A low-complexity adaptive multi-beam space-time receiver for CCI/ISI cancellation over frequency selective multipath channels

A space-time (ST) receiver is proposed for combating the cochannel interference (CCI) and intersymbol interference (ISI) in a frequency-selective multipath environment. The scheme involves two stages. First, a set of adaptive beamformers pointed at a prescribed angular sector in space is constructed on an oversampled antenna array, each providing effective suppression of CCI and reception of desired signals. Second, a fractionally-spaced decision feedback equalizer (DFE) follows to eliminate the ISI left in beamformer outputs. In particular, both the beamformers and DFE can be realized in the form of a generalized sidelobe canceller (GSC) with the aid of channel estimation, and partial adaptivity is incorporated for reduced complexity processing and improved convergence. The proposed ST receiver can be employed as a multi-beam smart antenna system which is suitable for cellular communications. Computer simulations demonstrate that it can achieve nearly the same performance as the optimal ST minimum mean square error (MMSE) DFE with a much lower implementation complexity.