Non-coherent detection for cooperative OFDM-based system over time-varying fading channels

In this paper, we investigate a non-coherent detection recursive scheme for a multi-relay cooperative orthogonal frequency division multiplexing (C-OFDM) wireless system. We consider a distributed space-time block code (STBC) system over time-varying fading channels, in which source-relay, relay-destination, and source-destination links experience different Doppler spreads. The cooperative diversity scheme is based on the amplify-and-forward (AaF) protocol and the decoding algorithm is derived based on the generalized maximum likelihood sequence estimation (GMLSE). We show that our proposed decoder allows recursive implementation, that does not require any channel state information (CSI). Simulation results demonstrate that the recursive decoder achieves sufficient results even under quasi-static fading assumption. The bit error rate (BER) performance of the proposed scheme over time-varying channel, exhibits near quasi-static channel performance at low to medium signal-to-noise ratio (SNR). Using the assistance of 5 relays and under particular assumptions, the gain advantage is almost 5 dB.