Reducing the signalling overhead for wireless VoIP transmission using weighted prioritisation

Abstract

User scheduling in future cellular networks is a complex and much-studied problem, further complicated in the increasingly relevant scenario of delay-sensitive VoIP applications. In such cases, the full buffer model that attempts to maximise the total sum-rate of the individual users does not adequately capture the satisfaction level of the users. As a result, fairness needs to be introduced and this is done in this paper through a modification of the weighted fair queuing (WFQ) approach to resource allocation that uses buffer status reports from mobile terminals (MTs). Put another way, user rates are weighted by respective buffer fill levels. In addition to outperforming both maximum sum-rate and the ldquoconventionalrdquo proportional fair scheduling (PFS) algorithm in terms of the number of satisfied users for VoIP applications, the WFQ used is shown to be able to help reduce the signalling overhead: it is demonstrated here that the weights applied can be adapted depending on the frequency with which the resource allocation is updated. This enables the system to benefit from the reduction in signalling overhead (which arises from a reduced resource allocation update rate) at a diminished loss of performance. Results are based on practical simulation scenarios that can be applied to both LTE and W-CDMA systems and are revealing in terms of the user capacities these systems can offer under realistic levels of traffic load.