Automatic antenna tilt control for capacity enhancement in UMTS FDD

Simulations were performed to evaluate the effect of adaptively adjusting the base station antenna vertical tilt angle to adapt to the current geographical traffic load distribution and thereby achieve an overall capacity increase in UMTS FDD. The capacity increase is very dependant on the traffic conditions. Using a generic 21-cell scenario and positioning three traffic hotspots within the area with varying position relative to the base stations, the capacity increase was in the order of 30% on average at a 99% grade-of-service. The capacity improvement by using tilt adjustment increases with increasingly unbalanced traffic, as expected. Automatic tilt control represents a viable alternative for interference reduction purposes and thereby provisioning of better overall network capacity during dynamically changing traffic situations.