【作者】 刘丽娜；

【导师】 朱刚；

【作者基本信息】 北京交通大学 ， 通信与信息系统， 2014， 博士

【摘要】 随着无线通信技术的高速发展,用户希望通信网络在保持移动性与覆盖性的同时,实现低速场景下的高速数据接入业务。长期演进(Long Term Evolution, LTE)系统支持多种带宽,可以满足不同业务的速率要求；重视用户数据业务体验,相比传统网络可以提供更高的峰值速率和用户吞吐量；增加小区边界传输速率,保障用户在任何时间任何地点的数据业务有效接入。LTE网络的这些技术特性,契合了用户对于数据业务的需求,具有良好的应用前景。在提供高质量数据传输业务的同时,LTE网络也对频谱效率提出了更高的要求,但是频率资源复用而产生的网络干扰会成为限制系统性能的重要因素。干扰管理可以在保证频谱效率的同时,通过系统级频率规划和链路级信号处理技术,提高网络与用户的通信质量,使其成为近几年的研究热点。本文以LTE系统为背景,重点研究了干扰协调技术、干扰消除技术,并对LTE网络的干扰来源、干扰特点以及干扰指标进行了分析和优化。论文的主要研究内容与创新点如下：(1)针对中心用户性能未受到额外关注的问题,提出了一种新的部分频率复用结构,进一步降低了产生同频干扰的概率。该结构在保证小区边缘用户资源正交的前提下,将小区中心用户的资源分为专用频段与共用频段两部分,并为专用频段设置更高的优先级。相比传统分配算法,该结构在注重边缘用户性能的同时,也重视中心用户的体验。中心用户在使用专用频段时,享有更高的发射功率,提高了有用信号占比；同时,边缘用户的干扰来源减少,降低了受到同频干扰影响的几率。在确定资源分配策略后,分别对中心用户和边缘用户的信道容量、系统吞吐量、中断概率以及干扰矫正因子四个参数进行定量分析。(2)针对中心用户与边缘用户资源占用比例不均衡的问题,在部分频率复用结构基础上,提出了一种自适应资源调整算法。通过对已分配资源的动态调整,使得中心用户与边缘用户的资源比例更适合实际通信环境,或在突发状况发生时实现不同的资源分配侧重。资源的调整比例根据用户受到的干扰情况而设定,系统可以利用权重因子调节动态资源的最大比例或决定是否采用动态策略。在两种部分频率复用结构中分析了提出的算法,并对比了两种结构中算法实现的差异性。仿真结果从吞吐量、用户信道状况、误码率等角度对算法性能进行了评估。(3)针对系统对于干扰消除技术计算复杂度的顾虑,提出了一种上行链路接收端执行的干扰消除算法。接收机通过重构和移除干扰信号,使更新后的原始接收信号只包括有用信号与噪声。算法在对计算复杂度和成本不敏感的基站一侧执行,不会给用户终端带来额外的开销。同时,在信道状态未知的情况下,算法利用训练序列的传输结果和插值方法完成数据信号的信道估计,更具实际应用价值。仿真结果验证了提出的干扰消除算法在不同载波分配方式下的有效性,并分析了不同通信场景中的算法特性。(4)在分析LTE网络干扰来源的基础上,对干扰指标中的信干噪比参数进行了深入研究。从用户角度出发,建立了权衡吞吐量利用率和用户花费的效用函数,设立兼顾性能体验和网络开销两方面影响的优化目标,引导用户在两者间理性权衡自身需求。通过建立效用函数的微分博弈模型,利用微分博弈算法求解时间连续型效用函数的最优解,得到用户权衡通信质量与开销后的信干噪比决策。利用仿真讨论了算法在不同干扰场景中的性能表现,阐释了造成算法性能差异的原因。更多还原

【Abstract】 With the rapid development of wireless communication technology, the subscribers expect communication networks to provide a high-speed data access service in the low-speed moving scene, and also maintain the mobility and coverage at the same time. Long Term Evolution (LTE) networks support multiple bandwidths to satisfy the needs of dif-ferent data services. They focus on users’ experience, by providing higher peak trans-mission rate and users’ throughput than traditional networks. Moreover, the transmission rate in cell boundary area guarantees effective data service access at anywhere and any-time. These technical characteristics of LTE networks meet with users’ data services requirements perfectly, and therefore the networks have a good application prospect. At the same time, LTE networks also put forward a request of higher spectral efficiency uti-lizing frequency resource reuse, which will generate interference and be a major limiting factor in the system performance. By using system-level resource planning and link-level signal processing techniques, interference management guarantees the spectral efficiency as well as the communication quality of users and networks, consequently, it has become a hot issue in recent years. With the background of LTE networks, this dissertation stud-ies interference coordination technology, researches interference cancellation technology, analyzes the characteristics of interference sources and finally optimizes the interference index parameter. The main contents and innovations of this dissertation are summarized as follows:(1) Aiming at the problem that the performance of cell center users is not paid addi-tional attention, a new fractional frequency reuse structure is proposed, which can decline the probability of co-channel interference simultaneously. In this structure, the resources allocated to cell edge users are kept orthogonal, while the resources allocated to cell center users are divided into two parts, namely, dedicated bands and shared bands. The dedicated bands are placed with higher priority than the shared bands. Compared to the traditional fractional frequency reuse structure, the presented structure not only focuses on the performance of cell edge users, but also concerns the experience of cell center users. When center users are using the dedicated bands, they will have a higher trans-mit power which will increase the proportion of the desired signal in received signal. Meanwhile, for cell edge users, the amount of interference sources and the probability of being affected by co-channel interference are both reduced. After the resource allocation method being determined, the performance of center users and edge users are analyzed in four aspects, including channel capacity, throughput, outage probability and interference correction factor.(2)To solve the problem of resource-ratio imbalances among cell center users and cell edge users, an algorithm for self-adaptive resource dynamic adjustment based on the fractional frequency reuse structure is proposed. By adjusting the allocated resources, the proportion of the resources occupied by center users and edge users will be closer to that in the actual communication environment, and the resources can also focus on different users in case of an emergency. The adjusting proportional factor is determined by users’ interference environment, and with the weight factor, the system will choose either to adjust the largest number of dynamic resources or to decide whether self-adaption is used or not. The algorithm is analyzed in two fractional frequency reuse structures, and the implementation differences in the two structures are compared. Simulation results eval-uate the algorithm performance in several perspectives like throughput, users’channel condition, bit error ratio and so on.(3) Due to the concern related to computational complexity of the interference can-cellation technology, an uplink interference cancellation algorithm performed in receiver is proposed. Once the interference signals are reconstructed, the receiver will remove them from the original received signal, and then the updated received signal only con-tains the desired signal and noises. The algorithm is performed in the base station which is less sensitive to the computational complexity and cost; therefore it will add no ex-tra users’overhead. Compared with the methods that assume channel state information available, the channel estimation of the presented method is implemented by using trans-mission results of training sequences and the interpolation algorithm, so that has more practical values. Simulation results verify the effectiveness of the presented algorithm under different subcarrier allocation schemes, and the algorithm characteristics are also analyzed in various communication scenarios.(4) On the basis of interference sources analysis, the signal-to-interference noise ratio (SINR) parameter as one of the most important interference indexes is deeply stud-ied. Considering both throughput efficiency and the cost of users, a utility function is built. The optimized target takes two aspects into account, including performance ex-perience and network charges. It will guide users to make rational decisions combined with practical needs. The differential game model of utility function is established, and the differential game method is used to obtain the optimal solution to the utility func-tion. The algorithm performance is discussed in different scenarios, and the reasons for performance differences are also analyzed.更多还原