Closed loop mode 1 transmit diversity with high speed downlink packet access

In this paper we consider the performance of a closed loop mode 1 transmit diversity in WCDMA network when high speed downlink packet access (HSDPA) scheme is used. Motivation for the use of multiple antennas arises from the expected gains in the performance of a wireless link. In closed loop mode 1 technique base station uses a suitable weight, which corresponds to phase adjustment, for its second transmission antenna according to UE´s feedback commands. The study of the effects of it to the system´s performance in a dynamic environment is extremely crucial due to the fact that phase adjustment may lead to destructive combining or received phases due to mobility and feedback errors and, as a consequence, might even lead to performance losses rather than gains for the system. In this paper we study the effect of mobility, feedback errors and feedback delays to the system performance and draw conclusions about the achieved capacity gains/losses.