Browse Prior Art Database

SUPERVISION OF PORTABLE RADIOTELEPHONES WITH VOICE-ACTUATED TRANSMISSION

IP.com Disclosure Number: IPCOM000005440D
Original Publication Date: 1982-Jan-01
Included in the Prior Art Database: 2001-Oct-10
Document File: 3 page(s) / 192K

Publishing Venue

Motorola

Related People

Larry Puhl: AUTHOR

Abstract

High capacity radiotelephone systems such as the Motorola DYNATAC system require extensive supervision of the mobiles and portables in the system. The DYNATAC system (see U.S. Patent No. 3,906,166) divides the service area into cells. Service for a particular mobile or portable is transferred from cell to cell as the unit travels through the system. Periodic monitoring of signal strength is required to ac- complish this. This periodic monitoring becomes a problem with VOX (Voice Operated Transmission) because the portable is only transmitting when the user is talking. A "power up" digital command message could be sent to the portable, but every transmission of a digital message to the portable inter- rupts voice reception and is therefore not desirable unless absolutely necessary. The portable unit can be monitored only when the unit is VOXed-up, but this would leave gaps in the supervision during long periods of novoice activation at the portable.

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m@Imm&.kd Technical Developments Volume 2 January 1962

SUPERVISION OF PORTABLE RADIOTELEPHONES WITH VOICE-ACTUATED TRANSMISSION

By Larry Puhl

STATEMENT OF PROBLEM

   High capacity radiotelephone systems such as the Motorola DYNATAC system require extensive supervision of the mobiles and portables in the system. The DYNATAC system (see U.S. Patent No. 3,906,166) divides the service area into cells. Service for a particular mobile or portable is transferred from cell to cell as the unit travels through the system. Periodic monitoring of signal strength is required to ac- complish this. This periodic monitoring becomes a problem with VOX (Voice Operated Transmission) because the portable is only transmitting when the user is talking. A "power up" digital command message could be sent to the portable, but every transmission of a digital message to the portable inter- rupts voice reception and is therefore not desirable unless absolutely necessary. The portable unit can be monitored only when the unit is VOXed-up, but this would leave gaps in the supervision during long periods of novoice activation at the portable.

   One could arrange a monitoring "queue" for mobiles and a separate one for portables SO that por- tables could be checked when they are on the air. However, it is desirable to have the same Supervision method apply to mobiles, as well as portables. Using only one method is simpler than two separate methods, one for mobiles and one for portables.

   A further problem relates to the supervision of portables in a multi-cell service area and the use Of supervision to avoid interference. The use of a plurality of supervisory audio tones (SAT tones), in con- junction with the RF channel reuse plan is proposed to alleviate interference problems. The SAT tones are selected from a frequency band above the audio range and are used to associate subscriber units with cell sites. The SAT tone is sent from the base site to the mobile/portable, is transponded back and is compared to the tone originally sent. This confirms that the base site is listening to a mobile/portable assigned to it.

   Reducing interference is easier with mobiles than with portables, because the mobile transmitter is always on. Therefore, it is able to "capture" the FM receiver in the base site, thus preventing remote foreign mobiles from being heard. When a portable is VOXed down, it is possible for portables associated with other cell sites to be heard. Therefore, portables need a method to minimize interference.

SOLUTION

A method for supervision of VOX opera!ed portable radiotelephones is suggested here, which can be implemented in hardware or software. Refer to Figures 1 and 2 for the following description.

   Base site A in Figure 1 is maintaining voice paths to the portable and mobile. Each voice path con- sists Of a forward channel originating at base site A and a reverse channel originating at the mobile and portable. The mobile keeps its reverse channel on continuously...