RF simulcasting system with dynamic wide-range automatic synchronization
First Claim
1. In a simulcasting transmission system that wirelessly continually simulcasts a radio signal from plural transmission sites, a method of achieving substantially synchronous signal transmission timing of said simulcasted radio signal by said plural transmission sites, said method comprising the following steps performed by at least one of said plural transmission sites:
- (a) receiving, over a link having an inherent propagation time delay, at least one of a voice signal and a data signal for simulcast transmission;
(b) delaying said received voice or data signal by an additional, adjustable delay;
(c) receiving at least one timing pulse train over said same link used to communicate said voice or data signal, said timing pulse train having a pulse timing characteristic;
(d) generating a reference timing pulse train having a pulse timing characteristic;
(e) comparing the pulse timing characteristic of said generated reference timing pulse train with the pulse timing characteristic of said timing pulse train received over said link;
(f) automatically adjusting the delay provided by said delaying step (b) based on results of said comparison; and
(g) while performing said steps (e) and (f), continuing to perform said receiving step (a) and said delaying step (b), and continuing to simulcast said delayed received signal.
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Accused Products
Abstract
A new simulcast dynamic delay adjustment capability for a radio frequency (RF) simulcasting repeater system continually, dynamically adjusts the amount of delay applied to a T1 data stream to ensure common synchronization at multiple simulcast transmitter sites. A Global Positioning System (GPS) distributed time standard provides timing references at a control point and at each transmit site. The control point sends a version of its GPS timing reference signal to each transmit site over links also used to carry signals for transmission over-the-air. The transmit sites compare the arrival time of the land line-distributed reference signal with the output of a version of the same signal produced by a local GPS signal. The result of the comparison is used to adjust an amount of additional delay introduced to equalize delays for different transmission site links. This arrangement eliminates the need for resynchronization of the control point, allows for automatic, dynamic correction/compensation of path delay changes, and can correct delays over a wide range not known ahead of time with the delay amount being independent of over-the-air timing reference signal frequencies--all without loss of service.
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Citations
38 Claims
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1. In a simulcasting transmission system that wirelessly continually simulcasts a radio signal from plural transmission sites, a method of achieving substantially synchronous signal transmission timing of said simulcasted radio signal by said plural transmission sites, said method comprising the following steps performed by at least one of said plural transmission sites:
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(a) receiving, over a link having an inherent propagation time delay, at least one of a voice signal and a data signal for simulcast transmission; (b) delaying said received voice or data signal by an additional, adjustable delay; (c) receiving at least one timing pulse train over said same link used to communicate said voice or data signal, said timing pulse train having a pulse timing characteristic; (d) generating a reference timing pulse train having a pulse timing characteristic; (e) comparing the pulse timing characteristic of said generated reference timing pulse train with the pulse timing characteristic of said timing pulse train received over said link; (f) automatically adjusting the delay provided by said delaying step (b) based on results of said comparison; and (g) while performing said steps (e) and (f), continuing to perform said receiving step (a) and said delaying step (b), and continuing to simulcast said delayed received signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. In a simulcasting transmission system having plural transmission sites continually simulcasting a signal at a transmission timing, a method of synchronizing the transmission timing of said plural transmission sites comprising:
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(a) continually receiving, over a link having an inherent propagation time delay, at least one of a voice signal and a data signal for simulcast transmission and also continually receiving, over said same link used to communicate said voice or data signal, a first periodic reference timing pulse train signal having a pulse timing characteristic; (b) delaying said received voice or data signal and said received first periodic reference timing pulse train signal by an additional, adjustable delay; (c) generating a second periodic reference timing pulse train signal having a pulse timing characteristic; (d) comparing the pulse timing characteristic of said first periodic reference timing pulse train signal with the pulse timing characteristic of said second periodic reference timing pulse train signal; and (e) automatically adjusting said delay provided by said delaying step (b) based on results of said comparison. - View Dependent Claims (17)
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18. In a simulcasting transmission system that substantially continually simulcasts signals from plural transmission sites, a method of ensuring synchronous transmission timing comprising:
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(a) receiving plural signals including a reference timing pulse train signal over a link from a control point, said link also carrying voice or data signals to be simulcasted by said simulcasting transmission system; (b) delaying all of said received plural signals by a same adjustable time delay and simulcasting at least some of said received delayed signals; (c) comparing an arrival time of said delayed reference timing pulse train signal with a locally generated reference timing signal; and (d) automatically adjusting said adjustable time delay based on the results of said comparison to correct the timing of said simulcasted signal(s). - View Dependent Claims (19, 20)
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21. In a simulcasting transmission system that substantially continually simulcasts a voice or data signal substantially concurrently from plural transmission sites, a method of achieving substantially synchronous signal transmission timing by said plural transmission sites, a method comprising the following steps:
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sending, from a control point over communications links, the voice or data signal for transmission to each of the plural sites and also sending, over the communications links, a timing pulse train signal to each site; receiving said voice or data signal and said timing pulse train signal at at least one of the transmission sites, said received timing pulse train signal having a certain arrival timing; generating a reference timing based on a Global Positioning System reference; comparing the generated reference timing with the arrival timing of said received timing pulse train signal; automatically delaying the received voice or data signal by an adjustable delay, and adjusting the delay based at least in part on results of said comparison; and simulcasting said delayed voice or data signal. - View Dependent Claims (22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35)
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36. A simulcasting transmission system of the type including a simulcasting control point coupled by corresponding plural links to plural simulcasting transmission points, the plural simulcasting transmission points simulcasting a voice or data signal so that the simulcasted voice or data signal can be received from any of said plural simulcasting transmission points at substantially the same time over substantially the same radio transmitting frequency, said system characterized by the following equipment installed at each of the transmission points:
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a receiver coupled to at least one of said links that receives plural signals including a reference timing pulse train signal from the control point over said at least one link; a delay circuit that delays all of said received plural signals, including said reference timing pulse train signal, by a same adjustable time delay; a comparing circuit that compares an arrival time of said delayed reference timing pulse train signal with a locally generated reference timing signal derived from at least one Global Positioning System reference; a delay adjusting circuit that automatically adjusts said adjustable time delay bused on the results of said comparison; and a transmitter coupled to said delay circuit, said transmitter continually transmitting at least some of said received, delayed plural signals. - View Dependent Claims (37, 38)
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Specification