Distributed Space-Time Block Coded OFDM with Subcarrier Grouping

It has been shown that relaying systems can offer spatial and multipath diversity in amplify-and-forward (AF) relay-assisted transmission over frequency-selective fading channels when trellis coded modulation (TCM) is applied as an outer code. However, the price for such advantages is the high decoding complexity. To overcome this disadvantage, the technique of subcarrier grouping is applied for orthogonal frequency division multiplexing (OFDM)-based relaying systems. If there exists a strong line-of-sight path in the relay-to-destination link, it is shown that the system can achieve both maximal spatial and multipath diversity gains. When all the underlying channels are frequency-selective, simulation results indicate that the full spatial and multipath diversity gains can also be realized.