Browse Prior Art Database

SUBSCRIBER RACE CONDITION DETERMINATION IN APCO SYSTEMS

IP.com Disclosure Number: IPCOM000008718D
Original Publication Date: 1998-Jun-01
Included in the Prior Art Database: 2002-Jul-05
Document File: 2 page(s) / 101K

Publishing Venue

Motorola

Related People

Janahan Vivekanandan: AUTHOR [+3]

Abstract

In a wide area multiple site trunked communi- cation system it is possible for multiple subscriber units to request to communicate on the same group at approximately the same time. This is called a subscriber unit race condition. This is possible in a multiple site system since each site could simulta- neously receive the group call request. Since group calls are a one way transmission, only one of the requesting subscriber units can source audio while all others should receive audio. A mechanism must be created which can coordinate these multiple requests such that only one subscriber unit transmits and the remaining requesting subscriber units receive the transmitting unit's audio.

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MOTOROLA Technical Developments

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SUBSCRIBER RACE CONDITION DETERMINATION IN APCO SYSTEMS

by Janahan Vivekanandan, Daniel J. McDonald and Gregory A. Godsell

INTRODUCTION

  In a wide area multiple site trunked communi- cation system it is possible for multiple subscriber units to request to communicate on the same group at approximately the same time. This is called a subscriber unit race condition. This is possible in a multiple site system since each site could simulta- neously receive the group call request. Since group calls are a one way transmission, only one of the requesting subscriber units can source audio while all others should receive audio. A mechanism must be created which can coordinate these multiple requests such that only one subscriber unit transmits and the remaining requesting subscriber units receive the transmitting unit's audio.

DESCRIPTION OF THE INVENTION AND ITS OPERATION

  The goal for solving this problem is to provide a mechanism in which all units have an opportunity to receive a subscriber unit's transmission before placing a subsequent request. Therefore, a sub- scriber unit user should know that there is audio present for the group before possibly interrupting the existing transmission. The fixed network equip- ment (FNE) controller(s) will be responsible for regulating which subscriber unit will be the audio source for a call and which subscriber units will be receiving audio for the call.

DETERMINATION OF TRUCE

  When the fixed network controller receives a group call request, it will attempt to grant the request, Assuming the call can be granted, the fixed end will grant the request and start a timer, TRACE. This timer will be used to mark the time window in which a race condition exits. The duration of the TRKC timer will depend on the requesting device and the configuration of the requester's site. The rules

for determining the length of TRACE are as follows:

* If either the initial requester or the subsequent requestor is a console device then the duration of TRACE
is zero (i.e. subsequent requests will not be considered to be race conditions). Since console devices are full duplex devices, they are capable of receiving and transmitting audio simultaneously. Hence there i...