Packet processing systems and methods

1. A method comprising:

generating a legacy long training symbol (LTS) at a transmit processor, wherein the legacy LTS comprises a first plurality of subcarriers;

generating an extended LTS, wherein the extended LTS comprises a second plurality of subcarriers, wherein the first plurality of subcarriers has fewer subcarriers than the second plurality of subcarriers, wherein the extended LTS comprises the legacy LTS, and wherein the generating the extended LTS comprises inserting additional subcarriers at spectral band edges of the legacy LTS; and

transmitting the extended LTS.

2. The method of claim 1 , wherein the first plurality of subcarriers comprises 52 subcarriers.

3. The method of claim 1 , wherein the additional subcarriers are inserted at both spectral band edges of the legacy LTS.

4. The method of claim 1 , further comprising inserting the extended LTS in a packet.

5. The method of claim 4 , wherein inserting the extended LTS in a packet comprises inserting the extended LTS in an IEEE 802.11 compliant packet.

6. The method of claim 4 , wherein inserting the extended LTS in a packet comprises inserting the extended LTS in an orthogonal frequency division multiplexed (OFDM) packet.

7. The method of claim 1 , wherein the extended LTS is encoded multiple times and cyclically shifted, and wherein a multipath channel can be computed by an antenna observing the extended LTS.

8. The method of claim 7 , wherein encoding the extended LTS multiple times comprises performing Walsh coding with small cyclic shifts.

9. The method of claim 7 , wherein encoding the extended LTS multiple times comprises performing Walsh coding with large cyclic shifts.

10. A system comprising:

a transmit processor comprising:

waveshape logic, comprising digital circuitry, configured to form:

a legacy long training symbol (LTS), wherein the legacy LTS comprises a first plurality of subcarriers; and

an extended long training symbol (ELTS), wherein the ELTS comprises a second plurality of subcarriers, wherein the first plurality of subcarriers has fewer subcarriers than the second plurality of subcarriers, wherein the extended LTS comprises the legacy LTS, and wherein the logic is further configured to insert additional subcarriers at spectral band edges of the legacy LTS; and

a radio configured to transmit the extended LTS.

11. The system of claim 10 , wherein the first plurality of subcarriers comprises 52 subcarriers.

12. The system of claim 10 , wherein the additional subcarriers are inserted at both spectral band edges of the legacy LTS.

13. The system of claim 10 , wherein the logic is further configured to insert the ELTS in a packet.

14. The system of claim 13 , wherein the logic is configured to insert the ELTS in an IEEE 802.11 compliant packet.

15. The system of claim 13 , wherein the logic is configured to insert the ELTS in an orthogonal frequency division multiplexed (OFDM) packet.

16. A system comprising:

means for generating a legacy long training symbol (LTS), wherein the legacy LTS comprises a first plurality of subcarriers;

means for generating an extended LTS (ELTS), wherein the ELTS comprises a second plurality of subcarriers, wherein the first plurality of subcarriers has fewer subcarriers than the second plurality of subcarriers, wherein the ELTS comprises the legacy LTS, and wherein means for generating the ELTS further comprises inserting additional subcarriers at spectral band edges of the legacy LTS; and

means for transmitting the ELTS.

17. The system of claim 16 , wherein the first plurality of subcarriers comprises 52 subcarriers.

18. The system of claim 16 , wherein the additional subcarriers are inserted at both spectral band edges of the legacy LTS.

19. The system of claim 16 , further comprising means for inserting the ELTS in a packet.

20. The system of claim 19 , wherein the packet is an IEEE 802.11 compliant packet.