Distributed Spectral Access Schemes for Cognitive Radio Networks

In this paper, we study the distributed spectral access technique for multi-band interference channels over cognitive radio networks (CRNs). We propose some novel shared carrier assignment (SCA) and exclusive carrier assignment (ECA) schemes using orthogonal frequency division multiple access (OFDMA) in CRNs, and compare their performance under different system parameters. Based on SCA we propose a signal-to-interference-plus-noise ratio (SINR) threshold based iterative waterfilling (IWF) method which improves the sum rate than the original IWF method. Furthermore, we design a closed-form iterative approach to implement IWF which avoids numerical search. For ECA we propose an OFDMA splitting algorithm to achieve both proportional fairness and near-optimal throughput. Effects of various parameters (such as spectral mask, SNR, and the interference level) are illustrated by simulation results, which show that ECA is preferred to SCA in the case of non-trivial interference and for medium to high SNRs.