Spectrum Sharing with Adaptive Power Management for Throughput Enhancement in Dynamic Access Networks

Cognitive radios (CRs) are emerging as a promising technology to enhance spectrum utilization through opportunistic on-demand access. Many spectrum access/sharing algorithms for CR networks (CRNs) have been designed assuming multiple transceivers per CR user. However, in practice, such an assumption may not hold due to hardware cost. In this paper, we address the problem of assigning channels to CR transmissions, assuming one transceiver per CR. The primary goal of our design is to maximize the number of simultaneous CR transmissions with respect to both spectrum assignment and transmission power. Energy conservation is also treated, but as a secondary objective. The problem is posed as a utility maximization problem subject to target rate demand and interference constraints. Because the optimization problem is known to be NP-hard, we present centralized and distributed solutions that leverage the unique capabilities of CRs and the peculiar characteristics of their operating environment. We first consider a single-hop CRN, for which we introduce a CSMA-like MAC protocol that uses an access window (AW) for exchanging control information prior to data transmissions. This approach allows us to realize a centralized algorithm in a distributed manner. We then develop a distributed MAC protocol (WFC-MAC) for a multi-hop CRN. WFC-MAC improves the CRN throughput through cooperative channel assignment. It incurs low processing overhead. We compare the performance of our schemes with CSMA/CA variants. The results show that our schemes significantly decrease the blocking rate of CR transmissions, and hence improves the network throughput.