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RUTHLESS PREEMPTION FOR EMERGENCY CALLS IN RF CONTENTION SITUATIONS

IP.com Disclosure Number: IPCOM000004913D
Original Publication Date: 2001-Jul-11
Included in the Prior Art Database: 2001-Jul-11
Document File: 2 page(s) / 22K

Publishing Venue

Motorola

Related People

Steve VanSickle: AUTHOR [+2]

Abstract

RUTHLESS PREEMPTION FOR EMERGENCY CALLS IN RF CONTENTION SITUATIONS

This text was extracted from a WORD97 document.
This is the abbreviated version, containing approximately 86% of the total text.

RUTHLESS PREEMPTION FOR EMERGENCY CALLS IN RF CONTENTION SITUATIONS

By Steve VanSickle, Laura Kleinschmidt

BACKGROUND/ PROBLEM

The present invention relates to internal digital signal prioritization operation in a comparator. In conventional systems, each radio ID has the same priority and is processed on a first, come first served basis. If one subscriber has the channel and another subscriber attempts to make a call where at least one good copy of the signal is received, the first subscriber will retain control of the channel. For the majority of situations this operation is perfectly acceptable. In an emergency situation, however, it would be preferable for the emergency call to override the previous call and gain control of the channel.

When an emergency call is attempted, the call starts with an emergency alarm data packet followed by emergency digital voice packets. If there is no activity on the channel the data packet will be routed to the console operator where an emergency indication will be displayed. The corresponding audio will also be routed to the console as well as repeated back out to the transmitters. However, if there is activity on the channel, the data frame will be discarded and the audio will be queued up but will not be routed until the channel becomes available. (That is assuming the subscriber initiating the emergency is still keyed up when the channel becomes available.)

SOLUTION

The solution to this is in providing a method for ruthless preemption of a non-emergency call when an emergency call is attempted on the same channel. When a user initiates an emergency call on the same channel on which a non-emergency call is in progress, if the comparator receives at least one good copy of the emergency user's signal, the comparator will prioritize the emergency call over the non-emergency call. In order to do this, the comparator would be modified to detect an emergency call and would give this call priority over other calls being processed. This would need to be done not only for the initial emergency data packet, but also for the following voice packets.

For the emergency data packet, the comparator will simply recognize this as an emergency packet and give it priority over other signals being processed allowing it to take over the existing signals and be sent on to the console.

For voice this would work a little different. The comparator will not know immediately that this is an emergency call. The comparator needs to look into the Link Control (LC) information, embedded in the voice packets, to determine if this is an emergency call. If so, it would give this subscriber's audio priority over any other signals being processed. However, due to the LC information being spread across multiple voice packets, the comparator will be unable to determine this is an emergency call until up to 360 ms into the call. During this time, due to delay...