A receive space diversity architecture for OFDM systems using orthogonal designs

In wireless communications, multiple receive antennas can be used with orthogonal frequency division multiplexing (OFDM) to significantly improve system capacity and performance. However, the complexity of such combination can be very large because multiple discrete Fourier transform (DFT) blocks, each for one receive antenna, are required to fully take advantage of the space diversity. In this paper, based on orthogonal designs, we present a general receiver architecture for an OFDM system employing multiple receive antennas. Using the proposed architecture, the number of DFT blocks, the number of receive antennas and system performance can be effectively traded off. As a result, with a little performance degradation, one can reduce system complexity and consequently reduce the power consumption in the receivers. The proposed receivers can also be featured as a performance enhancing scheme for an existing OFDM system where performance improvement is achieved through the use of software radio and without major modifications to the existing system hardware. For example, with only one DFT block, the performance can be improved by 5.1 dB using one more antenna. Finally, it is shown that the proposed scheme exhibits superior performance to that of selection diversity especially when the channels are rich in frequency diversity.