Impact of rate control on the capacity of an Iub link: multiple service case

Universal Mobile Telecommunication System (UMTS) networks are capable of serving packet-switched data applications at bit rates as high as 384 kbps. Multiplexing multiple data sessions in the radio access networks (RAN) of a UMTS network brings a tremendous capacity gain with respect to the circuit-switched networks, however the utilization of resources are very low due to the bursty nature of data traffic. This paper studies the capacity and utilization of the downlink of the Iub interface, which lies between the radio network controller (RNC) and the base station (NodeB) in a UMTS network. In earlier work, we presented simulation results that indicate that the Iub link utilization is very low with bursty web browsing data especially if each data user is allowed to peak at 384 kbps. Thus, we introduced a rate control algorithm by which the MAC layer constrains the peak rate of a user based on current load conditions. In this paper, we extend that study to the case where multiple service classes (64, 128 and 384 kbps) are multiplexed on the same Iub link. There are some fundamental differences between the ways it is implemented in the multi-service case. We tested the multiservice rate control algorithm with some mixed service scenarios where we noted significant increase in capacity.