A QoS-guaranteed Adaptive Cooperation Scheme In Cognitive Radio Network

The increasing number and variety of wireless devices is asking for more wireless spectrum and higher quality of service(QoS),while the amount of spectrum available for these devices remains limited.Several measurements have shown that in a certain geographic area,the licensed spectrum bands are not efficiently used,and cognitive radio technique has been proposed to improve the utilization of the limited spectrum resources by exploiting the existence of spectrum holes.Another proposal is the cooperation technique,which has been widely used in cognitive radio network.Due to different goals,cooperation in different layers can bring different benefits.Most works about cooperation focus on the cooperation relay selection,while the demand mechanism of cooperation receives little attention.Too little cooperation may not help rech the original target and too much cooperation may hurt the performance of the network because of overload.Recent works begin to study this problem.In this paper we consider the network layer cooperation,whereby primary users select some secondary users to relay packets,in return for more favourable spectrum access rules for secondary users.Under this cooperation scheme,we investigate how the cooperative decision is made can enlarge the throughput of the whole network,where a QoS(Quality of Service)-guaranteed adaptive cooperation scheme is developed.Our scheme can guarantee the QoS of primary users and update its frequency division cooperation scheme dynamically according to the status of network.Our algorithm requires knowledge of only instantaneous queue lengths at secondary nodes and the predictable end-to-end delay.Our scheme consists of three parts:1)The global level cooperation algorithm,which deals with the delay-QoS demand.2)The local level cooperation algorithm,which deals with the bandwidth-QoS demand and focuses on the cooperative relay selection.3)The adaptive cooperation algorithm,where the cooperative scheme adjusts itself with the change of environment.Main contributions of this paper can be summarized as follows.1)The proposal of QoS-guaranteed cooperation scheme.The QoS of primary nodes is guaranteed by the global and local level cooperation algorithm,especially the cooperative relay selection scheme.2)The development of the adaptive cooperation scheme.It makes our cooperation scheme robust by the adaptive cooperation algorithm.In order to prove the effects of our QoS-guaranteed adaptive cooperation scheme,we implement it on NS2 platfrom and compare it with non-cooperation scheme and SCRP algorithm.Simulation results reveal that our proposed scheme significant outperforms previous works in terms of throughput.