Systems and methods for distributing GPS clock to communications devices
A method for synchronizing network elements to a global clock derived from the GPS clock acquired by a plurality of base stations. The global clock is distributed to controllers of various networks, and from there to network access devices. The network access devices further distribute the global clock to various wire-line and local wireless networks and from there, to the users served by these networks. The user equipment is enabled with a simple clock discipliner that adjusts the local clock to the global clock, resulting in a reliable synchronization across the converged communication networks.
1. A method of distributing a global clock to a plurality of networked devices connected over a converged network, comprising:
acquiring a Global Positioning System (GPS) clock with a plurality of base transceiver stations at a GPS clock acquiring stage and each of said plurality of base transceiver stations deriving a global clock from said GPS clock;
transmitting, over one or more wired connections, said global clocks from said plurality of base transceiver stations to a control stage having a plurality of controllers which control the base transceiver stations;
distributing said global clocks from the control stage to a network access stage over the one or more wired connections, wherein devices within the control stage select a best clock for distribution to the network access stage, wherein the best clock is closest to an average of the global clocks measured over a period of time; and
distributing the best global clock from said network access stage to all networked devices connected over the converged network, wherein devices within the network access stage select the best clock for distribution to the networked devices.
2. The method of claim 1 , wherein said global clock is a one-pulse-per-second clock signal, with a 200 ms duration and a rise time of 30 ns.
3. The method of claim 1 , wherein said GPS clock acquiring stage includes first and second base station transceiver stations (BTSs), wherein when the first BTS fails to acquire or provide said GPS clock, the second BTS continues to provide the global clock to said control stage.
4. The method of claim 1 , wherein said control stage includes first and second controllers, and when the first controller fails to receive or provide said global clock, the second controller continues to provide the global clock to said network access stage.
5. The method of claim 1 , wherein said network access stage includes first and second access devices, and when the first access device fails to receive or provide said global clock, the second access device continues to provide the global clock to said networked devices.
6. The method of claim 1 , wherein said networked devices include a femto cell provided within a customer premise, said femto cell being comprised of a micro base station (MBS) serving a plurality of wireless-enabled terminals.
7. The method of claim 6 , further comprising, at said femto cell:
receiving said global clock at said MBS from the converged network over an access interface;
transmitting said global clock to said wireless-enabled terminals over an air interface using a predetermined periodic bit sequence inherent to said air interface; and
synchronizing all said wireless-enabled terminals with said global clock.
8. The method of claim 7 , wherein said access interface between said converged network and said MBS is provided over a wired connection available at said customer premise.
9. The method of claim 7 , further comprising:
adjusting a terminal clock inherently provided at each said wireless-enabled terminal to said global clock provided by said predetermined periodic bit sequence.