【作者】 朱亚洲；

【导师】 郑国莘；

【作者基本信息】 上海大学 ， 通信与信息系统， 2011， 博士

【摘要】 随着无线通信发展,用户对无线网络的数据速率和服务品质的要求越来越高。因此,下一代无线蜂窝系统引入了可以获得更高频谱效率的多输入多输出(MIMO)技术,并采用全频率复用的方式进行组网。这种部署将产生小区间干扰,会严重地降低MIMO技术带来的高频谱效率。因此,作为抑制小区间干扰的有效方法,基站协作(也称协作多点传输)技术的研究已经引起了学术界和工业界的极大关注。协作多点传输(CoMP)技术旨在避免或利用干扰来提高蜂窝边界和平均数据速率。但是,所有的CoMP方案存在大容量和低延时的回传链路需求,复杂度高,数据和信道状态信息交换量大等实际的挑战性问题。另外,高速铁路已经成为3G(3rd Generation)和4G(4th Generation)业务的一个很大的商业应用场景,而传统的铁路无线通信系统存在频谱效率低和切换过于频繁的问题,急需设计关键物理层技术来实现高速铁路宽带无线通信系统。针对以上问题,论文对已有的基站协作算法进行了相应的改进,并通过MATLAB仿真进行了实验验证。另外,也对如何将CoMP技术应用到高速铁路宽带无线系统进行了理论讨论。本论文取得如下主要研究成果:(1)针对集中式多基站协同处理方式中整个系统的反馈开销很大的缺点,提出一种基于反馈增强的组播单频网预编码方案。该方案在各用户端采用最小均方算法自适应获得等效信道并将其量化,然后反馈至基站端。从而,基站端通过迫零准则来获得最佳预编码矢量。基于基站间的用户信息交互,基站执行联合式协作多点传输来消除小区间干扰。实验证明该方案能有效地提高系统性能。(2)针对分布式多基站协同处理方式如何利用本地信道状态信息消除小区间干扰同时又能在每个蜂窝内支持多个用户进行了研究,提出了一种基于汤姆林森-哈拉希玛预编码的分布式预编码方案。具体为,在传输到每个用户组的过程中,每个基站根据本地获得的信道状态信息,为每个用户组设计相应的前向预编码和反馈滤波器。然后,基于基站端之间的信息交换,每个基站执行分布式CoMP来同时服务小区每个用户组。仿真结果表明该方案能取得较好的性能。(3)针对Jafar提出的原始的干扰对齐预编码方案,提出了两种有效的非迭代算法。基于最大化信噪比准则的预编码方案用来最大化相应无干扰等效信道的信息速率。而基于最小化均方误差的预编码方案用来改进相应无干扰等效信道的误比特率(Bit Error Ratio:BER)。分析表明,两种优化方案均能有效的利用天线资源,并具有低复杂度的特性。另外,仿真结果表明,两种次优算法有效地改进了系统性能。(4)研究了CoMP系统的可行性问题,论文提出了一种可行的基于机会干扰对齐的联合预编码和调度方案,该方案能消除信道状态信息的交换所带来的开销。具体地讲,首先,每个基站端给出了基于机会干扰对齐的联合预编码和调度过程。然后,在每个选择的用户端,基于构建的预编码矩阵和相应的本地信道状态信息,设计了一种可行的两阶段接收机。仿真结果表明,该方案明显的改善了系统性能。(5)研究了CoMP技术在高速铁路宽带无线系统中的应用,论文首先提出一种高速铁路宽带无线接入系统的网络结构。然后,在此网络结构基础上,针对单数据流场景,提出了一种基于光载无线(RoF)的CoMP方案。针对多个数据流的场景,论文又进一步提出了基于全球定位系统辅助估计离开角的预编码技术来执行基于RoF的CoMP方案。分析表明,两种方案都能减少车载台频繁切换同时避免了高速列车上的旅客终端设备的切换,并提高系统的传输功率的效率和系统的吞吐量。更多还原

【Abstract】 With the development of wireless communications, demands for both high quality and high speed are increasing. Multi input multi output (MIMO) technology and full frequency reuse will be widely used in next generation cellular systems. These deployment trends lead to a lot of interference between different cells, which will severely degrade the high spectral efficiency achieved by MIMO technology. Therefore, as an effective method of Inter-cell Interference (ICI) suppression, researches on base station (BS) cooperation (i.e., coordinated multi-point transmission) technologies have attracted much focus from both academic and industrial fields. The coordinated multi-point transmission (CoMP) techniques aim to avoid or exploit interference to improve the cell edge and average data rates. However, all COMP schemes come with the technical challenges of increased demand on backhaul with high capacity and low latency, high complexity, much overhead for data and channel station information (CSI) exchange, and so on. In addition, high speed railway has become a huge business application scenario of 3G (3rd Generation) and 4G (4th Generation). However, to overcome low spectral efficiency and over-frequent handoff problems in traditional railway wireless communication system, it is imperative to design the key physical layer techniques enabling broadband wireless communications (BWC) for high speed trains.To overcome the shortcomings of primitive CoMP algorithms, improving methods have been presented and further tested through MATLAB simulations in this dissertation. In addition, the specific application in BWC for high speed trains has been studied based on CoMP. The major contributions of the dissertation are as follows:(1)A feedback enhanced based multicast broadcast single frequency network precoding scheme is proposed to reduce large feedback overhead for central BS coordination processing. In this algorithm, the users apply least mean square algorithm to capture the effective channel adaptively and feedback the quantified channel to the BSs. Then, the BSs obtain the best precoding vector through Zero-forcing criterion. Basing on information exchange, the BSs can do joint CoMP transmission to mitigate the ICI. The simulation results indicate that the proposed algorithm can effectively improve the performance of system.(2)A distributed precoding scheme based on Tomlinson-Harashima Precoding is proposed for distributed BS coordination processing, which can eliminate the overhead for the CSI exchange, efficiently exploit the available spatial degrees of freedom and support multiple users per cell. In this scheme, relying on the local CSI, each BS designs one forward precoder and one feedback filter per user group for the transmission from itself to corresponding user group. Then, based on information exchange among the BSs, each BS do distributed CoMP to simultaneously serve each user group. The simulation results demonstrate good performance of the proposed scheme.(3)To improve the original interference alignment (IA) based precoding scheme proposed by Jafar, two effective and non-iterative algorithms are presented. One of those algorithms is the maximum signal to noise ratio based precoding scheme, which is employed to maximize the information rate of the corresponding noninterfering effective channel. The other is the minimum mean square error based precoding scheme, which is adopted to improve the bit error rate of the corresponding noninterfering effective channel. It is analytically shown that the proposed algorithms exploit antenna resources effectively and have low complexity. Moreover, the proposed algorithms are shown to achieve good performance.(4)The feasibility study for CoMP is performed, and the dissertation proposes a novel joint precoding and scheduling scheme with opportunistic interference alignment (OIA). First, at each BS, the precoding and scheduling process based on OIA is presented. Then, at each selected user, a feasible two-stage receiver is designed based on the constructed percoding matrices and the corresponding local CSI. It is demonstrated that the proposed scheme achieves good performance.(5)The application of CoMP technology in BWC for high speed trains is studied, and this dissertation first proposes a network structure for BWC systems for high speed trains. Based on the network structure, a Radio-over-Fiber (RoF) based CoMP scheme is proposed for the single stream scenario. In the two stream scenario, the global positioning system assisted angle of departure estimation based precoding technology is further proposed as an appropriate implementation form for the RoF based CoMP scheme. It is analytically shown that the proposed algorithms can address the issue of handover and improve power efficiency and system throughput.更多还原