【作者】 朱义君；

【导师】 胡捍英；

【作者基本信息】 解放军信息工程大学 ， 通信与信息系统， 2010， 博士

【摘要】 近年来,协同思想在通信领域得到了成功的运用和发展,基于中继的协作技术已成为现代移动通信和无线接入的关键技术之一,并在多种通信标准中出现。运用协同通信理论,可以获得分集增益、提高传输速率、扩展网络覆盖、节省终端功耗。可以预见,随着以宽带化、异构化、自组织化和个性化为特征的物联网兴起和发展,协同将在通信领域得到更为广泛的应用。本文结合未来移动通信中协作和中继的典型应用场景,围绕“如何提高能量效率”,“如何提高系统容量”,“如何降低中断概率”等三个关键问题展开研究。论文的主要工作和创新点如下:1、在源节点和协作节点功率总和受限,且各自峰值功率受限条件下,将非对称解码转发协作的遍历容量优化问题等效为一个极大极小问题,给出了这个极大极小问题的解。通过对节点位置、功率分配和时隙分配的联合优化,设计了中断概率的优化算法,提出了一种简化的功率参数和时隙参数分配方法。理论分析和数值仿真表明,这种简化的参数优化方法较好的逼近了联合优化方法性能,且二者相对于对称解码转发协作而言,均有明显的分集增益。2、提出了一种基于顺序统计量的协作节点选择方法,解决了单个节点功率和处理能力受限条件下的多个协作伙伴的选择问题。分析了节点选择数量与系统中断概率之间的关系表达式,设计了最佳节点数量确定算法。针对中断概率表达式复杂的问题,运用顺序统计量的分布特性,给出了中断概率的上界解析式和下界解析式。3、在低信噪比条件下,引出了中断容量比率的概念,从而建立了协作通信的功率利用率与中断容量之间的关系。提出了一种基于反馈的新型中继方案,其核心是根据节点的状态反馈,动态调整协作策略,克服了解码转发易因协作节点译码错误而浪费能量开销的缺陷。理论分析和仿真表明,新型方案达到了多点协作的中断容量比率界,有效改善了低信噪比条件下解码转发协作的中断概率和吞吐量性能。4、分析比较了不同协作方式在蜂窝网中的应用效果,研究表明,相比于多用户协作方式,多中继协作方式在改善网络容量、中断概率和能量效率等方面更有优势。在多中继协作的蜂窝通信中,网络效用最大化是一个包括中继节点选择、功率分配和业务质量配置等在内的跨层设计问题。基于这一问题的非凸特性,研究了穷举搜索注水法和机会式功率均分法,分别求得了最优解和近似解。针对穷举搜索注水法复杂度高、难以直接应用,而机会式功率均分法性能又太差的问题,提出了一种分布式执行的逐层分解凸优化方法,在求得次优解的同时,将算法复杂度降低为与用户数成线性关系。5、研究了一种增强型的放大转发中继方案,证明了采用矩阵奇异值分解时,前向信道矩阵、反向信道矩阵和转发矩阵的特征值应当满足的排列关系,给出了采用放大转发中继时基站和用户之间互信息最大的理论依据。更多还原

【Abstract】 Recently, the idea of cooperation is successfully applied and developed in the field of communication. Technology based on relay cooperation has become one of the key technologies of modern mobile communication and wireless access, and has emerged in several communication standards. By using cooperative communication theory,we can acquire more diversity gain, higher transmission rate, extended network coverage and less terminal power consumption. It could be predicted that cooperation is going to be widely applied in the field of communication along with the rise and development of the Internet of things, which has the characteristics of broadband, heterogeneity, slef-organization and individuality.Together with the typical cooperation and relay applications in the future mobile communication, this paper researches the following three key problems: how to enhance the utilization of energy, how to improve the capacity of system and how to decrease the outage probability of system. The paper’s main contents and innovation are as follows:1 When the total power and own peak power of source and cooperative nodes are limited, equate the question of optimizing asymmetry decode-and-forward cooperative ergodic capacity with the max-min question, further the solution are given. Aiming at joint optimization of nodes’relative location, power allocation and slot allocation, an optimized algorithm of outage probability is designed, and a method of simplified power and slot parameters allocation is bought forward. The theoretical analysis and numerical simulation reveal that this simplified parameters optimization method approaches the performance of joint optimization method, and both methods have distinct diversity gain relativing to symmetry decode-and-forward cooperation.2 A method of cooperative nodes selection based on order statistics is come up, which solve the problem of selecting multiple cooperative partners when the power and processing capability of single node is limited. After analyzing the relation expression between node number and outage probability of system, a decided algorithm of optimal node number is put forward and the upper and lower bound analytic expression of outage probability is worked out using the distributing characteristic of order statistics.3 The concept of outage capacity ratio is put forward in low SNR, based on which the relation of energy utilization and outage capacity in cooperative communication is founded. A new joint relay scheme based on feedback is brought forward, which adjusts the cooperative strategy dynamically based on the feedback state of nodes, and this scheme overcomes the problem that decode-and-forward is prone to cause waste of energy because of the cooperative nodes’decoding errors. The theoretical analysis and numerical simulation reveal that the new method achieves the outage capacity ratio bound of multi-node cooperation and improves the performance of decode-and-forward’s outage probability and throughput in low SNR.4 The application effect of different modes of cooperation are analyzed and compared in cellular network. The research shows that multi-relay cooperation has better performance than multi-user cooperation in aspects of network capacity, outage probability and energy efficiency. In the cellular communication of multi-relay cooperation, maximum utilization of the network is a cross-layer design problem, which contains relay selection, power allocation and quality of service configuration. Exhaustion search water-filling method and opportunistic equal power method are researched based on the non-convex characteristic of this problem, and the optimal solution and approximate solution are extracted. Aiming at the complexness of exhaustion search water-filling method and poor performance of opportunistic equal power method, a hierarchical decomposable convex optimization based on distributed execution method is proposed, which gets the suboptimal solution at the same time the algorithm complexness is reduced to linear relation of users’number.5 An enhanced amplify-and-forward relay scheme is researched, and eigenvalues’sequences of the forward channel matrix, reverse channel matrix and relay matrix are demonstrated when singular value decomposition is used, which gives the theoretical basis of maximizing the mutual information between base stations and users.更多还原