基于SCMA的蜂窝系统下行链路无线资源管理研究

发布时间：2018-10-29 15:51

【摘要】：5G网络在用户连接、系统容量、时延、稳定性和服务质量等方面对下一代通信技术尤其是多址接入技术提出了极大的挑战。非正交多址接入(non-orthogonal multiple access, NMA)技术由于其技术特性可以实现传统时频资源上承载更多用户数据而备受业界推崇。以华为公司为主提出的稀疏码分多址接入(Sparse Code Multiple Access, SCMA)技术就是其中之一。SCMA通过使用稀疏码本可实现系统的不同过载,且SCMA可以根据实际情况灵活配置参数来产生不同的码本资源数,使系统海量链接的实现成为可能,此外SCMA上行链路可以采用基于竞争机制的Grant-Free接入机制,从而大大降低系统时延及信令开销,因此,其在满足5G通信需求方面存在巨大潜能。鉴于无线资源管理(Radio Resource Management, RRM)在各种无线通信网络的重要意义以及SCMA技术与5G通信需求之间的高度契合,本文研究基于SCMA的无线通信系统中的RRM将具有重要的理论及现实意义。本文主要针对基于SCMA的无线蜂窝系统下行链路中进行了RRM研究。由于SCMA这一新的多址技术的引入,使系统中无线资源基本单元将由时域、频域、SCMA码域等多个维度来共同定义,且SCMA码本还与时频域之间有密切的关联关系。鉴于该关联关系以及无线信道所具有的频选衰落特性,故当下行用户使用不同SCMA码本或将同一码本分配给不同下行用户使用时,将获得不同的系统性能。但目前关于SCMA的研究中对用户使用码本都是随机选择的,因此在本文SCMA无线蜂窝下行链路模型中,将采用一种基于信道状态信息(Channel State Information, CSI)的SCMA码本选择方案,来最大化系统容量。此外,由于功率管控也是RRM的重要内容,而目前SCMA研究中还没有有效的功率管控方案成果,因此本文也对SCMA下行链路功率分配方案进行了研究,主要在基于CSI的码本选择结果基础上,借鉴经典的注水功率分配算法来进一步优化SCMA系统容量。同时为与SCMA系统进行同步比较,本文也对具有相同系统资源数目配置、采用类似资源分配算法的OFDMA下行链路系统容量进行了仿真。仿真结果表明,本文基于CSI的SCMA码本选择策略及功率分配算法比现有研究常用的码本随机选择及功率均分方案下的系统容量性能表现更佳,同时由于SCMA的过载特性,相比OFDMA系统也能获得更好的系统容量性能。最后本文还就SCMA下行链路的其他三种场景(SU-SCMA、单用户多SCMA层/码本传输以及用户QoS保障要求),对该基于CSI的SCMA码本选择策略及功率分配算法的适用性作了较详细的分析。由分析可知,文中基于SCMA的下行链路RRM算法具有很好的适用性,是一种提升SCMA系统相关性能的有效RRM方法。
[Abstract]:5G network poses a great challenge to the next generation communication technology, especially the multiple access technology, in the aspects of user connection, system capacity, delay, stability and quality of service. Non-orthogonal multiple access (non-orthogonal multiple access, NMA) technology is popular in the industry because of its technical characteristics, which can carry more user data on traditional time-frequency resources. The sparse code division multiple access (Sparse Code Multiple Access, SCMA) technology proposed by Huawei is one of them. SCMA can realize different system overload by using sparse codebook. Moreover, SCMA can flexibly configure parameters according to the actual situation to generate different codebook resources, which makes it possible to realize mass links in the system. In addition, SCMA uplink can adopt Grant-Free access mechanism based on competitive mechanism. As a result, the system delay and signaling overhead are greatly reduced, so it has great potential in meeting 5G communication requirements. In view of the importance of wireless resource management (Radio Resource Management, RRM) in various wireless communication networks and the high degree of compatibility between SCMA technology and 5G communication requirements, The study of RRM in wireless communication system based on SCMA will have important theoretical and practical significance. This paper mainly focuses on the research of RRM in the downlink of wireless cellular system based on SCMA. Because of the introduction of SCMA, the basic unit of wireless resources in the system will be defined by several dimensions such as time domain, frequency domain, SCMA code domain and so on, and the SCMA codebook is closely related to time-frequency domain. In view of the correlation relationship and the frequency-selective fading characteristics of the wireless channel, different system performance will be obtained when the current row user uses different SCMA codebooks or allocates the same codebook to different downlink users. However, the current research on SCMA is random selection for users. Therefore, in the SCMA wireless downlink model, a SCMA codebook selection scheme based on channel state information (Channel State Information, CSI) will be adopted. To maximize system capacity. In addition, since power control is also an important part of RRM, and there is no effective power control scheme in the current SCMA research, this paper also studies the SCMA downlink power allocation scheme. Based on the results of codebook selection based on CSI, the classical water injection power allocation algorithm is used to optimize the capacity of SCMA system. At the same time, in order to synchronize with SCMA system, this paper also simulates the capacity of OFDMA downlink system with the same system resource allocation and similar resource allocation algorithm. The simulation results show that the SCMA codebook selection strategy and power allocation algorithm based on CSI are better than those under random codebook selection and power sharing schemes, and the performance of the system is better because of the overload characteristics of SCMA. Compared with OFDMA system, it can also achieve better system capacity performance. Finally, the other three scenarios of SCMA downlink (SU-SCMA, single user multiple SCMA layer / codebook transmission and user QoS guarantee requirements) are also discussed. The selection strategy of SCMA codebook and the applicability of power allocation algorithm based on CSI are analyzed in detail. The analysis shows that the downlink RRM algorithm based on SCMA has good applicability and is an effective RRM method to improve the performance of SCMA system.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN929.53

【相似文献】