Performance of absolute and recursive feedback methods with HSUPA closed loop transmit diversity

3GPP is investigating uplink transmit diversity alternatives for High Speed Uplink Packet Access. This paper presents a closed loop beamforming transmit diversity scheme where NodeB determines the transmit antenna weight vectors and feedback is used for signaling the optimal weights to the user equipment. Two promising feedback method candidates are presented and benchmarked in various conditions on system level against the baseline performance without transmit diversity. In each time slot the absolute feedback method signals the whole weight vector information, while the recursive feedback method signals only a single bit and the weight vector is recursively calculated from multiple bits sent over consecutive time slots. The results show that both feedback methods are capable of providing gain over the baseline in simulated conditions. However, while the recursive feedback method requires less signaling bits per slot, it is more vulnerable to the effects of weight signaling errors due to the signaling error propagation.