Local Position System - Preliminary Design Specification | ECE 441, Study Guides, Projects, Research of Electrical and Electronics Engineering

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ECE441 Senior Design

Preliminary Design Specification

Group 8 John Salle Dustin Stallings Kevin Baker Drew Haven

Table of Contents

• 1 Revision History ……………………………………………………………….
• 2 Introduction ……………………………………………………………………
  • 2.1 Customer Requirements and Product Background……………………..
  • 2.2 Competitive Analysis……………………………………………….......
  • 2.2.1 Product Space Analysis………………………………………...
  • 2.2.2 Target Feature Set………………………………………………
  • 2.3 References………………………………………………………………
  • 2.4 Naming Conventions Used……………………………………………..
• 3 Architectural Overview ……………………………………………………….
  • 3.1 Implementation Approaches……………………………………………
• 4 Top Level Description …………………………………………………………
  • 4.1 Top Level Block Diagram…………………………………………..….
  • 4.1.1 Top Level Interface Definition…………………………………
    • 4.1.2 Environment ……………………………………………………

whole, so reducing costs in each unit as much as possible is of the utmost importance. 2.2 Competitive Analysis Refer to Table 2. 2.2.1 Product Space Analysis The three main designs under consideration were the active RFID tag system, the passive RFID system, and the FM transmission system. For the purpose of this project we decided to go with the FM transmission system as opposed to the others for a variety of reasons. Although the RFID systems consumed less power than the FM transmitters there were several big disadvantages. The main one being transmission range, where the passive system is limited to a range of around 12ft. and the active system has a range of around 30m. Even though active systems could achieve a range of 30m, we decided it would still be too complicated and costly to implement this design, especially compared to the FM system, which has a range of about 150m. Another disadvantage for RFID is the very small power in these systems, along with over complicated antennas and limited resources like static free rooms to work in; RFID isn't very feasible for this project. The thing that is missing among the competition in this case also is a good FM transmission based tracking system. There were several competitors using RFID systems to keep track of warehouse shipping pallets or for store security, but there were relatively few FM based designs. This was another reason for choosing FM transmission for this system. Being that there are so many RFID systems around, it seems that it would be a better idea to make a longer range FM tracking system as it could serve a role that is not being currently filled.

Table 2. Product Name Manufacture r Operating Frequency Range^ Power Requirements Cost^ Application s Dimension s Weight^ Memory^ Connectivit y Other Small Reader Active Wave Transmit - 433MHz Receive - 868, 917, 927 MHz 30m to tag, 85m from tag 12V DC, 1.5A^ ≈^ $^ RFID Tag Reader 2.6x4.3x6. inches 4.5oz. 128g Yes Ethernet and WLAN (2.4GHz or 5.2Hz Reads and Writes RFID tags PC Reader Active Wave Transmit - 433MHz Receive - 868, 917, 927 MHz 24m to tag, 45m from tag 5V DC via PCMCIA slot ≈^ $^ RFID Tag Reader 54 x x10mm 1.3oz. 36.9g Yes PCMCIA Type 2, or optional antenna Reads and Writes RFID tags, already PC connected Mini Tag[1] Active Wave Receive - 433MHz Transmit - 868, 917, 927 MHz Receive and transmit at 30m 3V Li-ion battery^ $5-$100^ RFID Tag^ 34 x x12mm .4oz. 11g 256Kbits^ RF Small, 1- years battery life Mini FM Transmitter[2] cana kit^ 88-108MHz^ 150m transmission^ 4 AA Batteries^ $^ Data Transmission 5 x 3.5cm^ N/A^ No^ FM Two modes of operation: microphone and line RFID Paper Tag[3] GAO^ 13.56 MHz^ up to 1m^ None, powered from reader $1. Store Security, Barcode Replacement 46 x 82mm N/A Yes RF Super Cheap, no range RFID Passive Tag[4] Intermec^ 915 MHz^ up to 13 ft^ None, powered from reader N/A^ Container Tracking 1.28 x4.13 x 1.25 inches N/A^ Yes^ RF^ Cheap, medium range Linear Delta 3 Garage Door Opener[5] Linear 310 MHz N/A 9V battery $12.75 Garage Door Opener N/A N/A No FM (^) medium rangeCheap,

2.4 Naming Conventions Used RFID – Radio Frequency Identification FM – Frequency Modulation 3 Architectural Overview This project, called the local positioning system (LPS), is used to keep track of a number of people in a specified area as a means of security, safety or recreation. LPS is similar to GPS, however it can be used on a smaller and much cheaper scale than GPS, and can be scaled to work for many more applications. In order for this system to work, the mobile transceiver is designed to be easily worn by the user. In this case, the mobile transceiver is created to be about the size of a pager and include some sort of clip. This way it can easily be worn by a user during various activities. In addition, the mobile transceiver is designed to consume very little power by way of only transmitting every few seconds. Such a method will increase battery life to approximately 1 year. The mobile transceivers communicate with base transceivers scattered throughout the desired locations. This is accomplished by the base transceiver sending out a signal to search for the mobile transceivers. From here the mobile transceivers in the area will send back a unique signal to the base transceiver which will keep track of the time it took for this process to complete. All this information will be sent from the base transceivers to the central server. The central server will perform calculations to determine the distance between the mobile transceivers and the base transceivers, and will provide a location to within 2 meters accuracy. This new location, along with all previous locations, will be stored in a database, so users can obtain them as needed. The central server will also display user location path from the database on screen for anyone logged on to the server. The user’s locations will be displayed with red and blue dots. A red point indicates the most current location, and blue shows past positions. The display will also indicate the information of the mobile transceiver wearer, as well as the time for each recorded position. 3.1 Implementation Approaches Several different approaches could have been implemented to complete this design. One of which and perhaps the most attractive option is the RFID Tag system. This would be a good implementation which would have much of what the project needs; further analysis shows that it is not very feasible. One thing that doesn’t work is the range of the tags and readers. Although this seems possible at first, the low power passive tags, which require no battery, have a maximum range of about 5m. As for the active tag the range of both the reader and the tag is limited to around 30m. Considering that the specifications of the system need someone to be tracked over a large area, RFID is clearly not an option because of range issues alone as it would require far too many readers. Another problem is cost. With a budget of $500 this system clearly requires a low cost, and with RFID readers and tags at $200 plus, the budget will be broken almost immediately. Another approach that was researched was implementing a proximity to receiver

design. For this design there would be multiple receivers with a 10m range that would pick up any mobile transmitters in their vicinity. When a transmitter is detected the receiver would throw up a flag and tell the system that the user is within a 10m radius. The problem with this design is that the receivers would not be able to specify where exactly the transmitter is within this 10m radius, which would create a lot of error in specifying user location. Along with this, FM transmitters can transmit approximately 150m, which means they could be picked up by the receivers at a distance far greater than 10m. Because of this the receivers would think that the transmitters were within 10m, when they actually may be over 100m away. A short range RFID tag would have resolved this issue, but as stated earlier, the tags were too expensive. The method in which the receivers were to be connected was another issue. Using a serial connection would be both easier and cheaper than an Ethernet connection to implement. This is due to the microcontrollers with serial connectors being cheaper than those with Ethernet connectors. Along with this, serial interfacing is much simpler than using Ethernet. 4 Top Level Description As shown in Figure 4.1, this system consists of five major components: a mobile transceiver, a base-station transceiver, a data collection server, a central server/database, and a user-interface. The mobile transceiver is a small device that users will carry with them as they move around the system’s defined area. The base-station is responsible for communicating with the mobile transceiver. The data collection server is a computer programmed to handle information obtained by the base-station, and pass it to the central server. The central server/database will compile data from the data collection server, perform calculations to determine the mobile transceiver’s position, and store the values in the database. The user-interface is a graphical user-interface which extracts information from the database as needed by the user. It is important to note that this system is a local positioning system, able to track the position of the system’s mobile transceivers only within a defined local area. The most basic implementation would require two base-station transceivers; whereas, the system could be expanded to incorporate more than three base-stations to increase the system’s operating area. Another important note is that a data collection server is required at each base-station transceiver location. Each mobile transceiver is programmed with a unique ID number. As users receive the device, their name is entered and stored in a database with the unique ID attached to it. In addition, each activated device’s ID number is added to a list of all active mobile devices, which will be referred to as the active device list. As each device moves with its user around the defined area of the system, its position is tracked by base-stations positioned throughout the area. Each base-station cycles through the active device list, transmitting a signal for each ID number. Incorporated in the signal is a header which corresponds to the unique ID it is searching for. The mobile transceiver responds to the signal only if the header matches its ID. The base-station uses a timer/counter to keep track of the elapsed time between the time it sent the signal, and the time it receives a response from the mobile transceiver. The elapsed time data is stored in the data collection server, and sent to the central server for position calculations.

FM Transmitter FM Receiver FM Receiver FM Transmitter Battery Array Mobile Transceiver^ Base Transceiver Microcontroller Freq 1 Freq 2 Antenna Antenna FM Rx Antenna Antenna Antenna FM Tx Antenna SPI Note: Drawing only shows one iteration of the system. Multiple base stations and many mobile systems will be used, the number based on the size of the implementation To Server FM Rx Antenna FM Tx Antenna Microcontroller UART FM Control Interface FM Tx FM Rx FM Control Interface SPI FM Tx FM Rx Figure 4. 4.1 Top Level Block Diagram MOSI MISO SCK spi_mosi spi_miso sck spi_mosi spi_miso sck FM Control Interface fm_out fm_in FM Transmitter TLP 315 FM Receiver RLP 434 fm_out fm_in Data In Digital Data Out Vcc Vcc battery _ 4. 5 v Antenna Antenna 2 3 4 8 2 4 Antenna Antenna FM Control Interface fm_out fm_in FM Transmitter TLP 434 FM Receiver RLP 315 fm_out Data In^ fm_in Digital Data Out Vcc Vcc power _supply Antenna Antenna 2 3 4 8 2 4 Antenna Antenna Microcontroller Microcontroller Mobile Transceiver Base Transceiver fm_freq 1 fm_freq 2 S cs cs MOSI MISO SCK spi_mosi spi_miso sck spi_mosi spi_miso sck cs cs^ S To Server UDR Figure 4.1. 4.1.1 Top Level Interface Definition

Signal Protocol Explanation spi_mosi SPI Data output to the FM control interface. 4.5 volt software controlled square wave. spi_miso SPI Data input from the FM control interface. 4.5 volt software controlled square wave. sck SPI Clock 0-4.5 volts clock signal at a frequency to be determined later, with a duty cycle of 50%. cs SPI 4.5 volt digital signal to the fm control interface. Low enabled. udr RS-232 Serial connection between base microcontroller and data collection server. +3 to -3 volts. Even parity dserv_cserv TCP Category5 100Base T Ethernet connection, 100 Ω impedance, up to 100 MHz transmission frequency fm_out None Software controlled digital square signal, 0 to 4.5 volts. fm_in None Software controlled digital square signal. 0 to 4.5 volts. antenna FM Frequency modulated signal generated by the TLPxxx. Frequency depends on direction of signal. fm_freq1 FM Input FM signal of base transceivers/Output FM signal of mobile transceivers. Uses a frequency of 315Mhz fm_freq2 FM Output FM signal of base transceivers/Input FM signal of mobile transceivers. Uses a frequency of 434Mhz Note: Signals in the base and mobile transceivers that are counterparts are named similarly; however the signals are not the same and are physically separated.