ABSTRACT
Recently, several receive optimization schemes have been proposed for OFDM-SDMA systems and have been analyzed in terms of bit error rate (BER) performance improvements [1-4,10]. In Ref. [3], a minimum BER (MBER) detector that adaptively computes the optimal weights at the receiver was proposed. The scheme has better BER performance than the minimum mean square error (MMSE)-based algorithms presented in Ref. [4]. In Ref. [10] on the other hand, it was demonstrated that eigen-beamforming-based design can be used in an OFDMSDMA system to provide improvement in system performance compared to the conventional systems. In Ref. [11], a new adaptive beamforming algorithm that targets the direct maximization of the OFDM-SDMA channel capacity, tagged here multiple input-multiple output (MIMO) capacity-aware as the beamforming scheme, was proposed. Using the steepest-ascent gradient of the OFDM-SDMA channel capacity, the algorithm adaptively seeks the transmitting weighting vectors that maximize the capacity of the OFDM-SDMA channel for each user, and thus enhance the overall system capacity. It is shown in Ref. [11] that the capacity of the multiantenna-aided OFDM-SDMA system whose transmitting weights have been computed using the proposed algorithm is significantly higher than that of the conventional systems such as eigen-beamforming in Ref. [10].
