双向中继系统中跨层功率分配方案研究
发布时间：2018-11-18 15:03
【摘要】：作为协作中继技术之一的双向中继由于可以显著地提高无线通信网络中的频谱效率而得到极大的关注,但现有的大部分研究都集中在双向中继的物理层,且部分基于统计时延保障的跨层功率分配仅考虑单向中继信道。目前涉及双向中继的跨层优化研究较少,双向中继传输对于上层带来的影响也未被充分挖掘。本文针对上述问题,利用可以在数据链路层和物理层间交换信息的QoS(Qua1ity of Service)指数来表征统计时延需求,在保障数据链路层统计时延需求的前提下,优化功率的分配使得双向中继系统的性能最优。论文首先概述了双向中继通信系统的基本模型和物理层网络编码的基本概念,简述中继传输协议中应用最为广泛的两类:放大转发协议(Amp1ify-and-Forward)和译码转发协议(Decode-and-Forward)。然后利用有效容量理论得到一种基于时延QoS保障的跨层双向中继系统模型,建立了上层数据链路层与物理层之间的联系,把寻找最优化传输方案问题建模为求解系统有效容量加权和最大值的问题。并且可以证明该问题是一个凸优化问题,存在唯一的最优解。论文接着对基于AF协议的双向中继系统进行最优跨层功率分配的求解。首先分别求得不同时隙下双向中继的可达速度域,再将不同速率代入有效容量加权和最大化问题中,通过拉格朗日乘子法针对不同的场景(例如两时隙的固定增益或放大增益双向中继系统、三时隙的固定增益或放大增益双向中继系统)下的不同最大化问题进行求解,给出最优功率分配因子的算法,最终得到最优的功率分配方案。仿真结果表明对于放大转发双向中继系统,论文给出的最优功率分配方案与等功率分配方案、直接传输方案相比能显著地提高系统性能。论文最后对基于DF协议的双向中继系统最优跨层功率分配进行了分析讨论。由于在两时隙双向中继中存在谁先译码用户节点信息的问题,所以在基于等时隙分配的情况下,给出了两时隙协议中MAC阶段连续译码的最优信道状态区域划分准则,并以此准则确定用户节点译码的先后顺序和不同划分区域下的最大速率表达式。利用次梯度法更新λ至最优值和拉格朗日乘子法求偏导数,分别得到三时隙与两时隙的最优功率分配因子算法和最优功率分配方案。仿真结果表明在低信噪比情况下两时隙控制协议更有优势,在高信噪比情况下三时隙控制协议更有优势。
[Abstract]:As one of the cooperative relay technologies, bidirectional relay has attracted much attention because it can significantly improve the spectrum efficiency in wireless communication networks. However, most of the existing researches are focused on the physical layer of bidirectional relay. And the cross-layer power allocation based on statistical delay guarantee only considers unidirectional relay channel. At present, there are few researches on cross-layer optimization of bidirectional relay, and the influence of bidirectional relay transmission on upper layer is not fully exploited. In order to solve the above problems, QoS (Qua1ity of Service) exponent), which can exchange information between the data link layer and the physical layer, is used to represent the demand of statistical delay. Optimal power allocation makes the performance of bidirectional relay system optimal. Firstly, the basic model of bidirectional relay communication system and the basic concept of physical layer network coding are summarized. The two most widely used relaying protocols are amplified forwarding protocol (Amp1ify-and-Forward) and decoded forwarding protocol (Decode-and-Forward). Based on the effective capacity theory, a cross-layer two-way relay system model based on delay QoS is proposed, and the relationship between the upper layer data link layer and the physical layer is established. The problem of finding an optimal transmission scheme is modeled as the problem of solving the weighted and maximum effective capacity of the system. It can be proved that the problem is a convex optimization problem with unique optimal solution. Then, the optimal cross-layer power allocation is solved for the bidirectional relay system based on AF protocol. First, the reachable speed domain of two-way relay in different time slots is obtained, and then the different rates are substituted into the effective capacity weighting and maximization problem. The Lagrange multiplier method is used to solve different maximization problems in different scenarios such as bidirectional relay system with fixed gain or amplification gain with two slots and bidirectional relay system with fixed gain or amplification gain with three slots. The algorithm of the optimal power allocation factor is given, and the optimal power allocation scheme is obtained. The simulation results show that the proposed optimal power allocation scheme can significantly improve the system performance compared with the equal power allocation scheme for amplifying and forwarding bidirectional relay systems. Finally, the optimal cross-layer power allocation of bidirectional relay system based on DF protocol is analyzed and discussed. Because of the problem of who first decodes the user node information in two-slot bidirectional relay, the optimal channel state region partition criterion for MAC phase continuous decoding in two-slot protocol is given based on equal time slot allocation. The order of decoding and the maximum rate expression under different partition regions are determined by this criterion. The sub-gradient method is used to update the 位 to optimal value and Lagrange multiplier method to obtain the partial derivative. The optimal power allocation factor algorithm and the optimal power allocation scheme for the three time slots and two time slots are obtained respectively. The simulation results show that the two-slot control protocol is more advantageous in the case of low signal-to-noise ratio, and the three-slot control protocol is more advantageous in the case of high signal-to-noise ratio.
【学位授予单位】：安徽大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN92
[Abstract]:As one of the cooperative relay technologies, bidirectional relay has attracted much attention because it can significantly improve the spectrum efficiency in wireless communication networks. However, most of the existing researches are focused on the physical layer of bidirectional relay. And the cross-layer power allocation based on statistical delay guarantee only considers unidirectional relay channel. At present, there are few researches on cross-layer optimization of bidirectional relay, and the influence of bidirectional relay transmission on upper layer is not fully exploited. In order to solve the above problems, QoS (Qua1ity of Service) exponent), which can exchange information between the data link layer and the physical layer, is used to represent the demand of statistical delay. Optimal power allocation makes the performance of bidirectional relay system optimal. Firstly, the basic model of bidirectional relay communication system and the basic concept of physical layer network coding are summarized. The two most widely used relaying protocols are amplified forwarding protocol (Amp1ify-and-Forward) and decoded forwarding protocol (Decode-and-Forward). Based on the effective capacity theory, a cross-layer two-way relay system model based on delay QoS is proposed, and the relationship between the upper layer data link layer and the physical layer is established. The problem of finding an optimal transmission scheme is modeled as the problem of solving the weighted and maximum effective capacity of the system. It can be proved that the problem is a convex optimization problem with unique optimal solution. Then, the optimal cross-layer power allocation is solved for the bidirectional relay system based on AF protocol. First, the reachable speed domain of two-way relay in different time slots is obtained, and then the different rates are substituted into the effective capacity weighting and maximization problem. The Lagrange multiplier method is used to solve different maximization problems in different scenarios such as bidirectional relay system with fixed gain or amplification gain with two slots and bidirectional relay system with fixed gain or amplification gain with three slots. The algorithm of the optimal power allocation factor is given, and the optimal power allocation scheme is obtained. The simulation results show that the proposed optimal power allocation scheme can significantly improve the system performance compared with the equal power allocation scheme for amplifying and forwarding bidirectional relay systems. Finally, the optimal cross-layer power allocation of bidirectional relay system based on DF protocol is analyzed and discussed. Because of the problem of who first decodes the user node information in two-slot bidirectional relay, the optimal channel state region partition criterion for MAC phase continuous decoding in two-slot protocol is given based on equal time slot allocation. The order of decoding and the maximum rate expression under different partition regions are determined by this criterion. The sub-gradient method is used to update the 位 to optimal value and Lagrange multiplier method to obtain the partial derivative. The optimal power allocation factor algorithm and the optimal power allocation scheme for the three time slots and two time slots are obtained respectively. The simulation results show that the two-slot control protocol is more advantageous in the case of low signal-to-noise ratio, and the three-slot control protocol is more advantageous in the case of high signal-to-noise ratio.
【学位授予单位】：安徽大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN92
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