Pre-RAKE and multiuser detection techniques in UTRA-TDD systems

This paper is concerned with the application of pre-RAKE processing in the up link of a DS-CDMA system for a wireless Local Loop (WLL) scenario with time division duplex (TDD) access. It is well known that RAKE processing allows optimum time diversity gain in a multipath channel. An alternative approach, known as pre-RAKE processing, exploits the channel reciprocity in TDD systems in the up and down links to perform the optimum combination at the transmitter with the consequent receiver simplification. Typically, the pre-RAKE works at the base station, transmitting all users information with their particular pre-distortion. In this paper we explore another possibility, that is, each user performs its own pre-distortion, in order to simplify the synchronization and multiuser detection at the base station. Several simulations show its feasibility in comparison with standard multiuser detection techniques