Research Of Spectrum Sharing In Cognitive Radio Networks

In cognitive radio networks, secondary users are allowed to transmit in an opportunistic way in authorized spectrum when the spectrum is idle, which makes it reality that primary users share spectrum with secondary users. So the current problem of the shortage of spectrum could be solved. Spectrum sharing is the most important technology of cognitive radio.It could be divided into two steps, spectrum allocation and spectrum access.Spectrum allocation takes charge of deciding the bandwidth of users, while spectrum access cares about collision avoidance of multi-users access.As one of the most important radio resource management technology in wireless communication systems, packet scheduling could content to different QoS requirement of services and provide ordered multi-users access for the systems. By designing of good scheduling algorithms, packet scheduling could not only guarantee system fairness, but also enhance system throughput. So it could achieve the objective of utilizing spectrum efficiently, which is the same as spectrum sharing in cognitive radio networks.In this paper, the situation of spectrum sharing among secondary users with non-real-time services in a centralized cognitive radio networks is considered. QoS of non-real-time services mainly include low requirements of time delay and high requirements of rate and reliability. According to such QoS characteristics of non-real-time services, an efficient spectrum sharing algorithm is designed in our study. The algorithm arranges secondary users to access spectrum with an improved scheduling scheme, and allocates spectrum with adaptive transmission rate according to the wireless channel quality of the access users. Simulation shows that this algorithm could effectively improve the average users'profile and enhance the system spectrum efficiency.