Quality of service provision under channel fading

Abstract

Advanced communications satellite systems provide packet-switched high-speed transport services for various user applications, ranging from data services to imagery, voice, and video. Satellite uplinks and downlinks may experience various channel fades due to weather, blockages, terrestrial multipath, or jamming. A suite of mitigation techniques have been proposed to mitigate the wide range of channel impairments and optimize the use of available spectrum to deliver the highest possible data rate while satisfying quality of service (QoS) requirements. These techniques include channel interleaving and forward error correction (FEC) in the physical layer, dynamic coding and modulation (DCM) and automatic repeat request (ARQ) in the data link layer, prioritized packet forwarding in the network layer, and application codec adaptation (ACA) in the application layer. Since each mitigation strategy could potentially interact between layers, it is essential not only to assess the performance of each mitigation technique, but also to understand how multiple techniques work together. 12 This paper describes an emulation study of channel impairment mitigation using a combination of DCM, absolute priority scheduler (APS), and ACA. This is a continuation of our cross-layer mitigation studies previously published in [1,2]. Multiple video streams in different priorities were employed to demonstrate how underlying mitigation techniques work together to preserve the QoS of multiple applications under various channel fades. This paper presents the test bed architecture, mitigation techniques, test configurations, and test results.