Tilting and Beam-shaping for Traffic Load Balancing in WCDMA Network

This paper summarizes recent developments in semi-smart antenna systems for geographic load balancing in cellular mobile communication systems by cooperatively changing the antenna radiation patterns and compares the performance with cooperatively down tilted antennas. Cooperative coverage is advantageous, e.g. in the presence of hotspots. For semi-smart antennas the ideal shape for a cell in the context of its neighbours is determined using the bubble oscillation algorithm (BOA) and the pattern is then given to the semi-smart antenna for further radiation pattern synthesis. The adjustment process differs for different antenna systems and mostly depends on the antenna´s physical capabilities on pattern shaping. This paper then considers the special case of adaptively tilting through the use of electrical down-tilt (EDT) antennas, and compares the system capacity performance between EDT and semi-smart antennas for traffic load balancing. Coverage under load balancing is optimal with respect to the whole network, rather than just for individual antennas. The results show that both the adaptive approaches give benefit, with different site costs in relation to practical antenna system complexity