Research On Power Control Technology And Capacity Of A CDMA Cellular System

The user capacity in FDMA/TDMA cellular system is frequency limited, while in CDMA cellular system, it is interference limited. Any method to decrease transmits power and interference to other users will increase the user capacity and communication quality.Power control is one of the most important approaches to effectively combat the "Near-Far Effects" to suppress system interferences and to increase the system capacity. This dissertation is concerned with power control algorithms in mobile communication systems. The main work of this dissertation is recapitulated as follows.Firstly, this paper introduces the system structure and feature of CDMA cellular system that are relative to power control. Power control consists of forward link (downlink) power control and backward link (uplink) power control. The function of forward link power control is to allocate power in cell cite and decrease the interference from cell cite to user. The function of backward power control is to solve "Near-Far Effects" and to make the received power of every user equal at base.Secondly, on the base of studying the distributed power control algorithm we studied and analyzed a new algorithm which requires a much less iteration than the classical DPC algorithm. Simulations are used to validate the fact.Thirdly, we collaborate to design a simulation platform of CDMA cellular system. There are some parameters to be defined in order to make the power control algorithm work well. We should make a simulation before putting the algorithm into practice. Although there are some simplifications in the simulation, the simulated data could supply references to setting the parameters in practice and show a general tendency.Finally, this paper presents an approach to the evaluation of the reverse link capacity of a CDMA cellular system with multiform services. Simulations are used to validate the approximate analysis. And then the approximate analysis that takes into account imperfect power control, activity factors and different quality requirements is used to analyze the system capacity. The relation between user capacity and parameters of power control is obtained by a series of analysis and computer simulation.