Channel Mean Forwarded Regenerative Cooperative Demodulation in OFDM Systems
Jiqun Qi, Lei Cao · 2008
In this paper, we propose a channel mean forwarded (CMF) relay scheme with gammamin-MRC demodulator at the destination for cooperative OFDM systems. For regenerative cooperative communications, i.e., decode-and-forward (DF) scheme, using the classical MRC demodulator, may not give satisfactory system performance since the channel quality of the source-to-relay (S-R) link is not exploited at the destination. On the other hand, near-optimal lambda-MRC and cooperative-MRC (C-MRC) which are proposed to achieve full diversity, require the perfect instantaneous channel state information (CSI) of the S-R link being available at the destination. In our CMF scheme, the S-R channel is based on the classical first-order auto-regression AR(1) models, where the channel mean can be tracked. Based on the forwarded CSI of the S-R link, the destination can use gammamin-MRC demodulator, which combines signals coming from the source-to-relay-to-destination (S-R-D) link and the source- to-destination (S-D) link by appropriately predicted weights to achieve the full diversity. Simulations show that the performance of this CMF scheme is better than the classical MRC scheme. In slow-fading scenarios, the performance of this CMF scheme can approach the one that the perfect square of the channel norm of the S-R link is available at the destination. Even in fast-fading scenarios, the CMF scheme can also achieve better performance than the classical MRC scheme. In addition, we provide the performance of the direct one-hop scheme for fair comparison as well.