Adaptive base station sector antenna pre-selection transmitter diversity using CDMA forward link signal for indoor wireless LAN

In a typical indoor environment such as in a building, delay spread tends to be small, which causes frequency non-selective fading. Therefore resolvable paths at the RAKE receiver can not be obtained, and effective path diversity can not be achieved. This paper proposes an artificial path diversity system in which one or multiple sectors at the base station are pre-selected according to the channel conditions for transmitting data. Each sector's signal is delayed by several chips to create artificial paths which can then be combined by using a RAKE receiver at the mobile station creating a diversity effect for an indoor environment. Moreover, only pre-selected sector antennas .transmit signals to reduce inefficient signal usage in the sectors whose paths are blocked by using all sectors, therefore the transmission power is used efficiently at the base station. As a result of sector selection, the better BER performance and the reduction of interference signals between different channels can be achieved by means of sector selection. The performance of the proposed system is analyzed and demonstrated by computer simulation in a Rayleigh and log-normal fading indoor environment.