Comparison of structures for TD-CDMA multi-user detector on the mobile

In downlink TD-CDMA multiple access scheme, the use of multi-user and multi-sensor detection gives great improvement compared to the Rake receiver. Nevertheless, the algorithmic ressources are limited on the mobile and that is why we study and compare some strategies for the practical implementation of the well known linear detector. We consider two linear discrete-time structures with finite number of taps, called Tc-structure and Ts-structure. The first is a wide-band and free structure which performs one single fractional filtering per sensor. The second is an imposed structure consisting of a bank of Matched Filters followed by a bank of discrete equalizers working at symbol time. The determination of the coefficients is based on a temporal optimization. By means of simulations, these two practical detectors are studied for a small number of coefficients, which show very different behavior. Using a complexity analysis, the Ts-structure is shown to be more advantageous globally.