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“In order to get the TDMA scheme to work, the time-frames from each mobile station must be synchronized when received by the BTS (see figure [*]). This synchronization is achieved by using the concept of Timing Advance (TA), defined in [13]. The degree of synchronization is measured by the BTS on the uplink, by checking the position of the training sequence. This training sequence is mandatory in all frames transmitted from the MS. From these measurements, the BTS can calculate the Timing-Advance and send it back to the MS in the first downlink transmission. From the TA value received from the BTS, the MS know when to send the frame, so that it can arrive at the BTS in synchronism. The values of the TA is continously calculated and transmitted to the MS during the lifetime of a connection.”