Method and apparatus for coordinating clocks in a simulcast network

A method of calibrating a paging station clock to a system clock, said paging station clock being used to regulate the transmission of pages, said system clock being associated with a system controller that transmits to said paging station a paging data block, said paging data block including timing information and pages, said timing information comprised of a time mark and a time mark send time, said time mark send time indicating the time of transmit as indicated by said system clock of a previously transmitted time mark, the method including the steps of:

• storing a time of said system clock when said time mark is transmitted to said paging station;
• transmitting said stored time as said time mark send time in a subsequent paging data block;
• receiving said timing information at said paging station from said system controller;
• noting when said time mark arrives at said paging station as a local arrival time;
• compensating said local arrival time for a propagation delay of said paging data block between said system clock and said paging station;
• and
• calculating a station clock offset, said station clock offset used for correlating said paging station clock to said time of said system clock.

A method of simulcasting pages from a plurality of spaced apart paging stations, said pages originating from a system controller, each of the paging stations including a station clock, said method of simulcasting including the steps of:

• packaging a set of pages to be broadcast in a paging data block and providing said paging data block with a start time;
• transmitting said paging data block to the paging stations;
• transmitting from the paging stations the pages contained in said paging data block when said station clock at each paging station indicates a time that is equal to said start time in said paging data packet;
• periodically receiving timing information at the paging stations from said system controller, said timing information comprised of a time mark and a time mark send time, said time mark send time indicating the time of transmit as indicated by said system clock of a previously transmitted time mark;
• and
• resetting each station clock in accordance with said timing information, so that each station clock maintains the same time.

A paging system comprising:

• (a) a system controller including a system clock for maintaining a system time, said system controller generating timing information that is derived from said system clock, said system controller also generating pages;
• and
• (b) a plurality of paging stations for receiving said timing information, said timing information comprised of a time mark and a time mark send time, said time mark send time indicating the time of transmit as indicated by said system clock of a previously transmitted time mark, each of the said paging stations including:
• (i) a link receiver for receiving said timing information and said pages from said system controller;
• (ii) a transmitter that broadcasts said pages;
• and
• (iii) a station controller including a paging station clock that maintains a station time, said station controller receiving said timing information and pages from said system controller and forwarding said pages to said transmitter for broadcast;
• wherein said paging station clock of at least one of said paging stations utilizes said timing information contained in said paging data blocks to calibrate said paging station clock to said system clock.

A method of calibrating a paging station clock to a system clock, said paging station clock being used to regulate the transmission of pages, said system clock being located at a system controller that transmits timing information to said paging station, said timing information comprised of a time mark and a time mark send time, said time mark send time indicating the time of transmit as indicated by said system clock of a previously transmitted time mark, the method including the steps of:

• storing the time of said system clock when said time mark is transmitted to said paging station;
• transmitting to said paging station said stored time as said time mark send time;
• receiving said timing information at said paging station from said system controller;
• noting when said time mark arrives at said paging station as a local arrival time;
• compensating said local arrival time for a propagation delay of said timing information between said system clock and said paging station;
• and
• calculating a station clock offset, said station clock offset used for correlating said paging station clock to said time of said system clock.