Study On Power Control Technique In The Third Generation Mobile Communication System

CDMA is one of the promising technologies for future mobile communication system. Its several features can not be compared with other multiple access technologies. At the same time, CDMA communication system is an interference limited system, that is to say, various types of interference can influence the capability of the system and the Quality of Service of users in the system. So directly how to overcome interferences has become an urgent problem in the CDMA system. Power Control technology is proposed as a new method to deal with the problem, which can conquer Edge Effects and Near-Far Effects to enlarge the capacity of system and the Quality of Service.First, in this paper, power control technology is discussed, including its principle, methods of realization and status of research. And then discussed the application of RAKE receivers with multiples is widely used in cellular CDMA systems for exploiting path diversity, the closed-loop power control schemes should make use of the multi tap RAKE receivers for tracking the power variation due to path loss, slow fading, and fast fading. Comparing with traditional fixed-step power control, it gets smaller deviation.In a word, the adaptive algorithm can keep better tracking for the changes of the channel parameters by changing the adaptive step-size in this paper. The transmit power can compensate the channel fading fast and exactly, and the CDMA system performance can be improved obviously by using the adaptive algorithm.