tailieunhanh - Resource Management in Satellite Networks part 16

Resource Management in Satellite Networks part 16. This book provides significant knowledge on innovative radio resource management schemes for satellite communication systems that exploit lower layer adaptivity and the knowledge of layer 3 IP QoS support and transport layer behavior. The book integrates competencies considering all the parts of system design: propagation aspects, radio resource management, access protocols, network protocols, transport layer protocols, and more, to cover both broadband and mobile satellite systems | 132 Giovanni Giambene Cristina Parraga Niebla Victor Y. H. Kueh makes the state transition time from the contending to the active state to exceed the limit posed by the codec . the voice packet deadline typically of few tens of ms . For these systems a simple reservation scheme may be used where a reservation per call is made. In LEO systems however RTD is much smaller between 5 and 30 ms and PRMA techniques are applicable. A feasibility study for the adoption of PRMA in the LEO case is made in 11 - 14 including the selection of the permission probability p and the frame duration Tf. It should be noted that there is a substantial difference between the S-UMTS air interface and the air interface assumed by classical PRMA. PRMA relies solely on time division whereas S-UMTS can be characterized as a hybrid CDMA TDMA system. Therefore CDMA TDMA variations of PRMA must be considered such as the one proposed in 15 where UTs select a code in addition to a time slot in order to transmit their access bursts in a very similar fashion as we previously described. The flow chart shown below in Figure is an example of how S-UMTS channels can be used in order to adopt a PRMA-based scheme. We assume that a UT will require to use a Dedicated Channel DCH consisting of one Dedicated Control Channel DCCH and one or more Dedicated Traffic Channels DTCHs DCCH and DTCH are logical channels depending on the upper layer requirements. These requirements can be stated in the message part of the RACH burst. If the burst is not received properly the UT schedules a retransmission using the permission probability p which is announced by the system using the BCH channel as specified in 5 . Note also that by using different channels for contention RACH and data transmission DCH we keep the collision probability constant and independent of the already assigned DCH channels. This separation of contention and data channels constitutes a substantial difference from classical PRMA schemes. Note