Synchronization and training stage operation

1. A primary device comprising:

at least one processor circuit configured to:

transmit a first synchronization sequence to a secondary device;

detect a second synchronization sequence transmitted by the secondary device, the second synchronization sequence differing from the first synchronization sequence;

wait a first predetermined amount of time after completion of detection of the second synchronization sequence transmitted by secondary device, and, immediately upon expiration of the first predetermined amount of time, initiating a training stage, the first predetermined amount of time being known to the secondary device and the training stage comprising exchanging training frames with the secondary device; and

enter a data mode for data transmissions upon completion of the training stage, the data transmissions being distinct from the training frames.

2. The primary device of claim 1 , wherein the first and second synchronization sequences comprise pseudo-noise sequences that can be detected under narrow band interference (NBI) or burst noise conditions.

3. The primary device of claim 1 , wherein the at least one processor circuit is further configured to:

retransmit the first synchronization sequence to the secondary device when the second synchronization sequence is not detected after a second predetermined amount of time.

4. The primary device of claim 1 , wherein the at least one processor circuit is configured to perform the detecting using a matched filter-based correlator.

5. The primary device of claim 1 , wherein the at least one processor circuit, when in the training stage, is configured to:

transmit primary device scrambler initialization information to the secondary device, and receive secondary device scrambler initialization information from the secondary device;

transmit primary device data mode timing information to the secondary device, and receive secondary device data mode timing information from the secondary device;

initialize a scrambler based at least in part on the primary device scrambler initialization information and at a first time indicated by the primary device data mode timing information; and

initialize a descrambler based at least in part on the received secondary device scrambler initialization information and at a second time indicated by the received secondary device data mode timing information.

6. The primary device of claim 5 , wherein the at least one processor circuit is further configured to:

perform Reed-Solomon (RS) encoding on data for transmission;

subsequently scramble the encoded data using the initialized scrambler;

signal map the scrambled data to generate symbols; and

transmit the symbols to the secondary device.

7. The primary device of claim 5 , wherein the data for transmission comprises an operations, administration, and maintenance (OAM) block that is subsequently RS encoded and scrambled.

8. The primary device of claim 5 , wherein the at least one processor circuit is further configured to:

signal demap data received from the secondary device;

perform Reed-Solomon (RS) decoding on the demapped data; and

subsequently descramble the RS decoded data using the initialized descrambler.

9. The primary device of claim 1 , wherein at least one of the training frames comprises information that indicates when to complete the training stage and enter the data mode.

10. The primary device of claim 1 , wherein, when in the training stage, the at least one processor circuit is configured to:

exchange the training frames with the secondary device, wherein each training frame comprises an information field that indicates state transitions for the training stage and a partial Reed Solomon (RS) frame count that is used to determine when to enter the data mode.

11. A method for link establishment by a secondary device, the method comprising:

detecting a first synchronization sequence transmitted by a primary device;

waiting a first predetermined amount of time upon completion of detecting the first synchronization sequence;

transmitting a second synchronization sequence that differs from the first synchronization sequence after the first predetermined amount of time has elapsed; and

waiting a second predetermined amount of time after completion of transmission of the second synchronization sequence, and then entering a two-level pulse amplitude modulation (PAM2) training stage.

12. The method of claim 11 , wherein the first and second synchronization sequences comprise pseudo-noise sequences that can be detected under narrow band interference (NBI) or burst noise conditions.

13. The method of claim 11 , wherein the PAM2 training stage comprises:

waiting for the primary device to provide an indication that transmission of training frames may begin;

upon receiving the indication, transmitting secondary device scrambler initialization information and secondary device data mode timing information to the primary device;

receiving primary device scrambler initialization information and primary device data mode timing information from the primary device;

initializing a scrambler based at least in part on the secondary device scrambler initialization information and at a first time indicated by the secondary device data mode timing information; and

initializing a descrambler based at least in part on the received primary device scrambler initialization information and at a second time indicated by the primary device data mode timing information.

14. The method of claim 13 , wherein the first time differs from the second time.

15. The method of claim 11 , wherein the PAM2 training stage comprises:

exchanging training frames with the primary device, wherein each training frame comprises an information field that indicates state transitions for the PAM2 training stage and a partial Reed Solomon (RS) frame count that is used to determine when to enter a data mode.

16. The method of claim 15 , further comprising:

exchanging scrambler initialization information and data mode timing information with the primary device via the information fields of the training frames.

17. A computer program product comprising code stored in a non-transitory computer-readable storage medium, the code comprising:

code to detect a first synchronization sequence transmitted by a primary device;

code to wait a first predetermined amount of time upon completion of detecting the first synchronization sequence;

code to transmit a second synchronization sequence that differs from the first synchronization sequence after the first predetermined amount of time has elapsed; and

code to wait a second predetermined amount of time after completion of transmission of the second synchronization sequence, and then immediately entering a training stage, the second predetermined amount of time being known to the primary device and the training stage comprising exchanging training frames with the primary device; and

code to enter a data mode for data transmissions upon completion of the training stage, the data transmissions being distinct from the training frames.

18. The computer program product of claim 17 , wherein the first and second synchronization sequences comprise pseudo-noise sequences that can be detected under narrow band interference (NBI) or burst noise conditions.

19. The computer program product of claim 17 , wherein the code to enter the training stage comprises:

code to wait for the primary device to provide an indication that transmission of training frames may begin;

code to, upon receiving the indication, transmit secondary device scrambler initialization information and secondary device data mode timing information to the primary device;

code to receive primary device scrambler initialization information and primary device data mode timing information from the primary device;

code to initialize a scrambler based at least in part on the secondary device scrambler initialization information and at a first time indicated by the secondary device data mode timing information; and

code to initialize a descrambler based at least in part on the received primary device scrambler initialization information and at a second time indicated by the primary device data mode timing information, wherein the first time differs from the second time.

20. The computer program product of claim 17 , wherein the training stage is a two-level pulse amplitude modulation (PAM2) training stage, and

each training frame comprises an information field that indicates state transitions for the training stage and a partial Reed Solomon (RS) frame count that is used to determine when to enter the data mode, and the code to enter the training stage comprises:

code to exchange scrambler initialization information and data mode timing information with the primary device via the information fields of the training frames.