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Gains and limits of diversity techniques in cognitive radio systems

机译:认知无线电系统中分集技术的得失

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摘要

Cognitive radio (CR) is one of promising techniques to alleviate the spectrum scarcity resulting from the increasing demand for wireless services and the exclusive spectrum allocation policy. CR allows unlicensed users (secondary users) to access the under-utilized spectrum assigned to licensed users (primary users) if quality-of-service (QoS) requirements of primary users can be satisfied. However, the performance of secondary users’ communications is severely degraded by the QoS constraints imposed on the secondary users for the primary users. Diversity techniques for the secondary users help overcome the performance degradation by mitigating or exploiting the fluctuation of fading channels. We overview recent results on diversity techniques in CR and discuss fundamental limits and gains of diversity techniques inCR systems.
机译:认知无线电(CR)是缓解频谱短缺的一种有前途的技术,这种频谱稀缺是由于对无线服务的需求不断增长以及专有频谱分配策略所致。如果可以满足主要用户的服务质量(QoS)要求,CR允许非许可用户(辅助用户)访问分配给许可用户(主要用户)的未充分利用的频谱。但是,由于对主要用户施加在辅助用户上的QoS限制,使得辅助用户的通信性能严重降低。次要用户的分集技术通过减轻或利用衰落信道的波动来帮助克服性能下降。我们概述了CR中有关分集技术的最新结果,并讨论了CR系统中分集技术的基本局限性和收益。

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