In cognitive radio network (CRN), the utilization of wireless spectrum can be dramatically improved with the secondary user (SU) opportunistically access the licensed channels. With the help of spectrum sensing technology, the SU can dynamically access a large number of spectrum holes. However, how to allocate the spectrum holes between SUs becomes a thorny problem. The utilization of proper allocation scheme not only reduces the transmission delay of SUs, but also increases the throughput of the system. In this paper, we focus on queuing theory based spectrum allocation schemes in CRN, and discuss two useful queue models. At last, we propose a novel spectrum allocation scheme based on M/M/c, and present some new ideas.
