无公共控制信道的认知无线电Ad Hoc网络频谱切换研究
On the Spectrum Handoff for Cognitive Radio Ad Hoc Networks without Common Control Channel
摘要：
认知无线电（CR）技术是一种很有前途的解决方案，以提高频谱利用率，使非授权用户利用频谱的机会主义的方式。由于非授权用户是授权频谱的临时访问者，当授权用户收回频谱时，他们被要求腾出频谱。由于授权用户出现的随机性，对授权和非授权通信的中断通常难以防止。在本章中，提出了一个积极的频谱切换框架CR ad hoc网络，以解决这些问题。在所提出的框架中，信道切换策略和主动频谱切换协议，提出了让未授权用户腾出信道之前，授权用户利用它，以避免不必要的干扰。针对非授权用户的网络协调方案也被纳入到频谱切换协议的设计中，以实现信道会合。此外，提出了一种分布式信道选择方案，以消除非授权用户之间的冲突。在我们提出的框架中，未授权用户相互协调，而不使用公共控制信道。我们比较了我们提出的主动频谱切换协议与反应频谱切换协议，在该协议下，未授权用户切换信道发生冲突后，与授权传输。仿真结果表明，我们的主动频谱切换优于反应式频谱切换方法在更高的吞吐量和更少的冲突授权用户。此外，我们提出了一种新的三维离散时间马尔可夫链来描述反应性频谱中断的过程，并分析了非授权用户的性能。我们验证了我们提出的马尔可夫模型对模拟和频谱切换场景中的其他参数的兴趣得到的数值结果。
英文摘要：
Cognitive radio (CR) technology is a promising solution to enhance the spectrum utilization by enabling unlicensed users to exploit the spectrum in an opportunistic manner. Since unlicensed users are temporary visitors to the licensed spectrum, they are required to vacate the spectrum when a licensed user reclaims it. Due to the randomness of the appearance of licensed users, disruptions to both licensed and unlicensed communications are often difficult to prevent. In this chapter, a proactive spectrum handoff framework for CR ad hoc networks is proposed to address these concerns. In the proposed framework, channel switching policies and a proactive spectrum handoff protocol are proposed to let unlicensed users vacate a channel before a licensed user utilizes it to avoid unwanted interference. Network coordination schemes for unlicensed users are also incorporated into the spectrum handoff protocol design to realize channel rendezvous. Moreover, a distributed channel selection scheme to eliminate collisions among unlicensed users is proposed. In our proposed framework, unlicensed users coordinate with each other without using a common control channel. We compare our proposed proactive spectrum handoff protocol with a reactive spectrum handoff protocol, under which unlicensed users switch channels after collisions with licensed transmissions occur. Simulation results show that our proactive spectrum handoff outperforms the reactive spectrum handoff approach in terms of higher throughput and fewer collisions to licensed users. In addition, we propose a novel three dimensional discrete-time Markov chain to characterize the process of reactive spectrum handoffs and analyze the performance of unlicensed users. We validate the numerical results obtained from our proposed Markov model against simulation and investigate other parameters of interest in the spectrum handoff scenario.
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