具有时变时滞的CDMA自适应功率控制及其MATLAB仿真

【作者】 曹丽莎；

【导师】 韩存武；

【作者基本信息】 北方工业大学 ， 检测技术与自动化装置， 2012， 硕士

【摘要】 CDMA(码分多址,Code Division Multiple Access)技术是无线通信技术的重要研究方向,也是3G通信以及4G通信的关键技术,如何提高系统性能、增大用户容量是国内外专家学者研究的重大课题之一。由于CDMA本身的特点,阴影效应、角效应、多径衰落等干扰的产生是不可避免的,因此能够减少干扰、提高通信质量的多种技术逐渐的发展成熟起来,如Rake接收机技术、智能天线等技术等。功率控制技术也是CDMA移动通信系统为保证通信稳定、增大系统容量所采用的重要技术之一。对移动台终端和基站进行良好的功率控制可以克服CDMA移动通信技术本身所特有的缺陷,更可以提高用户通信质量,减少用户的电池电量消耗。但是,通过研究CDMA移动通信系统功率控制的发展史以及其各个子方向可以看出,目前这些功率控制算法有的解决了确定系统的时滞补偿,有的解决了固定时滞的非确定系统模型辨识,而对于非确定系统的时变时滞的辨识与补偿仍未有较好的解决方案。本文针对具有参数不确定性和时变时滞的CDMA系统的功率控制问题,提出了一种基于信道参数和时滞估计的自适应功率控制算法。该算法的建立与推导包括以下若干部分：一是分析CDMA通信系统的信噪比模型并推导出适用于最小二乘算法的广义迭代系统模型以及具有时变时滞的广义迭代系统模型；二是针对时变时滞提出时变时滞估计算法,针对参数不确定性提出系统时变参数的估计算法以及相应的控制率；三是对所提出的算法进行仿真。仿真结果表明本文所提出的针对于CDMA移动通信系统的自适应功率控制算法可以有效地补偿参数不确定性和时变时滞的影响,能够平稳、快速地进行功率调节,满足了CDMA移动通信系统对用户功率控制平稳、超调、响应时间的需求,也满足了无线通信终端对功率控制快、平、稳的要求。更多还原

【Abstract】 CDMA (Code Division Multiple Access) technology is one of the most important technologies in wireless communication systems, and it is the key technology for3G and4G communications. Thus, how to improve the performance of CDMA system and increase the user capacity is a hot topic in the wireless field. In order to minimize the various interferences in CDMA wireless communication system and improve the system performance, many kinds of technologies are adopted, such as RAKE receiver technology, smart antenna technology, and so on. Power control technology is also one of these technologies to improve system performance.A better power control to the BS (base station) and MS (mobile station) can improve the communication quality and reduce the battery’s consumption. However, there is little power control method which can propose a better solution to the problem of parameter uncertainty and time-varying delay.This paper develops adaptive power control to CDMA wireless systems with uncertainty parameter and time-varying delay. The adaptive power control algorithm presented here is based on channel parameter and time delay estimations. It can estimate the time-varying delay and the parameter uncertainty effectively, and adjust the power stably as well as fleetly.The algorithm is proposed in three steps:first, analyze the SIR mathematics model of CDMA wireless communication system, and get the generalized iteration system model which can be used in Least Squares algorithm; second, estimate the system delay time as well as the system parameters are estimated, then calculate the adaptive control law according to the estimation results; finally, do the simulation work to demonstrate the effectiveness of the proposed algorithm.Simulation results show that the proposed algorithm can estimate and compensate for the affects of time-varying delay and parameter uncertainty rapidly. It can also adjust the transmission power smoothly and fast.更多还原