Channel estimation study of CDMA downlink for fixed beam BTS

The quality of channel estimation made by the user terminals has a crucial impact on downlink capacity of a CDMA network. In current CDMA systems the downlink channel estimation is performed by the help of common pilot signal. This primary pilot is transmitted to the entire cell at all times. In case of multi-beam base station (grid of fixed beams) each beam may have a secondary common pilot. This paper studies such radio environments in which the user terminal could employ both the primary and the secondary pilot signals in channel estimation in order to reduce the overhead due to multiple pilot signals. It was found out that it is possible to employ both the primary and the secondary pilot signals in typical macro cell radio environments. In flat fading channels the gain from using both pilots ranges from 0.3 dB to about 0.8 dB depending on the angular spreading of the desired signal at the base station antenna array.