Differential MIMO Spatial Multiplexing Employing PADM Based on Channel Prediction for Fast Time-Varying Channels

Abstract

This paper proposes a demodulation scheme based on channel prediction for differential multiple-input multipleoutput (MIMO) spatial multiplexing employing per-transmit antenna differential mapping (PADM). As PADM is one of the differential space-time trellis codings (DSTTCs), it requires per-survivor processing (PSP) based on the Viterbi algorithm (VA) for its demodulation. Therefore, PADM has excellent tracking performance on fast time-varying channels. However, aiming at higher frequency efficiency, PADM for a higher modulation index suffers from the following two disadvantages: (1) poor receiver sensitivity; (2) high computational complexity. In order to solve the items (1) and (2), this paper employs a spatial multiplexing structure and a state reduction algorithm for the VA, i.e., decision-feedback sequence estimation (DFSE), respectively. Finally, for a frequency efficiency of 4bps/Hz with two receive antennas, computer simulation results confirm that the proposed scheme has excellent bit error rate (BER) performance on fast time-varying channels in the case of the maximum Doppler frequency normalized by a symbol rate of 4%.