Abstract
Capacity and coverage represent, in addition to QoS, the three main requirements for W-CDMA based 3G mobile communication systems. These are conflicting requirements; i.e., optimizing one will be on the account of the other two. All three, however, depend largely on the interference levels in the system. Improvements on interference are thought to have a decisive effect on the performance of the 3G system and one important interference reduction technique is the utilization of smart antennae. In this paper, we analyze capacity/coverage on the uplink in W-CDMA system utilizing switched beam smart antennae, SBSA, using a simple model of the antenna, while satisfying a certain minimum level of QoS. Limits imposed by both interference from others and the limited uplink power available to any user in the cell are considered. Results of this paper are analytical formulae for capacity/coverage that take into consideration many of the important parameters of either the antennae or the WCDMA system. A sectional view of improvement gains, if any, of either capacity or coverage upon antenna upgrading/downgrading is provided. It is shown that improvements by the directional SBSA of either capacity or coverage, are only attained at high interference conditions; i.e., higher number of users when considering coverage improvement or smaller coverage areas when considering capacity. The higher the interference conditions are the higher gain over side lobes or more beams SBSA are needed to attain improvement.