Adaptive Resource Allocation and Rate Control for Heterogeneous Traffic on DBS Links

Abstract

In a Direct Broadcast Satellite (DBS) system, the capacity of the DBS forward satellite link may become a “bottleneck” operating under heterogeneous traffic and dynamically changing channel conditions. To meet this challenge, we propose an Adaptive Resource Allocation and Management (ARAM) system that attempts to maximize the utilization of the available capacity on the forward DBS link while maintaining Quality of Service (QoS) in the presence of channel effects and congestion in the network. The proposed algorithm attempts to maximize statistical multiplexing gain, under varying channel and traffic conditions, by distributing the rate reduction during congestion evenly among services, thus, providing graceful degradation during overload intervals. By using QoS reports and transmit queue monitoring, the ARAM system utilizes adaptive control of transmission attributes (channel and source rates). Since measures of congestion, QoS and channel variations involve observation over different time periods, the proposed adaptive control mechanism consists of four control strategies that are activated at different time scales: short (STC), short-to-medium (SMTC), medium (MTC) and long (LTC) term controls. Furthermore, in order to improve QoS of end-users, a signal-to-noise ratio (SNR) sensing technique is included to determine the channel state and correspondingly, set the appropriate forward error correction (FEC) rate to resolve the channel problems. The ARAM simulator is developed to show the benefits of employing the adaptive rate control mechanisms by comparing its performance with “no-control” case. The results show that the concept of source and channel rates adaptation offers a great potential in controlling the QoS and efficient link capacity utilization and system throughput, when traffic and channel conditions vary with time.