Performance Analysis of Dual-Hop OFDM Relay Systems with Subcarrier Mapping

In multihop OFDM relay systems the end-to-end average capacity can be increased by incorporating subcarrier mapping (SCM) at the relay nodes. In this paper, we propose an exact analytical technique of evaluating the average capacity of a dual-hop OFDM relay system with SCM in a Rayleigh fading channel. Closed-form expressions are derived for the probability density function of the end-to-end SNR of mapped subcarrier pairs. Comparison with simulation results confirms the accuracy of the proposed analytical technique. Also, the results show that an average capacity increase of the order of 10%-30% can be achieved using SCM in the low SNR regime. Moreover, the achievable percentage capacity increase with SCM is more when the average transmit power of the relay is less than that of the source.