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

The third generation mobile telecommunication systemutilizes wide-band CDMA as its multiple access. It aims at that whoever can communicate in whatever way whenever it is and wherever he is. Being wireless channel, the channel of CDMA system is very terrible medial of the nature. In the course of transferring information, there are several disadvantages as time-selective fading, frequency-selective fading, near-far effect, multiple access interference, white Gaussian noise and so on, which affect the reliability of CDMA system and lower the capacity of CDMA system.Because the CDMA system is a interference-limited system, all the technologies that can improve the performance of resisting interference, that's to say reliability can amplify the its capacity. The key technologies utilized by CDMA system are all aiming at improving the reliability. In this article, a predictive control algorithm for uplink transmission in code division multiple access systems is presented. Using the optimal linear prediction, the interference to the desired user for the future instant is estimated from current and past interference. The result is then used to derive the optimum power levels of the mobile transmitters in the system. Finally the article discusses the theory and method of a novel combined CDMA power control technology that using the advantages of power control and multiuser detection and proposes a combined power control algorithm which based on multiuser detection.