【作者】 李玉梅；

【导师】 张曙；

【作者基本信息】 哈尔滨工程大学 ， 通信与信息系统， 2010， 硕士

【摘要】 为对抗多径衰落,改善无线链路性能,现代无线通信系统广泛使用各种分集技术。无论是经典的还是现代的分集合并技术,原理都是将两条或多条信道上携带同样信息的信号副本合并起来,以增加接收信号整体的信噪比。多用户分集增益的大小由信道增益波动的分布决定,信道增益波动幅度越大、速度越快越适于获得多用户分集增益。实际系统中,环境中散射体的不足、视距路径的存在等会降低信道的波动幅度；如果信道衰落的速度同延迟限制相比太慢,则会使传输等不及信道达到其峰值。多天线阵列利用奇异值分解技术可形成独立的并行信道,提高吞吐量,但要求发射端获得准确的信道状态信息,不易实现。机会波束技术利用多用户分集达到与采用奇异值分解时相近的吞吐量,受到了广泛的关注。本文在波束形成的基础上介绍了机会波束形成技术。机会波束形成技术通过对用户的发射信号进行加权,使信道具有丰富的散射环境,各个信道之间尽量独立,人为放大信道增益波动的速度和幅度,从而在小幅度慢衰落信道中获得多用户分集增益,提高传输的可靠性。为增强波束的选择性,提高波束与用户信道的匹配度,我们将微时隙的概念引入机会波束形成系统中,进一步提高了系统性能。功率分配策略中,注水原理功率分配是最优的,但注水功率分配过于复杂不适于实际应用。在机会波束形成系统中,在为每个波束选择通信用户时进行了自适应的信道截断,所以我们可以采用截断信道反演策略进行功率分配。此方案与注水原理方案相比,信道容量稍有下降,但此算法仅需进行一个特征值分解运算,大大降低了系统复杂度。更多还原

【Abstract】 In order to combat multi-path fading and improve performance of the radio link, the modern wireless communication system uses a variety of diversity techniques. The principle of classical and modern diversity and combination is that, two or more channels carry copies of the signal which are to be combined to increase the overall received signal-noise ratio.Multi-user diversity gain is determined by the distribution of the fluctuations of the channel gain, the greater and faster of the fluctuations, the more suitable for accessing multi-user diversity gain. In the actual system, the lack of scattering in the environment and the existence of straight path will reduce the fluctuations of the channel; if the rate of the channel fading is too slow compared with the delay constraints, the transmission can not wait for the channel reaching its peak.Multi-antenna array using the singular value decomposition teconology can form independent parallel channels to improve throughput, but it requires the transmitter to obtain accurate channel state information, and it is not easy to carry out. The opportunistic beamforming uses multi-user diversity to achieve the similar throughput with the singular value decomposition teconology, amd it has been widely concerned.This paper introduces the opportunistic beamforming on the base of beam-forming. Opportunistic beamforming teconology weights the transmission signal to get rich scattering channel environment, and artificially amplify the speed and magnitude of the fluctuation to get independent channels, resulting in multi-user diversity gain in the slow-fading channel environment, and improving transmission reliability.In order to enhance the selectivity of beam and improve the matching of beam with the user, we introduced the concept of micro-slots opportunity beamforming, and further improved the system performance. We know the power distribution with water principle is the best strategy, but it is too complicated to applicate. In the opportunity beamforming system, the communication channels have been truncated when the base station select users for each beam, so we can use truncated channel inversion to allocate power for system. This principle will decline the channel capacity a little compared with water principle power allocation, but it only needs to carry out an operation of eigenvalue decomposition, with greatly reducing system complexity.更多还原