Methods and systems for implementing time-division duplexing in the physical layer

1. A physical-layer device, comprising:

a first sublayer to receive a first continuous bitstream from a media-independent interface and to provide a second continuous bitstream to the media-independent interface; and

a second sublayer to transmit first signals corresponding to the first continuous bitstream during a first plurality of time windows and to receive second signals corresponding to the second continuous bitstream during a second plurality of time windows distinct from the first plurality of time windows, wherein the first sublayer comprises:

one or more layers to generate a third bitstream based on the first continuous bitstream; and

a time-division duplexing adapter to adapt a rate of the third bitstream and insert pad bits into the third bitstream in locations corresponding to times during which the second sublayer does not transmit the first signals, the times comprising the second plurality of time windows.

2. The physical-layer device of claim 1 , wherein the second sublayer is to transmit the first signals and receive the second signals on a common frequency band.

3. The physical-layer device of claim 1 , wherein:

the first sublayer comprises a physical coding sublayer (PCS);

the second sublayer comprises a physical medium-dependent sublayer (PMD); and

the physical-layer device further comprises a physical medium attachment sublayer (PMA) coupled between the PCS and the PMD.

4. The physical-layer device of claim 1 , wherein:

time windows of the first plurality of time windows have a first duration;

time windows of the second plurality of time windows have a second duration;

guard intervals of a third duration separate respective time windows of the first and second pluralities of time windows; and

the time-division duplexing adapter is to adapt the rate of the third bitstream by a factor equal to a ratio of the first duration to a sum of the first, second, and third durations.

5. The physical-layer device of claim 1 , wherein:

the first continuous bitstream comprises data packets and idle packets; and

the one or more layers of the first sublayer are to delete the idle packets from the first continuous bitstream and insert parity bits into the data packets.

6. The physical-layer device of claim 1 , wherein the first sublayer comprises:

a time-division duplexing adapter to receive a fourth bitstream that corresponds to the second signals and to generate a fifth bitstream by adapting a rate of the fourth bitstream and deleting pad bits from the fourth bitstream, wherein the pad bits are situated in the fourth bitstream in locations corresponding to times during which the second sublayer does not receive the second signals, the times comprising the first plurality of time windows; and

one or more layers to generate the second continuous bitstream based on the fifth bitstream.

7. The physical-layer device of claim 6 , wherein:

time windows of the first plurality of time windows have a first duration;

time windows of the second plurality of time windows have a second duration;

guard intervals of a third duration separate respective time windows of the first and second pluralities of time windows; and

the time-division duplexing adapter is to adapt the rate of the fourth bitstream by a factor equal to a ratio of the second duration to a sum of the first, second, and third durations.

8. The physical-layer device of claim 6 , wherein:

the second continuous bitstream comprises data packets and idle packets;

the fifth bitstream comprises the data packets; and

the one or more layers of the first sublayer are to insert the idle packets into the first continuous bitstream and delete parity bits from the data packets.

9. A physical-layer device, comprising:

a first sublayer to receive a first continuous bitstream from a media-independent interface and to provide a second continuous bitstream to the media-independent interface; and

a second sublayer to transmit first signals corresponding to the first continuous bitstream during a first plurality of time windows and to receive second signals corresponding to the second continuous bitstream during a second plurality of time windows distinct from the first plurality of time windows, wherein:

the first sublayer is to generate a third bitstream based on the first continuous bitstream; and

the second sublayer comprises a rate adapter to generate a fourth bitstream by adapting a rate of the third bitstream and inserting gaps into the third bitstream in locations corresponding to times during which the second sublayer does not transmit the first signals, the times comprising the second plurality of time windows.

10. The physical-layer device of claim 9 , wherein the second sublayer further comprises one or more layers to convert the fourth bitstream into the first signals.

11. The physical-layer device of claim 9 , wherein:

the first continuous bitstream comprises data packets and idle packets; and

the first sublayer comprises one or more layers to delete the idle packets from the first continuous bitstream and insert parity bits into the data packets, to generate the third bitstream.

12. The physical-layer device of claim 11 , wherein:

the one or more layers of the first sublayer are further to group the data packets into bursts separated by pad bits in the third bitstream, the bursts having a first duration and the pad bits having a second duration; and

the rate adapter is to adapt a rate of the third bitstream by a factor equal to a ratio of the first duration to a sum of the first and second durations.

13. A physical-layer device, comprising:

a first sublayer to receive a first continuous bitstream from a media-independent interface and to provide a second continuous bitstream to the media-independent interface; and

a second sublayer to transmit first signals corresponding to the first continuous bitstream during a first plurality of time windows and to receive second signals corresponding to the second continuous bitstream during a second plurality of time windows distinct from the first plurality of time windows, wherein the second sublayer comprises:

one or more layers to convert the second signals to a fourth bitstream with gaps in locations corresponding to times during which the second sublayer does not receive the second signals, the times comprising the first plurality of time windows; and

a rate adapter to adapt a rate of the fourth bitstream and to remove the gaps from the fourth bitstream.

14. The physical-layer device of claim 13 , wherein the rate adapter is further to insert pad bits into the fourth bitstream.

15. The physical-layer device of claim 14 , wherein the first sublayer is to delete the pad bits from the fourth bitstream, delete parity bits from data packets in the fourth bitstream, and insert idle packets into the fourth bitstream, to generate the second continuous bitstream.

16. The physical-layer device of claim 1 , wherein:

the physical-layer device is situated in a coax line terminal;

the first plurality of time windows comprise downstream time windows; and

the second plurality of time windows comprises upstream time windows.

17. The physical-layer device of claim 1 , wherein:

the physical-layer device is situated in a coax network unit;

the first plurality of time windows comprise upstream time windows; and

the second plurality of time windows comprises downstream time windows.

18. A method of data communications, comprising:

receiving a first continuous bitstream from a media-independent interface;

providing a second continuous bitstream to the media-independent interface;

transmitting first signals corresponding to the first continuous bitstream during a first plurality of time windows;

receiving second signals corresponding to the second continuous bitstream during a second plurality of time windows distinct from the first plurality of time windows;

generating a third bitstream based on the first continuous bitstream;

adapting a rate of the third bitstream; and

inserting pad bits into the third bitstream in locations corresponding to times during which the physical-layer device does not transmit the first signals, the times comprising the second plurality of time windows;

wherein the third bitstream corresponds to the first signals.

19. The method of claim 18 , wherein:

the transmitting comprises transmitting the first signals on a frequency band; and

the receiving comprises receiving the second signals on the frequency band.

20. The method of claim 18 , wherein:

the first continuous bitstream comprises data packets and idle packets; and

generating the third bitstream comprises deleting the idle packets from the first continuous bitstream and inserting parity bits into the data packets.

21. The method of claim 18 , wherein:

the physical-layer device comprises PCS, PMA, and PMD sublayers; and

the generating, adapting, and inserting are performed in the PCS.

22. The method of claim 18 , wherein:

the physical-layer device comprises PCS, PMA, and PMD sublayers;

generating the third bitstream is performed in the PCS; and

the adapting and inserting are performed in the PMD.

23. The method of claim 18 , further comprising:

converting the second signals to a fourth bitstream with pad bits in locations corresponding to times during which the physical-layer device does not receive the second signals, the times comprising the first plurality of time windows; and

generating a fifth bitstream based on the fourth bitstream, wherein generating the fifth bitstream comprises:

adapting a rate of the fourth bitstream; and

deleting the pad bits from the fourth bitstream.

24. The method of claim 23 , further comprising generating the second continuous bitstream based on the fifth bitstream, wherein generating the second continuous bitstream comprises:

deleting parity bits from data packets in the fifth bitstream; and

inserting idle packets into the fifth bitstream.

25. The method of claim 24 , wherein:

the physical-layer device comprises PCS, PMA, and PMD sublayers;

generating the fourth bitstream is performed in the PMA; and

generating the fifth bitstream and second continuous bitstream are performed in the PCS.

26. A method of data communications, comprising:

receiving a first continuous bitstream from a media-independent interface;

providing a second continuous bitstream to the media-independent interface;

transmitting first signals corresponding to the first continuous bitstream during a first plurality of time windows;

receiving second signals corresponding to the second continuous bitstream during a second plurality of time windows distinct from the first plurality of time windows;

converting the second signals to a fourth bitstream with gaps in locations corresponding to times during which the physical-layer device does not receive the second signals, the times comprising the first plurality of time windows;

adapting a rate of the fourth bitstream; and

removing the gaps from the fourth bitstream.

27. The method of claim 26 , wherein:

the physical-layer device comprises PCS, PMA, and PMD sublayers; and

the converting, adapting, and removing are performed in the PMD.