Project Report Final

TRACKING AND POSITIONING SYSTEM Main Project Design Report By: ARJUN S JIBIN MATHEW MITHUN RAJ M N NAVIN MENON S RAJEESH RADHAKRISHNAN

Under the guidance of Ms SUCHITRA K

Department of Electronics and Communication Engineering, Amrita Institute of Technology & Science Amritapuri, Kollam-690525 2006-2007

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TRACKING AND POSITIONING SYSTEM

By: ARJUN S JIBIN MATHEW MITHUN RAJ M N NAVIN MENON S RAJEESH RADHAKRISHNAN Under the guidance of: Ms SUCHITRA K Department of Electronics and Communication Engineering, Amrita Institute of Technology & Science Amritapuri Kollam-690525 2006-2007

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ACKNOWLEDGEMENT

Our prostrations at the lotus feet of our beloved amma, Satguru Mata Amritanandamayi Devi; the guiding light and inspiration for all. Firstly all thanks to our Principal Dr.K.Sankaran for giving us all the facilities for the the project thereby helping us accomplish a goal we had been dreaming of for the past couple of years. Next we express our heartfelt gratitude to our guide Ms. Suchitra K who was unparallel in her efforts in making this project a reality. We would also like to add that had it not been for her continuous inspiration and guidance, our project would not have achieved even half the success that we enjoy today in its development. We would also like to thank our project coordinator Dr.Sundar Gopalan for providing us with all the facilities and all guidance necessary in making this project a reality. Special thanks to Br.Karthi B for the constant support and guidance that we received. Last we thank all the other members of the great project Security and Surveillance Systems who have helped each other in the long process of the design phase of the project. Thanks go to all people who have helped us directly or indirectly in the literary work of this project.

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CONTENTS

1. Abstract ………………………………………………………………….2 2. Introduction………………………………………………………...…….3 3. Project Discussion………………………………………………………..5 1) Literature Survey…………………………………………………5 2) Block diagram with explanation………………………………...11 3) Tools Required…………………………………………………..13 4) Programmer Hardware…………………………………………..13 5) Softwares Required……………………………………………...13 4. Project Planning and Timeline…………………………………………..14 5. Tools required from University………………………………………….15 6. Summary and Conclusion……………………………………………….16 7. Reference………………………………………………………………..17 8. Appendix………………………………………………………………..18

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ABSTRACT The problem of providing reliable and accurate position location of mobile units in wireless communication systems has attracted a lot of attention in recent years. There exist many incentives for wireless service providers to have such a system in place. Knowing a user’s location enables many new applications, often times called location-based services. They can use reliable position location as a means to optimize the performance and design of the wireless networks and can also additional features to the subscribers. The main objective of the project is to design and set up a system to track a radio frequency transmitter. The system consists basically of mobile stations and base stations. The Time Difference of Arrival (TDOA) technique is one of the most promising position location techniques for cellular-type wireless communication systems. In this technique the mobile unit which is to be tracked consist of the transmitter, the base stations consist of receiver. TDOA is concerned with tracking based on time difference of arrival of a signal emitted from the object to three or more receivers. The exact location of the radio frequency transmitter can be obtained by using four receivers. In fact the most striking fact about TDOA is that the change in magnitude of transmitting signal will not affect the accuracy of the system considerably, which makes it ideal for the future use. The ‘Security and Surveillance’ system consist of two levels of security checks that include biometric scanning and RFID based authentication. Biometric identification can provide extremely accurate, secured access to information; fingerprints, retinal and iris scans produce absolutely unique data sets when done properly. Automated biometric identification can be done very rapidly and uniformly, with a minimum of training. RFID technology plays a critical role in identifying articles and serving the growing need to combat counterfeiting and fraud. The ‘Tracking and Positioning’ allows for the monitoring of a person who has been authorized to access the secured area.

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INTRODUCTION The project ‘Tracking and positioning’ is a part of a ‘Security and Surveillance’ system which requires monitoring the positions of security personal within the secured area. The word "security" in general usage is synonymous with "safety," but as a technical term "security" means that something not only is secure but that it has been secured. The ‘Security and Surveillance’ system looks to provide all-round security to a restricted area (like a research lab) and also monitor the area round the clock so as to prevent a possible security breach. In this regard the ‘Tracking and Positioning’ system is of utmost importance as it allows a security official to monitor the position of the other security staff in the secured area and direct them appropriately as and when required. The ‘Security and Surveillance’ system aims to provide high end security that involves a sequence of Biometric scanning and RFID based authentication. A secure wireless communication link and a system to track the position of security personal within the secured area are other components of the system that enable to the monitor of the security status of the restricted area.

Since prehistoric times, people have been trying to figure out a reliable way to tell where they are and how to get to their destination and back home again. Such knowledge often meant survival and economic power in society. The systems that intent to use location in order to register user’s movement and to use the generated data for extracting useful knowledge define a new area of research that has technological as well as theoretical underpinnings. Location-based applications encompass a broad range of markets, including entertainment, fleet management, commerce, safety and systems applications. In all cases, maximizing position location accuracy and availability is the predominant requirement.

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One of the most straightforward solutions to meet the position location requirements is to use the Global Positioning System (GPS). However it is not an attractive option as the system increases the size and weight of hand set, and also causes drain of battery of hand set. To find the geographical location, the GPS receiver needs to have at least four satellites visible at all times, which is difficult in indoor calls. Other methods such as infrared (IR) or radio-frequency (RF) beacon tagging overcome this limitation of GPS, but often require the expensive deployment of new infrastructure. Wi-Fi based positioning builds on an already existing, widely available infrastructure and works indoors as well as outdoors. Another method of positioning is done by signal strength measurements from multiple access points. Since a change in signal strength is correlated to the distance between two stations, the locations can be estimated based on received signal strength indicator (RSSI) values. The system requires minimal setup time compared to other systems, which makes it readily available for real-world applications. This system gives a course estimate of the position. A much higher accuracy rather insensitive to fading is based on time of arrival (TOA). In future system, only the time difference of arrival (TDOA) or enhanced observed time difference (E-OTD) measurements may be possible to compute. The project ‘Tracking and Positioning’ aims to implement tracking to centrally locate the position of a person. The person to be tracked will be tagged i.e. he will have a ‘unique’ transmitter which would generate signals using which his position is to be tracked. Stationary base stations, placed appropriately within the secured area would monitor the signals received from the mobile transmitter and use a specific characteristic of the received signals (signal strength, timing delay etc.) to calculate the position of the transmitter within the secured area. The system aims to monitor the position of the tagged personal from a central control room which is to be achieved by providing the data from each of the base

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stations to a central processing unit that would use these data to simulate the motion of the personnel.

PROJECT DISCUSSION LITERATURE SURVEY METHODS USED FOR TRACKING and POSITIONING The use of RF signals has become an integral part of modern day tracking and positioning systems. Various signal parameters like signal strength, timing delay between the arrival of the signal at multiple receiver stations etc. Some of these technologies are as follows: METHOD 1: USING SIGNAL POWER In this method of tracking, the change in signal strength received at each of the stations is mapped to the transmitter coordinates. The locations can be estimated based on received signal strength indicator (RSSI) values from multiple access points. Signal power based positioning works indoor as well as outdoors thus overcoming the defect of GPS system. PATH LOSS MODEL

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The basic path loss model tells us that a drop in signal power or signal strength is correlated to distance. For example, if we disregard obstructions, multipath delay spread, scattering, refraction and diffractions effects, and assume all stations to be Stationary (i.e. no Doppler effect), we can model the signal loss by

, where Pr = Power measured at Receiver in Watts (W) Pt = Power measured at the transmitter in Watts (W) λ = Wavelength in Meters (m) r = Receiver to transmitter distance in Meters (m) Solving the above equation for r, we can easily determine the distance between receiver and transmitter based on the wavelength and the measured power at receiver and transmitter. Knowing the distance between multiple receivers and a transmitter, one can determine the location of the transmitter by triangulation. The described model clearly makes assumptions (e.g. no obstructions, no multipath delay spread) that clearly do not hold in the real world. Wireless LANs are mostly deployed indoors where there are many obstacles such as walls or furniture. One can augment the above propagation model by taking different types of materials or multiple building floors into account. However, propagation models quickly become overly complex if one aims at high level of accuracy. POSITION SIMULATION:

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RECEIVER 3

TRANSMITTER

RECEIVER 1

RECEIVER 4

RECEIVER 2

In order to simulate the position of the transmitter we require knowing the coordinates of the transmitter in terms of a specified origin. In this case the left hand corner is chosen as the origin and let r1, r2, r3 and r4 be the distances between the transmitter and the three receivers respectively.

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As from above figure the distance between the transmitter and each of the receivers can be obtained as:

r1= ((x-x1)2+(y-y1)2+ (z-z1)2)1/2 r2= ((x-x2)2+(y-y2)2+ (z-z2)2)1/2 r3= ((x-x3)2+(y-y3)2+ (z-z3)2)1/2 r4= ((x-x4)2+(y-y4)2+ (z-z4)2)1/2

The four equations mentioned above can be solved to obtain the (x, y, z) coordinates of the transmitter since the distance between the transmitter and each of the receivers i.e. r1, r2, r3 and r4 can be calculated by knowing the transmitted signal power and the received signal power at each of the four receivers.

ACCURACY OF THE SYSTEM: The system utilizes signal strength as the parameter to evaluate the position of the transmitter. The problem encountered by such a system is that it does not incorporate the drop in signal strength due to obstructions in the path between the transmitter and the receivers. For instance suppose a tagged person with the transmitter in his hand is standing facing receiver 1 and the system locates it at position ‘A’. Now the person just turns 1800 at the same position with receiver 1 behind him. This would register a fall in signal strength at the receiver 1 resulting in the mapping of the position of the transmitter to position B though actually the position hasn’t changed. The problem is far more sinister when there are other obstructions present.

Method 2: TIME DIFFERENCE OF ARRIVAL 11

It is the process of locating an object by accurately computing the time difference of arrival (TDOA) of a signal emitted from the object to three or more receivers. It is also known as hyperbolic positioning. It is commonly used in civil and military surveillance applications to accurately locate an aircraft, vehicle or stationary emitter by measuring the time difference of arrival (TDOA) of a signal from the emitter at three or more receiver sites. In this technique, a secondary network of base stations at transmitted locations is needed. These base stations effectively act as dummy handsets. At a synchronized time period, the mobile handset and a nearby dummy base station both capture a portion of the forward link signal from the actual base stations. The mobile then transmits its version of the captured signal to the dummy base station, which correlates that with its own version of the captured signal. Thus, the time difference of the signal arrival at the mobile and the dummy station is known. Since the coordinates of the dummy stations and the actual network base stations are known, this procedure gives the distance between the mobile and the actual base station. Performing three such measurements with three different actual base stations, the position of the mobile can be found using the triangulation method. If a pulse is emitted from a platform, it will arrive at slightly different times at two spatially separated receiver sites, the TDOA being due to the different distances of each receiver from the platform. In fact, for given locations of the two receivers, a whole series of emitter locations would give the same measurement of TDOA. Given two receiver locations and a known TDOA, the locus of possible emitter locations is a hyperboloid (a surface approximately shaped like two cones joined at the points). In simple terms, with two receivers at known locations, an emitter can be located onto a hyperboloid. Note that the receivers do not need to know the absolute time at which the pulse was transmitted - only the time difference is needed. Consider now a third receiver at a third location. This would provide a second TDOA measurement and hence locate the emitter on a second hyperboloid. The intersection of these two hyperboloids describes a curve on which the emitter lies. If a fourth receiver is now

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introduced, a third TDOA measurement is available and the intersection of the resulting third hyperboloid with the curve already found with the other three receivers defines a unique point in space. The emitter's location is therefore fully determined in 3D. In practice, errors in the measurement of the time of arrival of pulses mean that enhanced accuracy can be obtained with more than four receivers. In general, N receivers provide N-1 hyperboloids. When there are N > 4 receivers, the N-1 hyperboloids should, assuming a perfect model and measurements intersect on a single point.

POSITION SIMULATION: Consider an emitter at unknown location (x,y,z) which we wish to locate. Consider also a system comprising four receiver sites at known locations: a central site, C, a left site, L, a right site, R and a fourth site, Q. The travel time (T) of pulses from the emitter (at x,y,z) to each of the receiver locations is simply the distance divided by the pulse propagation rate (c):

If the site C is taken to be at the coordinate system origin,

Then the time difference of arrival between pulses arriving directly at the central site and those coming via the side sites can be shown to be:

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Where

the location of the left receiver site is, etc, and

is the speed of

propagation of the pulse, often the speed of light. Each equation defines a separate hyperboloid. The corresponding system must then solve for the unknown target location (x, y, z) in real time. All the other symbols are known.

ACCURACY OF THE SYSTEM TDOA is, in general, far more accurate for locating an object than techniques such as triangulation (as it is easier to measure time accurately than it is to form a very narrow beam). The accuracy of TDOA is a function of several variables, including: •

The geometry of the receiver(s) and transmitter(s)

•

The timing accuracy of the receiver system

•

The accuracy of the synchronization of the transmitting sites or receiving sites. This can be degraded by unknown propagation effects.

•

The bandwidth of the emitted pulse(s)

•

Uncertainties in the locations of the receivers

BLOCK DIAGRAM

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MOBILE UNIT

CENTRAL BASE STATION

RECEIVER 4 BS 1

BS 2

RECEIVER 2

RECEIVER 3

MICROCONTROLLER

MICROCONTROLLER BS 3

RECEIVER 1

MICROCONTROLLER

USB INTERFACE

SIMULATION

BLOCK DIAGRAM DESCRIPTION

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The system is to implement tracking using Time Difference of Arrival (TDOA). The block diagram level description of the system involves the following blocks:

MOBILE UNIT: The mobile unit is the tag that is to be used to track the position of the security personnel. Thus the mobile unit is a transmitter which sends out pulses at regular intervals. The choice of the pulse waveform depends on the bandwidth constraints of the wireless channel link between the mobile unit and the base stations.

BASE STATION: These pulses are received by the four receiver base stations namely Base station 1, Base station 2, Base station 3 and Base station 4. The pulses are received and the timing delay or the difference between the arrival of the pulses at each of the three receivers (Base Stations 1, 2 and 3) and the central receiver can be calculated. Using a micro-controller coupled to the central receiver and each of the other three receivers the time difference of arrival at each of the three receivers can be calculated. These delays are then employed to calculate the (x, y, z) coordinates of the mobile unit.

PC INTERFACING: The time difference data corresponding to each of the three receivers is then coupled to a computer through a USB port. The data so received is used to calculate and simulate the 3-D position of the transmitter. USB interfacing is achieved using PIC microcontroller.

TOOLS REQUIRED

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1. Digital trainer kit 2. PC with required soft wares. 3. Digital Storage Oscilloscope(350 MHz) PROGRAMMER HARDWARE 1.

Microcontroller

2.

Programmer of microcontroller.

SOFTWARES REQUIRED 1. Matlab 2. PSpice 3. MPLab ASM 4. Embedded C

PROJECT PLANNING and TIMELINE 17

January

December November

MONTH WEEK week3

TASKS Study of different transmitter and receiver circuits and antennas to

week4

be used

week3

Design the suitable transmitter circuit and the transmitting antenna.

week4 Design the suitable receiver circuit and the receiver antenna. week1

Learn programming of microcontroller

week2

Circuit implementation of the transmitter and the transmitting

week3

antenna

week4

Circuit implementation of the receiver and the receiving antenna

February

week1 week2 week3 week4 week1 March

Program a microcontroller to digitize the receiver output Integration of receiver and transmitter system Circuit implementation of other 3 receiver and antenna combine.

week2 week3 week4

Integrate and troubleshoot( if required) the transmitter/receiver system.

TOOLS REQUIRED FROM THE UNIVERSITY

1. Lab facility 2. PCs with required softwares 3. DSO with high bandwidth 18

4. Function generators with high frequency output 5. Internet access

SUMMARY AND CONCLUSION The proposed ‘Tracking and Positioning’ system forms an integral part of the high end ‘Security and Surveillance System’. The Security and Surveillance System provides high level security to a restricted area which includes biometric identification, RFID Authentication, Tracking and positioning of personnel and secured wireless communication

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link between security officials. Tracking and Positioning System helps in monitoring any authorized personnel entering the restricted area and to direct them as and when required. There are mainly two different methods for tracking, one being signal power positioning, which works on the principle that a change in signal strength is correlated to the distance between two stations and we can estimate locations based on received signal strength indicator (RSSI) values from multiple access points. The other one being TDOA which deals with locating an object accurately by the time difference of arrival of a signal emitted from the object to three or more receivers. A mathematical approach to TDOA has been briefed, which high-lightens the precision of the system. The accuracy of TDOA is a function of several variables, which includes the geometry of the receiver(s) and transmitter(s), the timing accuracy of the receiver system, bandwidth of the emitted pulse, etc. The efficiency of the system being a function of the time difference of the transmitted signal, TDOA holds advantage over other existing systems as the accuracy of the system is not appreciably affected by drop in signal strength. The ‘Tracking and Positioning’ system can be used to monitor the position of the tagged personal from a central control room.

REFERENCES

1) Muhammad Aatique,”Evaluation of TDOA techniques for position location in CDMA systems”, Virginia Polytechnic Institute and State University.

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2) E. Hepsaydir and W. Yates, “Performance Analysis Of Positioning Using Existing CDMA Networks", IEEE Position Location and Navigation Systems, pp. 190-192, 1994. 3) Fredrik

Gustafsson

and

Fredrik

Gunnarsson,”

Positioning

using

TIME

DIFFERENCE OF ARRIVAL measurements,” Department of Electrical Engineering Linkoping University, SE-581 83 Linkoping, Sweden. 4)

Adam Harder, Lanlan Song, and Yu Wang, Towards an Indoor Location System Using RF Signal Strength in IEEE 802.11 Networks, Proceedings of the International Conference on Information Technology: Coding and Computing (ITCC’05), 2005.

5) http://www.era.cz/en/news 6) http://en.wikipedia.org/wiki/Multilateration

APPENDIX Angle of Arrival

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Angle of Arrival, or AoA, is a technique for determining the direction of propagation of a radio-frequency wave incident on an antenna array. The technique calculates the direction by measuring the Time Difference of Arrival (TDOA) at individual elements of the array -- from these delays the AoA can be calculated. Generally this TDOA measurement is made by measuring the difference in received phase at each element in the antenna array. E-OTD - Enhanced Observed Time Difference The E-OTD method is based on measurements in the MS

(Mobile Station) of the

Enhanced Observed Time Difference of arrival of bursts from nearby pairs of Base Stations. It is employed to calculate the position of the MS and may be used for LCS

(LoCation

Service). GPS The Global Positioning System, usually called GPS, is the only fully-functional satellite navigation system. A constellation of more than two dozen GPS satellites broadcasts precise timing signals by radio, allowing any GPS receiver to accurately determine its location (longitude, latitude, and altitude) in any weather, day or night, anywhere on Earth. RFID Radio Frequency Identification (RFID) is an automatic identification method, relying on storing and remotely retrieving data using devices called RFID tags or transponders. An RFID tag is an object that can be attached to or incorporated into a product, animal, or person for the purpose of identification using radio waves. Chip-based RFID tags contain silicon chips and antennas.

RSSI RSSI is an initialism for Received Signal Strength Indication. RSSI is a measurement of the received radio signal strength (energy integral, not the quality).

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