THROUGHPUT DELAY FOR MIXED-LENGTH, MIXED-PERIOD PACKETS WITH BUSY-SENSE MULTIPLE-ACCESS PROTOCOL

Abstract

Packet TM of asynchronous multi-instrumented spacecraft requires framing of packets having different lengths and different arrival intervals. A similar situation would occur in a general message networking application with messages of arbitrary length and arrival rate at a network node. Use of a bus-system for packet transfer, or an order wire for message transfer, requires a minimum rate of status inquiry, and of data read rate, to insure stability and non-overloading. Our paper offers a rather general, but compact, throughput delay analysis suited to packet characteristics from uniform to source-dependent period and length. Arrival probability may vary from “soft” or uniform to “hard” arrival induced by slotted delay. The arrival probability is modular in source packet-period. A closed solution form, though expressible, is not tractable, and a recursive solution was used to obtain numerical results. Computed throughput delays for various combinations of identical sources and mixed sources are illustrated. For identical sources, under “hard” periodic arrival probability, channel slotting is desirable to maintain channel capacity. Some comparative results are offered. For mixed sources with source-dependent packet length and rate, slotting may not be feasible or efficient. Only read-rate controls the expected throughput. The analysis and results shown should prove helpful both to further study and present application of packet TM and message networking.