Optimal Precoding and MMSE Receiver Designs for MIMO WCDMA

2times2 unitary preceding based on receiver feedback is applied alongside spatial multiplexing at the base station in HSDPA (D-TxAA) when the mobile terminal supports MIMO transmissions [1]. This precoding will influence achievable sum- rate of the MIMO channel if it influences the Signal-to- Interference-plus-Noise Ratio (SINR) of streams at the receiver (RX) output. We propose a set of MIMO HSDPA receivers, all based upon a LMMSE chip-level matrix filter (equalizer) front end, and introduce the notion of joint bias for the MIMO chip equalizer. Statistical properties of the spatial model thus obtained are exploited to analyze the performance of proposed MIMO receivers. It is shown that precoding choice depends upon the MIMO receiver and the extent of its impact depends on the MIMO RX.