reports displaying actual stops, customer locations, mileage traveled, and elapsed time at each location, and real-time access to vehicle tracking data and reports. Vehicle tracking system can be active, passive or both depending upon the application. Here are steps involved in the vehicle tracking: i. Data capture: Data capturing is the first step in tacking your vehicle. Data in a vehicle tracking system is captured through a unit called automated vehicle unit. The automated vehicle unit uses the Global Positioning System (GPS) to determine the location of the vehicle. This unit is installed in the vehicle and contains interfaces to various data sources. This paper considers the location data capture along with data from various sensors like fuel, vehicle diagnostic sensors etc. ii. Data storage: Captured data is stored in the memory of the automated vehicle unit. iii. Data transfer: Stored data are transferred to the computer server using the mobile network or by connecting the vehicle mount unit to the computer. iv. Data analysis: Data analysis is done through software application. A GIS mapping component is also an integral part of the vehicle tracking system and it is used to display the correct location of the vehicle on the map. 1.8 Vehicle Tracing in India Vehicle tracking system in India is mainly used in transport industry that keeps a real-time track of all vehicles in the fleet. The tracking system consists of GPS device that brings together GPS and GSM technology using tracking software. The attached GPS unit in the vehicle sends periodic updates of its location to the route station through the server of the cellular network that can be displayed on a digital map. The location details are later transferred to users via SMS, e-mail or other form of data transfers. There are various GPS software and hardware developing companies in India working for tracking solutions. However, its application is not that much of popular as in other countries like USA, which regulates the whole GPS network. In India it is mostly used in Indian transport and logistics industry and not much personal vehicle tracking. 10
  • But with better awareness and promotion the market will increase. Let’s have a look at its current application in India using vehicle tracking though in less volume. a) Freight forwarding Logistic service providers are now increasingly adopting vehicle-tracking system for better fleet management and timely service. The system can continuously monitor shipment location and so can direct the drivers directly in case of any change of plan. Fleet managers can keep an eye on all activities of workers, vehicle over speed, route deviation etc. The driver in turn can access emergency service in case of sickness, accident or vehicle breakdown. All in turn supports money and time management, resulting better customer service. b) Call centers In commercial vehicle segments the taxi operators of various call centers are now using vehicle tracking system for better information access. However, its application is in its infant stage in India and if adequate steps are taken in bringing the cost of hardware and software low then it can be used for tracking personal vehicle, farming (tractor), tourist buses, security and emergency vehicle etc. Again Government needs to cut down the restriction imposed upon the availability of digital maps for commercial use and this will encourage software industry in developing cost-effective tracking solutions. Though, sales of both commercial and passenger vehicles are growing but price of tracking service is very high and this is the key issue in Indian market. Hence, it’s important for market participants to reduce prices of GPS chips and other products in order to attract more and more users. As far as Indian vehicle tracking and navigation market is concerned the recent association of India with Russian Global Navigation Satellite System (GLONASS) will act as a catalyst in the improvement of vehicle tracking system. This will give an advantage in managing traffic, roadways and ports and also as an important tool for police and security agency to track stolen vehicles. Hence, in near future there is large prospect for the utility of vehicle tracking system in India, which can revolutionize the way we are communicating. 11
  • Chapter 2 Block Diagram of VTS 2.1 Block Diagram of Vehicle Tracing Using GSM and GPS Modem Figure 2.1 Block diagram 2.2 Hardware Components  AT89S52  GPS MODULE  GSM MODULE  RS232  MAX 232  RELAY  LCD In this project AT89S52 microcontroller is used for interfacing to various hardware peripherals. The current design is an embedded application, which will continuously monitor a moving Vehicle and report the status of the Vehicle on demand. For doing so an AT89S52 microcontroller is interfaced serially to a GSM Modem and GPS Receiver. A GSM modem is used to send the position (Latitude and Longitude) of the vehicle from a remote place. The GPS modem will continuously give the data i.e. the latitude and longitude indicating the position of the vehicle. The GPS modem gives many parameters as the output, but only the NMEA data coming out is read and displayed on to the LCD. The same data is sent to the mobile at the other end from where the position of the vehicle is demanded. An EEPROM is used to store the mobile number. The hardware interfaces to microcontroller are LCD display, GSM modem and GPS Receiver. The design uses RS-232 protocol for serial communication between the modems and the microcontroller. A serial driver IC is used for converting TTL voltage 12
  • levels to RS-232 voltage levels. When the request by user is sent to the number at the modem, the system automatically sends a return reply to that mobile indicating the position of the vehicle in terms of latitude and longitude. As the Micro Controller, GPS and GSM take a sight of in depth knowledge, they are explained in the next chapters. 2.2.1 GPS GPS, in full Global Positioning System, space-based radio-navigation system that broadcasts highly accurate navigation pulses to users on or near the Earth. In the United States’ Navstar GPS, 24 main satellites in 6 orbits circle the Earth every 12 hours. In addition, Russia maintains a constellation called GLONASS (Global Navigation Satellite System). Working of GPS GPS receiver works on 9600 baud rate is used to receive the data from space Segment (from Satellites), the GPS values of different Satellites are sent to microcontroller AT89S52, where these are processed and forwarded to GSM. At the time of processing GPS receives only $GPRMC values only. From these values microcontroller takes only latitude and longitude values excluding time, altitude, name of the satellite, authentication etc. E.g. LAT: 1728:2470 LOG: 7843.3089 GSM modem with a baud rate 57600. A GPS receiver operated by a user on Earth measures the time it takes radio signals to travel from four or more satellites to its location, calculates the distance to each satellite, and from this calculation determines the user’s longitude, latitude, and altitude. The U.S. Department of Defense originally developed the Navstar constellation for military use, but a less precise form of the service is available free of charge to civilian users around the globe. The basic civilian service will locate a receiver within 10 meters (33 feet) of its true location, though various augmentation techniques can be used to pinpoint the location within less than 1 cm (0.4 inch). With such accuracy and the ubiquity of the service, GPS has evolved far beyond its original military purpose and has created a revolution in personal and commercial navigation. Battlefield missiles and artillery projectiles use GPS signals to determine their positions and velocities, but so do the U.S. space shuttle and the International Space Station as well as commercial jetliners and private airplanes. Ambulance fleets, family automobiles, and railroad locomotives 13
  • benefit from GPS positioning, which also serves farm tractors, ocean liners, hikers, and even golfers. Many GPS receivers are no larger than a pocket calculator and are powered by disposable batteries, while GPS computer chips the size of a baby’s fingernail have been installed in wristwatches, cellular telephones, and personal digital assistants. Triangulation The principle behind the unprecedented navigational capabilities of GPS is triangulation. To triangulate, a GPS receiver precisely measures the time it takes for a satellite signal to make its brief journey to Earth—less than a tenth of a second. Then it multiplies that time by the speed of a radio wave—300,000 km (186,000 miles) per second—to obtain the corresponding distance between it and the satellite. This puts the receiver somewhere on the surface of an imaginary sphere with a radius equal to its distance from the satellite. When signals from three other satellites are similarly processed, the receiver’s built-in computer calculates the point at which all four spheres intersect, effectively determining the user’s current longitude, latitude, and altitude. (In theory, three satellites would normally provide an unambiguous three-dimensional fix, but in practice at least four are used to offset inaccuracy in the receiver’s clock.) In addition, the receiver calculates current velocity (speed and direction) by measuring the instantaneous Doppler effect shifts created by the combined motion of the same four satellites. Augmentation Although the travel time of a satellite signal to Earth is only a fraction of a second, much can happen to it in that interval. For example, electrically charged particles in the ionosphere and density variations in the troposphere may act to slow and distort satellite signals. These influences can translate into positional errors for GPS users—a problem that can be compounded by timing errors in GPS receiver clocks. Further errors may be introduced by relativistic time dilations, a phenomenon in which a satellite’s clock and a receiver’s clock, located in different gravitational fields and traveling at different velocities, tick at different rates. Finally, the single greatest source of error to users of the Navstar system is the lower accuracy of the civilian C/A-code pulse. However, various augmentation methods exist for improving the accuracy of both the military and the civilian systems. 14
  • When positional information is required with pinpoint precision, users can take advantage of differential GPS techniques. Differential navigation employs a stationary “base station” that sits at a known position on the ground and continuously monitors the signals being broadcast by GPS satellites in its view. It then computes and broadcasts real-time navigation corrections to nearby roving receivers. Each roving receiver, in effect, subtracts its position solution from the base station’s solution, thus eliminating any statistical errors common to the two. The U.S. Coast Guard maintains a network of such base stations and transmits corrections over radio beacons covering most of the United States. Other differential corrections are encoded within the normal broadcasts of commercial radio stations. Farmers receiving these broadcasts have been able to direct their field equipment with great accuracy, making precision farming a common term in agriculture. Another GPS augmentation technique uses the carrier waves that convey the satellites’ navigation pulses to Earth. Because the length of the carrier wave is more than 1,000 times shorter than the basic navigation pulses, this “carrier-aided” approach, under the right circumstances, can reduce navigation errors to less than 1 cm (0.4 inch). The dramatically improved accuracy stems primarily from the shorter length and much greater numbers of carrier waves impinging on the receiver’s antenna each second. Yet another augmentation technique is known as geosynchronous overlays. Geosynchronous overlays employ GPS payloads “piggybacked” aboard commercial communication satellites that are placed in geostationary orbit some 35,000 km (22,000 miles) above the Earth. These relatively small payloads broadcast civilian C/A-code pulse trains to ground-based users. The U.S. government is enlarging the Navstar constellation with geosynchronous overlays to achieve improved coverage, accuracy, and survivability. Both the European Union and Japan are installing their own geosynchronous overlays. 2.2.2 GSM GSM (or Global System for Mobile Communications) was developed in 1990. The first GSM operator has subscribers in 1991, the beginning of 1994 the network based on the standard, already had 1.3 million subscribers, and the end of 1995 their number had increased to 10 million! There were first generation mobile phones in the 70's, there are 2nd generation mobile phones in the 80's and 90's, and now there are 3rd gen phones which are about to 15
  • enter the Indian market. GSM is called a 2nd generation, or 2G communications technology. In this project it acts as a SMS Receiver and SMS sender. The GSM technical specifications define the different entities that form the GSM network by defining their functions and interface requirements. 2.2.3 RS232 Interface In telecommunications, RS-232 is the traditional name for a series of standards for serial binary single-ended data and control signals connecting between a DTE (Data Terminal Equipment) and a DCE (Data Circuit-terminating Equipment). It is commonly used in computer serial ports. The standard defines the electrical characteristics and timing of signals, the meaning of signals, and the physical size and pin out of connectors. The current version of the standard is TIA-232-F Interface between Data Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary Data Interchange, issued in 1997. An RS-232 port was once a standard feature of a personal computer for connections to modems, printers, mice, data storage, un-interruptible power supplies, and other peripheral devices. However, the limited transmission speed, relatively large voltage swing, and large standard connectors motivated development of the universal serial bus which has displaced RS-232 from most of its peripheral interface roles. Many modern personal computers have no RS-232 ports and must use an external converter to connect to older peripherals. Some RS-232 devices are still found especially in industrial machines or scientific instruments. Figure 2.2: 25 pin connector as described in the RS-232 standard The scope of the standard The Electronic Industries Association (EIA) standard RS-232-C[1] as of 1969 defines:  Electrical signal characteristics such as voltage levels, signaling rate, timing and slew-rate of signals, voltage withstand level, short-circuit behavior, and maximum load capacitance.  Interface mechanical characteristics, pluggable connectors and pin identification. 16
  •  Functions of each circuit in the interface connector.  Standard subsets of interface circuits for selected telecom applications. The standard does not define such elements as the character encoding or the framing of characters, or error detection protocols. The standard does not define bit rates for transmission, except that it says it is intended for bit rates lower than 20,000 bits per second. Many modern devices support speeds of 115,200 bit/s and above. RS 232 makes no provision for power to peripheral devices. Details of character format and transmission bit rate are controlled by the serial port hardware, often a single integrated circuit called a UART that converts data from parallel to asynchronous start-stop serial form. Details of voltage levels, slew rate, and short-circuit behavior are typically controlled by a line driver that converts from the UART's logic levels to RS-232 compatible signal levels, and a receiver that converts from RS-232 compatible signal levels to the UART's logic levels. History of RS 232 RS-232 was first introduced in 1962. The original DTEs were electromechanical teletypewriters, and the original DCEs were (usually) modems. When electronic terminals (smart and dumb) began to be used, they were often designed to be interchangeable with teletypewriters, and so supported RS-232. The C revision of the standard was issued in 1969 in part to accommodate the electrical characteristics of these devices. Since application to devices such as computers, printers, test instruments, and so on was not considered by the standard, designers implementing an RS-232 compatible interface on their equipment often interpreted the requirements idiosyncratically. Common problems were non-standard pin assignment of circuits on connectors, and incorrect or missing control signals. The lack of adherence to the standards produced a thriving industry of breakout boxes, patch boxes, test equipment, books, and other aids for the connection of disparate equipment. A common deviation from the standard was to drive the signals at a reduced voltage. Some manufacturers therefore built transmitters that supplied +5 V and -5 V and labeled them as "RS-232 compatible". Later personal computers (and other devices) started to make use of the standard so that they could connect to existing equipment. For many years, an RS-232-compatible port was a standard feature for serial communications, such as modem connections, on 17
  • many computers. It remained in widespread use into the late 1990s. In personal computer peripherals, it has largely been supplanted by other interface standards, such as USB. RS- 232 is still used to connect older designs of peripherals, industrial equipment (such as PLCs), console ports, and special purpose equipment, such as a cash drawer for a cash register. The standard has been renamed several times during its history as the sponsoring organization changed its name, and has been variously known as EIA RS-232, EIA 232, and most recently as TIA 232. The standard continued to be revised and updated by the Electronic Industries Alliance and since 1988 by the Telecommunications Industry Association (TIA).[3] Revision C was issued in a document dated August 1969. Revision D was issued in 1986. The current revision is TIA-232-F Interface between Data Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary Data Interchange, issued in 1997. Changes since Revision C have been in timing and details intended to improve harmonization with the CCITT standard V.24, but equipment built to the current standard will interoperate with older versions. Related ITU-T standards include V.24 (circuit identification) and V.28 (signal voltage and timing characteristics). Limitation of Standard Because the application of RS-232 has extended far beyond the original purpose of interconnecting a terminal with a modem, successor standards have been developed to address the limitations. Issues with the RS-232 standard include:  The large voltage swings and requirement for positive and negative supplies increases power consumption of the interface and complicates power supply design. The voltage swing requirement also limits the upper speed of a compatible interface.  Single-ended signaling referred to a common signal ground limits the noise immunity and transmission distance.  Multi-drop connection among more than two devices is not defined. While multi- drop "work-arounds" have been devised, they have limitations in speed and compatibility.  Asymmetrical definitions of the two ends of the link make the assignment of the role of a newly developed device problematic; the designer must decide on either a DTE-like or DCE-like interface and which connector pin assignments to use. 18
  •  The handshaking and control lines of the interface are intended for the setup and takedown of a dial-up communication circuit; in particular, the use of handshake lines for flow control is not reliably implemented in many devices.  No method is specified for sending power to a device. While a small amount of current can be extracted from the DTR and RTS lines, this is only suitable for low power devices such as mice.  The 25-way connector recommended in the standard is large compared to current practice. Standard details In RS-232, user data is sent as a time-series of bits. Both synchronous and asynchronous transmissions are supported by the standard. In addition to the data circuits, the standard defines a number of control circuits used to manage the connection between the DTE and DCE. Each data or control circuit only operates in one direction, that is, signaling from a DTE to the attached DCE or the reverse. Since transmit data and receive data are separate circuits, the interface can operate in a full duplex manner, supporting concurrent data flow in both directions. The standard does not define character framing within the data stream, or character encoding. Voltage levels Figure 2.3 Diagrammatic oscilloscope trace of voltage levels for an uppercase ASCII "K" character (0x4b) with 1 start bit, 8 data bits, 1 stop bit. This is typical for start-stop communications, but the standard does not dictate a character format or bit order. The RS-232 standard defines the voltage levels that correspond to logical one and logical zero levels for the data transmission and the control signal lines. Valid signals are plus or minus 3 to 15 volts; the ±3 V range near zero volts is not a valid RS-232 level. 19�
  • Figure 2.4 Upper Picture: RS232 signaling as seen when probed by an actual oscilloscope (Tektronix MSO4104B) for an uppercase ASCII "K" character (0x4b) with 1 start bit (always), 8 data bits, 1 stop bit and no parity bits (8N1) The standard specifies a maximum open-circuit voltage of 25 volts: signal levels of ±5 V, ±10 V, ±12 V, and ±15 V are all commonly seen depending on the power supplies available within a device. RS-232 drivers and receivers must be able to withstand indefinite short circuit to ground or to any voltage level up to ±25 volts. The slew rate, or how fast the signal changes between levels, is also controlled. For data transmission lines (TxD, RxD and their secondary channel equivalents) logic one is defined as a negative voltage, the signal condition is called marking, and has the functional significance. Logic zero is positive and the signal condition is termed spacing. Control signals are logically inverted with respect to what one sees on the data transmission lines. When one of these signals is active, the voltage on the line will be between +3 to +15 volts. The inactive state for these signals is the opposite voltage condition, between −3 and −15 volts. Examples of control lines include request to send (RTS), clear to send (CTS), data terminal ready (DTR), and data set ready (DSR). Because the voltage levels are higher than logic levels typically used by integrated circuits, special intervening driver circuits are required to translate logic levels. These also protect the device's internal circuitry from short circuits or transients that may appear on the RS-232 interface, and provide sufficient current to comply with the slew rate requirements for data transmission. Because both ends of the RS-232 circuit depend on the ground pin being zero volts, problems will occur when connecting machinery and computers where the voltage between the ground pin on one end and the ground pin on the other is not zero. This may also cause a hazardous ground loop. Use of a common ground limits RS-232 to applications with relatively short cables. If the two devices are far enough apart or on 20�
  • separate power systems, the local ground connections at either end of the cable will have differing voltages; this difference will reduce the noise margin of the signals. Balanced, differential, serial connections such as USB, RS-422 and RS-485 can tolerate larger ground voltage differences because of the differential signaling. Unused interface signals terminated to ground will have an undefined logic state. Where it is necessary to permanently set a control signal to a defined state, it must be connected to a voltage source that asserts the logic 1 or logic 0 level. Some devices provide test voltages on their interface connectors for this purpose. Connectors RS-232 devices may be classified as Data Terminal Equipment (DTE) or Data Communication Equipment (DCE); this defines at each device which wires will be sending and receiving each signal. The standard recommended but did not make mandatory the D-subminiature 25 pin connector. In general and according to the standard, terminals and computers have male connectors with DTE pin functions, and modems have female connectors with DCE pin functions. Other devices may have any combination of connector gender and pin definitions. Many terminals were manufactured with female terminals but were sold with a cable with male connectors at each end; the terminal with its cable satisfied the recommendations in the standard. Presence of a 25 pin D-sub connector does not necessarily indicate an RS-232-C compliant interface. For example, on the original IBM PC, a male D-sub was an RS-232- C DTE port (with a non-standard current loop interface on reserved pins), but the female D-sub connector was used for a parallel Centronics printer port. Some personal computers put non-standard voltages or signals on some pins of their serial ports.The standard specifies 20 different signal connections. Since most devices use only a few signals, smaller connectors can often be used. The following table lists commonly used RS-232 signals and pin assignments. The signals are named from the standpoint of the DTE. The ground signal is a common return for the other connections. The DB-25 connector includes a second "protective ground" on pin 1. Data can be sent over a secondary channel (when implemented by the DTE and DCE devices), which is equivalent to the primary channel. Pin assignments are described in shown in Table 2.2: 21
  • Table 2.1. Commonly used RS-232 signals and pin assignments Signal Origin DB-25 pin Name Typical purpose Abbreviation DTE DCE Data Terminal Ready Indicates presence of DTE to DCE. DTR ● 20 Data Carrier Detect DCE is connected to the telephone line. DCD ● 8 Data Set Ready DCE is ready to receive commands or data. DSR ● 6 Ring Indicator DCE has detected an incoming ring signal on the telephone line. RI ● 22 Request To Send DTE requests the DCE prepare to receive data. RTS ● 4 Clear To Send Indicates DCE is ready to accept data. CTS ● 5 Transmitted Data Carries data from DTE to DCE. TxD ● 2 Received Data Carries data from DCE to DTE. RxD ● 3 Common Ground GND common 7 Protective Ground PG common 1 22
  • Table 2.2 Pin assignments Signal Pin Common Ground 7 (same as primary) Secondary Transmitted Data (STD) 14 Secondary Received Data (SRD) 16 Secondary Request To Send (SRTS) 19 Secondary Clear To Send (SCTS) 13 Secondary Carrier Detect (SDCD) 12 Ring Indicator' (RI), is a signal sent from the modem to the terminal device. It indicates to the terminal device that the phone line is ringing. In many computer serial ports, a hardware interrupt is generated when the RI signal changes state. Having support for this hardware interrupt means that a program or operating system can be informed of a change in state of the RI pin, without requiring the software to constantly "poll" the state of the pin. RI is a one-way signal from the modem to the terminal (or more generally, the DCE to the DTE) that does not correspond to another signal that carries similar information the opposite way. On an external modem the status of the Ring Indicator pin is often coupled to the "AA" (auto answer) light, which flashes if the RI signal has detected a ring. The asserted RI signal follows the ringing pattern closely, which can permit software to detect distinctive ring patterns. The Ring Indicator signal is used by some older uninterruptible power supplies (UPS's) to signal a power failure state to the computer. Certain personal computers can be configured for wake-on-ring, allowing a computer that is suspended to answer a phone call. Cables The standard does not define a maximum cable length but instead defines the maximum capacitance that a compliant drive circuit must tolerate. A widely used rule of thumb indicates that cables more than 50 feet (15 m) long will have too much capacitance, unless special cables are used. By using low-capacitance cables, full speed 23
  • communication can be maintained over larger distances up to about 1,000 feet (300 m).[8] For longer distances, other signal standards are better suited to maintain high speed. Since the standard definitions are not always correctly applied, it is often necessary to consult documentation, test connections with a breakout box, or use trial and error to find a cable that works when interconnecting two devices. Connecting a fully standard- compliant DCE device and DTE device would use a cable that connects identical pin numbers in each connector (a so-called "straight cable"). "Gender changers" are available to solve gender mismatches between cables and connectors. Connecting devices with different types of connectors requires a cable that connects the corresponding pins according to the table above. Cables with 9 pins on one end and 25 on the other are common. Manufacturers of equipment with 8P8C connectors usually provide a cable with either a DB-25 or DE-9 connector (or sometimes interchangeable connectors so they can work with multiple devices). Poor-quality cables can cause false signals by crosstalk between data and control lines (such as Ring Indicator). If a given cable will not allow a data connection, especially if a Gender changer is in use, a Null modem may be necessary. Conventions For functional communication through a serial port interface, conventions of bit rate, character framing, communications protocol, character encoding, data compression, and error detection, not defined in RS 232, must be agreed to by both sending and receiving equipment. For example, consider the serial ports of the original IBM PC. This implementation used an 8250 UART using asynchronous start-stop character formatting with 7 or 8 data bits per frame, usually ASCII character coding, and data rates programmable between 75 bits per second and 115,200 bits per second. Data rates above 20,000 bits per second are out of the scope of the standard, although higher data rates are sometimes used by commercially manufactured equipment. Since most RS-232 devices do not have automatic baud rate detection, users must manually set the baud rate (and all other parameters) at both ends of the RS-232 connection. In the particular case of the IBM PC, as with most UART chips including the 8250 UART used by the IBM PC, baud rates were programmable with arbitrary values. This allowed a PC to be connected to devices not using the rates typically used with modems. 24
  • Not all baud rates can be programmed, due to the clock frequency of the 8250 UART in the PC, and the granularity of the baud rate setting. This includes the baud rate of MIDI, 31,250 bits per second, which is generally not achievable by a standard IBM PC serial port. MIDI-to-RS-232 interfaces designed for the IBM PC include baud rate translation hardware to adjust the baud rate of the MIDI data to something that the IBM PC can support, for example 19,200 or 38,400 bits per second. RTS/CTS handshaking In older versions of the specification, RS-232's use of the RTS and CTS lines is asymmetric: The DTE asserts RTS to indicate a desire to transmit to the DCE, and the DCE asserts CTS in response to grant permission. This allows for half-duplex modems that disable their transmitters when not required, and must transmit a synchronization preamble to the receiver when they are re-enabled. This scheme is also employed on present-day RS-232 to RS-485 converters, where the RS-232's RTS signal is used to ask the converter to take control of the RS-485 bus - a concept that does not otherwise exist in RS-232. There is no way for the DTE to indicate that it is unable to accept data from the DCE. A non-standard symmetric alternative, commonly called "RTS/CTS handshaking," was developed by various equipment manufacturers. In this scheme, CTS is no longer a response to RTS; instead, CTS indicates permission from the DCE for the DTE to send data to the DCE, and RTS indicates permission from the DTE for the DCE to send data to the DTE. RTS and CTS are controlled by the DTE and DCE respectively, each independent of the other. This was eventually codified in version RS-232-E (actually TIA-232-E by that time) by defining a new signal, "RTR (Ready to Receive)," which is CCITT V.24 circuit 133. TIA-232-E and the corresponding international standards were updated to show that circuit 133, when implemented, shares the same pin as RTS (Request to Send), and that when 133 is in use, RTS is assumed by the DCE to be ON at all times. Thus, with this alternative usage, one can think of RTS asserted (positive voltage, logic 0) meaning that the DTE is indicating it is "ready to receive" from the DCE, rather than requesting permission from the DCE to send characters to the DCE. Note that equipment using this protocol must be prepared to buffer some extra data, since a transmission may have begun just before the control line state change. 25
  • RTS/CTS handshaking is an example of hardware flow control. However, "hardware flow control" in the description of the options available on an RS-232- equipped device does not always mean RTS/CTS handshaking. 3-wire and 5-wire RS-232 Minimal “3-wire” RS-232 connections’ consisting only of transmit data, receive data, and ground, is commonly used when the full facilities of RS-232 are not required. Even a two-wire connection (data and ground) can be used if the data flow is one way (for example, a digital postal scale that periodically sends a weight reading, or a GPS receiver that periodically sends position, if no configuration via RS-232 is necessary). When only hardware flow control is required in addition to two-way data, the RTS and CTS lines are added in a 5-wire version. Seldom used features The EIA-232 standard specifies connections for several features that are not used in most implementations. Their use requires the 25-pin connectors and cables, and of course both the DTE and DCE must support them. a) Signal rate selection The DTE or DCE can specify use of a "high" or "low" signaling rate. The rates as well as which device will select the rate must be configured in both the DTE and DCE. The prearranged device selects the high rate by setting pin 23 to ON. b) Loopback testing Many DCE devices have a loopback capability used for testing. When enabled, signals are echoed back to the sender rather than being sent on to the receiver. If supported, the DTE can signal the local DCE (the one it is connected to) to enter loopback mode by setting pin 18 to ON, or the remote DCE (the one the local DCE is connected to) to enter loopback mode by setting pin 21 to ON. The latter tests the communications link as well as both DCE's. When the DCE is in test mode it signals the DTE by setting pin 25 to ON. A commonly used version of loopback testing does not involve any special capability of either end. A hardware loopback is simply a wire connecting complementary pins together in the same connector Loopback testing is often performed with a specialized DTE called a bit error rate tester (or BERT). 26
  • Timing Signals Some synchronous devices provide a clock signal to synchronize data transmission, especially at higher data rates. Two timing signals are provided by the DCE on pins 15 and 17. Pin 15 is the transmitter clock, or send timing (ST); the DTE puts the next bit on the data line (pin 2) when this clock transitions from OFF to ON (so it is stable during the ON to OFF transition when the DCE registers the bit). Pin 17 is the receiver clock, or receive timing (RT); the DTE reads the next bit from the data line (pin 3) when this clock transitions from ON to OFF. Alternatively, the DTE can provide a clock signal, called transmitter timing (TT), on pin 24 for transmitted data. Data is changed when the clock transitions from OFF to ON and read during the ON to OFF transition. TT can be used to overcome the issue where ST must traverse a cable of unknown length and delay, clock a bit out of the DTE after another unknown delay, and return it to the DCE over the same unknown cable delay. Since the relation between the transmitted bit and TT can be fixed in the DTE design, and since both signals traverse the same cable length, using TT eliminates the issue. TT may be generated by looping ST back with an appropriate phase change to align it with the transmitted data. ST loop back to TT lets the DTE use the DCE as the frequency reference, and correct the clock to data timing. Other Serial interfaces similar to RS-232  RS-422 (a high-speed system similar to RS-232 but with differential signaling)  RS-423 (a high-speed system similar to RS-422 but with unbalanced signaling)  RS-449 (a functional and mechanical interface that used RS-422 and RS-423 signals - it never caught on like RS-232 and was withdrawn by the EIA)  RS-485 (a descendant of RS-422 that can be used as a bus in multidrop configurations)  MIL-STD-188 (a system like RS-232 but with better impedance and rise time control)  EIA-530 (a high-speed system using RS-422 or RS-423 electrical properties in an EIA-232 pinout configuration, thus combining the best of both; supersedes RS- 449)  EIA/TIA-561 8 Position Non-Synchronous Interface Between Data Terminal Equipment and Data Circuit Terminating Equipment Employing Serial Binary Data Interchange 27
  •  EIA/TIA-562 Electrical Characteristics for an Unbalanced Digital Interface (low- voltage version of EIA/TIA-232)  TIA-574 (standardizes the 9-pin D-subminiature connector pinout for use with EIA-232 electrical signaling, as originated on the IBM PC/AT)  SpaceWire (high-speed serial system designed for use on board spacecraft). 2.2.4 MAX232 IC The MAX232 is an integrated circuit that converts signals from an RS-232 serial port to signals suitable for use in TTL compatible digital logic circuits. The MAX232 is a dual driver/receiver and typically converts the RX, TX, CTS and RTS signals. The drivers provide RS-232 voltage level outputs (approx. ± 7.5 V) from a single + 5 V supply via on-chip charge pumps and external capacitors. This makes it useful for implementing RS-232 in devices that otherwise do not need any voltages outside the 0 V to + 5 V range, as power supply design does not need to be made more complicated just for driving the RS-232 in this case. The receivers reduce RS-232 inputs (which may be as high as ± 25 V), to standard 5 V TTL levels. These receivers have a typical threshold of 1.3 V, and a typical hysteresis of 0.5 V. The later MAX232A is backwards compatible with the original MAX232 but may operate at higher baud rates and can use smaller external capacitors – 0.1 μF in place of the 1.0 μF capacitors used with the original device.[1] The newer MAX3232 is also backwards compatible, but operates at a broader voltage range, from 3 to 5.5 V. Pin to pin compatible: ICL232, ST232, ADM232, and HIN232. Figure 2.5 MAX232 chip 28
  • Voltage Levels It is helpful to understand what occurs to the voltage levels. When a MAX232 IC receives a TTL level to convert, it changes a TTL Logic 0 to between +3 and +15 V, and changes TTL Logic 1 to between -3 to -15 V, and vice versa for converting from RS232 to TTL. This can be confusing when you realize that the RS232 Data Transmission voltages at a certain logic state are opposite from the RS232 Control Line voltages at the same logic state. To clarify the matter, see the table below. Table 2.3 RS-232 Voltage Levels RS232 Line Type & Logic Level RS232 Voltage TTL Voltage to/from MAX232 Data Transmission (Rx/Tx) Logic 0 +3 V to +15 V 0 V Data Transmission (Rx/Tx) Logic 1 -3 V to -15 V 5 V Control Signals (RTS/CTS/DTR/DSR) Logic 0 -3 V to -15 V 5 V Control Signals (RTS/CTS/DTR/DSR) Logic 1 +3 V to +15 V 0 V The MAX232 IC is used to convert the TTL/CMOS logic levels to RS232 logic levels during serial communication of microcontrollers with PC. The controller operates at TTL logic level (0-5V) whereas the serial communication in PC works on RS232 standards (-25 V to + 25V). This makes it difficult to establish a direct link between them to communicate with each other. The intermediate link is provided through MAX232. It is a dual driver/receiver that includes a capacitive voltage generator to supply RS232 voltage levels from a single 5V supply. Each receiver converts RS232 inputs to 5V TTL/CMOS levels. These receivers (R1 & R2) can accept ±30V inputs. The drivers (T1 & T2), also called transmitters, convert the TTL/CMOS input level into RS232 level. The transmitters take input from controller’s serial transmission pin and send the output to RS232’s receiver. The receivers, on the other hand, take input from transmission pin of RS232 serial port and give serial output to microcontroller’s receiver pin. MAX232 needs four external capacitors whose value ranges from 1µF to 22µF. 29
  • Table 2.4 TX and RX pin connection Microcontroller MAX232 RS232 Tx T1/2 In T1/2 Out Rx Rx R1/2 Out R1/2 In Tx Pin Diagram The following is the block diagram of the MAX232 IC. Figure 2.6 Pin diagram of MAX232 Pin Description: Table 2.5 Pins assignment of MAX232 Pin No Function Name 1 Capacitor connection pins Capacitor 1 + 2 Capacitor 3 + 3 Capacitor 1 - 4 Capacitor 2 + 5 Capacitor 2 - 6 Capacitor 4 - 7 Output pin; outputs the serially transmitted data at RS232 logic level; connected to receiver pin of PC serial port T2 Out 30
  • 8 Input pin; receives serially transmitted data at RS 232 logic level; connected to transmitter pin of PC serial port R2 In 9 Output pin; outputs the serially transmitted data at TTL logic level; connected to receiver pin of controller. R2 Out 10 Input pins; receive the serial data at TTL logic level; connected to serial transmitter pin of controller. T2 In 11 T1 In 12 Output pin; outputs the serially transmitted data at TTL logic level; connected to receiver pin of controller. R1 Out 13 Input pin; receives serially transmitted data at RS 232 logic level; connected to transmitter pin of PC serial port R1 In 14 Output pin; outputs the serially transmitted data at RS232 logic level; connected to receiver pin of PC serial port T1 Out 15 Ground (0V) Ground 16 Supply voltage; 5V (4.5V – 5.5V) Vcc 2.2.5 Relay A relay is an electrically operated switch. Many relays use an electromagnet to operate a switching mechanism mechanically, but other operating principles are also used. Relays are used where it is necessary to control a circuit by a low-power signal (with complete electrical isolation between control and controlled circuits), or where several circuits must be controlled by one signal. The first relays were used in long distance telegraph circuits, repeating the signal coming in from one circuit and re- transmitting it to another. Relays were used extensively in telephone exchanges and early computers to perform logical operations. History of a Relay A simple device, which we now call a relay, was included in the original 1840 telegraph patent of Samuel Morse. The mechanism described acted as a digital amplifier, repeating the telegraph signal, and thus allowing signals to be propagated as far as desired. This overcame the problem of limited range of earlier telegraphy schemes. The earlier ‘relay’ or ‘repeater’ of Edward Davy of 1837/1838 was used in his electric telegraph. 31
  • Figure 2.7 UK Q-style signaling relay and base. A type of relay that can handle the high power required to directly control an electric motor or other loads is called a contactor. Solid-state relays control power circuits with no moving parts, instead using a semiconductor device to perform switching. Relays with calibrated operating characteristics and sometimes multiple operating coils are used to protect electrical circuits from overload or faults; in modern electric power systems these functions are performed by digital instruments still called "protective relays". Figure 2.8 Automotive-style miniature relay, dust cover is taken off Basic Design and Operation of a Relay A simple electromagnetic relay consists of a coil of wire wrapped around a soft iron core, an iron yoke which provides a low reluctance path for magnetic flux, a movable iron armature, and one or more sets of contacts (there are two in the relay pictured). The armature is hinged to the yoke and mechanically linked to one or more sets of moving contacts. It is held in place by a spring so that when the relay is de-energized there is an air gap in the magnetic circuit. In this condition, one of the two sets of contacts in the relay pictured is closed, and the other set is open. Other relays may have more or fewer sets of contacts depending on their function. The relay in the picture also has a wire connecting the armature to the yoke. This ensures continuity of the circuit between the moving contacts on the armature, and the circuit track on the printed circuit board (PCB) via the yoke, which is soldered to the PCB. 32
  • When an electric current is passed through the coil it generates a magnetic field that activates the armature and the consequent movement of the movable contact either makes or breaks (depending upon construction) a connection with a fixed contact. If the set of contacts was closed when the relay was de-energized, then the movement opens the contacts and breaks the connection, and vice versa if the contacts were open. When the current to the coil is switched off, the armature is returned by a force, approximately half as strong as the magnetic force, to its relaxed position. Usually this force is provided by a spring, but gravity is also used commonly in industrial motor starters. Most relays are manufactured to operate quickly. In a low-voltage application this reduces noise; in a high voltage or current application it reduces arcing. When the coil is energized with direct current, a diode is often placed across the coil to dissipate the energy from the collapsing magnetic field at deactivation, which would otherwise generate a voltage spike dangerous to semiconductor circuit components. Some automotive relays include a diode inside the relay case. Alternatively, a contact protection network consisting of a capacitor and resistor in series (snubber circuit) may absorb the surge. If the coil is designed to be energized with alternating current (AC), a small copper "shading ring" can be crimped to the end of the solenoid, creating a small out-of-phase current which increases the minimum pull on the armature during the AC cycle.[1] A solid-state relay uses a thyristor or other solid-state switching device, activated by the control signal, to switch the controlled load, instead of a solenoid. An optocoupler (a light-emitting diode (LED) coupled with a photo transistor) can be used to isolate control and controlled circuits. Pole and Throw Since relays are switches, the terminology applied to switches is also applied to relays. A relay will switch one or more poles, each of whose contacts can be thrown by energizing the coil in one of three ways:  Normally-open (NO): Contacts connect the circuit when the relay is activated; the circuit is disconnected when the relay is inactive. It is also called a Form A contact or "make" contact. NO contacts can also be distinguished as "early-make" or NOEM, which means that the contacts will close before the button or switch is fully engaged.  Normally-closed (NC): contacts disconnect the circuit when the relay is activated; the circuit is connected when the relay is inactive. It is also called a Form B contact or "break" contact. NC contacts can also be distinguished as "late-break" or NCLB, 33
  • which means that the contacts will stay closed until the button or switch is fully disengaged.  Change-over (CO): or double-throw (DT), contacts control two circuits: one normally-open contact and one normally-closed contact with a common terminal. It is also called a Form C contact or "transfer" contact ("break before make"). If this type of contact utilizes a "make before break" functionality, then it is called a Form D contact. The following designations are commonly encountered:  SPST – Single Pole Single Throw. These have two terminals which can be connected or disconnected. Including two for the coil, such a relay has four terminals in total. It is ambiguous whether the pole is normally open or normally closed. The terminology "SPNO" and "SPNC" is sometimes used to resolve the ambiguity.  SPDT – Single Pole Double Throw. A common terminal connects to either of two others. Including two for the coil, such a relay has five terminals in total.  DPST – Double Pole Single Throw. These have two pairs of terminals. Equivalent to two SPST switches or relays actuated by a single coil. Including two for the coil, such a relay has six terminals in total. The poles may be Form A or Form B (or one of each).  DPDT– Double Pole Double Throw. These have two rows of change-over terminals. Equivalent to two SPDT switches or relays actuated by a single coil. Such a relay has eight terminals, including the coil.  The "S" or "D" may be replaced with a number, indicating multiple switches connected to a single actuator. For example 4PDT indicates a four pole double throw relay (with 14 terminals).  EN 50005 are among applicable standards for relay terminal numbering; a typical EN 50005-compliant SPDT relay's terminals would be numbered 11, 12, 14, A1 and A2 for the C, NC, NO, and coil connections, respectively. Figure 2.9 Circuit symbols of relays. (C denotes the common terminal in SPDT and DPDT types.) 34
  • Uses of Relays o Amplify a digital signal, switching a large amount of power with a small operating power. Some special cases are: o A telegraph relay, repeating a weak signal received at the end of a long wire o Controlling a high-voltage circuit with a low-voltage signal, as in some types of modems or audio amplifiers, o Controlling a high-current circuit with a low-current signal, as in the starter solenoid of an automobile. 2.2.6 LCD A liquid crystal display (LCD) is a flat panel display, electronic visual display, or video display that uses the light modulating properties of liquid crystals (LCs). LCs do not emit light directly. LCDs are used in a wide range of applications, including computer monitors, television, instrument panels, aircraft cockpit displays, signage, etc. They are common in consumer devices such as video players, gaming devices, clocks, watches, calculators, and telephones. LCDs have replaced cathode ray tube (CRT) displays in most applications. They are available in a wider range of screen sizes than CRT and plasma displays, and since they do not use phosphors, they cannot suffer image burn-in. LCDs are, however, susceptible to image persistence. LCDs are more energy efficient and offer safer disposal than CRTs. Its low electrical power consumption enables it to be used in battery- powered electronic equipment. It is an electronically modulated optical device made up of any number of segments filled with liquid crystals and arrayed in front of a light source (backlight) or reflector to produce images in color or monochrome. The most flexible ones use an array of small pixels. The earliest discovery leading to the development of LCD technology, the discovery of liquid crystals, dates from 1888. By 2008, worldwide sales of televisions with LCD screens had surpassed the sale of CRT units. Following figure is a 16x2 LCD. Figure 2.10 A general purpose alphanumeric LCD, with two lines of 16 characters. 35�
  • Monochrome passive-matrix LCDs were standard in most early laptops (although a few used plasma displays) and the original Nintendo Game Boyuntil the mid-1990s, when color active-matrix became standard on all laptops. The commercially unsuccessful Macintosh Portable (released in 1989) was one of the first to use an active-matrix display (though still monochrome). Passive-matrix LCDs are still used today for applications less demanding than laptops and TVs. In particular, portable devices with less information content to be displayed, where lowest power consumption (no backlight), low cost and/or readability in direct sunlight are needed, use this type of display. Advantages and Disadvantages In spite of LCDs being a well proven and still viable technology, as display devices LCDs are not perfect for all applications. Advantages  Very compact and light.  Low power consumption.  No geometric distortion.  Little or no flicker depending on backlight technology.  Not affected by screen burn-in.  Can be made in almost any size or shape.  No theoretical resolution limit. Disadvantages  Limited viewing angle, causing color, saturation, contrast and brightness to vary, even within the intended viewing angle, by variations in posture.  Bleeding and uneven backlighting in some monitors, causing brightness distortion, especially toward the edges.  Smearing and ghosting artifacts caused by slow response times (>8 ms) and "sample and hold" operation.  Fixed bit depth, many cheaper LCDs are only able to display 262,000 colors. 8-bit S-IPS panels can display 16 million colors and have significantly better black level, but are expensive and have slower response time.  Low bit depth results in images with unnatural or excessive contrast.  Input lag  Dead or stuck pixels may occur during manufacturing or through use. 36
  • Chapter 3 Working of VTS 3.1 Schematic Diagram of VTS 3.2 Circuit Description The hardware interfaces to microcontroller are LCD display, GSM modem and GPS receiver. The design uses RS-232 protocol for serial communication between the modems and the microcontroller. A serial driver IC is used for converting TTL voltage levels to RS-232 voltage levels. When the request is sent by the number at the modem, the system automatically sends a return reply to that mobile indicating the position of the vehicle in terms of latitude and longitude. Figure 3.1 Schematic diagram of vehicle tracing using GSM and GPS 37
  • 3.3 Circuit Operation The project is vehicle positioning and navigation system we can locate the vehicle around the globe with 8052 micro controller, GPS receiver, GSM modem, MAX 232, Power supply. Microcontroller used is AT89S52. The code is written in the internal memory of Microcontroller i.e. ROM. With help of instruction set it processes the instructions and it acts as interface between GSM and GPS with help of serial communication of 8052. GPS always transmits the data and GSM transmits and receive the data. GPS pin TX is connected to microcontroller via MAX232. GSM pins TX and RX are connected to microcontroller. 3.3.1 Power The power is supplied to components like GSM, GPS and Micro control circuitry using a 12V/3.2A battery .GSM requires 12v,GPS and microcontroller requires 5v .with the help of regulators we regulate the power between three components. 3.3.2 Serial ports Microcontroller communicates with the help of serial communication. First it takes the data from the GPS receiver and then sends the information to the owner in the form of SMS with help of GSM modem. 3.4 Operating procedure: a) To store a Number into the kit i. Place a jumper at the pin no 32 “Store Number” as shown in the circuit diagram. ii. Switch on the kit. iii. Wait until you see “Waiting for Call” on the LCD display. iv. Now call from the mobile number from which you need to store the number. v. Wait until you see “Number stored” on the LCD. vi. Now remove the Jumper. b) Normal Operation i. Switch on the kit and wait until you see the Latitude and longitude on the display. ii. Now give a call from any mobile iii. The kit will send the location and UTC time to the number stored in its memory. 38
  • iv. For emergency the user can press the Button to send the Location to the number stored. v. For photos of this project check this link. Initially the GPS continuously takes the data from the satellite and stores the latitude and longitude positions in microcontroller’s buffer. If we want to know the path of the vehicle we need to send a message to the GSM which gets activated by receiving our message .at the same instant the GPS gets deactivated with the help of relay. As soon as the GSM gets activated it takes the last received latitude and longitude positions from the buffer and sends a message to the particular number which is executed in the program. After the message has been sent to the user the GSM gets deactivated and similarly the GPS gets activated. This is cyclic process 39
  • Chapter 4 Microcontroller AT 89S52 Why we use AT 89S52? AT89S52 microcontroller is a great family compatible with Intel MCS-51 . Atmel AT89S52 is created by, indicated by the initials "AT". This microcontroller has a low consumption, but 8-bit CMOS gives high performance with an internal flash memory of 8K bytes. This is done using flash memory technology and high density belonging to Atmel and is compatible with standard 80C51. Flash memory chip allows internal or scheduled to be reprogrammed by a non-volatile memory. By combining an 8-bit CPU with Flash memory programmable monolithic core, Atmel AT89S52 is very powerful microcontroller has high flexibility and is the perfect solution for many embedded applications. A microcontroller is an electronic structure of small size, usually containing a processor, memory and peripheral input / output programmable. Applications that use microcontrollers are automatic control, in areas such as car production, medical devices, remote control and more of the same gender. In 1976, Intel created the first microcontroller family called MCS. MCS 48 MCS 51 standard appearing in 1980. Currently, Intel does not make such microcontrollers, but major manufacturers such as Atmel and Infineon continued creating these devices. 4.1 Features The main features of the microcontroller are:  Compatibility with the MCS 51 family;  8-bit CPU frequency up to 33MHz;  RAM: 256 Bytes;  Flash memory: 8K bytes;  32 lines of programming input / output general nature;  8 sources of interruptions organized on two levels of priority;  3 timers / counters of 16 bits;  Watchdog Timer;  two data pointers;  1 serial port (full duplex UART);  ISP programming interface of 8K bytes; 40
  •  supports up to 10 000 rewrites;  contains the oscillator;  Short programming time. 4.2 The Pin Configuration AT89S52 microcontroller is a 40-pin; its meaning is expressed below. Pin number in parentheses is that given the fact that pin 1 is top left, and pin 40 in the top right. Vcc (40): Supply Voltage; GND (20): Grounding; Port 0 (39-32): Port 0 is a bidirectional port input / output 8-bit. As an output port, each pin is allotted eight TTL inputs. When port pins 0 are registered with a logical value, they can be used as high impedance inputs. Port 0 can also be configured as the least significant address and data during access to external program and data memory. Port 0 is also the recipient code during Flash programming and gives the result bits from the verification program. Closing transistor is required during program verification. Port 1 (1-8): Port 1 is also a bidirectional port input / output with internal pull-up (transistor is automatically closed). But for an output port can support four TTL inputs. When port 1 is written with a logical value, i.e. the transistor is closed; we can use the port for reading, otherwise, if the transistor is open for write port use. Port 1 also receives the least significant address bits during Flash programming and verification. In addition, pins 0 and 1 of port1 can be configured as timers and counters it is, and pins 5, 6, and 7 are used for programming interface. Port 2 (21-28): Port 2 is also a bidirectional port input / i.e. tire 8-bit internal pull- up. Port 2 is the one who gives the most significant bits of the address during extraction from external memory and external memory while accessing the data using 16-bit addresses. In this mode of use, Port 2 uses strong internal pull up the issue of a logical value. While access to external data memory that utilizes 8-bit addresses, port 2 is used for special function registers. Port 2 also receives the most significant address bits and some control signals during Flash programming and verification. Port 3 (10-17): Port 3 is also a bidirectional port input / output 8-bit internal pull-up by acting as port 1 and 2. Port 3 receives control signals for Flash memory programming Other special functions you can perform port 3 are:  pin 0 is there an alternative entrance to the serial port (RXD);  pin 1 is used as serial port output (TXD); 41
  •  pins 2 and 3 are used for external interrupt (INT0 #, # INT1);  pins 4 and 5 can be used interchangeably as timers (T0 and T1);  pin 6 is used as a signal to external memory write (# WR);  Pin 7 is used as the external signal read from memory (RD #). RST (9): acts as a reset RST entry. A high value on this pin between two machine cycles while the oscillator work, reset the device. This pin acts high for 98 oscillator periods after the watchdog stops. To disable this feature using DISRTO bit of special function registers at exactly the 8EH. The default state of bit DISRTO, feature RESET is active HIGH. ALE / PROG # (30): THE acronym comes from the Address Latch Enable, and this is what command buffer that stores the least significant address. During Flash memory programming this pin serves as input pulse programming: # PROG (Program Pulse Input). For normal operation, ALE issued at a time constant equal to 1/6 of oscillator frequency and can be used as a timer or external clock. By request, executes the function that OF can be disabled by setting bit special register at 8EH with logic value 0. With this bit set, ALE is active only for the instructions MOVX and MOVC. Disabling OF bit has no effect if the microcontroller is in external execution mode. PSEN (29): Acronym PSEN Program Store Enable is the control signal and means for external program memory. When AT89S52 code running external program memory, PSEN # is activated 2 times for each machine cycle, except the activation signal PSEN # is omitted during external data memory access. EA / VPP (31): EA acronym stands External Access Enable. # It must be connected to GRD to enable the device to extract the code from external program memory from address 0000H to address internal program executions FFFFH. Pentru # EA must be connected to Vcc. XTAL1 (19): XTAL1 is used as input to the inverting oscillator amplified the input clock operating circuit. XTAL2 (18): XTAL2 oscillator inverter output is amplified. 4.2.1 Special Function Registers (SFR) Not all addresses in the area where there are special function registers are occupied and the unoccupied may be absent on the chip. Access to read from these addresses will in general return random data and write access to will have an effect 42
  • indefinitely. Programmers should avoid writing in these locations, because these locations can be used in future for new features. In this case the reset or inactivation of these new bits will always be 0. Timer Registers: Control and status bits are contained in registers T2CON and T2MOD for timer 2. The pair of registers (RCAP2H, RCAP2L) are registers purchase or reload timer 2 for 16-bit mode and 16-bit acquisition mode auto reload. Registers of interruptions: Individual interrupt enable bits are in register IE. For the six types of interrupt sources can be set two levels of priority in the IP register. 4.3 Memory Organization MCS-51 family devices have separate address and data program. Up to 64K bytes each program or data memory can be addressed. a) Program memory If EA is pin # connected the GRD program calls are directed to external memory. If EA # is connected to Vcc, calls the program at address 0000H to 1FFFH are directly to internal memory, while those at 2000H up to FFFFH are directed to external memory. b) Data memory AT89S52 has a RAM of 256 bytes. The 128 Bytes additional to the 128 basic families occupies an address space parallel to the Registrar of Special Functions, and that these additional bytes of special function registers are accessible addresses, but physically they are in different spaces. When an instruction accesses an internal location in 7fh address, addressing mode used in the instruction specifies that the CPU accesses the upper 128 bytes of RAM or the RFS. It uses direct addressing to access the RFS space, and indirect addressing the senior access bytes RAM. 4.4 Watch Dog Timer: Watchdog Timer (WDT) is used as a recovery method in situations where the CPU is under software problems. The WDT counter consists of a 14-bit Watchdog Timer and Reset (WDTRST) which is in RFS. By default, the WDT is disabled, for activation, the user successively 0E1H 01EH and WDTRST register, i.e. the RFS's location 0A6H. Cans WDT is active, it will increment every machine cycle, while the oscillator will run. Rest period is dependent on the external clock frequency. The only way to disable the WDT is reset site. When WDT exceeds the maximum limit will send a reset pulse RST pin HIGH. 43
  • 4.4.1 Watchdog Timer for both modes of operation Power-down mode means stopping off WDT's oscilloscope. During Power-down mode of operation, the user must not maintain the WDT. There are two ways to exit Power-down mode: by a hard reset or via an external interrupt is Priority Power-down mode. When Power-down exits through a hardware reset, WDT service should act as if AT89S52 is reset. Power-down Exit through an interrupt is significantly different behavior. Interruption is maintained sufficiently long as the oscillator to stabilize. When termination is carried high, it is served. To prevent the WDT from resetting the device interrupt pin is held low, the WDT will not start until the interrupt will not be extended to a high level. This means, that the WDT will be cleared during the interrupt function to exit Power-down mode. To ensure that the WDT will not be exceeded during some states out of Power-down, it is better to be reset before entering Power-down mode. Before entering the Idle mode, bit WDIDLE the RFS is used to determine where to continue the WDT when it becomes active. The WDT continues to count during Idle mode as the default state. To prevent the WDT to reset the AT89S52 during Idle mode, the user should always set a timer that will periodically exit Idle, will service the WDT and enter Idle mode again. The WDT enabled WDIDLE bit will stop the count in Idle mode and continue counting out of the way. a) Switches AT89S52 is a vector of six stops: two external interrupts (INT0 # and #, INT2), three timers interrupts (Timer 0, 1 and 2) and serial port interrupt. Each of these interrupt sources can be individually enabled and disabled by setting or deleting a bit of special function registers IE. IE also contains a global disable bit, EA, which disables all interrupts at the same time. Bit position 6 is not implemented. But the programmer should not use this bit; it can be used in future AT89 products family. Interruption of Timer 2 is generated by "or logic" between bits TF2 and EXF2 you register T2CON.None of these indicators is not deleted when routine hardware orders indicate that area. In fact, routine order to determine which of the two bits TF2 or EXF2 generated interrupts, and that bit will be set in software. b) The idle In Idle mode, CPU is put into hibernation, while all peripherals remain active. The mode is invoked by software. Content on chip RAM and all special function registers remain unchanged while this mode is set. Idle mode can be enabled over any break or 44
  • hardware reset. When idle mode is terminated by a hardware reset, the device normally resumes program execution from where it was interrupted by two machine cycles before the internal reset algorithm to take control. The hardware on the same plate to prevent access to internal RAM during this event, but access to ports is blocked. To eliminate the possibility of unexpected writings of a port pin when idle mode is terminated by reset, the instruction as it is one that invokes idle mode should not write to a port pin or external memory. c) The power-down Power-down mode, the oscillator is set and instructions for calling Power-down mode is the last instruction executed. Track RAM on chip and special function registers retain their values until the Power-down mode ends. Exit Power-down can be initiated both by activating a hardware reset or external interrupt. Reset registry values change with special but not modify RAM on chip. Reset can be activated before VCC to return to its operating level and must remain active long enough to allow the oscillator resetting and stabilization. 45
  • Chapter 5 GSM Module 5.1 GSM History The acronym for GSM is Global System for Mobile Communications. During the early 1980s, analog cellular telephone systems were experiencing rapid growth in Europe, particularly in Scandinavia and the United Kingdom, but also in France and Germany. Each country developed its own system, which was incompatible with everyone else's in equipment and operation. This was an undesirable situation, because not only was the mobile equipment limited to operation within national boundaries, which in a unified Europe were increasingly unimportant, but there was also a very limited market for each type of equipment, so economies of scale and the subsequent savings could not be realized. The Europeans realized this early on, and in 1982 the Conference of European Posts and Telegraphs (CEPT) formed a study group called the Groupe Special Mobile (GSM) to study and develop a pan-European public land mobile system. The proposed system had to meet certain criteria:  Good subjective speech quality  Low terminal and service cost  Low terminal and service cost  Ability to support handheld terminals  Support for range of new services and facilities  Spectral efficiency  ISDN compatibility  Pan-European means European-wide. ISDN throughput at 64Kbs was never envisioned, indeed, the highest rate a normal GSM network can achieve is 9.6kbs. Europe saw cellular service introduced in 1981, when the Nordic Mobile Telephone System or NMT450 began operating in Denmark, Sweden, Finland, and Norway in the 450 MHz range. It was the first multinational cellular system. In 1985 Great Britain started using the Total Access Communications System or TACS at 900 MHz. Later, the West German C-Netz, the French Radio COM 2000, and the Italian RTMI/RTMS helped make up Europe's nine analog incompatible radio telephone systems. Plans were afoot during the early 1980s, however, to create a single European wide digital mobile service with advanced features and easy roaming. While North American groups concentrated on 46
  • building out their robust but increasingly fraud plagued and featureless analog network, Europe planned for a digital future. In 1989, GSM responsibility was transferred to the European Telecommunication Standards Institute (ETSI), and phase I of the GSM specifications were published in 1990. Commercial service was started in mid-1991, and by 1993 there were 36 GSM networks in 22 countries. Although standardized in Europe, GSM is not only a European standard. Over 200 GSM networks (including DCS1800 and PCS1900) are operational in 110 countries around the world. In the beginning of 1994, there were 1.3 million subscribers worldwide, which had grown to more than 55 million by October 1997. With North America making a delayed entry into the GSM field with a derivative of GSM called PCS1900, GSM systems exist on every continent, and the acronym GSM now aptly stands for Global System for Mobile communications. The developers of GSM chose an unproven (at the time) digital system, as opposed to the then-standard analog cellular systems like AMPS in the United States and TACS in the United Kingdom. They had faith that advancements in compression algorithms and digital signal processors would allow the fulfillment of the original criteria and the continual improvement of the system in terms of quality and cost. The over 8000 pages of GSM recommendations try to allow flexibility and competitive innovation among suppliers, but provide enough standardization to guarantee proper networking between the components of the system. This is done by providing functional and interface descriptions for each of the functional entities defined in the system. 5.2 Services Provided by GSM From the beginning, the planners of GSM wanted ISDN compatibility in terms of the services offered and the control signaling used. However, radio transmission limitations, in terms of bandwidth and cost, do not allow the standard ISDN B-channel bit rate of 64 kbps to be practically achieved. Telecommunication services can be divided into bearer services, teleservices, and supplementary services. The most basic teleservice supported by GSM is telephony. As with all other communications, speech is digitally encoded and transmitted through the GSM network as a digital stream. There is also an emergency service, where the nearest emergency-service provider is notified by dialing three digits. a) Bearer services: Typically data transmission instead of voice. Fax and SMS are examples. 47
  • b) Teleservices: Voice oriented traffic. c) Supplementary services: Call forwarding, caller ID, call waiting and the like. A variety of data services is offered. GSM users can send and receive data, at rates up to 9600 bps, to users on POTS (Plain Old Telephone Service), ISDN, Packet Switched Public Data Networks, and Circuit Switched Public Data Networks using a variety of access methods and protocols, such as X.25 or X.32. Since GSM is a digital network, a modem is not required between the user and GSM network, although an audio modem is required inside the GSM network to interwork with POTS. Other data services include Group 3 facsimile, as described in ITU-T recommendation T.30, which is supported by use of an appropriate fax adaptor. A unique feature of GSM, not found in older analog systems, is the Short Message Service (SMS). SMS is a bidirectional service for short alphanumeric (up to 160 bytes) messages. Messages are transported in a store-and-forward fashion. For point-to-point SMS, a message can be sent to another subscriber to the service, and an acknowledgement of receipt is provided to the sender. SMS can also be used in a cell-broadcast mode, for sending messages such as traffic updates or news updates. Messages can also be stored in the SIM card for later retrieval. Supplementary services are provided on top of teleservices or bearer services. In the current (Phase I) specifications, they include several forms of call forward (such as call forwarding when the mobile subscriber is unreachable by the network), and call barring of outgoing or incoming calls, for example when roaming in another country. Many additional supplementary services will be provided in the Phase 2 specifications, such as caller identification, call waiting, multi-party conversations. 5.3 Mobile Station The mobile station (MS) consists of the mobile equipment (the terminal) and a smart card called the Subscriber Identity Module (SIM). The SIM provides personal mobility, so that the user can have access to subscribed services irrespective of a specific terminal. By inserting the SIM card into another GSM terminal, the user is able to receive calls at that terminal, make calls from that terminal, and receive other subscribed services. The mobile equipment is uniquely identified by the International Mobile Equipment Identity (IMEI). The SIM card contains the International Mobile Subscriber Identity (IMSI) used to identify the subscriber to the system, a secret key for authentication, and other information. The IMEI and the IMSI are independent, thereby allowing personal 48
  • mobility. The SIM card may be protected against unauthorized use by a password or personal identity number. GSM phones use SIM cards, or Subscriber information or identity modules. They're the biggest difference a user sees between a GSM phone or handset and a conventional cellular telephone. With the SIM card and its memory the GSM handset is a smart phone, doing many things a conventional cellular telephone cannot. Like keeping a built in phone book or allowing different ring tones to be downloaded and then stored. Conventional cellular telephones either lack the features GSM phones have built in, or they must rely on resources from the cellular system itself to provide them. Let me make another, important point. With a SIM card your account can be shared from mobile to mobile, at least in theory. Want to try out your neighbor's brand new mobile? You should be able to put your SIM card into that GSM handset and have it work. The GSM network cares only that a valid account exists, not that you are using a different device. You get billed, not the neighbor who loaned you the phone. This flexibility is completely different than AMPS technology, which enables one device per account. No switching around. Conventional cellular telephones have their electronic serial number burned into a chipset which is permanently attached to the phone. No way to change out that chipset or trade with another phone. SIM card technology, by comparison, is meant to make sharing phones and other GSM devices quick and easy. Figure5.1 Mobile station SIM port 49
  • On the left above: Front of a Pacific Bell GSM phone. In the middle above: Same phone, showing the back. The SIM card is the white plastic square. It fits into the grey colored holder next to it. On the right above: A new and different idea, a holder for two SIM cards, allowing one phone to access either of two wireless carriers. Provided you have an account with both. The SIM card is to the left of the body. 5.4 Base Station Subsystem: The Base Station Subsystem is composed of two parts, the Base Transceiver Station (BTS) and the Base Station Controller (BSC). These communicate across the standardized Abis interface, allowing (as in the rest of the system) operation between components made by different suppliers. The Base Transceiver Station houses the radio transceivers that define a cell and handles the radio-link protocols with the Mobile Station. In a large urban area, there will potentially be a large number of BTSs deployed, thus the requirements for a BTS are ruggedness, reliability, portability, and minimum cost. Figure 5.2 Base Station Subsystem. The BTS or Base Transceiver Station is also called an RBS or Remote Base station. Whatever the name, this is the radio gear that passes all calls coming in and going out of a cell site. The base station is under direction of a base station controller so traffic gets sent there first. The base station controller, described below, gathers the calls from many base stations and passes them on to a mobile telephone switch. From that switch come and go the calls from the regular telephone network. Some base stations are quite small; the one 50
  • pictured here is a large outdoor unit. The large number of base stations and their attendant controllers are a big difference between GSM and IS-136. 5.4.1 Base Station Controller The Base Station Controller manages the radio resources for one or more BTSs. It handles radio-channel setup, frequency hopping, and handovers, as described below. The BSC is the connection between the mobile station and the Mobile service Switching Center (MSC). Another difference between conventional cellular and GSM is the base station controller. It's an intermediate step between the base station transceiver and the mobile switch. GSM designers thought this a better approach for high density cellular networks. As one anonymous writer penned, "If every base station talked directly to the MSC, traffic would become too congested. To ensure quality communications via traffic management, the wireless infrastructure network uses Base Station Controllers as a way to segment the network and control congestion. The result is that MSCs route their circuits to BSCs which in turn are responsible for connectivity and routing of calls for 50 to 100 wireless base stations." Figure 5.3 Siemens BSC Many GSM descriptions picture equipment called a TRAU, which stands for Transcoding Rate and Adaptation Unit. Of course also known as a Trans-Coding Unit or TCU, the TRAU is a compressor and converter. It first compresses traffic coming from the mobiles through the base station controllers. That's quite an achievement because voice and data have already been compressed by the voice coders in the handset. Anyway, it crunches that data down even further. It then puts the traffic into a format the 51
  • Mobile Switch can understand. This is the Trans-Coding part of its name, where code in one format is converted to another. The TRAU is not required but apparently it saves quite a bit of money to install one. Here's how Nortel Networks sells their unit: “Reduce transmission resources and realize up to 75% transmission cost savings with the TCU." "The Trans-Coding Unit (TCU), inserted between the BSC and MSC, enables speech compression and data rate adaptation within the radio cellular network. The TCU is designed to reduce transmission costs by minimizing transmission resources between the BSC and MSC. This is achieved by reducing the number of PCM links going to the BSC, since four traffic channels (data or speech) can be handled by one PCM time slot. Additionally, the modular architecture of the TCU supports all three GSM vocoders (Full Rate, Enhanced Full Rate, and Half Rate) in the same cabinet, providing you with a complete range of deployment options." Figure 5.4 Siemens’ TRAU Voice coders or vocoders are built into the handsets a cellular carrier distributes. They're the circuitry that turns speech into digital. The carrier specifies which rate they want traffic compressed, either a great deal or just a little. The cellular system is designed this way, with handset vocoders working in league with the equipment of the base station subsystem. 5.5 Architecture of the GSM Network A GSM network is composed of several functional entities, whose functions and interfaces are specified. Figure 1 shows the layout of a generic GSM network. The GSM 52
  • network can be divided into three broad parts. The Mobile Station is carried by the subscriber. The Base Station Subsystem controls the radio link with the Mobile Station. The Network Subsystem, the main part of which is the Mobile services Switching Center (MSC), performs the switching of calls between the mobile users, and between mobile and fixed network users. The MSC also handles the mobility management operations. Not shown is the Operations and Maintenance Center, which oversees the proper operation and setup of the network. The Mobile Station and the Base Station Subsystem communicate across the Um interface, also known as the air interface or radio link. The Base Station Subsystem communicates with the Mobile services Switching Center across the A interface. As John states, he presents a generic GSM architecture. Lucent, Ericsson, Nokia, and others feature their own vision in their own diagrams. Lucent GSM architecture/ Ericsson GSM architecture / Nokia GSM architecture / Siemens’s GSM architecture Figure 5.5 General architecture of a GSM network 5.6 Radio Link Aspects The International Telecommunication Union (ITU), which manages the international allocation of radio spectrum (among many other functions), allocated the bands 890-915 MHz for the uplink (mobile station to base station) and 935-960 MHz for the downlink (base station to mobile station) for mobile networks in Europe. Since this range was already being used in the early 1980s by the analog systems of the day, the CEPT had the foresight to reserve the top 10 MHz of each band for the GSM network that was still being developed. Eventually, GSM will be allocated the entire 2x25 MHz bandwidth. 53
  • 5.7 Multiple Access and Channel Structure: Since radio spectrum is a limited resource shared by all users, a method must be devised to divide up the bandwidth among as many users as possible. The method chosen by GSM is a combination of Time- and Frequency-Division Multiple Access (TDMA/FDMA). The FDMA part involves the division by frequency of the (maximum) 25 MHz bandwidth into 124 carrier frequencies spaced 200 kHz apart. One or more carrier frequencies are assigned to each base station. Each of these carrier frequencies is then divided in time, using a TDMA scheme. The fundamental unit of time in this TDMA scheme is called a burst period and it lasts 15/26 ms (or approx. 0.577 ms). Eight burst periods are grouped into a TDMA frame (120/26 ms, or approx. 4.615 ms), which forms the basic unit for the definition of logical channels. One physical channel is one burst period per TDMA frame. i) Traffic channels A traffic channel (TCH) is used to carry speech and data traffic. Traffic channels are defined using a 26-frame multi-frame, or group of 26 TDMA frames. The length of a 26- frame multi-frame is 120 ms, which is how the length of a burst period is defined (120 ms divided by 26 frames divided by 8 burst periods per frame). Out of the 26 frames, 24 are used for traffic, 1 is used for the Slow Associated Control Channel (SACCH) and 1 is currently unused (see Figure 2). TCHs for the uplink and downlink are separated in time by 3 burst periods, so that the mobile station does not have to transmit and receive simultaneously, thus simplifying the electronics. ii) Control channels Common channels can be accessed both by idle mode and dedicated mode mobiles. The common channels are used by idle mode mobiles to exchange the signaling information required to change to dedicated mode. Mobiles already in dedicated mode monitor the surrounding base stations for handover and other information. Dedicated mode means a mobile is in use. 5.8 Frequency Hopping The mobile station already has to be frequency agile, meaning it can move between a transmit/ receive, and monitor time slot within one TDMA frame, which normally are on different frequencies. GSM makes use of this inherent frequency agility to implement slow frequency hopping, where the mobile and BTS transmit each TDMA frame on a 54
  • different carrier frequency. The frequency hopping algorithm is broadcast on the Broadcast Control Channel. Since multipath fading is dependent on carrier frequency, slow frequency hopping helps alleviate the problem. In addition, co-channel interference is in effect randomized. Here's a huge difference between conventional cellular (IS-136) and GSM: frequency hopping. When enabled, slots within frames can leapfrog from one frequency to another. In IS-136, by comparison, once assigned a channel your call stays on that pair of radio frequencies until the call is over or you have moved to another cell. 5.9 Discontinuous Reception Another method used to conserve power at the mobile station is discontinuous reception. The paging channel, used by the base station to signal an incoming call, is structured into sub-channels. Each mobile station needs to listen only to its own sub- channel. In the time between successive paging sub-channels, the mobile can go into sleep mode, when almost no power is used. 5.10 Power Control There are five classes of mobile stations defined, according to their peak transmitter power, rated at 20, 8, 5, 2, and 0.8 watts. To minimize co-channel interference and to conserve power, both the mobiles and the Base Transceiver Stations operate at the lowest power level that will maintain an acceptable signal quality. Power levels can be stepped up or down in steps of 2 dB from the peak power for the class down to a minimum of 13 dBm (20 mill watts). We need only enough power to make a connection. Any more is superfluous. If you can't make a connection using one watt then two watts won't help at these near microwave frequencies. Using less power means less interference or congestion among all the mobiles in a cell. The mobile station measures the signal strength or signal quality (based on the Bit Error Ratio), and passes the information to the Base Station Controller, which ultimately decides if and when the power level should be changed. Power control should be handled carefully, since there is the possibility of instability. This arises from having mobiles in co-channel cells alternating increase their power in response to increased co-channel interference caused by the other mobile increasing its power. This in unlikely to occur in practice but it is (or was as of 1991) under study. 55
  • Two points: The first is that the base station can reach out to the mobile and turn down the transmitting power the handset is using, Very cool. The second point is that a digital signal will drop a call much more quickly than an analog signal. With an analog radio you can hear through static and fading. But with a digital radio the connection will be dropped, just like your landline modem, when too many 0s and 1s go missing. You need more base stations, consequently, to provide the same coverage as analog. 5.11 Network Aspects Ensuring the transmission of voice or data of a given quality over the radio link is only part of the function of a cellular mobile network. A GSM mobile can seamlessly roam nationally and internationally, which requires that registration, authentication, call routing and location updating functions exist and are standardized in GSM networks. In addition, the fact that the geographical area covered by the network is divided into cells necessitates the implementation of a handover mechanism. These functions are performed by the Network Subsystem, mainly using the Mobile Application Part (MAP) built on top of the Signaling. The signaling protocol in GSM is structured into three general layers [1], [19], depending on the interface, as shown in Figure 3. Layer 1 is the physical layer, which uses the channel structures discussed above over the air interface. Layer 2 is the data link layer. Across the Um interface, the data link layer is a modified version of the LAPD protocol used in ISDN (external link), called LAPDm. Across the A interface, the Message Transfer Part layer 2 of Signaling System Number 7 is used. Layer 3 of the GSM signaling protocol is itself divided into 3 sub layers.  Radio Resources Management  Controls the setup, maintenance, and termination of radio and fixed channels,  Including handovers.  Mobility Management  Manages the location updating and registration procedures, as well as security and authentication.  Connection Management  Handles general call control, similar to CCITT Recommendation Q.931, and manages Supplementary Services and the Short Message Service. 56
  • Figure 5.6 Signaling protocol structure in GSM 5.12 Radio Resources Management The radio resources management (RR) layer oversees the establishment of a link, both radio and fixed, between the mobile station and the MSC. The main functional components involved are the mobile station, and the Base Station Subsystem, as well as the MSC. The RR layer is concerned with the management of an RR-session [16], which is the time that a mobile is in dedicated mode, as well as the configuration of radio channels including the allocation of dedicated channels. An RR-session is always initiated by a mobile station through the access procedure, either for an outgoing call, or in response to a paging message. The details of the access and paging procedures, such as when a dedicated channel is actually assigned to the mobile, and the paging sub-channel structure, are handled in the RR layer. In addition, it handles the management of radio features such as power control, discontinuous transmission and reception, and timing advance. 5.13 Handover In a cellular network, the radio and fixed links required are not permanently allocated for the duration of a call. Handover, or handoff as it is called in North America, is the switching of an on-going call to a different channel or cell. The execution and measurements required for handover form one of basic functions of the RR layer. There are four different types of handover in the GSM system, which involve transferring a call between:  Channels (time slots) in the same cell 57
  •  Cells (Base Transceiver Stations) under the control of the same Base Station Controller (BSC),  Cells under the control of different BSCs, but belonging to the same Mobile services Switching Center (MSC), and  Cells under the control of different MSCs. The first two types of handover, called internal handovers, involve only one Base Station Controller (BSC). To save signaling bandwidth, they are managed by the BSC without involving the Mobile services Switching Center (MSC), except to notify it at the completion of the handover. The last two types of handover, called external handovers, are handled by the MSCs involved. An important aspect of GSM is that the original MSC, the anchor MSC, remains responsible for most call-related functions, with the exception of subsequent inter-BSC handovers under the control of the new MSC, called the relay MSC. Handovers can be initiated by either the mobile or the MSC (as a means of traffic load balancing). During its idle time slots, the mobile scans the Broadcast Control Channel of up to 16 neighboring cells, and forms a list of the six best candidates for possible handover, based on the received signal strength. This information is passed to the BSC and MSC, at least once per second, and is used by the handover algorithm. The algorithm, for when a hand over decision should be taken is not specified in the GSM recommendations. There are two basic algorithms used, both closely tied in with power control. This is because the BSC usually does not know whether the poor signal quality is due to multipath fading or to the mobile having moved to another cell. This is especially true in small urban cells. The 'minimum acceptable performance' algorithm gives precedence to power control over handover, so that when the signal degrades beyond a certain point, the power level of the mobile is increased. If further power increases do not improve the signal, then a handover is considered. This is the simpler and more common method, but it creates 'smeared' cell boundaries when a mobile transmitting at peak power goes some distance beyond its original cell boundaries into another cell. The 'power budget' method uses handover to try to maintain or improve a certain level of signal quality at the same or lower power level. It thus gives precedence to handover over power control. It avoids the 'smeared' cell boundary problem and reduces co-channel interference, but it is quite complicated. 58
  • 5.14 Mobility Management The Mobility Management layer (MM) is built on top of the RR layer (radio resources), and handles the functions that arise from the mobility of the subscriber, as well as the authentication and security aspects. Location management is concerned with the procedures that enable the system to know the current location of a powered-on mobile station so that incoming call routing can be completed. 5.15 Location Updating A powered-on mobile is informed of an incoming call by a paging message sent over the PAGCH channel of a cell. One extreme would be to page every cell in the network for each call, which is obviously a waste of radio bandwidth. The other extreme would be for the mobile to notify the system, via location updating messages, of its current location at the individual cell level. This would require paging messages to be sent to exactly one cell, but would be very wasteful due to the large number of location updating messages. A compromise solution used in GSM is to group cells into location areas. Updating messages are required when moving between location areas, and mobile stations are paged in the cells of their current location area. In conventional cellular location messages are sent to the exact cell a mobile is in. To review, the VLR Data Base, or Visited or Visitor Location Register, contains all the data needed to communicate with the mobile switch. Levine says this data includes:  Equipment identity and authentication-related data  Last known Location Area (LA)  Power Class and other physical attributes of the mobile or handset  List of special services available to this subscriber  More data entered while engaged in a Call  Current cell  Encryption keys The location updating procedures, and subsequent call routing, use the MSC and two location registers: the Home Location Register (HLR) and the Visitor Location Register (VLR). When a mobile station is switched on in a new location area, or it moves to a new location area or different operator's PLMN, it must register with the network to indicate its current location. In the normal case, a location update message is sent to the new MSC/VLR, which records the location area information, and then sends the location 59
  • information to the subscriber's HLR. The information sent to the HLR is normally the SS7 address of the new VLR, although it may be a routing number. The reason a routing number is not normally assigned, even though it would reduce signaling, is that there is only a limited number of routing numbers available in the new MSC/VLR and they are allocated on demand for incoming calls. If the subscriber is entitled to service, the HLR sends a subset of the subscriber information, needed for call control, to the new MSC/VLR, and sends a message to the old MSC/VLR to cancel the old registration. A procedure related to location updating is the IMSI (International Mobile Subscriber Identity) attach and detach. A detach lets the network know that the mobile station is unreachable, and avoids having to needlessly allocate channels and send paging messages. an attach is similar to a location update, and informs the system that the mobile is reachable again. The activation of IMSI attach/detach is up to the operator on an individual cell basis. 5.16 Authentication and Security Since the radio medium can be accessed by anyone, authentication of users to prove that they are who they claim to be is a very important element of a mobile network. Authentication involves two functional entities, the SIM card in the mobile, and the Authentication Center (AUC). Each subscriber is given a secret key, one copy of which is stored in the SIM card and the other in the AUC. During authentication, the AUC generates a random number that it sends to the mobile. Both the mobile and the AUC then use the random number, in conjunction with the subscriber's secret key and a ciphering algorithm called A3, to generate a signed response (SRES) that is sent back to the AUC. If the number sent by the mobile is the same as the one calculated by the AUC, the subscriber is authenticated. The same initial random number and subscriber key are also used to compute the ciphering key using an algorithm called A8. This ciphering key, together with the TDMA frame number, use the A5 algorithm to create a 114 bit sequence that is XORed with the 114 bits of a burst (the two 57 bit blocks). Enciphering is an option for the fairly paranoid, since the signal is already coded, interleaved, and transmitted in a TDMA manner, thus providing protection from all but the most persistent and dedicated eavesdroppers. Another level of security is performed on the mobile equipment itself, as opposed to the mobile subscriber. As mentioned earlier, each GSM terminal is identified by a unique 60
  • International Mobile Equipment Identity (IMEI) number. A list of IMEIs in the network is stored in the Equipment Identity Register (EIR). The status returned in response to an IMEI query to the EIR is one of the following: White-listed: The terminal is allowed to connect to the network. Grey-listed: The terminal is under observation from the network for possible problems. Black-listed: The terminal has either been reported stolen, or is not type approved (the correct type of terminal for a GSM network). The terminal is not allowed to connect to the network. 5.17 Communication Management The Communication Management layer (CM) is responsible for Call Control (CC), supplementary service management, and short message service management. Each of these may be considered as a separate sub layer within the CM layer. Call control attempts to follow the ISDN procedures specified in Q.931, although routing to a roaming mobile subscriber is obviously unique to GSM. Other functions of the CC sub layer include call establishment, selection of the type of service (including alternating between services during a call), and call release. Figure 5.7 Call routing for a mobile terminating call 5.18 Call Routing Unlike routing in the fixed network, where a terminal is semi-permanently wired to a central office, a GSM user can roam nationally and even internationally. (With, if needed, a properly enabled handset.) The directory number dialed to reach a mobile subscriber is called the Mobile Subscriber ISDN (MSISDN), which is defined by the E.164 numbering plan. This number includes a country code and a National Destination 61
  • Code which identifies the subscriber's operator. The first few digits of the remaining subscriber number may identify the subscriber's HLR within the home PLMN. An incoming mobile terminating call is directed to the Gateway MSC (GMSC) function. The GMSC is basically a switch which is able to interrogate the subscriber's HLR to obtain routing information, and thus contains a table linking MSISDNs to their corresponding HLR. A simplification is to have a GSMC handle one specific PLMN. It should be noted that the GMSC function is distinct from the MSC function, but is usually implemented in an MSC. PLMN: Public land mobile network. In this context a cellular telephone network. PLMN is chiefly a European usage. The routing information that is returned to the GMSC is the Mobile Station Roaming Number (MSRN), which is also defined by the E.164 numbering plan. MSRNs are related to the geographical numbering plan, and not assigned to subscribers, nor are they visible to subscribers. The most general routing procedure begins with the GMSC querying the called subscriber's HLR for an MSRN. The HLR typically stores only the SS7 address of the subscriber's current VLR, and does not have the MSRN (see the location updating section). The HLR must therefore query the subscriber's current VLR, which will temporarily allocate an MSRN from its pool for the call. This MSRN is returned to the HLR and back to the GMSC, which can then route the call to the new MSC. At the new MSC, the IMSI corresponding to the MSRN is looked up, and the mobile is paged in its current location area. 62
  • Chapter 6 GPS Receiver 6.1 GPS History The Global Positioning System (GPS) is a Global Navigation Satellite System (GNSS) developed by the United States Department of Defense. It is the only fully functional GNSS in the world. It uses a constellation of between 24 and 32 Medium Earth Orbit satellites that transmit precise microwave signals, which enable GPS receivers to determine their current location, the time, and their velocity. Its official name is NAVSTAR GPS. Although NAVSTAR is not an acronym, a few acronyms have been created for it. The GPS satellite constellation is managed by the United States Air Force 50th Space Wing. GPS is often used by civilians as a navigation system. After Korean Air Lines Flight 007 was shot down in 1983 after straying into the USSR's prohibited airspace, President Ronald Reagan issued a directive making GPS freely available for civilian use as a common good. As suggested by physicist D. Fanelli. A few years before, Since then, GPS has become a widely used aid to navigation worldwide, and a useful tool for map-making, land surveying, commerce, scientific uses, and hobbies such as geo-caching. Also, the precise time reference is used in many applications including the scientific study of earthquakes. GPS is also a required key synchronization resource of cellular networks, such as the Qualcomm CDMA air interface used by many wireless carriers in a multitude of countries. The first satellite navigation system, Transit, used by the United States Navy, was first successfully tested in 1960. Using a constellation of five satellites, it could provide a navigational fix approximately once per hour. In 1967, the U.S. Navy developed the Imation satellite which proved the ability to place accurate clocks in space, a technology that GPS relies upon. In the 1970s, the ground-based Omega Navigation System, based on signal phase comparison, became the first worldwide radio navigation system. The design of GPS is based partly on similar ground-based radio navigation systems, such as LORAN and the Decca Navigator developed in the early 1940s, and used during World War II. Additional inspiration for the GPS came when the Soviet Union launched the first Sputnik in 1957. A team of U.S. scientists led by Dr. Richard B. Kershner were monitoring Sputnik's radio transmissions. They discovered that, because of the Doppler Effect, the frequency of the signal being transmitted by Sputnik was higher as the satellite approached, and lower as it continued away from them. They 63
  • realized that since they knew their exact location on the globe, they could pinpoint where the satellite was along its orbit by measuring the Doppler distortion. 6.1.1 Working and Operation When people talk about "a GPS," they usually mean a GPS receiver. The Global Positioning System (GPS) is actually a constellation of 27 Earth-orbiting satellites (24 in operation and three extras in case one fails). The U.S. military developed and implemented this satellite network as a military navigation system, but soon opened it up to everybody else. Each of these 3,000- to 4,000-pound solar-powered satellites circles the globe at about 12,000 miles (19,300 km), making two complete rotations every day. The orbits are arranged so that at anytime, anywhere on Earth, there are at least four satellites "visible" in the sky. A GPS receiver's job is to locate four or more of these satellites, figure out the distance to each, and use this information to deduce its own location. This operation is based on a simple mathematical principle called trilateration. GPS receiver calculates its position on earth based on the information it receives from four located satellites. This system works pretty well, but inaccuracies do pop up. For one thing, this method assumes the radio signals will make their way through the atmosphere at a consistent speed (the speed of light). In fact, the Earth's atmosphere slows the electromagnetic energy down somewhat, particularly as it goes through the ionosphere and troposphere. The delay varies depending on where you are on Earth, which means it's difficult to accurately factor this into the distance calculations. Problems can also occur when radio signals bounce off large objects, such as skyscrapers, giving a receiver the impression that a satellite is farther away than it actually is. On top of all that, satellites sometimes just send out bad almanac data, misreporting their own position. Differential GPS (DGPS) helps correct these errors. The basic idea is to gauge GPS inaccuracy at a stationary receiver station with a known location. Since the DGPS hardware at the station already knows its own position, it can easily calculate its receiver's inaccuracy. The station then broadcasts a radio signal to all DGPS-equipped receivers in the area, providing signal correction information for that area. In general, access to this correction information makes DGPS receivers much more accurate than ordinary receivers. 64
  • Figure 6.1 G.P.S receiver communicating with the satellite and sending information through the wireless mobile phone 6.2 GPS Data Decoding G.P.S receiver continuously sends data and the microcontroller receives the data whenever it requires. The data sent by the G.P.S is a string of characters which should be decoded to the standard format. This is done by the program which we implement in the controller. 65
  • Chapter 7 KEIL Software 7.1 Introduction Many companies provide the 8051 assembler, some of them provide shareware version of their product on the Web, Kiel is one of them. We can download them from their Websites. However, the size of code for these shareware versions is limited and we have to consider which assembler is suitable for our application. 7.2 KEIL uVision2 Kiel uVision2is an IDE (Integrated Development Environment) that helps you write, compile, and debug embedded programs. It encapsulates the following components:  A project manager.  A make facility.  Tool configuration.  Editor.  A powerful debugger.  To help you get started, several example programs Creating Your Own Application in uVision2 To create a new project in uVision2, you must:  Select Project - New Project.  Select a directory and enter the name of the project file.  Select Project - Select Device and select an 8051, 251, or C16x/ST10 device from the Device Database  Create source files to add to the project.  Select Project - Targets, Groups, and Files. Add/Files, select Source Group1, and add the source files to the project.  Select Project - Options and set the tool options. Note when you select the target device from the Device Database™ all-special options are set automatically. You typically only need to configure the memory map of your target hardware. Default memory model settings are optimal for most 66
  • 7.3 KEIL Software Programing Procedure How to write embedded C program in Keil Software? Following steps are to be followed in order to develop, code and test the equipment with software. 7.3.1 Procedure Steps Step-1: Install KEIL MicroVision-2 in your PC, Then after Click on that “KEIL UVision- 2” icon. After opening the window go to toolbar and select Project Tab then close previous project. Step-2: Next select New Project from Project Tab. Step-3: Then it will open “Create New Project” window. Select the path where you want to save project and edit project name. Step-4: Next it opens “Select Device for Target” window, It shows list of companies and here you can select the device manufacturer company. Step-5: For an example, for your project purpose you can select the chip as 89c51/52 from Atmel Group. Next Click OK Button, it appears empty window here you can observe left side a small window i.e, “Project Window”. Next create a new file. Step-6: From the Main tool bar Menu select “File” Tab and go to New, then it will open a window, there you can edit the program. Step-7: Here you can edit the program as which language will you prefer either Assembly or C. Step-8: After editing the program save the file with extension as “.c” or “.asm”, if you write a program in Assembly Language save as “.asm” or if you write a program in C Language save as “.c” in the selected path. Take an example and save the file as “test.c”. Step-9: 67
  • Then after saving the file, compile the program. For compilation go to project window select “source group” and right click on that and go to “Add files to Group”. Step-10: Here it will ask which file has to Add. For an example here you can add “test.c” as you saved before. Step-11: After adding the file, again go to Project Window and right click on your “c file” then select “Build target” for compilation. If there is any “Errors or Warnings” in your program you can check in “Output Window” that is shown bottom of the Keil window. Step-12: Here in this step you can observe the output window for “errors and warnings”. Step-13: If you make any mistake in your program you can check in this slide for which error and where the error is by clicking on that error. Step-14: After compilation then next go to Debug Session. In Tool Bar menu go to “Debug” tab and select “Start/Stop Debug Session”. Step-15: Here a simple program for “LED’s Blinking”. LEDS are connected to PORT-1. you can observe the output in that port. Step-16: To see the Ports and other Peripheral Features go to main toolbar menu and select peripherals. Step-17: In this slide see the selected port i.e, PORT-1. Step-18: Start to trace the program in sequence manner i.e., step by step execution and observe the output in port window. Step-19: After completion of Debug Session Create an Hex file for Burning the Processor. Here to create an Hex file go to project window and right click on Target next select “Option for Target”. Step-20: 68
  • It appears one window; here in “target tab” modify the crystal frequency as you connected to your microcontroller. Step-21: Next go to “Output’ tab. In that Output tab click on “Create HEX File” and then click OK. Step-22: Finally Once again compile your program. The Created Hex File will appear in your path folder. 7.4 Applications of KEIL Software Select Project - Rebuild all target files or Build target. i) Debugging an Application in uVision2: To debug an application created using uVision2, You must:  Select Debug - Start/Stop Debug Session.  Use the Step toolbar buttons to single-step through your program. You may enter G, main in the Output Window to execute to the main C function.  Open the Serial Window using the Serial #1 button on the toolbar.  Debug your program using standard options like Step, Go, Break, and so on. ii) Peripheral Simulation:  The uvision2 debugger provides complete simulation for the CPU and on chip peripherals of most embedded devices. To discover which peripherals of a device are supported, in u vision2. Select the Simulated Peripherals item from the Help menu. You may also use the web-based device database. We are constantly adding new devices and simulation support for on-chip peripherals so be sure to check Device Database often. 69
  • Chapter 8 Applications When some technology comes to be used at practical level it happens to cherish both plus as well as minus points of its own. But sometimes technology may be positive in itself but its application can be misused. Before we go ahead to give space to any technology in our house or work place we should have pre-estimates of its fall outs. The positive aspects of the tracking system can be summarized as follows: i. Core benefit of tracking vehicle is that one can monitor one’s vehicle from a distance whether on individual or commercial level. It helps busy parents to keep a watch on the children even from their office and control their roaming here and there. Thus can put a check on their rash driving. This gives immense relief to business owners as it gives them information about the misuse of company vehicle or delay in delivering services or driver’s violation of speed code, if any. All this keeps a check on wastage of fuel, time and ensures the better services. With the use of this technology one need not enquire the location of the vehicle by phone again and again. One can get all the required details just by a click on the internet. Map on the screen displays the position of vehicle at a particular time. ii. In view of long journeys and night journeys by car the technology can provide a safety network to the person in condition of emergency. It can cut time of journey short by providing the information regarding location, speed, distance from the destination leading to best route planning. iii. Best feature of the technology is that it is easy to use. just an automated unit is needed to be installed in the vehicle and connected to the centre which may be provided by some company. This instrument is monitored by the GPS tracking company which keeps all the records or its customer’s locations. All details of location etc are communicated to the user by cell phone or internet connection. Increasing productivity of your mobile workers. iv. It helps monitoring employee driving habits and activities. v. Helps you locate your employees are on-the-road. vi. Helps you verify the employee time sheet. vii. Helps you in monitoring all your vehicles. 70
  • viii. Helps you in timely delivery of the consignments ix. Helps you monitor the vehicle speeds x. Helps you in tracking the movement of vehicles on the road The negative aspects of the tracking system can be summarized as follows: No technology is free from dark areas. This technology helps monitoring vehicles and children as well and ensures increased productivity at commercial level and safety at personal level. But at the same time it encroaches the privacy of the individual. The liberty of the person gets restricted. This may lead to business owner to measure the performance of the employee by these stats only and there leaves no room for human analysis. Thus technology carries its whites and blues. It depends on the user how to make it. 8.1 Applications Commercial fleet operators are by far the largest users of vehicle tracking systems. These systems are used for operational functions such as routing, security, dispatch and collecting on-board information. These systems are also used in consumer vehicles as devices for preventing theft and retrieving stolen/lost vehicles. The signal sent out by the installed device help the police to track the vehicle. These tracking systems can be used as an alternative for traditional car alarms or in combination with it. Installing tracking systems can thus bring down the insurance costs for your vehicle by reducing the risk factor. Vehicle Tracking systems often have several alternatives, like sending automatic alerts to a phone or email if the vehicle is moved without due authorization. They can also work as one layer of several combined security measures. Apart from security concerns, the tracking systems can also help users such as taxi services to improve their customer service. The systems enable the operators to identify the empty taxis and direct the nearest one to pick up the customer. Vehicle tracking systems can also be applied for monitoring driving behavior for both commercial and individual situations. Parents for instance can use tracking devices to keep an eye on their teenage son’s driving. The applications for this project are in military, navigation, automobiles, aircrafts, fleet management, remote monitoring, remote control, security systems, teleservices, etc. 71
  • Some main advantages of implementing this system are as follows:  Fleet monitoring  Vehicle scheduling  Route monitoring  Driver monitoring  Accident analysis  Geo-fencing geo-coding 8.2 Limitations  This program is highly sensitive to the camera position and the environment, so a considerable amount of tuning has to be done each time a new video is taken or camera position is changed and even more so if the video is of an entirely new environment.  The other limitation is the traffic problem, the program will not able to detect which vehicle to track if it finds some vehicle in the -6*step_y and +6*step_y of the current guess. If the nearby vehicle is same as the one in the model. As in our data images if we bring maruti-800 near the car than the probability of error increases manifolds.  If there is noise in the edge detected image, we can't really track the vehicle. What is meant by noise is that if some humans are coming near to the car then the edge detected image will have the edges of that human or animal or tree, then the program will try to match those edges with the car model. The program might treat this match as a success but really it will be off the track.  We could not model the curves in the maruti-800, like in some images the driver and the steering can be seen, but we could not find a solution for that. Also the body of the Maruti can be best modeled as combination of curves and the lines.  Also if distance between the vehicle positions in the two consecutive frames is too much then this tracking program can't detect the vehicle in the second frame and will try to track it in the subsequent frame.  The main limitation of the software is the real time implementation, this can’t be implemented with this much time efficiency in any of the real time applications. This limitation is mainly due to the processing time. 72
  • Chapter 9 Result Analysis We a team of 4 members have successfully completed our Project on Tracking Down Vehicle and Locking it remotely using GPS and GSM technologies. We first tried to understand the working of our project through the schematic and then we proceeded to build the circuit as per the schematic. Initially we faced few problems with the GPS modem, as it won’t work efficiently inside buildings. And also the GSM modem suffered problems with the coverage area of the Mobile Service Provider. So, we used Airtel as it has maximum coverage area. In order to solve this problem we can use dedicated servers and purchasing satellite space so that we can track down the vehicle anytime and anywhere. The overall developed circuit looks as in the following figure: Fig 9.1 Picture of VTS kit The above circuit works mainly by receiving messages from a mobile phone. There are three messages/commands by which we can track and control the vehicle. They are, i) TRACK ii) LOCKD iii) NLOCK 73
  • i) TRACK: Initiates the GPS modem and receives the Latitude and Longitude position and this information will be sent to the mobile from which it received the message. ii) LOCKD: When this message is sent, then the Microcontroller initiates the motor which is located in between the passage of fuel to stop and which in turn stops the vehicle. iii) NLOCK: This command makes the motor to start again so that the vehicle starts running. This project can further be crafted by restricting the usage of limited mobile numbers to get access to the device. This can be made by altering the program. The message which is sent to the mobile will be as shown in the following figure. Fig 9.2 Message received from the VTS kit With the knowledge in Electronics and Communications we have successfully completed our project with perfect results. 74
  • Chapter 10 Conclusion and Future Scope The project titled “tracing down the vehicle using GSM and satellite communication” is a model for vehicle tracking unit with the help of gps receivers and GSM modem. Vehicle Tracking System resulted in improving overall productivity with better fleet management that in turn offers better return on your investments. Better scheduling or route planning can enable you handle larger jobs loads within a particular time. Vehicle tracking both in case of personal as well as business purpose improves safety and security, communication medium, performance monitoring and increases productivity. So in the coming year, it is going to play a major role in our day-to-day living. We have completed the project as per the requirements of our project. Finally the aim of the project i.e. to trace the vehicle is successfully achieved. Future Scope  We can use the EEPROM to store the previous Navigating positions up to 256 locations and we can navigate up to N number of locations by increasing its memory.  We can reduce the size of the kit by using GPS+GSM on the same module.  We can increase the accuracy up to 3m by increasing the cost of the GPS receivers.  We can use our kit for detection of bomb by connecting to the bomb detector.  With the help of high sensitivity vibration sensors we can detect the accident.  Whenever vehicle unexpectedly had an accident on the road with help of vibration sensor we can detect the accident and we can send the location to the owner, hospital and police.  We can use our kit to assist the traffic. By keeping the kits in the entire vehicles and by knowing the locations of all the vehicles.  If anybody steals our car we can easily find our car around the globe. By keeping vehicle positioning vehicle on the vehicle. 75
  • References [1]. Chen, H., Chiang, Y. Chang, F., H. Wang, H. (2010). Toward Real-Time Precise Point Positioning: Differential GPS Based on IGS Ultra Rapid Product,SICE Annual Conference, The Grand Hotel, Taipei, Taiwan August 18-21. [2]. Asaad M. J. Al-Hindawi, Ibraheem Talib, “Experimentally Evaluation of GPS/GSM Based System Design”, Journal of Electronic Systems Volume 2 Number 2 June 2012 [3]. Chen Peijiang, Jiang Xuehua, “Design and Implementation of Remote monitoring system based on GSM,” vol.42, pp.167-175. 2008. [4]. V.Ramya, B. Palaniappan, K. Karthick, “Embedded Controller for Vehicle In-Front Obstacle Detection and Cabin Safety Alert System”, International Journal of Computer Science & Information Technology (IJCSIT) Vol 4, No 2, April 2012. [5]. [6]. [7]. [8]. [9]. [10]. 76 Final Cover Pages A Certificate Final Index Papers DECLARATION ACKNOWLEDGEMENT Final Full Document 1.3 Active versus Passive Tracking i) Mobile phone based tracking ii) Wireless Passive Tracking iii) Via satellite in real time Technology 1.5 Typical Architecture Major constituents of the GPS based tracking are 1.6 History of Vehicle Tracking 1.7 Vehicle Tracking System Features 1.8 Vehicle Tracing in India a) 52TFreight forwarding b) 52TCall centers Triangulation Voltage levels Connectors Cables RTS/CTS handshaking 3-wire and 5-wire RS-232 a) Signal rate selection b) Loopback testing Timing Signals 2.2.6 LCD 4.2 The Pin Configuration b) Data memory 4.4.1 Watchdog Timer for both modes of operation 5.1 GSM History 5.4 Base Station Subsystem: 5.5 Architecture of the GSM Network i) Traffic channels ii) Control channels 5.9 Discontinuous Reception 5.10 Power Control 5.11 Network Aspects 5.12 Radio Resources Management 5.13 Handover 5.15 Location Updating 5.16 Authentication and Security 5.17 Communication Management 5.18 Call Routing 6.1 GPS History 6.1.1 Working and Operation Applications  We can use the EEPROM to store the previous Navigating positions up to 256 locations and we can navigate up to N number of locations by increasing its memory.