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RECOVERY OF TSBK'S IN A MULTI-CAST SYSTEM VIA VOTING SCAN

IP.com Disclosure Number: IPCOM000009747D
Original Publication Date: 2000-May-01
Included in the Prior Art Database: 2002-Sep-16
Document File: 1 page(s) / 64K

Publishing Venue

Motorola

Related People

John Hamrick: AUTHOR [+2]

Abstract

In an effort to reduce the cost of a simulcast system a multicast system has been created. In these systems the outbound (to the subscriber) audio is transmitted from several base repeaters at the same time. Each of these base repeaters transmits on a dif~ ferent frequency. In order to provide a wide area roaming capabil~ ity, the subscriber radios scans the different station transmit frequencies. When activity is found on one of the frequencies, the radio quickly checks the remaining frequencies to detennine which frequency has the strongest signal. The radio will then select the frequency with the strongest signal and unmute.

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MOTOROLA

Technical Developments

RECOVERY OF TSBK'S IN A MULTI-CAST SYSTEM VIA VOTING SCAN

by John Hamrick and David Mills

In an effort to reduce the cost of a simulcast system a multicast system has been created. In these systems the outbound (to the subscriber) audio is transmitted from several base repeaters at the same time. Each of these base repeaters transmits on a dif~ ferent frequency.

In order to provide a wide area roaming capabil~ ity, the subscriber radios scans the different station transmit frequencies. When activity is found on one of the frequencies, the radio quickly checks the remaining frequencies to detennine which frequency has the strongest signal. The radio will then select the frequency with the strongest signal and unmute.

On a digital voice call the radio will see carrier activity on the first frequency. It will then scan all the other possible frequencies in its vote scan list (up to a maximum of 6) to see if there is activity on any other frequency. The radio will then select the strongest signal and unmute.

In the case of the voice call the radio will have missed the header and most of the first voice frame (and possibly part of the second voice frame) while the radio is scanning the other frequencies. This makes the radio enter the digital voice call late. In a late entry condition the radio may miss up to 720 msec of audio as it tries to detennine the call type and the call's encryption information.

In digital systems signalling control packet...