Automatic delay compensated simulcasting system and method

A method for synchronizing signal transmission in a simulcast system, the method comprising:

• a) generating a timing packet at a source site, the timing packet containing a GPS timestamp associated with the source site wherein the GPS timestamp is obtained from a GPS receiver located at the source site;
• b) transmitting the timing packet and a content signal over a link to a plurality of transmitter sites;
• c) delaying transmission of the received content signal by an adjustable amount of delay at the transmitter site, wherein delaying transmission of the received content signal, comprises:
• receiving said IP packets at a jitter buffer, and in response to an applied clock signal, adjustably delaying said packets according to an IP network delay determined from said comparing step, such that
• (i) when the determined network delay is static, drives said jitter buffer to clock said packets at the same rate said packets are received at said jitter buffer,
• (ii) when the determined network delay is increasing, drives said jitter buffer to clock said packets at a rate reduced with respect to the rate said packets are received at said jitter buffer, and
• (iii) when the determined network delay is decreasing, drives said jitter buffer to clock said packets at a rate increased with respect to the rate said packets are received at said jitter buffer;
• d) at each transmitter site, comparing the GPS timestamp in the received timing packet to a GPS timestamp associated with the transmitter site to determine a differential ΔT representative of the difference between said timestamps;
• and
• e) at each transmitter site and in response to the comparison delaying the received content signal by an amount related to ΔT;
• whereby the content signals at the plurality of transmitter sites are substantially synchronized.

A simulcast transmitter site comprising:

• a receiver for receiving a timing packet and a content signal from an Internet protocol (IP) link,
• the timing packet containing a GPS timestamp, wherein the timing packet and the GPS timestamp are generated at a source site;
• a comparator for comparing the GPS timestamp in the received timing packet to a GPS timestamp associated with the transmitter site to determine a differential ΔT representative of the difference between the compared timestamps;
• and
• a delay processor, comprising a jitter buffer configured to receive said timing packets, that is responsive to an applied clock signal to provide an adjustable delay to said packets responsive to the comparator and configured to delay the received content signal by an amount related to ΔT, such that the content signals at said plurality of transmitter sites are substantially synchronized;
• wherein said delay processor includes a frequency locked loop for generating said clock signal,
• wherein said delay processor is responsive IP network delay determined from said comparison so that said clock signal;
• (i) when the determined network delay is static, is configured to drive said jitter buffer to clock said packets at the same rate said packets are received at said jitter buffer,
• (ii) when the determined network delay is increasing, is configured to drive said jitter buffer to clock said packets at a rate reduced with respect to the rate said packets are received at said jitter buffer, and
• (iii) when the determined network delay is decreasing, is configured to drive said jitter buffer to clock said packets at a rate increased with respect to the rate said packets are received at said jitter buffer.