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General Multibeam Satellite Switching Method

IP.com Disclosure Number: IPCOM000048482D
Original Publication Date: 1982-Feb-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 4 page(s) / 23K

Publishing Venue

IBM

Related People

Bongiovanni, G: AUTHOR [+3]

Abstract

An algorithm is presented which achieves the minimum transmission time for any given traffic demand matrix in a general multibeam satellite Switching/Time Division Multiplex Access (SS/TMMA) system with M uplink beams, N downlink beams, and K connection points. Furthermore , the system is allowed to have the flexibility of different speeds on downlink and uplink beams.

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General Multibeam Satellite Switching Method

An algorithm is presented which achieves the minimum transmission time for any given traffic demand matrix in a general multibeam satellite Switching/Time Division Multiplex Access (SS/TMMA) system with M uplink beams, N downlink beams, and K connection points. Furthermore , the system is allowed to have the flexibility of different speeds on downlink and uplink beams.

In a SS/TDMA system, a satellite has a number of spot-beam antennas and a solid-state RF switch which provides connections between uplink and downlink beams to accommodate the traffic demand. A TDMA frame is divided into a number of switching modes, and to each switching mode a fixed switching configuration is assigned. The traffic demand is characterized by a traffic matrix D, where an entry d(ij) in D represents the traffic demand from uplink beam i to downlink beam j. measured in units of slot time. A "scheduling algorithm" then depicts a way to decompose the given traffic matrix D into component "switching matrices": D=D(1)+D(2)+... D(L), where a switching matrix characterizes a particular switching configuration and the corresponding traffic load being switched. The largest entry in a switching matrix D(i) dictates the "transmission time" corresponding to D(i), and is denoted by D(i). To maximize transponder throughput, one must minimize the total transmission time", (see article) for the complete traffic matrix D.

Previously, the component switching matrix in the above decomposition was always assumed to have at most one positive entry in each row and in each column. This is because the uplink and downlink beams were assumed to have the same speed. Suppose we use the rows in the traffic demand matrix D to designate the source regions and the columns the destination regions. Also, we assume that the speed (channel capacity) of the downlink beam is sufficient to support an a-degree multiplexing of the uplink beams, onto a downlink beam, where alphaless than not equal to 1 is an integer. Then in the decomposition of D, a component switching matrix may now have up to alpha positive entries in a column and at most one positive entry in a row. The "transmission time" of a component switching matrix is again equal to the largest entry in the matrix. If we assume the uplink to be faster than the downlink so that we implement a B- degree multiplexing of uplinks in the satellite, then we have exactly the opposite situation. We consider the general case when the system has M uplink beams, N downlink beems, and K "connection points". Thus the traffic demand matrix is of dimension MxN, and in each component switching matrix there can be at most K positive entries. Suppose the downlink speed is Alpha times the uplink speed and the degree of multiplexing is a, then we have the constraint that (see original). Technical details can be found in (*).

Given an MxN traffic matrix D, let T be the sum of all entries in D. Let R be the max...