中继OFDM系统的功率分配算法研究

发布时间：2019-03-14 12:59

【摘要】：为了解决距离或者障碍物对通信质量的影响,无线中继技术越来越被人们重视并被广泛的研究;为了获得更高的频谱效率,OFDM技术也被广泛应用在各种通信场景中。将中继技术与OFDM技术相结合,可以更加充分的发挥两者的优势,改善通信质量,提高频谱利用率,为人们提供满意的服务。无线资源分配是中继OFDM系统的关键技术之一,对功率和子载波进行合理地分配能够提高系统性能。本文对无线中继OFDM系统的资源分配算法进行了研究,分别从中继转发方式、功率分配与子载波配对等方面提出了资源分配的优化算法,主要内容如下:(1)以最大化系统容量为目标,在系统总发射功率受限的情况下,应用改进型的中继方式,研究了一种包含功率分配、子载波配对和中继选择的资源分配算法,该算法首先使源节点在第二时隙通过与相应中继节点相同的子载波再次发送直传信号给目的节点,为系统提供额外的分集增益,再应用最优化方法计算各个节点在不同子载波对上的功率,最后应用匈牙利算法进行子载波配对。设计了算法的详细步骤并实现了仿真,分析了功率、子载波对个数和中继个数对系统性能的影响。(2)在双向多中继OFDM网络中,提出了一种功率分配与子载波配对的联合算法。与基于中继选择的算法不同,本文允许所有中继转发同一子载波对,以提高系统的分集增益。该算法在系统总功率受限的条件下,首先应用柯西不等式优化分配了各个中继的最优功率,简化原有的最优系统模型;再应用二分法,通过最大化子载波对的等效信道增益计算出源节点与中继节点的功率分配,最后通过凸规划分配不同子载波对的功率,并结合子载波配对获得系统的最大容量。仿真结果表明,与最优单中继选择算法和中继分用子载波算法相比,该算法的平均信道容量明显提高。(3)在单中继多用户的OFDM系统中,提出了一种最大化系统能量效率的资源分配算法。该算法在最大总功率和最小总传输速率的约束下,结合完整的信道状态信息,构建了使能量效率最大化的功率和子载波联合优化问题。由于能量效率的优化模型为非线性混合整数规划问题,求解极为复杂,为了降低该问题的复杂度,首先采用Dinkelbach方法将该优化模型变为线性凸规划,然后基于对偶规划对简化后的线性规划问题进行求解,最后结合匈牙利算法与次梯度算法求出最优解。该算法基于改进的DF中继方式,当中继与源节点或者中继与目的节点之间的信道状态较差时,可以动态的决定是否使用中继辅助传输信号,在保证系统业务速率需求的前提下,应用低复杂度的方法,大大提高了系统的能量效率。
[Abstract]:In order to solve the influence of distance or obstacle on communication quality, wireless relay technology has been paid more and more attention and widely studied. In order to obtain higher spectrum efficiency, OFDM technology has also been widely used in various communication scenarios. The combination of relay technology and OFDM technology can give full play to the advantages of the two technologies, improve communication quality, improve spectrum efficiency, and provide satisfactory services for people. Radio resource allocation is one of the key technologies in relay OFDM system. Reasonable allocation of power and subcarriers can improve the performance of the system. In this paper, the resource allocation algorithm of wireless relay OFDM system is studied, and the optimization algorithm of resource allocation is proposed from relay forwarding mode, power allocation and sub-carrier matching, and so on. The main contents are as follows: (1) in order to maximize the capacity of the system, an improved relay method is applied to solve the problem of power allocation under the condition that the total transmit power of the system is limited. A resource allocation algorithm for subcarrier pairing and relay selection, which first enables the source node to transmit direct signals to the destination node again in the second time slot via the same subcarrier as the corresponding relay node, providing additional diversity gain for the system. Then the optimal method is used to calculate the power of each node on different sub-carrier pairs. Finally, the Hungarian algorithm is used to carry out the sub-carrier pairs. The detailed steps of the algorithm are designed and simulated, and the influence of power, the number of sub-carrier pairs and the number of relays on the performance of the system is analyzed. (2) in two-way multi-relay OFDM network, the performance of the system is analyzed. A joint algorithm of power allocation and sub-carrier pairing is proposed. Unlike the relay selection-based algorithm, all relays are allowed to forward the same subcarrier pair to improve the diversity gain of the system. Under the condition that the total power of the system is limited, this algorithm firstly optimizes the allocation of the optimal power of each relay by using Cauchy inequality, and simplifies the original optimal system model. Then the power allocation between the source node and the relay node is calculated by maximizing the equivalent channel gain of the sub-carrier pair. Finally, the power of different sub-carrier pairs is allocated by convex programming, and the maximum capacity of the system is obtained by combining the sub-carrier pairs. The simulation results show that compared with the optimal single relay selection algorithm and relay sub-carrier algorithm, the average channel capacity of the proposed algorithm is significantly improved. (3) in a single relay multi-user OFDM system, the average channel capacity of the proposed algorithm is significantly higher than that of the single relay multi-user system. A resource allocation algorithm is proposed to maximize the energy efficiency of the system. Under the constraints of maximum total power and minimum total transmission rate, combined with complete channel state information, this algorithm constructs a joint optimization problem of power and sub-carrier to maximize energy efficiency. Since the optimization model of energy efficiency is a nonlinear mixed integer programming problem, the solution is very complex. In order to reduce the complexity of the problem, the Dinkelbach method is firstly used to transform the optimization model into linear convex programming. Then the simplified linear programming problem is solved based on dual programming. Finally, the optimal solution is obtained by combining the Hungarian algorithm and the sub-gradient algorithm. The algorithm is based on the improved DF relay mode. When the channel state between the relay and the source node or the relay and destination node is poor, it can dynamically determine whether to use the relay auxiliary transmission signal, while guaranteeing the system traffic rate requirements. The energy efficiency of the system is greatly improved by using the method of low complexity.
【学位授予单位】：南京邮电大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN929.53

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