Dual-Hop Non-regenerative OFDM Relay Systems with Chunk-Based Power Allocation

In this paper, we propose dual-hop non-regenerative Orthogonal Frequency Division Multiplexing (OFDM) relay systems without signal buffering and processing delay due to Fast Fourier Transform (FFT) and Inverse FFT (IFFT) at the Relay Node (RN). One scheme uses per subcarrier Power Allocation (PA) at Source Node (SN) and per chunk PA at RN to improve the achievable rate. Another scheme employs per chunk PA at both SN and RN. Numerical results in mobile communication environments show that both schemes improve the achievable rates compared to conventional simple amplify-and-forward relay systems with per subcarrier PA at RN. In particular, the latter scheme can obtain almost the same or slightly higher achievable rates by selecting an appropriate chunk size in severe frequency selective channel and by setting any chunk size in highly frequency-correlated channels. Therefore, chunk-based PA at both SN and RN can be found a beneficial PA for dual-hop OFDM relay systems in terms of competitive achievable rates and relatively small amount of required channel information to calculate allocated power.