Method and apparatus for synchronization of high-bit-rate digital subscriber line signals
View Patent ↗Timing information, such as stratum 1 traceable synchronization information, is transmitted in a high-bit-rate digital subscriber line (HDSL) transport frame by timing the transport frame using a corresponding timing reference signal. In an illustrative embodiment, a central office modem maps a DS1 payload at 1.544 Mbps into HDSL transport frames at 1.552 Mbps, using a DS1 timing reference signal generated by, e.g., a building integrated timing supply (BITS) having global positioning system (GPS) capability. The transport frame is transmitted by the central office modem to a customer premises modem which demaps the transport frames to recover the DS1 payload and the DS1 timing reference signal. The recovered timing reference signal is then delivered to an external timing input of a computer, set-top box or other customer premises equipment (CPE). Synchronization status messages (SSMs) may be included in the timing information transmitted between the central office and customer premises modems. The invention is applicable to DSL signals other than HDSL2, including, e.g., single-pair HDSL signals, multiple-pair HDSL signals, as well as other types of signals used in conjunction with the transport of information over existing wired connections.
1. A method for communicating information from a transmitter to a receiver in a communication system, the method comprising the steps of:
processing in the transmitter a payload signal and a transmitter-side timing reference signal to generate a digital subscriber line transport signal including frequency and phase information associated with the transmitter-side timing reference signal; and
transmitting the transport signal from the transmitter to the receiver, such that the receiver can recover at least a portion of the frequency and phase information and derive therefrom a receiver-side timing reference signal used to control timing in the receiver;
wherein the digital subscriber line transport signal is configured to include the frequency and phase information associated with the transmitter-side timing reference signal by providing in the transmitter a local oscillator adapted to receive the transmitter-side timing reference signal as an external timing reference.
2. The method of claim 1 wherein the payload signal is a DS1 payload having a data rate of 1.544 Mbps.
3. The method of claim 1 wherein the timing reference signal is a DS1 timing reference signal having a data rate of 1.544 Mbps.
4. The method of claim 1 wherein the timing reference signal includes stratum 1 traceable synchronization information.
5. The method of claim 1 wherein the digital subscriber line transport signal comprises a sequence of HDSL2 transport frames having a data rate of 1.552 Mbps.
6. The method of claim 1 wherein the timing information includes at least one synchronization status message associated with the timing reference signal.
7. The method of claim 1 wherein the timing reference signal is generated by a building integrated timing supply having GPS capability.
8. The method of claim 1 wherein the timing reference signal comprises a transmit clock generated by an add-drop multiplexer associated with the transmitter.
9. An apparatus for use in communicating information in a communication system, the apparatus comprising:
a transmitter operative to process a payload signal and a transmitter-side timing reference signal to generate a digital subscriber line transport signal including frequency and phase information associated with the transmitter-side timing reference signal, and to transmit the transport signal to a receiver, such that the receiver can recover at least a portion of the frequency and phase information therefrom and derive therefrom a receiver-side timing reference signal used to control timing in the receiver;
wherein the digital subscriber line transport signal is configured to include the frequency and phase information associated with the transmitter-side timing reference signal by providing in the transmitter a local oscillator adapted to receive the transmitter-side timing reference signal as an external timing reference.
10. The apparatus of claim 9 wherein the payload signal is a DS1 payload having a data rate of 1.544 Mbps.
11. The apparatus of claim 9 wherein the timing reference signal is a DS1 timing reference signal having a data rate of 1.544 Mbps.
12. The apparatus of claim 9 wherein the timing reference signal includes stratum 1 traceable synchronization information.
13. The apparatus of claim 9 wherein the digital subscriber line transport signal comprises a sequence of HDSL2 transport frames having a data rate of 1.552 Mbps.
14. The apparatus of claim 9 wherein the timing information includes at least one synchronization status message associated with the timing reference signal.
15. The apparatus of claim 9 further including a building integrated timing supply having an output coupled to a timing reference signal input of the transmitter, and wherein the building integrated timing supply has GPS capability.
16. The apparatus of claim 9 wherein the timing reference signal comprises a transmit clock generated by an add-drop multiplexer associated with the transmitter.
17. An apparatus for use in communicating information in a communication system, the apparatus comprising:
a receiver operative to receive a digital subscriber line transport signal including frequency and phase information associated with a transmitter-side time reference signal and a transmitter of the system, the transport signal being generated in the transmitter by processing a payload signal and a transmitter-side timing reference signal, wherein the receiver is further operative to recover at least a portion of the frequency and phase information from the transport signal and derive therefrom a receiver-side timing reference signal used to control timing in the receiver;
wherein the digital subscriber line transport signal is configured to include the frequency and phase information associated with the transmitter-side timing reference signal by providing in the transmitter a local oscillator adapted to receive the transmitter-side timing reference signal as an external timing reference.
18. The apparatus of claim 17 wherein the payload signal is a DS1 payload having a data rate of 1.544 Mbps.
19. The apparatus of claim 17 wherein the timing reference signal is a DS1 timing reference signal having a data rate of 1.544 Mbps.
20. The apparatus of claim 17 wherein the timing reference signal includes stratum 1 traceable synchronization information.
21. The apparatus of claim 17 wherein the digital subscriber line transport signal comprises a sequence of HDSL2 transport frames having a data rate of 1.552 Mbps.
22. The apparatus of claim 17 wherein the timing information includes at least one synchronization status message associated with the timing reference signal.