Browse Prior Art Database

SIMULCAST REMOTE SITES DELAY MONITORING METHOD

IP.com Disclosure Number: IPCOM000006161D
Original Publication Date: 1991-Jul-01
Included in the Prior Art Database: 2001-Dec-10
Document File: 2 page(s) / 97K

Publishing Venue

Motorola

Related People

Andy Davis: AUTHOR [+2]

Abstract

Simulcast systems require a linear delay adjust- ment for each transmitter site. This delay adjustment is used to "phase" or synchronize the transmission of the data/audio signal at each site. This delay compensates for the different path lengths from the central site to the remote sites. Both analog and digital equipment is available to transfer the audio/data signals from the central site to the remote sites. Microwave systems are the most common form of the distribution network between the central sites and the remote sites. Leased lines from the phone company are another alternative.

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MOlOROLA INC. Technical Developments Volume 13 July 1991

SIMULCAST REMOTE SITES DELAY MONITORING METHOD

by Andy Davis and Zoran Ulicevic

  Simulcast systems require a linear delay adjust- ment for each transmitter site. This delay adjustment is used to "phase" or synchronize the transmission of the data/audio signal at each site. This delay compensates for the different path lengths from the central site to the remote sites. Both analog and digital equipment is available to transfer the audio/data signals from the central site to the remote sites. Microwave systems are the most common form of the distribution network between the central sites and the remote sites. Leased lines from the phone company are another alternative.

  Analog distribution systems require better phase and frequency response performance than typical phone lines provide. This is one reason analog phone lines are not used for simulcast systems. Digital distribution systems do not have this problem. A requirement of both analog and digital distribution systems is that the delay of the line being leased not change. This is because there is no currently available method to quickly and automatically determine the new delay. The PON used in Motorola Trunked Simulcast systems is capable of quickly and automatically changing the delays but currently only uses predetermined values. This requirement is the main obstacle preventing the use of leased lines from the phone company. It is also a serious restriction in large digital systems where there may be many possible paths from the central site to a remote site (DACS).

  Figure 1 shows a method for continuously monitoring the delay behveen the central site and each remote sit,e. This delay is compared with a predetermined "normal" delay and the difference is forwarded to the device which can change the site delays. This allows the distribution path between the

central and remote site to be switched at any time and the delay change automatically determined and compensated for. This eliminates the restriction of using leased phone line and cross connect type systems. The system shown is a digital distribution system althou...