Enhancing satellite broadcasting services using multiresolution modulations

In this paper we propose to take advantage of the energy link margin that can exist of satellite connections to enrich the DVB-S services with Web-like interactive services. The exploitation of such a margin is obtained by using multiresolution modulation techniques. The system architecture analysed is asymmetrical, composed of a satellite forward link and a narrowband terrestrial reverse link. ATM is adopted to support different QoS for different types of information delivered. The satellite propagation delay and the traffic and congestion control of ATM suggest to modify the slow start and the congestion avoidance of the TCP. Our approach is based on the combination of a fixed window flow control at the transport layer with the ATM traffic and congestion control. Our analysis shows that the system performance is satisfactory if some bounds of the TCP buffer size are respected and the spacing of the resource management cells is within a given range of values.