Method for coordinating propagation delays in a satellite linked simulcast network using a benchmark station

• US 5,697,051 A
• Filed: 10/27/1995
• Issued: 12/09/1997
• Est. Priority Date: 08/11/1993
• Status: Expired due to Term

• Current Assignee: Quarterhill Inc. (f/k/a Wi-LAN Inc.)
• Original Assignee: Glenayre Electronics Incorporated (EDCI Holdings Incorporated)
• Inventors: Fawcett, Glenn S.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): Sobutka, Philip J.
• Application Number:
  US08/549,055
• Time in Patent Office: 774 Days
• Field of Search: 455/12.1, 455/13.1, 455/13.2, 455/7, 455/38.1, 455/51.1, 455/51.2, 455/53.1, 455/67.1, 455/67.6, 455/69, 455/70, 455/502, 455/503, 375/356, 340/825.44, 340/825.14, 340/825.47, 370/517, 370/519
• US Class Current: 455/13.2
• CPC Class Codes: H04B 7/2126 using a reference station
• CPC Class Codes: H04B 7/2625 using common wave
• CPC Class Codes: H04B 7/2662 Arrangements for Wireless System Synchronisation
• CPC Class Codes: H04H 20/67 Common-wave systems, i.e. using separate transmitters operating on substantially the same frequency
• CPC Class Codes: H04W 56/0065 using measurement of signal travel time

Abstract

A clock synchronization system for synchronizing a number of paging stations (24) with a system controller (23). Each paging station has a clock that includes a counter (52) that indicates the current local time and which is sequentially incremented by a counter advance signal applied thereto. A voltage controlled oscillator (58) generates the clocking signal that controls the advancement of the counter. A CPU (50) in the system controller monitors the time indicated by the counter and compares it to timing information received from a system clock. The timing information includes a time mark and a time mark send time. The system clock transmits to each paging system the time mark. At a future time, the system clock transmits the time mark send time which is the precise time at which the time mark was transmitted. The paging stations each measure the time interval between the time at which the time mark arrived and the time at which the time mark was transmitted by the system clock period. By subtracting the time at which the time mark was transmitted by the system clock and the propagation time to each paging station, each paging station can determine and correct the error in its clock.

Claims

1. A method of determining a coordinated propagation delay of a signal between a system controller and a plurality of paging stations, said signal being transmitted over a satellite link, said plurality of paging stations including a benchmark paging station and at least one other paging station, said method comprising the steps of:

measuring a propagation delay at a first time for the signal propagating between the system controller and said benchmark station;

measuring the propagation delay at a second time for the signal propagating between the system controller and said one other paging station;

measuring the propagation delay at said second time for the signal propagating between the system controller and said benchmark station; and

setting said coordinated propagation delay for said one other paging station as the propagation delay of said one other paging station at said second time less the difference in propagation delays for said benchmark station at said second time and said first time.