Effect of Timing Adjust Algorithms on Iub Link Capacity for Voice Traffic in W-CDMA Systems

The goal of the timing adjust algorithm in UMTS networks is to adjust the arrival times of downlink frames from RNC to the Node B so that the frames arrive within a predefined time window before the scheduled transmission time of the frame. The algorithm provides feed back from Node B to the RNC causing delay or advance of the next transmitted frame based on arrival time of the current frame. In this paper we present a study of the timing adjust algorithms in UNTS networks on the Iub link capacity for voice traffic. Through simulation we present estimates of call carrying capacities and statistical multiplexing gain on Iub link of different capacities. Based on our study of traces from our simulation studies we present an analytical framework to explain the impact of the timing adjust algorithm on the statistics of Iub delay for voice traffic.