Performance of Spatial Multiplexing in High Speed Downlink Packet Access System

In this paper we study the performance of 2times2 per-antenna rate control (PARC) on high speed downlink packet access (HSDPA) system and compare that to the corresponding 1times1 and 1times2 reference schema. Special cases of PARC-2times2 selective transmit diversity (STD) and 2times2 dual streaming-are also studied. 2times2 PARC is a dual stream multiple-input multiple-output (MIMO) scheme, which by default utilizes dual streaming transmission except in those conditions where dual stream transmission is not feasible. In those conditions STD is used, meaning that weaker antenna is switched off and the transmission occurs only from the stronger antenna. The selection of PARC mode is based on the channel quality indicator (CQI) measured and reported by the mobile terminal. In this paper we compare the system level performance of PARC against it sub-modes, i.e., STD and dual streaming. Dual streaming sub-mode means that both data streams are always transmitted even though the channel conditions at the user equipment (UE) would not support that. Performances of the schema is done both in terms of user throughput and in system capacity. Conclusions on the results are drawn