Channel estimation with array processing for the uplink of UMTS-TDD

Channel estimation is critical to coherent RAKE receiver performance. This paper deals with channel estimation based on the standard algorithm suggested for UTRA-TDD by 3GPP. It proposes a spatial pre-combination technique that exploits the spatial structure of the received multipath signal to improve the channel estimator performance. Self and multiple access interference is partially cancelled before the channel estimation algorithm. The performance of the estimation algorithm is assessed by resorting to simulations in typical UMTS-TDD scenarios and the correlation coefficients between the complex channel and the estimates are computed. The effect of imperfect channel estimation on the performance of RAKE1D and RAKE2D receivers is analyzed in a multiuser scenario.