Base Station Cooperative Technologies And Its Applications In Broadband Wireless Communications For High Speed Trains

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.