Distributed Power Control Algorithm And Implementation In CDMA Wireless Communication System

This thesis researches one of the key technology of the 3^rd generation mobile system: power control. Power control is one of the most important approaches to effectively combat the near-far problem and corner problem, to suppress system interferences and to increase the system capacity. The aim of power control is to adjust the transmit power fast according to mobile environment, so it can make the communication quality keep on a certain level and not make too much disturb on other users. CDMA (Code Division Multiple Access) is one of the promising technology for future mobile communication system because of its several features with which other multiple access technology can not compare: higher efficiency of frequency allocation, robust multipath effect, macro diversity mitigating interference, soft capacity, low power, soft handoff, simple frequency design, easy access, and so on. So this thesis researches power control algorithm mainly in CDMA system. The main work of this dissertation is recapitulated as follows.Firstly, we discuss the principles and method of power control according to power control rules, based on which the key factors are concluded. The factors are analyzed in details include the control delay, precision, method and algorithms. It provides principles for designing and Implementation of power control algorithms.Secondly, on the base of analysis of the centralized and distributed algorithms, the principle of centralized algorithm and distributed algorithm are concluded and analyzed, especially analyze iterative method of distributed power control deeply. A general framework of constructing and analyzing iterative power control algorithms and a general method of convergence analysis are proposed; Based on the front work, we analyze and compare some classical distributed power control, including DAP(Distributed autonomous Power Control) and FDPC( Fully Distributed Power Control) algorithms, from their astringency and iterative speed, and point out their limitations; By improved the launch, we prove the classical distributed power control. Emulations indicate it has fast convergence speed of DAP, and the same as FDPC, its launch power can't overrun.Thirdly, SIR and control step are deep related with power control effect. Aim at stability and validity of power control algorithm, we analyze the power control infections of SIR and choice of control step from system capacity and errors, as well asthe relations between system capacity and power control stability.Finally, aim at the speed and performance of distributed power control algorithm, based on better performance DAP algorithm, we put forward a new distributed power control algorithm, it solve the problem that the algorithm is not constringency when the number of user is grow. And it has been proved the new algorithm could convergence under expectation average meaning. Simulation results prove that new algorithm could reach faster speed, which offer a new technique for fact communication system.