Impact of Amplitude Component on HSUPA Closed Loop Transmit Diversity Performance

3GPP is investigating uplink transmit diversity alternatives for High Speed Uplink Packet Access (HSUPA). This paper addresses uplink transmit diversity from the perspective of Closed Loop Beamforming (CLBF) when amplitude component is included in the beamforming codebook. This allows transmitter to divide the total transmit power unequally to transmit antennas based on the feedback from the NodeB. This study includes the investigation of the potential benefits of antenna selection and amplitude adaptation as part of the feedback. Furthermore, the focus will be on evaluating corresponding system level performance when long term antenna imbalance is assumed. The studies show that there are achievable gains and thus system performance may be enhanced by applying the amplitude component, especially when the antenna imbalance is high. However, the trends indicate that gains are mainly seen by the cell edge users, thus introducing amplitude component in the codebook increases coverage and fairness.