【作者】 陈婷；

【导师】 李平安；

【作者基本信息】 武汉理工大学 ， 通信与信息系统， 2008， 硕士

【摘要】 无线通信环境的多径效应,严重制约了通信系统的发展,如何克服信道衰落效应,已经成为无线通信的一个研究热点。近几年,多天线技术由于具有抑制干扰能力强、支持高速传输,以及能提高系统容量等优点已受到越来越多的关注。多天线技术包括智能天线和空间分集两种技术。智能天线是利用阵列天线之间的相关性,在空间形成定向波束,使主瓣对准期望用户方向,旁瓣或零陷对准干扰用户方向,从而达到抑制多用户干扰、提高系统容量的目的,它是解决频率资源匿乏的一种有效途径。空间分集则是利用天线之间的不相关性,来较好地对抗多径干扰。我国具有自主知识产权的3G标准时分双工同步码分多址技术(TD-SCDMA)中已采用了智能天线技术。为了弥补时域信号处理或空域信号处理各自的局限,本文将分集技术引入到TD-SCDMA系统中,与智能天线技术相结合,利用无线信道的空时结构特征,达到同时抑制多用户干扰和抵抗多径干扰的目的。本文的主要贡献包括:1)针对TD-SCDMA通信系统,提出了一种单阵列双波束的发射分集方案。该方案关键在于在发射端利用空时分组编码技术(STBC)将一路信号变为两路信号,并利用一个阵列产生的两个波束发送出去。与传统的单波束TD-SCDMA系统相比,该方案在不增加阵元的情况下能够提高系统性能。2)针对TD-SCDMA通信系统,提出了另外一种双子阵双波束的发射方案。该方案核心是利用两个阵列形成两个波束发送经过空时分组编码的信号,利用不同波束之间的非相关性来提高TD-SCDMA通信系统的性能。3)参照TD-SCDMA标准建立了系统模型及无线信道模块,并通过MATLAB软件实现了两种方案的链路级仿真。最后MATLAB中的仿真结果表明:在TD-SCDMA系统中引入新方案后系统性能有较大的提高。更多还原

【Abstract】 In modern mobile communications, the performance of communication systems is severely limited by fading effects of the wireless channel. Therefore how to overcome the channel fading and improve the spectrum efficiency and data rate becomes a very important research topic. Multiple-antennas techniques have received wide interests in recent years due to its high data rate, high spectrum efficiency, strong abilities of suppressing the interference and so on. Multiple antennas techniques can be classified into two categories, one is the so call smart antennas, another is the spatial diversity approach. Smart antennas system, which introduces advanced adaptive array processing, produces space beams with main beam directing at the direction of desired user and null steering beams directing at the directions of interfers, thus suppressing or canceling the interfering signals. Therefore, it can improve the signal-to-interference ratio to enlarge the system capacity. Spatial diversity takes advantage of the irrelevant among individual antennas to combate against the multi-path fading, however it is another multiple antennas constructions.Time division synchronous code division multiple access (TD-SCDMA) system is a 3rd Generation communication standard put forward independently by China. Smart Antenna has considerd to be an effient technology in this system. In this paper, spatial diversity is proposed to combined with smart antennas in the TD-SCDMA system tegother, which can take advantage of the space-time channel characteristic to eliminate multiple access interference, as well as multi-path interference.The primary works are as follows:1) A space-time coded two-beams transmit diversity schemes is presented for TD-SCDMA system. The two-beams are based on one circular array with 4-unit antennas. Compared with the traditional signal beamforming in TD-SCDMA system, the new scheme has better performance on the same antenna array.2) In additionally, two-beams can be generated by two independent circular arrays. This scheme is successful implemented in this paper. The modified schemes which employed by two independent beams, obtains diversity gain which improves the performance of system.3) Based on the TD-SCDMA standard and channel parameters, simulations are carried out by Matlab software and the results show that the new schemes are effective.更多还原