When Do We Need Rate Control for Dedicated Channels in UMTS?

The Universal Mobile Telecommunication System (UMTS) offers rate controlled radio bearers for best effort traffic. The purpose of rate control is to maximize resource utilization and concurrently to provide best-effort users with an acceptable grade-of-service. Due to the user behaviour or the used application of a mobile subscriber we distinguish between two types of best-effort users. The time-based users stay for a certain time within the network and download an arbitrary amount of data. Volume-based users leave the network after they have downloaded a specific data volume. The contribution of this work is an evaluation of time-based and volume-based best-effort traffic over rate-controlled DCHs by analytic means and with a detailed packet-level simulation. The results of both approaches are qualitative equal: while the rate control mechanism works effectively for time-based users and allows any rate, the assigned rates for the volume-based users take values between two extremes, either the minimal or the maximal rate