中文摘要：

认知无线电用户节点能够感知自身周围的无线环境,并且能使用授权用户未占用的无线频谱资源。由于认知用户可用频谱机会的动态特性,认知无线电网络中的组播是一个具有挑战性的问题。目前,研究者们已经提出了多种在认知无线电网络中进行有效组播的方案,包括基于优化理论,网络编码,强化学习的方案等。本文陈述了认知无线电网络组播路由面临的挑战,并对已有的无线电网络中的组播协议进行了全面的综述,最后给出了未来的研究方向。

英文摘要：

In cognitive radio networks,the secondary users equipped with cognitive radio can sense the wireless environment itself and access the＂spectrum hole＂unoccupied by the primary user. Multicasting in cognitive radio networks is a challenging problem due to the dynamic nature of spectrum opportunities available to the secondary users. Various approaches,including those based on optimization theory,network coding,reinforcement learning,have been proposed for performing efficient multicast in cognitive radio networks. This paper provides the challenges of multicasting in CRNs,provides a comprehensive survey of protocols that have been proposed for multicasting in cognitive radio networks,and finally gives future research directions.