Sensitivity of optimum downtilt angle for geographical traffic load distribution in WCDMA

The target of this paper is to evaluate the impact of geographical traffic load distribution the optimum downtilt angle of macrocellular WCDMA network. Moreover, the aim is to solve the feasibility of the usage of fast rate RET and to evaluate its possible capacity gain with respect to distribution of traffic load. The simulation results have revealed how allowed range of downtilt angles varies between 6 ◦ and 14 ◦ depending on whether the traffic is concentrated closer to cell edge or closer to base station. However, with this particular network configuration, 8 ◦ downtilt angle would provide almost the maximum uplink and downlink capacities with all simulated traffic distributions (maximum 5% degradation in downlink capacity). This indicates that there is no use for fast-rate adaptation of tilt angle with respect to changes in the geographical user distribution due to its low capacity gain and possibly complex implementation algorithm. This does not totally exclude the use of RET as it facilitates network optimization regarding tilt angles. Also, fast rate RET algorithm can be used for load balancing in high loaded networks.