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SYNCHRONIZATION BETWEEN DISCRETE SIMULCAST SYSTEMS

IP.com Disclosure Number: IPCOM000009487D
Original Publication Date: 1999-Sep-01
Included in the Prior Art Database: 2002-Aug-28
Document File: 2 page(s) / 113K

Publishing Venue

Motorola

Related People

Steven Goldberg: AUTHOR [+2]

Abstract

Same frequency simulcast systems need to maintain relatively close launch times between their transmitter sites. Usually in the order of microsec- onds. There may be other paging systems in the sur- rounding area, but as long as they do not have a mutual interference area or utilize different RF channels, there usually isn't a need for them to maintain a synchronization alignment. It has been found however that at the fringe of coverage a pager can loose contact with its own system, time sync to another system, and then return to its own area out of sync. The time it takes to realize this situation and re-acquire the correct system synchronization can be significant, and cause the pager to miss mes- sages sent to it.

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MO-LA Technical Developments

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SYNCHRONIZATION BETWEEN DISCRETE SIMULCAST SYSTEMS

by Steven Goldberg and Casey Hill

  The most obvious means is to have them trace their timing back to an accurate time reference such as GPS, or some other common time reference. Many service providers however do not want to rely on equipment they do not control, or are unwilling to cooperate or change existing equipment. They also have no desire to rely on information passed from other systems.

  This paper outlines a means to resolve the out- lined situation.

IMPLEMENTATION

  Figure 1 shows System A being monitored by System B. The monitoring system determines its timing offset from the other system. This can done without explicit communication with the other sys- tem, since for there to be a problem, both systems must be of the same synchronization type, such as members of the FEEXTM family. Transmission can therefore occur beginning only on specific timing boundaries.

System B

Fig. 1 Discrete System Monitoring

0 Mommla,lnc. 1999 148 September 1999

OUTLINE

  Same frequency simulcast systems need to maintain relatively close launch times between their transmitter sites. Usually in the order of microsec- onds. There may be other paging systems in the sur- rounding area, but as long as they do not have a mutual interference area or utilize different RF channels, there usually isn't a need for them to maintain a synchronization alignment. It has been found however that at the fringe of coverage a pager can loose contact with its own system, time sync to another system, and then return to its own area out of sync. The time it takes to realize this situation and re-acquire the correct system synchronization can be significant, and cause the pager to miss mes- sages sent to it.

  While the pager could be modified to acquire quicker, this in general would have detrimental effects on the complexity and battery discharge characteristics of the units. A preferable method would be to synchronize the distinct systems suffi- ciently to prevent this situation from being a problem.

System A

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Developments Technical 0 M MO-LA

  The adjustment time between the systems is determined by System B noting when relative to its own clock, System A's start of transmission is received, and subtracting off the speed of light times the distance between the two systems. One familiar with simulcast might initially bel...