A study on Non-contiguous Carrier Interferometry code for Cognitive Radio

Abstract

Non-contiguous Carrier Interferometry (NC-CI) signature waveforms have been proposed for Dynamic Spectrum Access (DSA) and Cognitive Radio (CR) system in the literature. Walsh-Hadamard (WH) codes cannot ensure orthogonality for non-contiguous carrier allocation, when the number of noncontiguous carrier is not a multiple of 4. In literature, NC-CI and binary orthogonal codes of any code length are proposed for non-contiguous spectrum allocation. In this paper the crosscorrelation properties of NC-CI signature waveforms for noncontiguous CI orthogonal frequency division multiplexing (NC-CI/OFDM) and NC-CI multicarrier code division multiple access (NC-CI/MC-CDMA) have been evaluated through simulation and analysis over AWGN channel. Time domain NC-CI waveforms have also been examined for non-contiguous allocation. Crosscorrelation analysis and time domain waveforms show that NC-CI codes maintain orthogonality over non-contiguous subcarrier allocation in single user and multiuser environments. For WH code, it has been shown that orthogonality can be maintained with a loss of data rate.