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CHANNEL ACTIVITY SENSITIVE WATCH DOG TIMER FOR ACK/NACK RECEPTION MONITORING

IP.com Disclosure Number: IPCOM000007660D
Original Publication Date: 1996-May-01
Included in the Prior Art Database: 2002-Apr-12
Document File: 1 page(s) / 63K

Publishing Venue

Motorola

Related People

Ray Van Tassle: AUTHOR [+2]

Abstract

AFCO 25 specifies a packet data service that must coexist on a shared channel with voice. When oper- ating the data service, ACKS and NACKS are trans- mitted back and forth as appropriate. Watch dog timers are used to monitor timely receipt of such messages. Voice can capture the channel, however, and delay transmission of the ACK/NACK. If the timer expires before an ACK can be received because of intervening voice, retransmission of the original message may be unnecessarily initiated.

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MOTOROlA ,Technical Developments

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CHANNEL ACTIVITY SENSITIVE WATCH DOG TIMER FOR ACWNACK RECEPTION MONITORING

by Ray Van Tassle and Mike Crowley

  AFCO 25 specifies a packet data service that must coexist on a shared channel with voice. When oper- ating the data service, ACKS and NACKS are trans- mitted back and forth as appropriate. Watch dog timers are used to monitor timely receipt of such messages. Voice can capture the channel, however, and delay transmission of the ACK/NACK. If the timer expires before an ACK can be received because of intervening voice, retransmission of the original message may be unnecessarily initiated.

  In operation, the base end sends a packet to a mobile radio, then allows a period oftime (typically 4-5- seconds) for the mobile radio to send the ACK. If this ACK is not received within this period, the base will re-transmit the message.

  An ACK message only takes about 50 msec, so allowing 500 msec (OS set) gives us 10X the mini- mum time, which is plenty of time for the mobile radio to send the ACK.

  This watch dog timer effectively "watches" two different kinds of "time;" real time and available- data-transmission time. When the watch dog begins, the real time count is first, and a predetermined period of time (e.g., 4.5 seconds) is counted down,

regardless ofwhat activity is occuring on the chan- nel (data, voice, noise, or nothing). Once the real time count is complete, the watch dog begins a sec- ond count, this time counting down av...