Novel frequency domain space-time adaptive architectures for OFDM systems

Adaptive antenna arrays can be used to improve the performance of orthogonal frequency division multiplexing (OFDM) wireless communications systems. The unique structure of OFDM suggests adaptation in the frequency domain after the FFT demodulation. A number of authors have looked at adaptive weighing schemes for individual and preformed groups of subcarrier frequency bins to achieve spatial diversity and thereby improve performance in strong interference and cochannel signal scenarios. In this paper two OFDM frequency domain weighting architectures, borrowed from the radar community, will be examined that address serious channel distortion and interference conditions that can disrupt the orthogonal subband nature of OFDM and degrade performance. The new algorithms exploit the induced correlation between subcarriers under these stressing conditions and can therefore improve performance.