Comparative study of frequency agile data transmission schemes for cognitive radio transceivers

Abstract – In this paper, we present a compara-tive study of two frequency agile data transmission schemes employed by cognitive radio transceivers for use in dynamic spectrum access (DSA) networks. The transmission schemes under study, non-contiguous orthogonal frequency division multiplexing (NC-OFDM) and a modified form of multicarrier code division mul-tiple access (MC-CDMA), are based on conventional OFDM and MC-CDMA schemes. Besides providing a degree of error robustness while yielding large data throughputs, the schemes under study are designed to avoid interference with incumbent user transmis-sions via subcarrier deactivation, i.e., nulling, in or-der to operate within a DSA network. Although several studies comparing conventional OFDM and MC-CDMA have been conducted in the literature, and the relative performance of NC-OFDM and the variant of MC-CDMA schemes is intuitive, there has not been a quantitative performance evaluation of these schemes when used within a DSA network. The quantitative evaluation corroborates with the intu-itive assessment that NC-OFDM exhibits a greater degree of error robustness when avoiding incumbent transmissions relative to the variant of MC-CDMA.