Uplink Connection Scheduling for Flat-Rate Data Services in the UMTS Network

To attract more users to mobile packet services, Universal Mobile Telecommunication System (UMTS) operators have been prompting flat-rate packet services. Since usage does not incur cost, flat-rate users tend to stay online longer and occupy most of the radio channel resources. We consider a UMTS network serving two types of user connections: normal user connections (NUCs) and flat-rate user connections (FRUCs). Our goal is to maximize the revenue of the operator by giving a priority to NUCs over FRUCs without discontenting the flat-rate users, in order not to lose the flat-rate users to other operators. Uplink FRUCs may be asked to subrate or suspend transmission when the radio network is fully utilized. Four combinations of scheduling techniques, including queueing, guard channels (GCs), preemption, and rate adaptation, have been studied, and analytic models using Markov processes were used to evaluate their performances. We proposed a cost function representing the revenue loss due to both blocked NUCs and lost flat-rate users. The system parameters used in our analysis are based on realistic operation data. Our analytic results indicate that the revenue loss can be minimized by using waiting queues (WQs) and preemption. Rate adaptation is ineffective in minimizing the revenue loss because subrated connections are less efficient in using the radio spectrum. GCs for NUCs are unnecessary when a WQ or preemption is used. This paper may be valuable for UMTS operators in serving flat-rate users.