Improvement of GSM E-CITA localization algorithms' accuracy based on velocity estimation and further restriction of serving cell areas
Original Publication Date: 2003-Jun-25
Included in the Prior Art Database: 2003-Jun-25
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There are many reasons for determining the position of mobile users in GSM networks, e.g. intercellular traffic distribution, location dependent services and emergency calls. A key factor for the success of any localization technology is its accuracy. Within the network based solutions, which means that the mobile equipment remains unchanged, one can determine the following methods: At first there is the method of using the plain Cell ID (CI), which just returns the weighted center of the serving cell as a position estimate. Cell ID plus Timing Advance (CI + TA) based methods also take into account an estimate of the mobile's distance to the Base Transceiver Station (BTS) but not the direction. Last there is the Enhanced Cell ID Timing Advance (E-CITA) method which also uses the signal strength RXLEV (Reception Level). For estimating the position of a Mobile Station (MS) using E-CITA every cell is divided into small squares called pixels (e.g. 5x5 m or 25x25 m) and must have a so-called prediction file associated with it that contains the predicted field strength or predicted path loss for every position (pixel) inside the cell. Beside the field strength of the serving cell the algorithm also relies on the predicted field strength of max. 6 out of up to 32 neighboring cells, so the predicted field strength of these cells are also needed for every pixel in the serving cell. An RF (Radio Frequency) planning tool calculates these values.