Trellis-coded-modulation-OFDMA for spectrum sharing in cognitive environment

In this paper, we consider an underlay spectrum sharing system and propose utilizing discrete rate Trellis Coded Modulation Orthogonal Frequency Division Multiple Access (TCM-OFDMA) technique in the secondary system. Downlink radio resource allocation schemes are then proposed for such system. Simulation results indicate that using the proposed scheme, we can significantly increase the sum rate compared to conventional uncoded OFDMA schemes with only a moderate increase in system complexity. It is also shown that in cases where the secondary network is unable to achieve higher rates by increasing the total power and/or interference threshold, utilizing TCM-OFDMA acts as a smart alternative.