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cellular positioning

cellular positioning. What is cellular positioning?. Determining the position of a Mobile Station (MS), using location sensitive parameters. Positioning Parameters. Cell-ID Received Signal Strength Intensity (RSSI) Timing Advance (TA) Uplink Time (Difference) Of Arrival (TDOA)

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cellular positioning

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  1. cellular positioning

  2. What is cellular positioning? • Determining the position of a Mobile Station (MS), using location sensitive parameters

  3. Positioning Parameters • Cell-ID • Received Signal Strength Intensity (RSSI) • Timing Advance (TA) • Uplink Time (Difference) Of Arrival (TDOA) • Downlink Observed Time Differences (E-OTD) • Angle of Arrival (AOA)

  4. Triangulation In trigonometry and geometry, triangulation is the process of determining the location of a point by measuring angles to it from known points at either end of a fixed baseline, rather than measuring distances to the point directly. The point can then be fixed as the third point of a triangle with one known side and two known angles.

  5. Cell ID Cell identity is the most simplistic and cost-effective way to provide position information. It simply determines which cell of a wireless network the device is using and reports its location. This method typically provides location information accurate within a kilometer or two. Fortunately, there are ways to improve the accuracy of cell identity. Some cells are divided into sections, thereby reducing the total area of the possible location

  6. Cell id contin.. To get an even more accurate reading on the location, a technique called timing advance (TA) can be used. TA provides a way to find out how far a user is away from the base station, thereby dramatically reducing the possible locations for that user When these positioning methods are combined, they are commonly referred to as cell global identity-timing advance or CGI-TA. This approach can yield results that are accurate within 100 to 200 meters (100 to 200 yards). accuracy of CGI-TA is better in cities than in rural areas due to the higher density of base stations in populated areas

  7. Time of Arrival (TOA) Even when timing advance information is available, CGI-TA does not provide accurate-enough information for most location-based services. Using a time of arrival (TOA) approach—also known as time difference of arrival (TDOA). Rather than using one base station to determine the location, TOA uses information gathered from three or more base stations. These time differences have to be very accurate, requiring all of the base stations to be synchronized. GPS systems for synchronization or an atom clock.

  8. Time of Arrival (TOA) conted.. Since the signal moves at a fixed speed, the distance of the device to the base station can be determined. The distance from a single base station does not help a lot as it is not possible to know in which direction the mobile user is moving. By using the information from three base stations, it is possible to triangulate the coordinates of the user relative to the base stations. TOA technology does not require any changes to the handset itself. The accuracy of this solution is fairly decent, coming in at around 50 meters (50 yards) in urban areas and 150 meters (150 yards) in rural settings. TOA solutions are more practical on CDMA/CDMA2000 networks, as they are already synchronized

  9. Angle of Arrival (AOA) Angle of arrival (AOA) works in a similar fashion to TOA, but instead of using the time it takes for a signal to reach three base stations, it uses the angle at which a device's signal arrives at the station. By comparing the angle-of-arrival data among multiple base stations (at least three), the relative location of a device can be triangulated. On its own, AOA is not commonly used, and is rarely discussed with LBS. That said, some systems may use the angle of arrival along with the time of arrival to get an even more accurate location.

  10. Handset-Based Solutions When more accuracy is needed, handset-based solutions are required. In these solutions the handset participates in the position determination. The accuracy of these technologies allows for the introduction of the third generation of location-based services, where precise location information is required. The two handset-based systems described next use similar ways of calculating location, with one major difference: E-OTD relies on base stations and GPS uses satellites.

  11. Enhanced Observed Time Difference (E-OTD) Enhanced observed time difference (E-OTD) technology works in a similar way to time of arrival, but the handset makes the time measurements instead of the base stations. E-OTD relies on measuring the time at which signals from the base station arrive at two geographically dispersed locations: the mobile device and a fixed measuring location called the location measuring unit (LMU). For accurate triangulation, at least three base stations have to participate in the calculation.

  12. E-OTD contd.. Once the measurements are taken, the E-OTD-enabled handset records the time differences from the three base stations. The distance between the mobile device and the base stations can then be calculated by comparing the time differences between the timing measurements. The time difference can be translated into a distance because the signals move at a fixed speed. E-OTD provides an accurate and cost-effective way t o determine a mobile position. The results are typically accurate within 50 to 100 meters

  13. GPS and A-GPS Global Positioning System (GPS) is the most popular positioning technology being used today. It uses 24 global satellites that orbit the Earth to send signals to a GPS-enabled receiver. The receiver can communicate with three or four satellites at any single point in time. For this to work, however, there has to be a line of sight between the receiver and the satellites, precluding the use of GPSs inside buildings. In many product offerings, the GPS receiver is a separate unit that can be connected to a mobile device using a cable hookup or wireless technology such as Bluetooth. Over the past several years, the size, power consumption, and cost of GPS chipsets have fallen, leading to widespread use of this technology in the mobile environment.

  14. A-GPS One solution to both the line-of-sight and time delay issues is network-assisted GPS or A-GPS. A-GPS uses modified handsets that receive the GPS signals and then send those readings to a network server. The server uses network-based GPS receivers to help the handset measure the GPS data. The network GPS receivers are placed around the network several hundred kilometers apart. They regularly collect GPS satellite data and provide this data to the handsets, enabling them to make timing measurements without having to decode the actual satellite messages. This makes a substantial difference in the time it takes to get the location information. Using A-GPS, the time is typically between one and eight seconds

  15. Applications of cellular positioning • Operator services • Billing • Network management • Location based services • Wireless Gaming • Assistance • Roadside assistance • Personal or vehicle emergency • Alarm management • Driving Directions • Tracking • Tracking criminals • Tracking external resources containers etc • Monitoring • Monitoring delivery process • Fleet & freight tracking • Personal Child Security • Mobile Worker management • Information • Traffic • Nearest service • news • navigation help • advertising • Information Directory

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