Efficient time-slot assignment algorithms for SS/TDMA systems with variable-bandwidth beams

Abstract

In this paper, we present efficient sequential and parallel algorithms for computation of time-slot assignments in SS/TDMA (satellite-switched/time-division multiple-access) systems with variable-bandwidth beams. These algorithms are based on modeling the time-slot assignment (TSA) problem as a network-flow problem. Our sequential algorithm, in general, has a better time-complexity than a previous algorithm due to Gopal, et al. (1982) and generates fewer switching matrices. If M (N) is the number of uplink (downlink) beams, L is the length of any optimal TSA, and /spl alpha/ is the maximum bandwidth of an uplink or downlink beam, our sequential algorithm takes O((M+N)/sup 3/min(MN/spl alpha/,L)) time to compute an optimal TSA when the traffic-handling capacity of the satellite is of the same order as the total bandwidth of the links. Our parallel algorithm uses L/2 processors and has a time-complexity of O((M+N)/sup 3/logL) on a PRAM model of parallel computation. We then generalize this algorithm to P/spl les/L/2 processors and describe an efficient implementation of the algorithm on a hypercube multiprocessor with P processors. A massively-parallel version of the algorithm runs in O((M+N)/sup 2/log(M+N)logL) time on (M+N)L/2 processors.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>