Distributed Coherent Receivers for Amplify-And-Forward Cooperative Systems without Instantaneous Channel Amplitude Information

Distributed coherent receivers, that require no instantaneous channel amplitude information, are developed for amplify-and-forward (AF) cooperative diversity systems. According to the availability of phase information at the relays and the destination, repetition-based and spectral-efficient distributed equal gain combining (DEGC) schemes are obtained. In the former scheme, relays transmit over separate orthogonal subchannels, whereas in the latter scheme all relays transmit simultaneously. An expression for evaluation of the symbol error probability is derived and it is demonstrated that these schemes achieve full spatial diversity. It is also shown that the spectralefficient DEGC scheme outperforms the repetition-based DEGC scheme especially by increasing the number of relays.