The Research On Power Control Strategy For CDMA Communication Systems

In CDMA mobile communication system, all mobile stations share a same carrier frequency. It is possible that signal of strong near signal interfere weak distance signal. At the same time, interfere determine the capacity of CDMA and QoS. The purpose of power control is to combat the "near-far" effect, suppress system interferences and increase the system capacity .It is one of the key technologies in CDMA system.This dissertation mainly studied the uplink power control algorithm in the CDMA mobile communication system, the main work of this dissertation is recapitulated as follows.(1) Base on the theory and knowledge of numerical linear algebra and matrix, linear and exponential distributed iterative power control algorithms are analyzed in detail. The convergence and convergence rate of algorithms is studied.(2) In recent years, game theory has emerged as a promised approach to solve the power control problem in wireless networks. Extend the research of game theoretic analysis to propose a cost function and deduct a new power control algorithm, verify the existence of Nash Equilibrium (NE). The comparison of this kind of new power control algorithm and DCPC is made by simulation. We may discover the proposed method enhance the algorithm convergence rate enormously, reduce the user average transmitted power, has very great practical value.Decision mechanism influences the game result. We made comparison of alternate decision mechanism and simultaneous decision mechanism. Simulation results show that the rate of convergence using alternate decision mechanism is obviously higher than that using simultaneous decision mechanism. Thus alternate decision mechanism could improve system performance.(3 ) In the third generation communication systems, unitary power control method can not satisfy the performance of CDMA system. Combined power and rate control is becoming a hot topic. In this dissertation, OVSF in multi-rate transmission is presented. In variable spreadinggain CDMA system, users collect appropriate power and transmission rate according the promulgate situation. We apply game theory to collect power and rate control to maximize users' net throughput. Simulation indicates that radio resource is assigned effectively in this way and users' satisfy QoS requirement and keep high transmit rate.