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Optimal Switching Algorithm for Multibeam Satellite Systems With Variable Bandwidth Beams

IP.com Disclosure Number: IPCOM000041434D
Original Publication Date: 1984-Jan-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 4 page(s) / 58K

Publishing Venue

IBM

Related People

Bongiovanni, G: AUTHOR [+5]

Abstract

In a Satellite-Switched Time Division Multiple Access (SS/TDMA) system the satellite has a number of spot beam antennas covering geographically distributed zones and a solid-state RF switch on board to provide connections between the various uplink and downlink beams. A TDMA frame is divided into several time slots, and each slot has corresponding to it a switching configuration permitting a certain amount of traffic to be transmitted. The objective is to ensure that all traffic in a given traffic matrix can be transmitted without conflict within the TDMA frame and to accomplish this with maximum transponder utilization. In the following we consider a SS/TDMA system with M uplink beams and N downlink beams, where uplink beam i has bandwidth bi and downlink beam j has bandwidth aj .

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Optimal Switching Algorithm for Multibeam Satellite Systems With Variable Bandwidth Beams

In a Satellite-Switched Time Division Multiple Access (SS/TDMA) system the satellite has a number of spot beam antennas covering geographically distributed zones and a solid-state RF switch on board to provide connections between the various uplink and downlink beams.

A TDMA frame is divided into several time slots, and each slot has corresponding to it a switching configuration permitting a certain amount of traffic to be transmitted. The objective is to ensure that all traffic in a given traffic matrix can be transmitted without conflict within the TDMA frame and to accomplish this with maximum transponder utilization. In the following we consider a SS/TDMA system with M uplink beams and N downlink beams, where uplink beam i has bandwidth bi and downlink beam j has bandwidth aj . The maximum traffic which can be handled by the satellite (in any given time slot) is assumed to be K. Multiplexing and demultiplexing are also assumed. An optimal time slot assignment algorithm to minimize the total transmission time for any given traffic demand matrix is proposed and analyzed. Mathematical Formulation A traffic matrix D is an MxN matrix with non-negative entries, where entry dij represents the traffic from uplink i to downlink j. The downlink bandwidths are represented by the vector a = (a1,a2,...,aN), where aj is a positive integer representing the bandwidth of the jth downlink. Similarly the vector of b represents the uplink bandwidths. The capacity of the satellite, K, is the maximum amount of traffic the satellite can carry in one time slot. Throughout the article we assume 1< K < min (Saj,Sbi). The jth column sum, cj, of a matrix is defined to be the sum of all entries in the jth column. Similarly, the ith row sum, ri, is defined as the sum of all entries in the ith row. We shall sometimes use the generic term line to refer to either a column or row of a matrix. A (a_ b_,) switching matrix (abSM) is an MxN matrix with non-negative integer entries and such that cj< aj, 1< <N, and ri< 1< <M. It represents the traffic which can be transmitted in one time slot. A complete abSM is defined as an MxN abSM with cj = aj, 1< <N, and ri = bi, 1< <M. A Quasi Doubly Stochastic (QDS) matrix is an NxN traffic matrix for which cj = S, 1< <N, and ri =

S, 1< <N, where S is some positive integer. S is called the line sum of the matrix. A Normalized Quasi Doubly Stochastic (NQDS) matrix is an MxN traffic matrix with cj/aj = S, 1< <N, and ri/bi = S, 1< <M. S is some positive integer and is referred to as the normalized line sum of the matrix. Fig. 3 provides an example of such a matrix.

The Traffic in a matrix is defined as the sum of all entries in that matrix. Problem Formulation Given a traffic matrix D, uplink and downlink speed vectors b and a and capacity of the satellite, K, to find a decomposition of D, D = D1 + D2 + D3 + .... Dt, such that: (i) all the...