Proof of Optimality of Ordered Subcarrier Pairing in Amplify-and-Forward OFDM Relay Systems without Diversity
Qing Yi Quan · Applied Mechanics and Materials · 2013
Amplify-and-forward (AF) orthogonal frequency division multiplexing (OFDM) relay systems without diversity are studied, with emphasizing on the subcarrier pairing at the relay node. Using the subcarrier pairing based on the signal-to-noise power ratios (SNRs) of subcarriers, it is proven that the ordered subcarrier pairing (OSP), according to normalized channel gains of the subcarriers of OFDM at two hops, is optimal in terms of system capacity, without any assumption for SNRs of subcarriers and types of power constraints. The proof about the optimality of OSP shows that in this kind of relay systems, the subcarrier pairing and power allocation are completely decoupled.