【作者】 唐菁敏；

【导师】 乐光新；

【作者基本信息】 北京邮电大学 ， 通信与信息系统， 2011， 博士

【摘要】 随着无线通信业务的迅猛发展,无线频谱资源的日益紧张与当前固定频谱分配制度下频谱利用率低下之间的矛盾日趋尖锐。感知无线电技术由于能够在不对授权用户造成干扰的前提下动态地利用暂时空闲的无线频谱资源,可有效提升频谱利用率,实现开放式频谱共享而得到广泛关注。此外,协同通信技术集合了分集和中继传输技术的优势,能够使用户在复杂环境下获得空间分集增益,有效提升系统性能。基于此,论文主要研究感知无线电技术与协同通信技术相结合对提升频谱利用率和改善系统性能的贡献。论文的工作主要包括以下几个方面：1、针对交叉共享方式(OS)下的两跳协作感知网络,研究了多个感知用户的协作感测策略,推导了在放大转发(AF)传输协议下感知系统的中断概率表达式,并提出了一种联合优化方案：在保证-定频谱感测性能指标的前提下,通过联合优化感测门限、感测时长等参数,从而最小化感知系统的中断概率,有效改善感知网络传输的可靠性。2、针对重叠共享(US)方式下的两跳协作感知网络进行了性能分析,推导了基于放大转发中继选择(AFRS)和解码转发中继选择(DFRS)协议的两跳感知网络中断概率近似表达式及分集度。在此基础上,提出了一种混合中继选择协议(HPRS),并推导了HPRS的中断概率近似表达式及分集度。和AFRS和DFRS协议相比,HPRS可以进一步改善感知网络中断性能,提升系统的可靠性。3、针对交叉共享方式下的多跳DF协作分集感知网络进行了性能分析,推导了在高信噪比条件下的中断概率近似表达式,并提出一种感测时长优化方案：通过对感测时长的优化,可最小化感知系统的中断概率,从而提升感知系统传输的可靠性。4、针对重叠共享方式下的多跳DF协作分集感知网络进行了性能分析,并推导了在高信噪比条件下感知网络的中断概率近似表达式及其分集度。由于DF不能获得空间分集增益,提出改进的选择性解码转发(SDF)算法,并推导了SDF感知网络中断概率表达式及分集度。与DF相比,SDF降低了感知网络中断概率,且能获得空间满分集增益。更多还原

【Abstract】 With the rapid development of wireless communications services, the contradiction between the spectrum resource scarcity and inefficient utilization under the current fixed spectrum allocation policy is becoming increasingly acute. Great attention has been paid to cognitive radio technology, which can dynamically reuse idle spectrum resources on the premise of the interference to the primary users avoided or limited to an acceptable level, improve spectrum efficiency and achieve open spectrum sharing policy. Besides, the cooperative communication technique can get spatial diversity gain and improve system performance effectively by converging the diversity and cooperative relay techniques. For this purpose, the dissertation focuses on the contribution of improving spectrum efficiency and system performance by combining cognitive radio and cooperative communication technologies. The major work is summarized as follows:1、By investigating the two-hop cooperative cognitive network in overlay sharing(OS) mode, a cooperative detection strategy for multiple cognitive user system is considered and outage probability formulation on the Amplify-and-Forward(AF) protocol is deduced. By optimizing the parameters such as sensing time and threshold, an optimization scheme has been proposed, which is proven to minimize the outage probability and improve transmission reliability of cognitive network on the premise of guarantee fixed detection performance.2、By analyzing the two-hop cooperative cognitive network in underlay sharing(US) mode, an approximate outage probability formulation and diversity order have been derived for amplify-and-forward with relay selection(AFRS) and decode-and-forward with relay selection(DFRS) protocol. On this condition, hybrid protocol with relay selection(HPRS) is proposed. Meanwhile, the approximate outage probability formulation and diversity order for HPRS were deduced. Compared with AFRS and DFRS protocol, the HPRS can achieve better outage performance and higher reliability.3、By analyzing the multi-hop cooperative cognitive diversity network in OS mode, an approximate outage probability formulation has been derived for decode-and-forward(DF) protocol in high signal-to-noise ratio. An optimal scheme is proposed, which can improve outage performance and transmission reliability of multi-hop cognitive system by optimizing sensing time.4、By analyzing the multi-hop cooperative cognitive diversity network in US mode, an approximate outage probability formulation and diversity order has been derived for DF protocol in high signal-to-noise ratio. As DF protocol cannot achieve space diversity gain, modified multi-hop selective decode-and-forward(SDF) protocol is proposed. An approximate outage probability formulation and diversity order are deduced for SDF protocol in high signal-to-noise ratio. Contrasted with DF protocol, SDF protocol can decrease outage probability and achieve the full space diversity.更多还原