Power Control in Wideband Cellular CDMA Systems

by

Christine Q. Cai

1998 M. Eng Thesis

Abstract

The third generation (3G) wireless systems will support varieties of voice and non-voice applications. Modeling of such heterogeneous networks is a very active research area. In the wireless environment, there are two competing multiple access methods: TDMA and CDMA. Each scheme has its unique problems in handling multimedia traffic. In this project, we investigate, by means of modeling and computer simulations, some problems associated with CDMA multimedia access. In particular, power control being one of the most critical issues in CDMA network is a major focus of this project. While power control has been studied in voice only wireless networks, the introduction of burst transmission modes with long silence gaps and variable bit rate requirements will change the nature of the problem.

The main thrust of the research is to develop appropriate models for power control in 3G wideband CDMA systems. The particular issues addressed in this project are power allocation among the different types of services, power control algorithm for the packet data services, and interference distribution in such systems. The proposed models have been tested by means of computer simulations. The simulated wideband CDMA system is based on the proposed 3G CDMA system. A test bed has been built upon an existing IS-95 based simulator.

The simulation results demonstrate that the relationship between power allocation plan and QoS is non-linear in wideband CDMA system, and the interference distribution in such a system is no longer Gaussian distributed. For the high rate data services, by employing a low transmission rate dedicated control channel, the implementation of power control of high rate supplemental channel can be simplified and more efficient. Power allocation plans should make all QoS to be only marginally kept above required tresholds when system capacity is reached

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