【作者】 史晶晶；

【导师】 杨克虎； 葛建华；

【作者基本信息】 西安电子科技大学 ， 通信与信息系统， 2013， 博士

【摘要】 无线通信系统中，信道的衰落是影响传输可靠性和有效性的主要因素。协作中继技术能抵抗无线信道中多径衰落的影响，在提高无线通信系统的覆盖范围，可靠性和有效性等方面具有巨大的潜力，成为无线通信领域的重要方向之一。然而，由于实际中继通信系统的半双工限制，传统的单向中继系统造成了频谱效率的损失。近年来，一种被称为双向中继系统的新技术应运而生，受到了广泛的研究。该技术可以提高系统吞吐量，弥补传统单向中继系统频谱效率低下的缺点。目前，双向中继技术已成为无线通信领域的研究热点之一。本论文主要以双向放大转发（AF，amplify-and-forward）中继系统为研究对象，设计低实现复杂度的新协作方案并进行性能分析。本论文的主要贡献总结如下：1.传输对称业务的双向AF中继系统的中继选择方案针对传输对称业务的双向AF多中继通信系统，提出了基于分布式时钟技术的中继选择方案，该方案具有较低的复杂度。此外，研究了Rayleigh衰落中该中继选择方案的中断性能，得到了中断概率下界的积分表达式和闭合表达式。通过Rayleigh衰落中的性能仿真比较发现，所推导的下界理论结果和仿真值之间的信噪比差距小于0.5分贝，而且该方案与现有的中断概率最优的中继选择方案相比，中断性能差距很小。因而该方案兼具良好的中断概率性能和低的实现复杂度，可以广泛的应用于实际系统中。2.传输非对称业务的双向AF中继系统中的中继选择方案针对传输非对称业务的双向AF多中继系统，提出了基于分布式时钟技术的中继选择方案，该方案具有较低的复杂度。此外，推导了Nakagami-m衰落中该方案的中断概率下界的积分表达式和闭合表达式。通过Nakagami-m衰落中的性能仿真比较发现，所推导的下界理论结果和准确值基本吻合，而且该方案与现有的中断概率最优的中继选择方案性能差距很小,具有良好的中断概率性能。3.传输非对称业务的双向AF中继通信系统性能分析针对传输非对称业务的双向AF多中继通信系统，提出了基于不等式等价变形的中断概率分析方法。该方法可以根据信道增益的累积分布函数直接计算出系统中断概率，具有很低的数学复杂度。而且该方法适用于各种无线信道，具有广泛的应用。根据该方法推导了Rayleigh衰落、Nakagami-m衰落中，传输非对称业务的单中继、多中继和多用户双向AF协作通信系统的闭合形式中断概率。通过性能仿真比较发现，使用该方法得到的理论结果在中高信噪比区域与仿真值非常吻合。4.认知频谱共享双向AF中继系统的性能分析针对认知频谱共享双向AF中继通信系统，推导了Rayleigh衰落中，认知频谱共享双向AF中继通信系统的中断概率和误码率的近似闭合表达式。计算机仿真结果表明在所有信噪比区域的理论分析所得的闭合形式与中断概率准确值之间完全吻合。此外，文中采用的推导方法还适用于其它无线衰落信道，可以广泛的应用于实际系统的性能估计。更多还原

【Abstract】 The channel fading is one of the main factors which affect reliability and validityin wireless communication systems. Cooperative relay technology can resist the impactof multi-path fading to improve the coverage, reliability and validity, and has become animportant research field of wireless communications. However, the half-duplexlimitation of relay causes the loss of spectral efficiency in traditional one-way relayingsystems. In recent years, two-way relaying technique has emerged and been extensivelystudied. The two-way relaying can improve the throughput and make up the spectruminefficiency of the traditional one-way relaying system. Currently, the two-way relayingtechnology has become one of the hot research areas in wireless communications. Inthis thesis, focusing on two-way amplify-and-forward (AF) relaying system, we designnovel low-implementation complexity relay selection schemes and investigate thesystem performance. The main contributions of this paper are summarized as follows:1. The relay selection scheme in symmetric two-way AF relaying systemsIn symmetric two-way multiple AF relaying systems, a relay selection schemebased on distributed time technology is proposed. The scheme has lowerimplementation complexity. In addition, the outage performance of the scheme isinvestigated in Rayleigh fading, and the integral and closed-form expressions of thelower bound are obtained. Simulations demonstrate that the signal-to-noise ratio (SNR)gap between the lower bound and the exact value is less than0.5dB. Moreover, theperformance gap between the proposed scheme and the existing outage-optimal relayselection scheme is very small. Thus the proposed scheme has both good outageperformance and lower complexity, and can be widely applied in practical systems.2. The relay selection scheme in asymmetric two-way AF relaying systemsIn asymmetric two-way multiple AF relaying systems, a relay selection schemebased on distributed time technology is proposed. The scheme has lowerimplementation complexity. In addition, the integral and closed-form expressions of thelower bound for the outage probability in Nakagami-m fading are derived. Simulationsdemonstrate that the obtained theoretical results are very consistent with the exactvalues in all SNR regions. Moreover, the performance gap between the proposedscheme and the existing outage-optimal relay selection scheme is very small. Thus theproposed scheme has good outage performance.3. The performance analysis of asymmetric two-way AF relaying systemsIn asymmetric two-way AF relaying systems, we propose an outage analysis method based on inequality equivalence deformation. Using the method, one can readilyevaluate the outage probability based on the cumulative distribution function of thechannel gain, requiring very low mathematical complexity. Moreover, the proposedmethod is applicable to a variety of wireless channels and has wide applications.According to the method, the closed-form expressions of the outage probability ofasymmetric single relaying, multiple relaying and multi-user two-way AF cooperationcommunication systems are derived in Rayleigh and Nakagami-m fadings, respectively.Simulations indicate that the obtained theoretical results are very consistent with theexact values in middle and high SNR regions.4. The performance analysis of cognitive two-way AF relaying with underlayspectrum sharingFocusing on cognitive two-way AF relaying with underlay spectrum sharing, theoutage and bit error probabilities are derived in Rayleigh fading, respectively.Simulations indicate that the obtained theoretical results coincide well with the exactvalues. Moreover, the deducing method can easily be extended to evaluate the systemperformance over other fading channels.更多还原