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METHOD TO DETERMINE TG AND ENCRYPTION KEY FOR USE IN A SUBSCRIBER TO LAND INTERCONNECT CALL

IP.com Disclosure Number: IPCOM000007667D
Original Publication Date: 1996-May-01
Included in the Prior Art Database: 2002-Apr-12
Document File: 2 page(s) / 81K

Publishing Venue

Motorola

Related People

Hans Christopher Sowa: AUTHOR [+2]

Abstract

The system is a Project 25 conventional land mobile radio system using conventional talk groups (TG). Subscriber to Land Interconnect calls are ini- tiated by the subscriber and are routed through a digital interface unit (DIU) and a mobile radio tele- phone interface (MRTI). Security is provided by the DIU. The interconnect call starts with the subscriber sending an interconnect access message. The DIU/MRTI will respond to this with a dial tone. Then the subscriber sends dialing digits and the DIU/MRTI responds with a ring tone and the phone call is connected with voice communications to follow.

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MOlYlROLA Technical Developments

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MlXHOD TO DETERMINE TG AND ENCRYPTION iKEY FOR USE IN A SUBSCRIBER TO LAND INTERCONNECT CALL

by Hans Christopher Sowa and Alan L. Wilson

SYSTEM BACKGROUND:

  The system is a Project 25 conventional land mobile radio system using conventional talk groups (TG). Subscriber to Land Interconnect calls are ini- tiated by the subscriber and are routed through a digital interface unit (DIU) and a mobile radio tele- phone interface (MRTI). Security is provided by the DIU. The interconnect call starts with the subscriber sending an interconnect access message. The DIU/MRTI will respond to this with a dial tone. Then the subscriber sends dialing digits and the DIU/MRTI responds with a ring tone and the phone call is connected with voice communications to follow.

THE PROBLEMS:

  A conventional TG radio user wants to do a subscriber to land interconnect call. If the subscriber is configured for selective squelch on receive, then the DIU needs to know the TG that the radio is using. If the DIU uses the wrong TG the subscriber will not hear the dial tone because the selective squelch will mute it.

  Another problem occurs if the DIU is con- figured to be secure only and multiple keys are used in the system. The problem is the DIU can only respond with a dial tone in secure and it does not

know the key that has been associated with the con- ventional TG.

THE SOLUTION:

  When the interconnect access message is sent from the subscriber it will include the TG, algo- rithm ID (ALG ID...