Method and apparatus for wide bandwidth mixed-mode wireless communications

1. A method comprising:

transmitting at a first frequency, using a communications device, a backward compatible portion of a mixed mode frame over a first channel, wherein the backward compatible portion comprises a signal field containing timing information for instructing, a receiver to ignore transmissions for a predetermined period of time by encoding the mixed mode frame with dummy length and rate fields;

transmitting at the first frequency, using the communications device, a copy of the backward compatible portion over a second channel adjacent to the first channel; and

transmitting at a second frequency, using the communications device, a greenfield portion of the mixed mode frame.

2. The method of claim 1 , wherein the predetermined period of time corresponds to a duration of time used to transmit the greenfield portion.

3. The method of claim 1 , wherein the timing information instructs the receiver to stay off of the first channel for the predetermined period of time.

4. The method of claim 1 , wherein the copy of the backward compatible portion comprises a second signal field containing second timing information for instructing the receiver to stay off the second channel for the predetermined period of time.

5. The method of claim 1 , wherein the backward compatible portion further comprises a short symbol used by the receiver to detect the mixed mode frame.

6. The method of claim 1 , wherein the backward compatible portion further comprises a guard interval.

7. The method of claim 1 , wherein the backward compatible portion further comprises a long training sequence used by the receiver to train an equalizer.

8. The method of claim 1 , wherein the secoLd frequency is higher than the first frequency.

9. The method of claim 1 , wherein the first frequency is 20 MHz, and wherein the second frequency is 40 MHz.

10. A method comprising:

receiving at a first frequency, using a receiving device, a backward compatible portion of a mixed mode frame over a first channel, wherein the backward compatible portion comprises a signal field containing timing information for encoding the mixed mode frame with dummy length and rate fields;

ignoring, using the receiving device, a first transmission over the first channel for a predetermined period of time indicated by the timing information;

receiving at the first frequency, using the receiving device, a copy of the backward compatible portion over a second channel adjacent to the first channel; and

ignoring, using the receiving device, a second transmission over the second channel for the predetermined period of time.

11. The method of claim 10 , wherein the predetermined period of time corresponds to a duration of time used to transmit a greenfield portion of the mixed mode frame.

12. The method of claim 10 , further comprising:

detecting the mixed mode frame based on a short symbol in the backward compatible portion.

13. The method of claim 10 , wherein the backward compatible portion further comprises a guard interval.

14. The method of claim 10 , further comprising:

training an equalizer based on a long training sequence in the backward compatible portion.

15. The method of claim 10 , wherein a second frequency is higher than the first frequency.

16. The method of claim 10 , wherein the first frequency is 20 MHz, and wherein a second frequency is 40 MHz.

17. A communications device comprising:

a backward compatible portion generator configured to generate:

a backward compatible portion of a mixed mode frame, wherein the backward compatible portion comprises a signal field containing timing information for instructing a receiver to ignore transmissions for a predetermined period of time, and

a copy of the backward compatible portion; and

a greenfield generator configured to:

generate a greenfield portion of the mixed mode frame, and

generate a dummy length and a dummy rate for the backward compatible portion and the copy of the backward compatible portion based on a transmission length of the greenfield portion.

18. The communications device of claim 17 , wherein the backward compatible portion generator is configured to use a signal symbol in the backward compatible portion to encode the mixed mode frame with the dummy length and the dummy rate.

19. The communications device of claim 17 , wherein the backward compatible portion generator is further configured to generate a short symbol for the backward compatible portion, and wherein the short symbol is used by a receiver to detect the mixed mode frame.

20. The communications device of claim 17 , wherein the backward compatible portion generator is further configured to generate a long training sequence for the backward compatible portion, wherein the long training sequence is used by a receiver to train an equalizer.