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Impact of channel estimation on the 3GPP-TD-CDMA

The 3GPP proposal for 3rd generation mobile phone systems comprises not only frequency division duplex (FDD) but also time division duplex (TDD) as duplex method for the JD-CDMA system. The TDD mode is an addition to the FDD mode to facilitate flexible, asymmetric data transfer of up- and downlink. Special structured pilot sequences are included into the data bursts and can be exploited to perform an efficient joint channel estimation of all active users as basis for multiuser detection. In this paper linear receiver concepts for the TDD mode are examined in terms of performance with focus on the influence of real, non-ideal channel estimation. RAKE receiver, zero forcing and minimum mean-square-error multiuser detectors are introduced and investigated by means of simulation for different environments using appropriate ITU channel models. Furthermore, an improved channel estimation procedure is presented, yielding significant performance enhancements for the multiuser detection algorithms.