移动通信系统中的快、慢速链路自适应传输方法研究

发布时间：2018-04-05 14:28

本文选题：移动通信系统　切入点：链路自适应　出处：《广西师范大学》2016年硕士论文

【摘要】：链路自适应技术对于提高衰落信道下移动无线通信系统的性能是一种非常合适的技术,是提高系统频谱效率和传输可靠性的有效手段。信道的状态是链路如何进行自适应的主要依据,例如在不同的信噪比区间使用不同级数的正交振幅调制(QAM, Quadrature Amplitude Modulation)技术。然而这里存在两个问题：(1)对应相同的目标误码率或者中断概率,不同衰落信道类型下的信噪比区间是不同的；(2)发送端基本上都需要接收端的信道反馈,这个过程会引入时延,从而使得反馈的信道状态信息成为过时的信息,根据过时信道状态信息判断的发送策略有可能降低移动通信系统的性能。鉴于以上,本文围绕链路自适应传输技术开展研究,取得了一些进展,具体体现在以下几个方面：(1)目前移动通信系统中采用的主要是快速链路自适应传输,研究表明慢速链路自适应传输在快速移动环境或者信道估计误差较大时的性能优于快速链路自适应传输且具有较低的反馈频度,因此本文开展了慢速链路自适应传输研究。通过分析慢速链路自适应与信道类型之间的物理联系,提出了一种基于信道类型判断的慢速链路自适应方法。该方法利用概率密度级数展开式逼近分布的方法判断移动通信链路的信道类型,然后在获得信道类型的基础上,根据移动通信链路的平均比特差错概率函数确定慢速链路自适应门限,以确定相适应的QAM调制级数。仿真结果表明,该方法在频谱效率和中断概率上优势显著,比现有慢速链路自适应算法的频谱效率可以高出约10%到20%。(2)为了应对过时信道状态信息对链路自适应传输性能的影响,提出了一种基于信道预测的快速链路自适应方法。该方法首先通过特定的条件概率密度函数预测无线信道信噪比,即利用过时的无线信道信噪比来预测发射时的无线信道信噪比,然后在获得无线信道预测信噪比的基础上,根据链路的即时比特差错概率函数确定快速链路自适应门限,从而自适应确定QAM调制级数。仿真结果表明,所提方法能有效应对过时信道状态信息对系统传输性能的影响,改善系统性能。
[Abstract]:The performance of link adaptive technology of mobile wireless communication system to improve the fading channel is a very suitable technique is an effective method to improve the system spectrum efficiency and transmission reliability. The status of the channel is mainly based on how to carry out the adaptive link, such as the use of different order than in the range of different signal-to-noise (QAM, quadrature amplitude modulation Quadrature Amplitude Modulation) technology. However, there are two problems: (1) corresponding to the same target BER or outage probability, different types of fading channel and the SNR range is different; (2) the sending end basically requires channel feedback, this process will lead to delay, which makes the channel state information feedback become outdated information, according to the outdated channel state information transmission strategy judgment may reduce the performance of mobile communication system in view of the above, This paper focuses on link adaptive transmission technology, has made some progress, embodies in the following aspects: (1) the current mobile communication system is mainly used to fast link adaptive transmission, studies show that the slow link adaptive transmission in a fast moving environment or the channel estimation error is better than fast link adaptive transmission is large and has the feedback frequency is low, so this paper developed slow link adaptive transmission research. Through the analysis of the physical connection between the slow link adaptation and channel type, presents a slow link adaptive method based on channel type judgment. This method uses the probability density distribution expansion approximation method to determine channel type mobile communication link, and then based on channel types, according to the average bit error probability function of mobile communication link Determine the slow link adaptive threshold, to determine the QAM modulation order to adapt. The simulation results show that the method in the spectral efficiency and outage probability can be a significant advantage, about 10% higher than 20%. to the spectral efficiency of the existing slow link adaptive algorithm (2) in order to cope with the outdated channel state information influence on the transmission performance of link adaptation. And proposes a fast link adaptive method based on channel prediction. Firstly, the method of prediction of wireless channel signal-to-noise ratio through the conditional probability density function is given, the wireless channel signal-to-noise ratio predicted by the outdated launch of the wireless channel SNR, then get wireless channel prediction based on SNR, according to fast link adaptive threshold instant bit error probability function of link, so as to determine the adaptive QAM modulation series. The simulation results show that the proposed method can effectively cope with. The influence of the time channel state information on the transmission performance of the system improves the performance of the system.

【学位授予单位】：广西师范大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN929.5

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