Browse Prior Art Database

CONTROLLED FALL BACK REPEAT OPERATION SIMULCAST SYSTEM

IP.com Disclosure Number: IPCOM000009340D
Original Publication Date: 1999-Jun-01
Included in the Prior Art Database: 2002-Aug-19
Document File: 3 page(s) / 164K

Publishing Venue

Motorola

Related People

Pete Biancalana: AUTHOR

Abstract

In order to provide contiguous talk-out coverage area that is larger than can be accommodated by a single base station transmitter, systems are contig- ured to provide simulcast transmission from multi- ple transmitters. The use of multiple transmitters will create areas in the coverage zone that will be reached by two or more transmitters. These areas are called simulcast overlap areas. In order to minimize interference between the transmitters, the modulat- ing signal is synchronized so that it is transmitted at the same time from each station.

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MOTOROLA Technical Developments

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CONTROLLED FALL BACK REPEAT OPERATION SIMULCAST SYSTEM

by Pete Biancalana

  In order to provide contiguous talk-out coverage area that is larger than can be accommodated by a single base station transmitter, systems are contig- ured to provide simulcast transmission from multi- ple transmitters. The use of multiple transmitters will create areas in the coverage zone that will be reached by two or more transmitters. These areas are called simulcast overlap areas. In order to minimize interference between the transmitters, the modulat- ing signal is synchronized so that it is transmitted at the same time from each station.

  Analog systems have typically handled this syn- chronization by using a single audio source and delivering it to each station at the same time for transmission. To implement this requirement a fair- ly expensive audio distribution network is required.

  Digital system design, as embodied in the ASTPO system, use a different method of synchro- nization. Since the audio is now digitized, it is dis- tributed from a central source, much like the analog counterpart. The digitized audio is delivered to each transmitter over a much less expensive link, typi- cally a leased phone line. The synchronization of the audio signal is accomplished by using a 1 Pulse Per Second signal from a GPS receiver. The digital audio packets sent from the central source also include a launch time parameter which is correlated to the 1 PPS signal from the GPS receiver. A typical system configuration is shown in Figure 1 on next

page.

  The connecting links between the station, receiver and comparator are typically 4 wire leased phone lines. These phone lines will at times fail and cause the station using that link to be disconnected from the comparator. When the link fails, a signifi- cant portion of the users in the total coverage area can lose communication capability, that is users in a particular atea will no longer be able to communicate with each other. In situations such as these, system designem provide backup communications capabilities.

  The simplest method of backup is to change the configuration of the station that is connected to the comparator through the link that is now failed. The configuration is changed from a simulcast station to a station that functions as a simple in cabinet repeater. The control for the switching of the station configurations is implemented at the designer dis- cretion using whatever means fit the application best.

  Two common methods of control are RF control or MOSCAD control. RP control is typically provid- ed by a DTMF decoder at the station site. The decoder receives a DTMF sequence originated by supervisory personnel and provides a logic input to the station to initiate the configuration change. MOSCAD is a Motorola system which can be used to provide logic outputs. Again originated by super- visory personnel, the MOSCAD S system will pro- vide a logic output which will...