In cognitive radio (CR) networks, the perceived reduction of applicationlayer quality of service (QoS), such as multimedia distortion, by secondaryusers may impede the success of CR technologies. Most previous work in CRnetworks ignores application layer QoS. In this paper we take an integrateddesign approach to jointly optimize multimedia intra refreshing rate, anapplication layer parameter, together with access strategy, and spectrumsensing for multimedia transmission in a CR system with time varying wirelesschannels. Primary network usage and channel gain are modeled as a finite stateMarkov process. With channel sensing and channel state information errors, thesystem state cannot be directly observed. We formulate the QoS optimizationproblem as a partially observable Markov decision process (POMDP). A lowcomplexity dynamic programming framework is presented to obtain the optimalpolicy. Simulation results show the effectiveness of the proposed scheme.
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