Automatic power saving for communication systems

1. A method to save power in data communication, the method comprising:

transmitting a plurality of symbols each of which containing an overhead portion and at least a portion of a respective data transmission unit (DTU) by:

transmitting a first symbol of the plurality of symbols which includes the overhead portion and the at least a portion of a respective DTU of the first symbol when the at least a portion of the respective DTU of the first symbol contains payload data; and

transmitting a second symbol of the plurality of symbols which includes the overhead portion without allocating power in a frequency spectrum to sub-carriers associated with the at least a portion of a respective DTU of the second symbol when the at least a portion of the respective DTU of the second symbol contains no payload data.

2. The method as recited in claim 1 , wherein each symbol contains a respective plurality of DTUs, and wherein transmitting a second symbol of the plurality of symbols which includes the overhead portion without allocating power in a frequency spectrum to sub-carriers associated with the at least a portion of a respective DTU of the second symbol when the at least a portion of the respective DTU of the second symbol contains no payload data comprises transmitting the second symbol which includes the overhead portion without allocating power in the frequency spectrum to the sub-carriers associated with the respective plurality of DTUs of the second symbol when each of the respective plurality of DTUs of the second symbol contains no payload data.

3. The method as recited in claim 1 , wherein the transmitting comprises transmitting in accordance with Very-high-speed Digital Subscriber Line 2 (VDSL2) standards.

4. The method as recited in claim 1 , further comprising:

determining whether or not a first DTU that corresponds to one or more of the plurality of symbols contains no payload data; and

marking the first DTU to indicate the first DTU as containing no payload data when it is determined that the first DTU contains no payload data.

5. The method as recited in claim 4 , wherein marking the first DTU comprises setting a value of a sequence identification (SID) in the overhead portion of the first DTU to 255.

6. The method as recited in claim 4 , wherein marking the first DTU comprises setting a value of a time stamp (TS) in the overhead portion of the first DTU to 255 and a value of a sequence identification (SID) in the overhead portion of the first DTU to 255.

7. The method as recited in claim 1 , further comprising:

setting a value of a sequence identification (SID) or both a value of a time stamp (TS) and a value of the SID in the overhead portion included in each symbol to indicate a nature of content of the at least a portion of a respective DTU of each symbol.

8. The method as recited in claim 7 , wherein the value of the SID is set to 255, or the value of the TS is set to 255 and the value of the SID is set to 255, to indicate the at least a portion of a respective DTU of a symbol as containing no payload data.

9. The method as recited in claim 7 , wherein the value of the TS is set to 255 and the value of the SID is set to 254 to indicate the at least a portion of a respective DTU of a symbol will be transmitted once and not stored in a retransmission queue or a transmitter.

10. A method to save power in data communication, the method comprising:

defining a second data transmission unit (DTU) such that the second DTU carries a first data packet that corresponds to a first DTU and a second data packet that corresponds to the second DTU; and

transmitting the first DTU and the second DTU without allocating power in a frequency spectrum to sub-carriers associated with the first DTU, the first DTU carrying no payload data and the second DTU carrying the first data packet and the second data packet as payload data.

11. The method as recited in claim 10 , wherein the first data packet corresponds to the first DTU, the second data packet corresponds to the second DTU and a third data packet corresponds to the third DTU, and wherein the first DTU, the second DTU, and the third DTU are transmitted without allocating power in the frequency spectrum to the sub-carriers associated with the first DTU and second DTU, the first DTU and the second DTU carrying no payload data and with the third DTU carrying the first data packet, the second data packet and the third data packet as payload data.

12. The method as recited in claim 10 , wherein the first data packet and the second data packet comprise first and second Voice over Internet Protocol (VoIP) data packets.

13. A networking device comprising:

memory; and

a communication unit coupled to the memory, the communication unit configured to:

transmit a plurality of symbols each of which containing an overhead portion and at least a portion of a respective data transmission unit (DTU) by:

transmitting a first symbol of the plurality of symbols which includes the overhead portion and the at least a portion of a respective DTU of the first symbol when the at least a portion of the respective DTU of the first symbol contains payload data; and

transmitting a second symbol of the plurality of symbols which includes the overhead portion without allocating power in a frequency spectrum to sub-carriers associated with the at least a portion of a respective DTU of the second symbol when the at least a portion of the respective DTU of the second symbol contains no payload data.

14. The networking device as recited in claim 13 , wherein each symbol contains a respective plurality of DTUs, and wherein the communication unit transmits the second symbol which includes the overhead portion without allocating power in the frequency spectrum to sub-carriers associated with the respective plurality of DTUs of the second symbol when each of the respective plurality of DTUs of the second symbol contains no payload data.

15. The networking device as recited in claim 13 , wherein the communication unit is further configured to:

determine whether or not a first DTU that corresponds to one or more of the plurality of symbols contains no payload data; and

mark the first DTU to indicate the first DTU as containing no payload data when it is determined that the first DTU contains no payload data.

16. The networking device as recited in claim 15 , wherein the communication unit marks the first DTU by setting a value of a sequence identification (SID) in the overhead portion of the first DTU to 255.

17. The networking device as recited in claim 15 , wherein the communication unit marks the first DTU by setting a value of a time stamp (TS) in the overhead portion of the first DTU to 255 and a value of a sequence identification (SID) in the overhead portion of the first DTU to 255.

18. The networking device as recited in claim 13 , wherein the communication unit is further configured to:

define a second DTU such that the second DTU carries a first data packet that corresponds to a first DTU and a second data packet that corresponds to the second DTU; and

transmit the first DTU and the second DTU without allocating power in the frequency spectrum to the sub-carriers associated with the first DTU, the first DTU carrying no payload data and the second DTU carrying the first data packet and the second data packet as payload data.

19. The networking device as recited in claim 18 , wherein the first data packet corresponds to the first DTU, the second data packet corresponds to the second DTU and a third data packet corresponds to the third DTU, and wherein the first DTU, the second DTU, and the third DTU are transmitted without allocating power in the frequency spectrum to the sub-carriers associated with the first DTU and the second DTU, the first DTU and the second DTU carrying no payload data and with the third DTU carrying the first data packet, the second data packet and the third data packet as payload data.

20. The networking device as recited in claim 18 , wherein the first data packet and the second data packet comprise first and second Voice over Internet Protocol (VoIP) data packets.