UMTS Air Interface Voice/Data Capacity - Part II: Forward Link Analysis
01 January 2001
Universal Mobile Telecommunication System (UMTS) is a 3rd generation wireless communication system based on Wideband CDMA (WCDMA) technologies. Compared to the 2nd Generation (2G) systems, UMTS can offer much larger capacity for voice service and support high-speed data for internet access and multimedia services. In this paper, we evaluate the air interface capacity for voice, data, integrated voice and data services in UMTS. We present our analytical and simulation models for the forward link only. The analysis on the reverse link is presented in a sequential paper. Compared to reverse link, the analysis on forward link is much more challenging because of users' different locations. Furthermore, soft handoff on forward link makes the analysis even more complicated. We present a novel analytical approach to model the transmission power distribution and soft handoff effect. We use different approximation methods to calculate capacity based on voice and/or data traffic loading. Finally, we derive the Erlang capacity expression for a single type of traffic and mixed types of traffic. We also developed a static system level simulator to evaluate capacity for UMTS. We compare our analytical results with simulations and show that our analytical approach has a very good match with simulations.