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User scheduling in satellite return links - a perfect graph paradigm

Current satellite systems offer flexibility with respect to different resources such as frequency and time. Building upon this flexibility the present paper investigates the user scheduling problem in satellite return links, focusing on the TDMA scheme of the MF-TDMA paradigm. In particular, a scenario is examined based on the MF-TDMA paradigm of the DVB-RCS2 standard, where different user terminals request access to the satellite return channel in a TDMA scheme. Each user requests access to transmit at a predefined rate. Under the assumed scenario the problem in hand, pertains to that of selecting a subset of non-overlapping users with respect to maximizing the aggregate system throughput. The present paper demonstrates how the problem in hand can be reduced to the maximum weight independent set problem for perfect graphs. This reduction provides an integer programing formulation for the problem, which can subsequently be relaxed to a linear programing problem, with tight relaxation. The problem is therefore formulated as a linear programing problem with integral optimal solutions which can be solved either by the ellipsoid method in polynomial time, or by simplex methods. Moreover, the linear programing formulation of the problem through the perfect graph paradigm, paves the way for the extension of the perfect graph approach to the MF-TDMA scheme, allowing the devise of efficient holistic optimization techniques in the future.