Channel estimation for power controlled 3G CDMA

The third generation (3G) direct sequence code division multiple access (DS/CDMA) wireless communications system has many advantages over the IS-95 systems, i.e., 2G CDMA. For example, a pilot channel is simultaneously transmitted with the traffic channel in the reverse link. Hence, a coherent reception can be employed using its pilot channel for fading channel estimation. However, any effects of a feedback closed loop power control (CLPC) scheme on the channel estimation have not been studied. The CLPC is employed in both 2G and 3G CDMA system for interference reduction purposes. This CLPC tries to maintain received signal power to a preset level at the base station by adjusting the transmitting power of a mobile station. Therefore, the channel estimation scheme at the base station will consecutively estimate such controlled channel, which is not the actual fading channel. Also, the power control error and group delay may degrade the estimation quality. In this paper, a simple scheme, which can estimate the actual channel, is presented for the power controlled 3G CDMA system