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A METHOD OF DATA FLOW CONTROL AND PREEMPTION TO IMPROVE RADIO CHANNEL UTILIZATION

IP.com Disclosure Number: IPCOM000006581D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2002-Jan-16
Document File: 3 page(s) / 238K

Publishing Venue

Motorola

Related People

Kenneth Rideout: AUTHOR

Abstract

Even a properly specified and designed radio data network may occasionally be presented with peak demand loads that are in excess of that statistically pro- filed, resulting in excessive delays and a high incidence of unsuccessful message transfers. Often it will be more desirable to defer or reduce the volume of lower prior- ity messages than to suffer the overall degradation that would otherwise result.

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MOTOROLA INC. Technical Developments Volume 16 August 1992

A METHOD OF DATA FLOW CONTROL AND PREEMPTION TO IMPROVE RADIO CHANNEL UTILIZATION

by Kenneth Rideout

ABSTRACT

  Even a properly specified and designed radio data network may occasionally be presented with peak demand loads that are in excess of that statistically pro- filed, resulting in excessive delays and a high incidence of unsuccessful message transfers. Often it will be more desirable to defer or reduce the volume of lower prior- ity messages than to suffer the overall degradation that would otherwise result.

  This method of data flow control and preemption employs subscriber unil channel utilization sensing. The remote data terminal equipment (specitically, the RF modem) senses the level of activity on the data channel and forwards this information locally to the connected DTE or integral application(s) equipment, as needed to regulate data channel use demand. Using this feedback mechanism, collectively it will be possible for the remote application equipments to both limit the peak activity level to within the "safe" operating range and beneficially maximize channel resource utilization.

  An algorithm which monitors and time-integrates the channel state information that is coded within the channel data block of the physical outbound data mes- sage, provides an in~dication of the average relative inbound channel utilization. The method described herein allows a radio data channel to be operated at or near its optimal utilization level, without network controller or host computer intervention, by dynamically regulating the flow of non-critical inbound messages.

BACKGROUND

  Motorola's proprietary MDC" and its DataT+A*C" Radio Data Link Access Protocol @D-LAP) signalling standards both incorporate Digital Sense Multiple Access (DSMA) controlled channel contention schemes. A char- acteristic of these systems is the increased average delay for message transfer with increased channel utilization. Further, with the potential for "collisions" of contending inbound messages and interference from other sources,

an automatic retry algorithm is included in the protocol to ensure that virtually alI messages will eventually get through, even though only up to four attempts will be permitted. However, at some level of increased demand for the use of the channel a practical channel utilization limit will be reached, beyond which despite retries, the number of unsuccessful message transfers will increase dramatically to an unacceptable level. Upon notification that a message did not get through, a remote DTE user may manually reinitiate their request, exacerbating the situation and possibly creating an avalanche condition which will further degrade system performance.

  Users arc generally unaware of this situation, except by observation of the excessive delays and the "No Acks: and may unwittingly continue to contribute to the tem- porary overload condition. The recovery period will d...