Beamforming Transmit Diversity Using Power Control Commands for High Speed Uplink Packet Access

摘要

3GPP is investigating uplink transmit diversity alternatives for High Speed Uplink Packet Access (HSUPA). This paper studies beamforming transmit diversity where the UE transmitter applies a weight vector to the transmit antennas. In contrast to the traditional beamforming where transmitter is aware of the channel state through channel state feedback, a practical scheme which relies on existing power control commands to calculate the weight vector is investigated. This approach allows autonomous determination of the weight vector by the UE. Additionally, an ideal algorithm which always selects the optimal weight vectors is presented in order to obtain upper boundary for the performance. Both algorithms are benchmarked in various conditions on system level against baseline performance without transmit diversity. The studies show that ideally open loop beamforming is capable of providing gain in simulated conditions. However, the power control command dependent realistic algorithm is able to provide gain only when the low velocity Pedestrian A 3 kmph channel is used. With more complex and higher velocity Vehicular A 30 kmph channel the realistic algorithm is not able to provide gain and reaches only baseline level performance.