认知协作无线网络中的中继选择与协同资源配置理论研究
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摘要
随着社会信息化进程的快速推进,人们对以宽带、移动以及物联网等泛在应用业务为代表的移动数据业务的需求正迅猛增长,随之而来的则是对无线通信网络带宽需求的急剧增加。从上世纪80年代开始商用的第一代模拟蜂窝通信系统到正在部署的第四代移动通信系统,无线移动通信技术取得了长足的发展和进步。然而,与业务和市场应用的快速增长相比,信息与通信技术的发展仍显得相对滞后,还面临诸多困难和挑战,如安全性、可扩展性、频谱短缺、服务质量等。
无线频谱资源：随着无线通信网络的快速发展,有限的频谱资源与快速增长的频谱需求之间的矛盾日益尖锐。一方面,在现有固定频谱分配模式下,当前的频谱资源已经基本分配殆尽；另一方面,根据检测,已授权频段在时间和空间上的利用效率很不均匀,造成了宝贵的频谱资源的极大浪费。为了缓解上述矛盾,“认知无线电”(Cognitive Radio, CR)的概念于1999年被首次提出,其核心思想就是打破传统的固定频谱分配机制,允许非授权用户在不影响授权用户的前提下,灵活、动态的进行频谱接入,以提高频谱资源在时间和空间上的使用效率。
链路可靠性和网络连通性：无线信道固有的时变特性和无线电信号传输时的广播色散特性、距离衰减特性以及异构网络中的干扰开放特性,是对无线传输的可靠性以及网络连通性的严峻挑战。为应对此挑战,配备了单一收发天线的多个节点互相协作,构成虚拟多天线的用户协作分集方案(user cooperation diversity,本文称为“协作通信”)被明确提出,其基本思想是系统中的每个终端都有一个或者多个伙伴,协作伙伴之间在传输自己信息的同时有责任帮助其他伙伴传输信息。这样,每个终端在传输信息的过程中,即利用了自己又利用了协作伙伴的空间信道,从而获得一定空间分集增益。可以预见,未来的无线通信系统必将是一个多网络共存、多应用需求共存、多覆盖范围互相渗透的异构网络。以上两个方面的矛盾已经成为制约整个无线通信发展的主要因素,然而,任何单一的技术都无法独立解决无线通信发展所面临的困难和挑战。基于此,本文融合了认知无线电技术和协作中继技术,借助认知无线电技术可以有效提升频谱资源的利用率,利用协作中继技术可提升无线传输的可靠性和异构网络的网络连通性。前者从挖掘系统自由度的角度提升系统有效性,后者从提高分集增益的角度提高系统可靠性。本论文研究认知协作无线网络中的中继选择及协同资源配置理论,旨在通过理论研究为基于认知无线电和协作中继技术的未来无线通信系统设计提供理论指导,为网络性能分析与比较提供理论依据,对以中继选择和载波分配为代表的无线资源管理协议设计提供理论和算法支撑。本论文研究的场景从单用户协作中继无线网络逐步扩展到多用户认知协作无线网络,所研究的问题从中继选择算法设计到联合中继选择与信道分配算法设计。在研究方法上,本文综合运用了组合优化理论、人工智能算法、凸优化等理论和方法。本论文中所研究的问题建模之后都是0-1整数规划问题,基于分支定界算法框架和其他优化理论可以设计全局最优算法,这些算法可作为其他算法的性能参考。当全局最优算法的复杂度仍较高时,本文设计了一些启发式算法用于降低复杂度。对于变量之间无耦合关系的问题,本文主要基于遗传算法进行了算法设计(如第二章)；对变量之间互相耦合的问题,遗传算法不再适用,针对此类问题本文设计了其他的启发式算法(如第三章)。对最优算法的复杂度已经非常低的,不再设计其他算法(如第四章)。本论文的研究工作受到了国家自然科学基金重点项目“基于认知无线电的中继与协同通信研究”(编号：60832008)和国家自然科学基金项目“异构无线传感器网络中的协作多媒体通信理论研究与实现”(编号：61061122)的支持。本论文的主要创新点如下：
1.研究了协作中继无线网络中的中继选择与协同资源配置理论。首先研究了单信源-多中继-单信宿的单用户场景,中继节点采用两跳放大转发信号处理方式,以最大化信宿端的信噪比为目标函数时的多中继选择算法。针对本问题,本文基于分支定界框架,借助线性凸化放松技术,设计了具有全局最优性能的多中继选择算法；为了降低运算复杂度,本文设计了基于自适应遗传算法的多中继选择算法,该算法可以快速找到最优解。针对多信源-多两跳译码转发中继-多信宿场景下的中继选择与载波分配问题,本文将中继选择和载波分配空间进行映射变换,通过对染色体编码方案以及选择、交叉、变异等3个核心遗传运算步骤的设计,本文提出了基于遗传算法的中继选择与信道分配策略。本创新点对应论文第二章的内容和发表论文列表中的4、5和6。
2.研究了单用户认知协作无线网络中的中继选择算法。该认知协作无线网络由单个主用户对-单个次用户对-多个次用户中继组成,其中由单次用户对-多次用户中继节点组成的次用户网络工作在主用户对的收发区域内。次用户采用underlay的频谱接入方式与主用户共享频谱资源,次用户中继节点采用两跳放大转发的工作方式,在满足主用户干扰温度限制的前提下,通过中继选择,最大化次用户对之间的信道容量。当次用户信宿节点采用最大比合并方式时,该问题被建模成为一个0-1背包问题,基于贪婪策略和最优单中继选择算法,本文设计了一种混合中继选择算法,仿真结果表明该算法可以克服贪婪算法在平均选中的中继节点数少于1时的性能缺陷且总能取到最优或近似最优性能。当次用户信宿节点采用等增益合并方式时,该问题建模为一个带约束的0-1非线性非凸整数规划问题,基于非凸优化理论,本文首先设计了一个能以任意0到1之间精度要求取到全局最优值的多中继选择算法,为进一步降低复杂度,本文设计了简化算法及具有二次方复杂度的迭代算法,仿真结果表明这些次优算法可在轻微性能损失下快速完成迭代过程并取到近似最优解。本创新点对应论文第三章的内容和发表论文列表中的1、2和3。
3.研究了多用户认知协作无线网络中的中继选择与载波分配问题。本文考虑的多用户场景有多主用户对-多次用户对-多次用户中继组成,次用户网络采用underlay动态频谱接入模式,次用户中继节点采用两跳译码转发的信号处理方式,在满足主用户干扰温度限制的条件下,通过设计中继选择和载波分配算法以最大化次用户系统的信道容量和。该问题被建模成为一个带复杂约束的非凸优化问题,通过问题等价转化本文把两个二维0-1系数矩阵的联合配置问题转化为一个三维0-1系数矩阵的配置问题,且把原问题转化为0-1线性规划问题。基于分支定界框架,本文设计的算法可以通过有限的几步迭代(平均少于2.5次)求得全局最优解。仿真结果表明,该算法的性能远低于穷举法且总能取到最优值。本创新点对应论文第四章的内容和发表论文列表中的7。
As the rapid development of social informatization process, the demand on mobile data services like broadband, mobile and the Internet of Things (IoT), etc. is growing rapidly, which brings sharp increases in demand of bandwidth of wireless communica-tion networks. From the first generation (1G) of cellular communication systems in the1980s to the coming fourth generation (4G) mobile communication systems, great progresses have been made in the wireless communication technologies. However, com-paring to the rapid growth of business and market applications, the information science and communication technologies are lagging behind and facing with many difficulties and challenges, e.g., security, scalability, spectrum shortage, Quality of Service (QoS), etc.
Radio spectrum resource:With the rapid development of wireless communi-cation networks, the conflict between the limited spectrum resources and the rapidly increasing in demand for spectrum is becoming increasingly acute. On one hand, almost all of the spectrum resource has been occupied under current spectrum management policy. On the other hand, there exists great waste on the valuable spectrum resources because of the underutilization of assigned spectrum band in both time and spatial dimensions. In1999, Cognitive Radio (CR) was first proposed as the most promising technology to solve the conflict. The main idea of CR is to break the fixed spectrum management mechanisms and to allow flexible and dynamic spectrum access of the unauthorized users under the constraints that the authorized users are not affected, which improves the spectrum efficiency in both time and spatial dimensions.
Link reliability and network connectivity:The time-varying wireless chan-nel, the dispersion and distance attenuation of radio signal propagation, and the in-terferences in the heterogeneous network all challenge the wireless link reliability and network connectivity in different ways. A virtual multi-antenna scheme, known as co-operative communication, has been proposed to deal with the challenge by allowing cooperation among multiple users each equipped with only single-transceiver antenna to explore the spatial diversity.
It can be predicted that the future wireless communication system will be a het-erogeneous network consisting of different network, different application requirements and the mutual penetration of different coverage. The afore mentioned conflicts have become the main factors that restrict on the development of the wireless communica-tions, and the difficulties and challenges in wireless communications can not be solved by any single technology. As a result, this dissertation relies on the combination of the CR and cooperative relay technologies to improve the spectrum efficiency, the wireless link reliability and network connectivity. CR enhances the system efficiency from the perspective of degree of freedom (DoF), while cooperative communication enhances the system reliability from the perspective of diversity gains. Researches on relay selection and resource allocation in cognitive and cooperative wireless networks aim at provid-ing theoretical guidance for the design of future wireless communication networks and a theoretical basis for the network performance analysis. Such researches also pro-vide theoretical and algorithmic support for the design of radio resource management protocol like relay selection and subcarrier allocation. The communication scenarios considered in this dissertation vary from single-user cooperative relaying wireless net-work to multi-user cognitive and cooperative wireless network, the corresponding for-mulated problems change from relay selection algorithm design to the algorithm design of joint relay selection and subcarrier allocation. To solve these formulated nonlinear non-convex0-1integer programming problems, based on combinatorial optimization, artificial intelligence algorithms, and convex optimization theory and methods, on one hand we design the globally optimal solution algorithm that can be used for perfor-mance analysis and to provide a performance benchmark, and on the other hand, we design practical solutions with lower complexity. Research in this dissertation was sup-ported by the National Natural Science Key Foundation of China "Research on Cogni-tive and Cooperative Communications"(No.60832008) and National Natural Science Foundation of China "Theory Research and Implementation of Cooperative Multime-dia Communication in Heterogeneous Wireless Sensor Network "(No.61061122). Main contributions of the dissertation are as follows.
1. The relay selection and resource allocation strategies in cooperative relay wireless networks are studied. For a single source-multiple relay nodes-single destination network, with relay nodes working in two-hop amplify-and-forward (AF) mode, we design the multiple relay selection algorithm to maximize the received SINR at des-tination. Based on branch and bound architecture and linear relaxation technique for nonconvex items, we design global optimal multiple relay selection algorithm. Moreover, in order to decrease the computational complexity, we design an adap-tive genetic algorithm which can be verified to reach the optimal performance with lower complexity. For multiple source-multiple relay nodes-multiple destination, with relay nodes working in two-hop decode-and-forward (DF), by designing the chromosome representation, survivor selection, crossover and mutation procedures, we design genetic algorithm based relay selection and subcarrier allocation algo-rithm to maximize the sum capacity of all users. This contribution corresponds to Chapter2and paper4,5and6as listed at the end of the dissertation.
2. The relay selection algorithms in single-user cognitive and cooperative wireless net-works are studied. The cognitive network which is composed of single secondary user pair and multiple two-hop AF cognitive relays work in the transmission scope of primary users. Cognitive network works in underlay mode to share the spec-trum with primary users. We design a relay selection algorithm to maximize the secondary suers'capacity subject to the interference temperature constraint of the primary user. When maximal ratio combining (MRC) is adopted by secondary destination, the problem is formulated as a0-1knapsack problem, based on greedy scheme and best-single scheme, we propose a hybrid scheme. The simulation re-sults show that the proposed scheme can overcome the drawback of greedy scheme and get near optimal performance. When equal gain combining (EGC) is adopted, the problem is formulated as0-1nonlinear nonconvex integer programming prob-lem, we first design the optimal relay selection scheme based on branch and bound architecture. Some simplified schemes and an iterative scheme with quadratic computing complexity are then proposed to decrease the complexity with slight sacrifice of performance. This contribution corresponds to Chapter3and paper1,2and3listed at the end of the dissertation.
3. The relay selection and subcarrier allocation problem in multicarrier based mul-tiuser cognitive and cooperative wireless networks is studied. The network consists of multiple primary user pairs (each including one transmitter and one receiver), multiple secondary user pairs and multiple secondary two-hop DF relay nodes, all the secondary users share spectrum with primary users in the underlay mode. The problem is first formulated as a nonconvex problem with complicated constraints, after equivalence transformation, the two two-dimension matrices are converted to a three-dimension0-1coefficient matrix and the problem is equivalently reformu-lated as a0-1linear programming problem. Based on branch and bound procedure, the proposed relay selection and subcarrier allocation algorithm can reach optimal solution within very limited number of iteration (less than2.5times after average). Simulation results prove that this algorithm has far less computing complexity than exhaustive scheme. This contribution corresponds to Chapter4and paper7listed at the end of the dissertation.
无线频谱资源：随着无线通信网络的快速发展,有限的频谱资源与快速增长的频谱需求之间的矛盾日益尖锐。一方面,在现有固定频谱分配模式下,当前的频谱资源已经基本分配殆尽；另一方面,根据检测,已授权频段在时间和空间上的利用效率很不均匀,造成了宝贵的频谱资源的极大浪费。为了缓解上述矛盾,“认知无线电”(Cognitive Radio, CR)的概念于1999年被首次提出,其核心思想就是打破传统的固定频谱分配机制,允许非授权用户在不影响授权用户的前提下,灵活、动态的进行频谱接入,以提高频谱资源在时间和空间上的使用效率。
链路可靠性和网络连通性：无线信道固有的时变特性和无线电信号传输时的广播色散特性、距离衰减特性以及异构网络中的干扰开放特性,是对无线传输的可靠性以及网络连通性的严峻挑战。为应对此挑战,配备了单一收发天线的多个节点互相协作,构成虚拟多天线的用户协作分集方案(user cooperation diversity,本文称为“协作通信”)被明确提出,其基本思想是系统中的每个终端都有一个或者多个伙伴,协作伙伴之间在传输自己信息的同时有责任帮助其他伙伴传输信息。这样,每个终端在传输信息的过程中,即利用了自己又利用了协作伙伴的空间信道,从而获得一定空间分集增益。可以预见,未来的无线通信系统必将是一个多网络共存、多应用需求共存、多覆盖范围互相渗透的异构网络。以上两个方面的矛盾已经成为制约整个无线通信发展的主要因素,然而,任何单一的技术都无法独立解决无线通信发展所面临的困难和挑战。基于此,本文融合了认知无线电技术和协作中继技术,借助认知无线电技术可以有效提升频谱资源的利用率,利用协作中继技术可提升无线传输的可靠性和异构网络的网络连通性。前者从挖掘系统自由度的角度提升系统有效性,后者从提高分集增益的角度提高系统可靠性。本论文研究认知协作无线网络中的中继选择及协同资源配置理论,旨在通过理论研究为基于认知无线电和协作中继技术的未来无线通信系统设计提供理论指导,为网络性能分析与比较提供理论依据,对以中继选择和载波分配为代表的无线资源管理协议设计提供理论和算法支撑。本论文研究的场景从单用户协作中继无线网络逐步扩展到多用户认知协作无线网络,所研究的问题从中继选择算法设计到联合中继选择与信道分配算法设计。在研究方法上,本文综合运用了组合优化理论、人工智能算法、凸优化等理论和方法。本论文中所研究的问题建模之后都是0-1整数规划问题,基于分支定界算法框架和其他优化理论可以设计全局最优算法,这些算法可作为其他算法的性能参考。当全局最优算法的复杂度仍较高时,本文设计了一些启发式算法用于降低复杂度。对于变量之间无耦合关系的问题,本文主要基于遗传算法进行了算法设计(如第二章)；对变量之间互相耦合的问题,遗传算法不再适用,针对此类问题本文设计了其他的启发式算法(如第三章)。对最优算法的复杂度已经非常低的,不再设计其他算法(如第四章)。本论文的研究工作受到了国家自然科学基金重点项目“基于认知无线电的中继与协同通信研究”(编号：60832008)和国家自然科学基金项目“异构无线传感器网络中的协作多媒体通信理论研究与实现”(编号：61061122)的支持。本论文的主要创新点如下：
1.研究了协作中继无线网络中的中继选择与协同资源配置理论。首先研究了单信源-多中继-单信宿的单用户场景,中继节点采用两跳放大转发信号处理方式,以最大化信宿端的信噪比为目标函数时的多中继选择算法。针对本问题,本文基于分支定界框架,借助线性凸化放松技术,设计了具有全局最优性能的多中继选择算法；为了降低运算复杂度,本文设计了基于自适应遗传算法的多中继选择算法,该算法可以快速找到最优解。针对多信源-多两跳译码转发中继-多信宿场景下的中继选择与载波分配问题,本文将中继选择和载波分配空间进行映射变换,通过对染色体编码方案以及选择、交叉、变异等3个核心遗传运算步骤的设计,本文提出了基于遗传算法的中继选择与信道分配策略。本创新点对应论文第二章的内容和发表论文列表中的4、5和6。
2.研究了单用户认知协作无线网络中的中继选择算法。该认知协作无线网络由单个主用户对-单个次用户对-多个次用户中继组成,其中由单次用户对-多次用户中继节点组成的次用户网络工作在主用户对的收发区域内。次用户采用underlay的频谱接入方式与主用户共享频谱资源,次用户中继节点采用两跳放大转发的工作方式,在满足主用户干扰温度限制的前提下,通过中继选择,最大化次用户对之间的信道容量。当次用户信宿节点采用最大比合并方式时,该问题被建模成为一个0-1背包问题,基于贪婪策略和最优单中继选择算法,本文设计了一种混合中继选择算法,仿真结果表明该算法可以克服贪婪算法在平均选中的中继节点数少于1时的性能缺陷且总能取到最优或近似最优性能。当次用户信宿节点采用等增益合并方式时,该问题建模为一个带约束的0-1非线性非凸整数规划问题,基于非凸优化理论,本文首先设计了一个能以任意0到1之间精度要求取到全局最优值的多中继选择算法,为进一步降低复杂度,本文设计了简化算法及具有二次方复杂度的迭代算法,仿真结果表明这些次优算法可在轻微性能损失下快速完成迭代过程并取到近似最优解。本创新点对应论文第三章的内容和发表论文列表中的1、2和3。
3.研究了多用户认知协作无线网络中的中继选择与载波分配问题。本文考虑的多用户场景有多主用户对-多次用户对-多次用户中继组成,次用户网络采用underlay动态频谱接入模式,次用户中继节点采用两跳译码转发的信号处理方式,在满足主用户干扰温度限制的条件下,通过设计中继选择和载波分配算法以最大化次用户系统的信道容量和。该问题被建模成为一个带复杂约束的非凸优化问题,通过问题等价转化本文把两个二维0-1系数矩阵的联合配置问题转化为一个三维0-1系数矩阵的配置问题,且把原问题转化为0-1线性规划问题。基于分支定界框架,本文设计的算法可以通过有限的几步迭代(平均少于2.5次)求得全局最优解。仿真结果表明,该算法的性能远低于穷举法且总能取到最优值。本创新点对应论文第四章的内容和发表论文列表中的7。
As the rapid development of social informatization process, the demand on mobile data services like broadband, mobile and the Internet of Things (IoT), etc. is growing rapidly, which brings sharp increases in demand of bandwidth of wireless communica-tion networks. From the first generation (1G) of cellular communication systems in the1980s to the coming fourth generation (4G) mobile communication systems, great progresses have been made in the wireless communication technologies. However, com-paring to the rapid growth of business and market applications, the information science and communication technologies are lagging behind and facing with many difficulties and challenges, e.g., security, scalability, spectrum shortage, Quality of Service (QoS), etc.
Radio spectrum resource:With the rapid development of wireless communi-cation networks, the conflict between the limited spectrum resources and the rapidly increasing in demand for spectrum is becoming increasingly acute. On one hand, almost all of the spectrum resource has been occupied under current spectrum management policy. On the other hand, there exists great waste on the valuable spectrum resources because of the underutilization of assigned spectrum band in both time and spatial dimensions. In1999, Cognitive Radio (CR) was first proposed as the most promising technology to solve the conflict. The main idea of CR is to break the fixed spectrum management mechanisms and to allow flexible and dynamic spectrum access of the unauthorized users under the constraints that the authorized users are not affected, which improves the spectrum efficiency in both time and spatial dimensions.
Link reliability and network connectivity:The time-varying wireless chan-nel, the dispersion and distance attenuation of radio signal propagation, and the in-terferences in the heterogeneous network all challenge the wireless link reliability and network connectivity in different ways. A virtual multi-antenna scheme, known as co-operative communication, has been proposed to deal with the challenge by allowing cooperation among multiple users each equipped with only single-transceiver antenna to explore the spatial diversity.
It can be predicted that the future wireless communication system will be a het-erogeneous network consisting of different network, different application requirements and the mutual penetration of different coverage. The afore mentioned conflicts have become the main factors that restrict on the development of the wireless communica-tions, and the difficulties and challenges in wireless communications can not be solved by any single technology. As a result, this dissertation relies on the combination of the CR and cooperative relay technologies to improve the spectrum efficiency, the wireless link reliability and network connectivity. CR enhances the system efficiency from the perspective of degree of freedom (DoF), while cooperative communication enhances the system reliability from the perspective of diversity gains. Researches on relay selection and resource allocation in cognitive and cooperative wireless networks aim at provid-ing theoretical guidance for the design of future wireless communication networks and a theoretical basis for the network performance analysis. Such researches also pro-vide theoretical and algorithmic support for the design of radio resource management protocol like relay selection and subcarrier allocation. The communication scenarios considered in this dissertation vary from single-user cooperative relaying wireless net-work to multi-user cognitive and cooperative wireless network, the corresponding for-mulated problems change from relay selection algorithm design to the algorithm design of joint relay selection and subcarrier allocation. To solve these formulated nonlinear non-convex0-1integer programming problems, based on combinatorial optimization, artificial intelligence algorithms, and convex optimization theory and methods, on one hand we design the globally optimal solution algorithm that can be used for perfor-mance analysis and to provide a performance benchmark, and on the other hand, we design practical solutions with lower complexity. Research in this dissertation was sup-ported by the National Natural Science Key Foundation of China "Research on Cogni-tive and Cooperative Communications"(No.60832008) and National Natural Science Foundation of China "Theory Research and Implementation of Cooperative Multime-dia Communication in Heterogeneous Wireless Sensor Network "(No.61061122). Main contributions of the dissertation are as follows.
1. The relay selection and resource allocation strategies in cooperative relay wireless networks are studied. For a single source-multiple relay nodes-single destination network, with relay nodes working in two-hop amplify-and-forward (AF) mode, we design the multiple relay selection algorithm to maximize the received SINR at des-tination. Based on branch and bound architecture and linear relaxation technique for nonconvex items, we design global optimal multiple relay selection algorithm. Moreover, in order to decrease the computational complexity, we design an adap-tive genetic algorithm which can be verified to reach the optimal performance with lower complexity. For multiple source-multiple relay nodes-multiple destination, with relay nodes working in two-hop decode-and-forward (DF), by designing the chromosome representation, survivor selection, crossover and mutation procedures, we design genetic algorithm based relay selection and subcarrier allocation algo-rithm to maximize the sum capacity of all users. This contribution corresponds to Chapter2and paper4,5and6as listed at the end of the dissertation.
2. The relay selection algorithms in single-user cognitive and cooperative wireless net-works are studied. The cognitive network which is composed of single secondary user pair and multiple two-hop AF cognitive relays work in the transmission scope of primary users. Cognitive network works in underlay mode to share the spec-trum with primary users. We design a relay selection algorithm to maximize the secondary suers'capacity subject to the interference temperature constraint of the primary user. When maximal ratio combining (MRC) is adopted by secondary destination, the problem is formulated as a0-1knapsack problem, based on greedy scheme and best-single scheme, we propose a hybrid scheme. The simulation re-sults show that the proposed scheme can overcome the drawback of greedy scheme and get near optimal performance. When equal gain combining (EGC) is adopted, the problem is formulated as0-1nonlinear nonconvex integer programming prob-lem, we first design the optimal relay selection scheme based on branch and bound architecture. Some simplified schemes and an iterative scheme with quadratic computing complexity are then proposed to decrease the complexity with slight sacrifice of performance. This contribution corresponds to Chapter3and paper1,2and3listed at the end of the dissertation.
3. The relay selection and subcarrier allocation problem in multicarrier based mul-tiuser cognitive and cooperative wireless networks is studied. The network consists of multiple primary user pairs (each including one transmitter and one receiver), multiple secondary user pairs and multiple secondary two-hop DF relay nodes, all the secondary users share spectrum with primary users in the underlay mode. The problem is first formulated as a nonconvex problem with complicated constraints, after equivalence transformation, the two two-dimension matrices are converted to a three-dimension0-1coefficient matrix and the problem is equivalently reformu-lated as a0-1linear programming problem. Based on branch and bound procedure, the proposed relay selection and subcarrier allocation algorithm can reach optimal solution within very limited number of iteration (less than2.5times after average). Simulation results prove that this algorithm has far less computing complexity than exhaustive scheme. This contribution corresponds to Chapter4and paper7listed at the end of the dissertation.
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