Joint Power And Rate Control In WCDMA System

As the development of the technology and people's increasing demand on communication, the cellular mobile communication system has stepped into the third generation. Viewed from the development of mobile communication, it faced with the sharp growth of users, various services, as well as much more demand on grade of service, so how to manage and utilize the radio resource effectively has become one of the most important issues. Power control and rate adaptation are two radio resource management functions. Power control can overcome near-far problem, reduce multiple-access interference and improve system capacity. Rate adaptation can optimize the data transmission and increase the system throughput. The integrated power control and rate adaptation can make the utilization of radio resource more effective. The research of joint of the two technologies is shown as follows.First, the rationale and application in WCDMA system of power control and rate adaptation is introduced. The disadvantage of conventional closed-loop power control is analyzed. In view of the loop delay which affects the performance of the conventional power control most, a channel fading step predict algorithm based on RLS adaptive filter is proposed. According to the prediction of the channel fading step, the next time sample's channel gain can be estimated, and the impaction of the loop delay can be alleviated. The method is more feasible because the base station need not know the transmission power all the time. The simulation results prove less power control mean square error can be achievable compared with the conventional power control. Further more, the RLS filter converges faster.Second, rate adaptation based on the distribution of received signal and the restrictions in implantation is specifically analyzed. The study of joint power control and rate adaptation based on WCDMA dedicated channel frame structure indicated this method can not utilize power resource of uses effectively. So a joint power and rate control based on system load is proposed. In this method, rate adaptation proceeds combined with cell load. When the cell load is light, increase the transmission rate for increasing the system throughput. Contrarily, decrease the transmission rate to guarantee the system coverage. The simulation results prove after power control is adopted, the rate adaptation can increase system throughput. The result demonstrates for data service only rate adaptation is not enough and power control is essential. Further more, joint power and rate control based on system load can achieve bigger system throughput.