On the Performance of MIMO Receive Beamforming in Frequency-Selective Channels

Linear transceivers prove efficiency and sometimes optimality under certain constraints. It is known that receive beamforming (matched filter) is diversity optimal in the case of SIMO channel whereas the MMSE MIMO receiver is diversity optimal for only a small set of spectral efficiency R b/s/Hz for an M × N MIMO channel. In this paper we analyze the matched filter MIMO receiver over a frequency selective channel under cyclic-prefix transmission. It is shown that for a frequency selective channel with ν+1 taps (where ν is the channel memory) the matched filter has a rate-dependent diversity that switches between (ν + 2) modes (with minimum of zero and a maximum of MN(ν + 1)) depending on the value of the operating R.