Packet scheduling for the delivery of multicast and broadcast services over S‐UMTS

Abstract

AbstractWe investigate the packet‐scheduling function within the access scheme of a unidirectional satellite system providing point‐to‐multipoint services to mobile users. The satellite system may be regarded as an overlay multicast/broadcast layer complementing the point‐to‐point third generation (3G) mobile terrestrial networks. The satellite access scheme features maximum commonalties with the frequency division duplex (FDD) air interface of the terrestrial universal mobile telecommunications system (T‐UMTS), also known as wideband code division multiple access (WCDMA), thus enabling close integration with the terrestrial 3G mobile networks and cost‐efficient handset implementations. We draw our attention on one of the radio resource management entities relevant to this interface: the packet scheduler. The lack of channel‐state information and the point‐to‐multipoint service offering differentiate the packet scheduler in the satellite radio interface from its counterpart in point‐to‐point terrestrial mobile networks. We formulate the scheduler tasks and describe adaptations of two well‐known scheduling disciplines, the multilevel priority queuing and weighted fair queuing schemes, as candidates for the time‐scheduling function. Simulation results confirm the significance of the transport format combination set (TFCS) with respect to both the resource utilization achieved by the scheduler and the performance obtained by the flows at packet‐level. The performance gap of the two schemes regarding the fairness provided to competing flows can be narrowed via appropriate selection of the TFCS, whereas the achieved delay and delay variation scores are ultimately dependent on the packet‐level dynamics of individual flows. Copyright © 2004 John Wiley & Sons, Ltd.