QoS Support on DVB-S2/RCS: IP-friendly Cross-Layer Approaches

Abstract

The rapid growth of Internet-related multimedia services has placed an enormous strain towards an optimal usage of the wireless time-variant capacity. DVB-S2 adaptive physical layer allows achieving near-Shannon capacity at the physical layer thus providing significant capacity gains with respect to using fixed physical layer. However, such gains may be lost if higher layers do no adapt coherently to the physical layer dynamics. In addition, different delay requirements of multimedia traffic requiring QoS provision introduce the well-known capacity-delay trade-off, which can be addressed with a proper design of the upper layers. This tutorial focuses on the design of an interactive Multibeam Broadband Satellite (MBS) system with QoS support. A DVB-S2/RCS transparent architecture and fixed terminals using adaptive physical layer will be considered. DVB-S2 transmission power and symbol rate are assumed to be constant, and hence ACM (Adaptive Coding and Modulation) yields a bit rate that is time and space dependant according to the channel conditions. DVB-RCS transmission power is assumed to be constant and DRA (Dynamic Rate Adaptation) along with AC (Adaptive Coding) yield both bit and symbol rate time and space dependant. During the tutorial, a number of cross-layer mechanisms will be introduced whereby the physical, the Medium Access Control (MAC) and the IP layers share knowledge of the channel dynamics in presence of ACM. The cross-layer design approach allows further improvements on packet data admission, scheduling and policing to maximize both capacity and user satisfaction while meeting QoS constraints.