【作者】 张峻峰；

【导师】 杨大成；

【作者基本信息】 北京邮电大学 ， 通信与信息系统， 2011， 博士

【摘要】 目前基本上所有面向4G演进的技术都不约而同的选择了以正交频分复用(Orthogonal Frequency Division Multiplexing, OFDM)技术为基础的多址方式,主要原因是OFDM对于大带宽(从5MHz-100MHz)有良好的可实现性,以及OFDM可以提供较高的频谱效率、较强的抗衰落能力以及与多天线技术的良好结合等诸多优点。在3GPP LTE中,OFDM系统是一种典型的同频组网系统,虽然OFDM技术子载波的正交性可以保证小区内信道的正交,但作为代价,OFDM系统带来的小区间同频干扰ICI问题非常严重。与CDMA不同,OFDMA无法通过扩频方式消除小区间的干扰。为了在保证频谱效率的同时,减少小区间干扰,目前的OFDM系统采用了较为灵活的干扰协调方式,并结合了干扰随机化和局部的干扰消除技术。但实践证明,这一系列的复杂方案虽然能够解决以上的部分问题,但对于系统整体性能,特别是小区边缘用户的吞吐量等性能的改善仍然无法满足实际运营的需要。因此,在3 GPP LTE-Advanced中,小区间干扰控制技术仍然备受关注。本论文主要针对3 GPP LTE-Advanced移动通信系统中的小区间干扰控制技术,进行了系统深入的研究。跳频方式是干扰随机化的一种重要技术,可以有效获得频率分集增益和干扰分集增益。本文讨论了3GPP LTE-Advanced中上行链路中的跳频技术。研究了跳频图样的设计准则。提出了一种子帧内与子帧间的子带和镜像联合跳频的跳频方案,适合任意传输带宽需求,既能保持系统单载波传输特性,又能避免数据包之间发生碰撞,也可以解决多颗粒度传输问题。干扰协调算法共存方案的提出,解决了在一个系统中同时存在调度用户和跳频用户如何复用的问题。另外对于跳频造成的HARQ重传碎片资源也给出了相应的解决方案。理论分析和仿真结果表明,该方案在绝大部分低速信道以及所有的高速信道的场景下都能够取得理想的频率分集增益和干扰分集增益,对解决小区间干扰控制问题有着良好的前景。LTE从考虑网络扁平化角度出发,放弃了上行联合接收,也就是在CDMA系统中常用的软切换方式,但随着BBU-RRU技术的兴起,影响原有基站间传输的瓶颈有望被打破,这样LTE-Advanced出于增强上行吞吐量特别是边缘用户吞吐量的考虑,重新引入了上行多小区之间的联合处理。本文研究了上行CoMP (Coordinated MultiPoint transmission/reception)技术的系统模型,分析了在干扰规律近似为对数正态分布下的香农容量,由分析和仿真证明上行CoMP技术对于提高系统性能,特别是提高小区边缘用户的性能是至关重要的。同时综合上行的资源灵活调度(干扰协调算法)、跳频技术和CoMP技术在资源利用上的冲突,提出了一种综合的资源复用方案以解决以上冲突。LTE-Advanced需要明显改进小区边缘速率,这对于无缝用户感受质量非常关键。本文建立了下行CoMP分析的模型,对影响下行CoMP增益的两个重要因素进行了分析,控制CoMP的增益,关键在于对CoMP执行地理区域的控制和多用户CoMP的引入,以CoMP和非CoMP的SINR等增益曲线比较的方式,形象的展现了如何寻找合适的CoMP地理区域。从系统吞吐量和系统边缘用户吞吐量比较结果看,无论是单用户还是多用户CoMP都不同程度的提高了系统吞吐量和系统边缘用户吞吐量,而且多用户CoMP对于绝对吞吐量的改善是非常明显和有潜力的。更多还原

【Abstract】 Orthogonal frequency division multiplexing (OFDM) is selected as the main access technique in almost all the possible evolution technologies targeting to 4G The main advantages are easy to implement the lager bandwidth from 5M to 100M, and the high bandwidth efficiency, the ability to combat multi-path fading, the compatible to MIMO. In 3GPP LTE, OFDM is an ordinary single carrier network. It provides the attractive property of intra-cell orthogonality. But OFDM is different from CDMA. Just like GSM, it cannot average the inter-cell interference by spreading processing and cause the strong inter-cell interference in OFDM system. In order to improve spectrum efficiency and reduce the interference, the flexible interference mitigation techniques including the coordination, cancellation and randomization are used, but in practices, these solutions can not improve the cell edge uses throughput and system throughput much more to target the operator’s requirements. So in 3GPP LTE-Advanced, current research, inter-cell interference controlling technology is also in hot debates. In this thesis, extensive research on key technology of inter-cell interference controlling is studied.The frequency hopping is an important technique in interference randomization. It can bring the frequency diversity gain and interference diversity gain. A new predefined pattern combinated with inter/intra TTI band hopping and mirror hopping based on the study of frequency hopping design principal is presented. The method can keep single carrier transmission and avoid collisions at the same time is suitable for various RBs transmission bandwidths. The solution for scheduled users and frequency hopping users coexisting is presented. For frequency hopping resource fragments caused by HARQ, a solution is gived according to this qucstion.The conclusion is verified by computer analyses and simulation. This method is suitable for most of low and all high moving speed scenarios and has a good prospect of application.LTE doesn’t use the uplink joint receiver just like the CDMA soft handover, as the flat network requirement. But as the BBU-RRU is widely used, the backhaul limit between base stations is broken, and in LTE-Advanced, the joint receiving is re-considered as a basic technique for improving the cell edge users’throughput. In this thesis, the system of uplink CoMP (Coordinated MultiPoint transmission/reception) is studied, the Shannon capacity is analyzed based on the property of interference is approximate log-normal distribution. From the analysis and simulation, the uplink CoMP is very important to improve the cell edge users’throughput and system performance. In the same time, a comprehensive solution is proposed in the combination with ICIC, frequency hopping and CoMP to avoid the resource collision of the three techniques.LTE-Advanced need the obvious improvement at cell edge, it is important for seamless quality requirement. The base model of downlink CoMP is founded, and I analyze the main two factors for CoMP gain. The key to the CoMP gain controlling are the CoMP geography area controlling and multi user CoMP. In the thesis, the gain curve of SINR for CoMP and non-CoMP is compared, and illuminates how to find the suitable CoMP geography area. From the system performance and cell edge performance, both single user CoMP and multi user CoMP improve the performance, and the multi-user CoMP has more potential gain for the throughput.更多还原