SUMMARYWe 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.
SUMMARYThis paper proposes a complete satellite access network solution for multimedia broadcast multicast service (MBMS) delivery based on T-UMTS standards. First, the benefits of MBMS delivery via satellite (SAT-MBMS) for both S/T-UMTS network operators are shown with market and business analysis. A new integrated S/T-UMTS architecture for MBMS delivery is proposed featuring an intermediate module repeater (IMR) for coverage of urban areas. The architectural options of IMR and terminals are discussed considering the relevant cost and complexity. The IMR propagation channel conditions are investigated and a new propagation channel model is proposed. The potential of advanced coding schemes such as the layered coding technique to tackle the channel variations in broadcast/multicast environment is outlined. The functional and protocol architecture are defined along with the interface between the satellite access network and the UMTS core network. Required modifications on the terrestrial access scheme sub-layers to support MBMS data are investigated and the relevant logical, transport and physical channels are selected. Based on the channel selection and the point-to-multipoint service nature, we define a generic radio resource management (RRM) strategy that takes into account both QoS and GoS requirements. The efficiency of the proposed solutions is evaluated in the presented simulation results, advocating the feasibility of the overall approach.
A new positioning method for location tracking in mobile satellite communication is described. In this method, terminals use the BCCH channel information about the spotbeams centre position to determine their own location. The advantage of this method is, that there is no great modification required to the hardware or software of the terminals. The effectiveness of this method for location tracking is verified against the Dynamic Location Update method using different type of paging methods.
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