Antenna Selection for Noncoherent Space–Time–Frequency-Coded OFDM Systems

This paper studies receive antenna selection (AS) for multiantenna systems that operate over frequency-selective channels, where the channel state information (CSI) is known neither at the transmitter nor at the receiver. We consider AS for noncoherent space-time-frequency (STF)-coded orthogonal frequency-division multiplexing (OFDM) systems that employ unitary signals. An OFDM receiver with a single radio-frequency chain is employed, and the selection is based on the received signal power, where the receive antenna with the largest received signal power averaged over all subcarriers is chosen. Theoretical analysis and simulations show that by using AS, the maximum spatial and multipath diversity can still be obtained without CSI at the receiver, which is the same as the full-complexity multiantenna OFDM systems. We simplify code design and decoding using subcarrier grouping, which enables us to apply existing full-diversity codes for noncoherent and differential STF-OFDM systems to each group, to obtain maximum spatial and multipath diversity when AS is used. We also present a low-complexity suboptimal decoder that can easily be implemented in practice.