Adaptive modulation in spectrum-sharing systems with delay constraints
ICC'09 Proceedings of the 2009 IEEE international conference on Communications
Effective capacity: a wireless link model for support of quality of service
IEEE Transactions on Wireless Communications
Quality-of-Service Driven Power and Rate Adaptation over Wireless Links
IEEE Transactions on Wireless Communications
Capacity of fading channels with channel side information
IEEE Transactions on Information Theory
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The spectrum of licensees can be shared by some secondary users in cognitive radio systems. However, the secondary transmitters are limited by an interference threshold constraint which is imposed by the primary receivers in order to ensure primary users' reliable communication. In this paper, we assume that a number of secondary transmitters are trying to transmit their data to some secondary receivers in the presence of primary transmitters and receivers and, therefore, their inflicted interference at the primary receivers should be less than a specific threshold. We consider the delay quality of service and use the idea of effective capacity to guarantee a desired delay quality of service for every secondary link. By maximizing the sum of effective capacities of the secondary links we propose adaptive modulation schemes to support the desired quality of service. Two different optimal (continuous) and suboptimal (discrete) schemes are proposed and the rate and power allocation is obtained for each scheme. The performance of these two schemes is also compared.