Postgraduate Conference Abstract

Communications and Signal Processing

Wang, Ling


POWER CONTROL IN CDMA SYSTEMS


Supervisor: Alan Adams, Sadettin Sali

Abstract
Power control is an effective technique to command the mobile station to transmit at the lowest power level possible while maintaining the desired signal quality and thereby minimizing the total interference which maximizes the system capacity. In CDMA, power control has been used to reduce the near-far effect and to prolong battery lifetime. The power control techniques fall into two categories: centralized or distributed power control. Central power control algorithms need full knowledge of the gain (or attenuation) in all propagation paths. It wastes computational resources. These two reasons make the algorithm impractical in real time for a large cellular system. Distributed power control needs only local information to adjust the transmitted power. It relies on distributed balancing power control scheme where the transmitter controls its power inversely proportional to the CIR registered by the receiver, where, the transmitted powers are adjusted asynchronously in discrete time steps. Combining this algorithm with step-wise cell removal algorithm, can obtain a minimum outage probability, however it takes more time for achieving minimum SIR than the centralized one due to the limited amounted of information. This study will initially concentrate on implementing DPC algorithms as primary purpose. Further joint capacity and quality control schemes will be added and their performances will be studied.