双层异构无线网络中资源管理关键技术研究

发布时间：2019-06-27 16:13

【摘要】：作为LTE-A系统中最有代表性的异构网络单元,Femtocell通过在室内部署低功率接入节点(FAP),能够有效地改善室内无线覆盖,为用户提供更好的无线数据服务。但由于FAP是用户根据自身要求自主安装,缺少专门的网络规划与优化,为传统Macrocell引入了额外干扰,使得双层网络的干扰问题变得更加复杂。为了降低此类干扰,本文对双层异构网络的无线资源配置展开研究,主要从功率控制和频率复用两个方面探索降低异构网络内部干扰的方案,研究内容围绕以下三个主题展开:首先,对双层网络中断概率进行分析。利用空间泊松点过程对Femtocell基站进行数学分析。在信号传输过程中,采用IMT-2000的路径损耗传播模型,利用Turk-Mani近似方法推导出Macrocell层和Femtocell层中断概率的理论值,并通过仿真分析,对理论推导的准确性进行验证。其次,研究了Femtocell覆盖及优化方案。根据Femtocell下行中断概率,求得Femtocell用户(FUE)距离宏基站(MBS)的最小距离和FAP的最低发射功率。利用FAP的最低发射功率作为约束条件对典型的功率控制方案进行改进,提出基于用户距离和中断概率的Femtocell覆盖及优化方案。仿真结果表明,提出方案不仅能有效地降低双层网络的中断概率、提升用户的通信质量,而且能节约系统的功率资源。最后,研究分析了双层网络频率复用方案。在对经典的部分频率复用方式(FFR)进行研究的基础上,提出了一种改进的适用于双层异构网络的FFR分配方式。在该方案中,整个系统频带被分为7个可用频段,分别复用给不同区域不同扇区的用户。宏小区中心区域的用户使用频率复用因子为1的一个子频带,边缘区域每个扇区内的用户使用频率复用因子为3的两个频带,同时保证相邻扇区间分配正交的频带。FAP通过感知宏小区的信号强度选择接入合适的子频带,从而减少双层网络间的干扰。通过与经典的FFR方案在子频带划分、信干噪比、中断概率及用户的平均传输速率等方面进行对比分析。实验仿真表明,改进的部分频率复用方式在性能指标上比其他FFR方式更具优越性。
[Abstract]:As the most representative heterogeneous network unit in LTE-A system, Femtocell can effectively improve indoor wireless coverage and provide better wireless data services for users by deploying low power access node (FAP), indoors. However, because FAP is installed independently by users according to their own requirements and lacks special network planning and optimization, the interference problem of double-layer network becomes more complex because of the introduction of additional interference for traditional Macrocell. In order to reduce this kind of interference, this paper studies the wireless resource allocation of double-layer heterogeneous networks, mainly from two aspects of power control and frequency reuse to explore the scheme to reduce the internal interference of heterogeneous networks. The research contents focus on the following three topics: firstly, the outage probability of double-layer networks is analyzed. The mathematical analysis of Femtocell base station is carried out by using the process of spatial Poisson point. In the process of signal transmission, the path loss propagation model of IMT-2000 is used, and the theoretical values of interrupt probability of Macrocell layer and Femtocell layer are derived by Turk-Mani approximate method, and the accuracy of the theoretical derivation is verified by simulation analysis. Secondly, the Femtocell coverage and optimization scheme are studied. According to the downlink interrupt probability of Femtocell, the minimum distance between Femtocell user (FUE) and macro base station (MBS) and the minimum transmission power of FAP are obtained. The typical power control scheme is improved by using the minimum transmission power of FAP as the constraint condition, and a Femtocell coverage and optimization scheme based on user distance and interrupt probability is proposed. The simulation results show that the proposed scheme can not only effectively reduce the interrupt probability of double-layer network, improve the communication quality of users, but also save the power resources of the system. Finally, the frequency reuse scheme of double-layer network is studied and analyzed. Based on the research of the classical partial frequency reuse (FFR), an improved FFR allocation method for double-layer heterogeneous networks is proposed. In this scheme, the whole system frequency band is divided into seven available frequency bands, which are reused to users in different regions and different sectors. The users in the central area of macro cell use a subband with frequency reuse factor 1, and the users in each sector in the edge region use two frequency bands with frequency reuse factor 3, while ensuring that the adjacent fan interval is allocated orthogonal frequency band. FAP accesses the appropriate subband by sensing the signal strength of macro cell, thus reducing the interference between double-layer networks. Compared with the classical FFR scheme, the subband division, signal-to-noise ratio (SNR), interrupt probability and average transmission rate of users are compared and analyzed. The experimental results show that the improved partial frequency reuse method has more advantages than other FFR methods in performance index.
【学位授予单位】：兰州交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.5

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