Clock priority chain level systems and methods

• US 8,165,169 B2
• Filed: 12/02/2008
• Issued: 04/24/2012
• Est. Priority Date: 12/02/2008
• Status: Active Grant

• Current Assignee: CommScope Technologies, LLC (CommScope Holding Company, Inc.)
• Original Assignee: ADC Telecommunications Incorporated (TE Connectivity Limited)
• Inventors: Hedin, John M., Stuart, Steven B., Forland, Jody
• Primary Examiner(s): Rao, Seema S
• Assistant Examiner(s): RUSSELL, WANDA Z
• Application Number:
  US12/326,372
• Publication Number:
  US 20100135276A1
• Time in Patent Office: 1,239 Days
• Field of Search: None
• US Class Current: 370/503
• CPC Class Codes: H04J 3/0641 Change of the master or reference, e.g. take-over or failure of the master

Abstract

Clock Priority Chain Level Systems and Methods are provided. In one embodiment, a method for determining clock priority for a multihost unit distributed antenna system is provided. The method comprises identifying which port of a plurality of ports is receiving a reference clock signal having a highest priority Network Chain Level (NCL) value, wherein the highest priority NCL value indicates a master clock priority level (MCPL) of a host unit providing a Master Clock and a chain level value indicating a chain depth; selecting a system clock reference port from the plurality of ports based on the highest priority NCL value; locking a local clock to a reference clock signal received on the selected system clock reference port; calculating an incremented NCL value based on the highest priority NCL value; and transmitting the incremented NCL value over the plurality of ports.

Claims

1. A method for determining clock priority for, the method comprising:

identifying which port of a plurality of ports is receiving a reference clock signal having a highest priority Network Chain Level (NCL) value, wherein the highest priority NCL value indicates a master clock priority level (MCPL) of a host unit providing a Master Clock and a chain level value indicating a chain depth that represents a number of links down a chain from the host unit providing the Master Clock;

selecting a system clock reference port from the plurality of ports based on the highest priority NCL value;

locking a local clock to a reference clock signal received on the selected system clock reference port;

calculating an incremented NCL value based on the highest priority NCL value; and

transmitting the incremented NCL value over the plurality of ports.

2. The method of claim 1, further comprising:

receiving a reference clock signal and an NCL value on each of the plurality of ports.

3. The method of claim 2, further comprising:

determining the highest priority NCL value based on the NCL value received on each of the plurality of ports.

4. The method of claim 3, further comprising:

re-determining the highest priority NCL value when communication with the host unit providing the Master Clock is interrupted.

5. The method of claim 1, further comprising:

determining the highest priority NCL value based on a number of point-to-point communication links through which the reference clock signal has propagated.

6. The method of claim 1, further comprising:

selecting a first host unit from a plurality of host units to be the host unit providing the Master Clock based on a relative ranking of MCPL values assigned to each of the plurality of host units.

7. The method of claim 1, further comprising

transmitting a conflict detection byte (CDB) periodically from each of the plurality of host units;

and

determining when two or more of the plurality of host units have are assigned the same MCPL value based on the conflict detection byte.

8. The method of claim 7, wherein the conflict detection byte comprises the MCPL of a host unit originating the conflict detection byte and a hop-counter.

9. The method of claim 7, wherein transmitting a CDB periodically from each of the plurality of host units further comprises transmitting each CDB periodically based on a pseudo-random timer.

10. The method of claim 1, wherein identifying which port of a plurality of ports is receiving a signal having a highest priority NCL value further comprises:

selecting an port having the lowest the port designation when at least two ports receive NCL values equal to the highest priority NCL value.

11. The method of claim 1, wherein selecting a system clock reference port from the plurality of ports based on the highest priority NCL value further comprises:

locking a local system clock to the frequency signal provided on the system clock reference port.

12. A radio head component of a multihost unit distributed antenna system, the radio head component comprising:

a plurality of ports for interfacing with a network of communication links, each of the communication links providing a medium for communicating data;

an arbitration logic module responsive to the plurality of ports, wherein the arbitration logic module determines a highest priority Network Chain Level (NCL) value based on information received on the plurality of ports and selects a system clock reference port from the plurality of ports based on the highest priority NCL value, wherein the highest priority NCL value indicates a master clock priority level (MCPL) of a host unit providing a Master Clock and a chain level value indicating a chain depth that represents a number of links down a chain from the host unit providing the Master Clock; and

a local system clock for maintaining an operating frequency for communicating via the plurality of ports, the local system clock locked to a reference clock signal received via the system clock reference port selected by the arbitration logic module.

13. The radio head component of claim 12, wherein the arbitration logic module calculates an incremented NCL value based on the highest priority NCL value;

and

wherein the incremented NCL value is transmitted as output from each of the plurality of ports.

14. The radio head component of claim 12, wherein the arbitration logic module selects a first port of the plurality of ports as the system clock reference port based on an NCL value received on the first port that indicates the least chain depth to the host unit providing the Master Clock.

15. The radio head component of claim 12, wherein the arbitration logic module determines the highest priority NCL value based on an NCL value received on each of the plurality of ports.

16. The radio head component of claim 12, wherein the arbitration logic module selects an port having the lowest the port designation as the system clock reference port when at least two ports receive NCL values equal to the highest priority NCL value.

17. A distributed antenna system, the system comprising:

a plurality of host units, each host unit coupled to at least one base transceiver station (BTS);

a plurality of remote units for wireless communication; and

a communication link network comprising a plurality of point-to-point communication links;

wherein a first host unit of the plurality of host units maintains a Master Clock and transmits a reference clock signal based on the Master Clock, wherein the reference clock signal based on the Master Clock is propagated through one or more of the plurality of point-to-point communication links to each of the plurality of remote units and each of the other host units of the plurality of host units;

wherein a first remote unit of the plurality of remote units arbitrates to select a system clock reference port for synchronizing with a first instance of the reference clock signal received from the communication link network based on a first Network Chain Level (NCL) value indicative of the number of point-to-point communication links through which the first instance of the reference clock signal has propagated, and wherein the first remote unit transmits an incremented NCL value back to the communication link network;

wherein a second unit of the plurality of host units arbitrates to select a system clock reference port for synchronizing with a second instance of the reference clock signal received from the communication link network based on a second Network Chain Level (NCL) value indicative of the number of point-to-point communication links through which the second instance of the reference clock signal has propagated, and wherein the second host unit transmits an incremented NCL value back to the communication link network.

18. The system of claim 17, wherein the first remote unit of the plurality of remote units comprises:

a plurality of ports, wherein at least one port of the plurality of ports is coupled to the communication link network by at least one of the plurality of point-to-point communication links;

an arbitration logic module responsive to the plurality of ports, wherein the arbitration logic module determines a highest priority NCL value based on NCL values received on the plurality of ports and selects the system clock reference port from the plurality of ports based on the highest priority NCL value; and

a local system clock for maintaining an operating frequency for communicating via the plurality of ports, the local system clock locked to a reference clock signal received via the system clock reference port selected by the arbitration logic module.

19. The system of claim 17, wherein a first host unit of the plurality of host units comprises:

a plurality of ports, wherein at least one port of the plurality of ports is coupled to the communication link network by at least one of the plurality of point-to-point communication links;

an arbitration logic module responsive to the plurality of ports, wherein the arbitration logic module determines the highest priority NCL value based on NCL values received on the plurality of ports and selects the system clock reference port from the plurality of ports based on the highest priority NCL value; and

a local system clock for maintaining an operating frequency for communicating via the plurality of ports, the local system clock locked to a reference clock signal received via the system clock reference port selected by the arbitration logic module.

20. The system of claim 17, wherein each of the a plurality of host units stores a unique MCPL value;

wherein the reference clock signal transmitted by the first host unit further includes an NCL value indicative of the MCPL value of the first host unit.