A Study on Spectrum Mapping for Amplify-and-Forward Relay Links under Frequency Selective Fading Channels

Aiming at improving end-to-end channel capacity of an amplify-and-forward relay system under frequency se- lective fading channels, this paper proposes a spectrum mapping technique, in which a predetermined part of spectrum is intentionally discarded and the non-discarded spectrum is mapped onto frequencies with high channel gains and transmitted to the destination node , while order of the non-discarded spectrum is kept unchanged so that de-mapping can be conducted in a blind fashion. Since the proposed scheme intentionally discards the predetermined part of spectrum and transmits the non-discarded spectrum over frequencies with high channel gains in every link, frequency selection diversity gain can be ob- tained and the end-to-end channel capacity of the relay system can be enhanced. Distortion caused by discarding of a part of spectrum is compensated for with the aid of nonlinear equalization or channel decoding techniques. Furthermore, because information needed by coordination signaling is solely indices of deployed frequencies in each link, overhead can be sub- stantially suppressed. Numerical results reveal that the proposed spectrum mapping achieves almost the same capacity with