基于OFDMA系统下行链路自适应无线资源分配优化研究

发布时间：2018-12-17 07:07

【摘要】：随着科技的不断发展和进步,人们对高速率通信服务的需求日益增长,而有限的频谱资源和恶劣的无线通信环境都会影响用户的通信体验。因此,为了满足蜂窝用户对更快更可靠的数据服务的需求,迫切需要一种合适的资源分配方式来合理的利用资源,获得更好的系统性能。正交频分复用多址接入技术已经越来越多地被应用在各种新兴和演进的蜂窝系统中,应用该技术能够有效减少符号间干扰,动态分配资源,从而提高系统整体性能。目前正交频分复用多址接入系统下行链路中资源分配方式主要包括基于子载波的资源分配和基于子载波块的资源分配两种方式。在子载波数量较大时,若对每个子载波进行分配算法复杂度会很大,因此本文针对子载波数量较大的情况,分别提出基于子载波块的自适应功率优化分配方案和基于人工鱼群算法的速率优化分配方案来进行最优分配。在功率优化中,根据相邻子载波之间的相关性进行载波聚合,形成子载波块,提出一种联合子载波块,功率和比特分配的方案,在总发射功率的约束下最大化系统吞吐量,并考虑到实际中比特的整数性质提出比特的数字化过程。仿真比较了本节算法与固定功率分配算法的吞吐量性能,结果显示在用户数量不断增大时,理论结果上两种算法性能几乎相同,但加入数字化过程后本文所提动态功率分配算法的吞吐量远大于固定功率分配。同时,基于子载波块的分配方式大大减小了分配过程的复杂度,节省了运行时间。在速率优化中,将用户的速率公平性加入到目标函数中,首先为各用户设置初始速率比例值,然后提出适应度函数衡量用户公平性和系统吞吐量之间的关系。在功率分配中利用人工鱼群算法的并行处理能力和全局快速寻优能力来实现最优功率分配。仿真实验中与Shen算法和Max-Min算法进行比较,结果表明该方案在系统总功率一定的条件下,获得的用户公平性约为0.98-0.99,接近于最大值1,系统容量相对于Shen算法和Max-Min算法约有0.17～0.49bit/s/Hz的提升。能够在获得最大系统传输速率的同时保证用户间的速率较好的公平性。
[Abstract]:With the continuous development and progress of science and technology, the demand for high-speed communication services is increasing, and limited spectrum resources and poor wireless communication environment will affect the user's communication experience. Therefore, in order to meet the needs of cellular users for faster and more reliable data services, an appropriate resource allocation method is urgently needed to make rational use of resources and obtain better system performance. Orthogonal Frequency Division Multiplexing (OFDMA) has been widely used in various new and evolving cellular systems. It can effectively reduce inter-symbol interference and dynamically allocate resources, thus improving the overall performance of the system. At present, in the downlink of orthogonal frequency division multiplexing (OFDMA) multiple access system, resource allocation mainly includes subcarrier based resource allocation and subcarrier block based resource allocation. When the number of subcarriers is large, the complexity of each subcarrier allocation algorithm will be very large, so this paper aims at the large number of subcarriers. An adaptive power allocation scheme based on subcarrier block and a rate optimal allocation scheme based on artificial fish swarm algorithm are proposed respectively. In power optimization, carrier aggregation is carried out according to the correlation between adjacent subcarriers to form sub-carrier blocks. A joint sub-carrier block, power and bit allocation scheme is proposed to maximize system throughput under the constraints of total transmission power. Considering the integer nature of bits in practice, the digitization process of bits is proposed. The throughput performance of this algorithm is compared with that of the fixed power allocation algorithm. The results show that when the number of users increases, the performance of the two algorithms is almost the same. However, the throughput of the proposed dynamic power allocation algorithm is much larger than that of the fixed power allocation algorithm. At the same time, the allocation method based on sub-carrier block greatly reduces the complexity of the allocation process and saves the running time. In rate optimization, the user's rate fairness is added to the objective function. First, the initial rate ratio is set for each user, and then the fitness function is proposed to measure the relationship between user fairness and system throughput. In power allocation, the parallel processing ability of artificial fish swarm algorithm and the global fast optimization ability are used to realize the optimal power allocation. Compared with Shen algorithm and Max-Min algorithm, the simulation results show that the fairness of the proposed scheme is 0.98-0.99 when the total power of the system is fixed, which is close to the maximum value of 1. Compared with the Shen algorithm and the Max-Min algorithm, the system capacity is about the increase of 0.17~0.49bit/s/Hz. It can obtain the maximum system transmission rate and ensure the fairness of the rate between users at the same time.
【学位授予单位】：宁夏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.5

【参考文献】