Modeling the 802.11 distributed coordination function in nonsaturated heterogeneous conditions
IEEE/ACM Transactions on Networking (TON)
Efficient Discovery of Spectrum Opportunities with MAC-Layer Sensing in Cognitive Radio Networks
IEEE Transactions on Mobile Computing
VoIP capacity analysis in cognitive radio system
IEEE Communications Letters
Optimal Transmission Strategies for Dynamic Spectrum Access in Cognitive Radio Networks
IEEE Transactions on Mobile Computing
Voice service support over cognitive radio networks
ICC'09 Proceedings of the 2009 IEEE international conference on Communications
Optimal channel sensing in wireless communication networks with cognitive radio
ICC'09 Proceedings of the 2009 IEEE international conference on Communications
Performance analysis of modified IEEE 802.11-based cognitive radio networks
IEEE Communications Letters
Sensing-Throughput Tradeoff for Cognitive Radio Networks
IEEE Transactions on Wireless Communications
Cognitive radio: brain-empowered wireless communications
IEEE Journal on Selected Areas in Communications
Cognitive Medium Access: Constraining Interference Based on Experimental Models
IEEE Journal on Selected Areas in Communications
IEEE Journal on Selected Areas in Communications
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We investigate a distributed contention-based spectrum access scheme in cognitive radio networks where ON/OFF periods of the channel by primary users follow discrete phase (PH) type distributions. The main motivation for ON/OFF having PH distributions is that the channel activity has a more general behavior depending on the primary users' traffic. In the past most other researchers assumed that ON/OFF periods of a channel follow a geometric distribution for the purpose of mathematical tractability even though this assumption is restrictive. We propose a distributed medium access control (MAC) scheme for the secondary users (SUs) which is characterized by a constant contention window size and a method to decide whether for each SU to participate in competition or not depending on the queueing delay of a head-of-line (HoL) packet. In order to investigate the performance of our proposed MAC protocol, we construct a two-dimensional Markov chain which incorporates both the proposed MAC scheme and the general channel activity. The resulting one-step transition probability matrix of the Markov chain has a very special structure. With the help of the censored Markov chain method, we provide a computationally efficient method to obtain the stationary distribution of the Markov chain. We then obtain the system capacity, which is defined as the maximum number of SUs that can be accommodated with a quality of service (QoS) guarantee on the packet dropping probability and the packet delay. Numerical examples show that the system capacity considerably depends on the distributions of ON/OFF periods and our proposed MAC scheme achieves a higher capacity than the existing one.