Browse Prior Art Database

PROBABILITY-BASED TIME-OUTS IN A PACKET DATA SYSTEM

IP.com Disclosure Number: IPCOM000009026D
Original Publication Date: 1999-Jan-01
Included in the Prior Art Database: 2002-Aug-01
Document File: 3 page(s) / 122K

Publishing Venue

Motorola

Related People

Mike Needham: AUTHOR [+2]

Abstract

Data communication systems which rely on acknowledgement-based out mechanism to re-send data packets in the event of no communication link. However, the acknowledgement may be a simple case, unnecessary re-transmission of data packets may occur.

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MO-LA Technical Developments

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PROBABILITY-BASED TIME-OUTS IN A PACKET DATA SYSTEM

by Mike Needham and Steve Gilbert

BACKGROUND

  Data communication systems which rely on acknowledgement-based out mechanism to re-send data packets in the event of no communication link. However, the acknowledgement may be a simple case, unnecessary re-transmission of data packets may occur.

  In most current data systems, time-out timers are an attempt to adapt to measured acknowledge- ment delays. These failures are due to error condi- tions on the channel from those due since if an acknowledgement fails due to errors, it is minimize delay. However, if an acknowledgement is not returned retransmissions would only aggravate the channel congestion.

INVENTION

  We propose a new method of time-out control in which the time due to traffic congestion is continu- ally calculated as of an acknowledgement being lost because of channel errors. When acknowledgement being delayed drops below the probability that (See the "Details" section for information on how to

  This is an improvement on previous time-out methods because account in determining whether a packet should be resenting for a likely delayed acknowledgement. This allows prompt (especially important for error-prone and throughput limited retransmissions for packets with delayed acknowl- edgements.

  This invention requires the transmitting data unit to make the amount ,of traffic congestion. Error conditions may be easily acknowledgments of data received with errors, such as with the co1 for iDEN. Assessments of channel ~ conditions based on gesta- tion can be assessed based on recent acknowledge- ment delays channel traffic by the data unit. Such information may also be

DETAILS

Calculation of delay probability:

  In an M/M/l queuing system, with a relative offered load of p. the probability of the queuing delay Tom being greater than the current time T,,w is given by the formula [ 11:

PCTDEL.>TNOW~ = Pe

41 -.,*z

where TUCK is the average packet transmission time. Note that TDEI re p resents the "excess" delay for an acknowledgement to be returned, that is, delay in excess of some known.

It is assumed that the acknowledgements will be queued behind to the relativeioffered load of the reverse channel (which can reverse channel). For cases where acknowledgment packets have on prioritized queues would be needed [2].

Calculation of error probability:

There are two possible cases in which an acknowledgement packet...