Packet processing systems and methods

1. A method, comprising:

receiving a plurality of packets from multiple transmit antennas, each packet having mixed mode segments; and

estimating a multipath channel at a receive processor for each of the multiple transmit antennas based on an extended long training symbol (ELTS) from the mixed mode segments.

2. The method of claim 1 , wherein estimating comprises performing Walsh coding with 2-ary orthogonal sequencing to determine the multipath channel for each transmit antenna of the multiple transmit antennas that sends at least some of the plurality of packets.

3. The method of claim 1 , wherein estimating comprises performing Walsh coding with 4-ary orthogonal sequencing to determine the multipath channel for each transmit antenna of the multiple transmit antennas that sends at least some of the plurality of packets.

4. The method of claim 1 , wherein estimating comprises performing Walsh coding with large cyclic shifts to determine the multipath channel for each transmit antenna of the multiple transmit antennas that sends at least some of the plurality of packets.

5. The method of claim 4 , wherein the large cyclic shifts comprise shifts greater than a multipath time spread.

6. The method of claim 4 , wherein the large cyclic shifts comprise a combination of a cyclic shift value corresponding to half of an orthogonal frequency division multiplexed (OFDM) symbol and a small cyclic shift corresponding to the ELTS in the mixed mode segments.

7. The method of claim 1 , wherein the ELTS from legacy and spatial multiplexing sections of a preamble and header portion of at least one packet in the plurality of packets.

8. The method of claim 7 , wherein the ELTS is in inverted form.

9. A system, comprising:

a receive processor, configured to communicate with at least one of a plurality of transmit antennas, the receive processor comprising:

receive logic, comprising digital circuitry, configured to estimate a multipath channel for each transmit antenna of the plurality of transmit antennas using an extended long training symbol (ELTS) from each mixed mode segment in a plurality of packets received from the at least one transmit antenna and to communicate the estimate.

10. The system of claim 9 , wherein the logic is configured to perform Walsh coding with 2-ary orthogonal sequencing to determine the multipath channel for each transmit antenna that sends at least some of the plurality of packets.

11. The system of claim 9 , wherein the logic is configured to perform Walsh coding with 4-ary orthogonal sequencing to determine the amplitude of the multipath channel for each transmit antenna that sends at least some of the plurality of packets.

12. The system of claim 9 , wherein the logic is configured to perform Walsh coding with large cyclic shifts to determine the multipath channel for each transmit antenna that sends at least some of the plurality of packets.

13. The system of claim 12 , wherein the large cyclic shifts comprise shifts greater than a multipath time spread.

14. The system of claim 12 , wherein the large cyclic shifts comprise a combination of a cyclic shift value corresponding to half of an orthogonal frequency division multiplexed (OFDM) symbol and a small cyclic shift corresponding to the ELTS in the mixed mode segments.

15. The system of claim 9 , wherein the logic is configured to use the ELTS from legacy and spatial multiplexing sections of a preamble and header portion of at least one packet in the plurality of packets.

16. The system of claim 15 , wherein the logic is configured to use the ELTS in inverted form.

17. A system, comprising:

means for receiving a plurality of packets from multiple transmit antennas, each packet having mixed mode segments; and

means for estimating a multipath channel for each transmit antenna of the multiple transmit antennas using an extended long training symbol (ELTS) from the mixed mode segments.

18. The system of claim 17 , wherein the means for estimating comprises means for performing Walsh coding with 2-ary orthogonal sequencing to determine the multipath channel for each other transmit antenna that sends at least some of the plurality of packets.

19. The system of claim 17 , wherein the means for estimating comprises means for performing Walsh coding with 4-ary orthogonal sequencing to determine the phase of the multipath channel for each other transmit antenna that sends at least some of the plurality of packets.

20. The system of claim 17 , wherein the means for estimating comprises means for performing Walsh coding with large cyclic shifts to determine the phase of the multipath channel for each other transmit antenna that sends at least some of the plurality of packets.

21. A method, comprising:

receiving a plurality of packets from multiple transmit antennas at a receive processor; and

at the receive processor, performing Walsh coding with large cyclic shifts to determine a multipath channel for each transmit antenna of the multiple transmit antennas that sends at least some of the plurality of packets,

wherein the large cyclic shifts comprise a combination of a cyclic shift value corresponding to half of an orthogonal frequency division multiplexed (OFDM) symbol and a small cyclic shift corresponding to the ELTS in the mixed mode segments.

22. The method of claim 21 , wherein the large cyclic shifts comprise shifts greater than a multipath time spread.

23. A system, comprising a receive processor, configured to communicate with at least one of a plurality of transmit antennas, the receive processor comprising:

receive logic, comprising digital circuitry configured to determine a phase and an amplitude of a multipath channel for each transmit antenna of a plurality of transmit antennas by performing Walsh coding with large cyclic shifts and to communicate the phase and amplitude,

wherein the large cyclic shifts comprise a combination of a cyclic shift value corresponding to half of an orthogonal frequency division multiplexed (OFDM) symbol and a small cyclic shift corresponding to the ELTS in the mixed mode segments.

24. The system of claim 23 , wherein the large cyclic shifts comprise shifts greater than a multipath time spread.

25. A method, comprising:

generating long training symbols (LTSs) for each legacy portion of packets corresponding to a plurality of transmit antennas;

generating a plurality of copies of legacy portion LTSs for each spatially multiplexed portion of the packets;

inverting and imposing a small cyclic shift to at least one copy of the plurality of copies of legacy portion LTSs for at least one transmit antenna of the plurality of transmit antennas; and

inverting and imposing a large cyclic shift to at least one copy of the plurality of copies of legacy portion LTSs for the at least one transmit antenna of the plurality of transmit antennas, the large cyclic shift corresponding to the combination of the small cyclic shift associated with the at least one transmit antenna and half of an orthogonal frequency division multiplexed (OFDM) symbol post guard removal.

26. A system, comprising:

a transmit processor, comprising:

waveshape logic, comprising software stored in a memory, the software configured to, upon execution by the transmit processor, cause the transmit processor to perform operations comprising:

generate long training symbols (LTSs) for each legacy portion of packets corresponding to a plurality of transmit antennas,

generate a plurality of copies of legacy portion LTSs for each spatially multiplexed portion of the packets,

invert and impose a small cyclic shift to at least one copy of the plurality of copies of legacy portion LTSs for at least one transmit antenna of the plurality of transmit antennas, and

invert and impose a large cyclic shift to at least one copy of the plurality of copies of legacy portion LTSs for the at least one transmit antenna of the plurality of transmit antennas, the large cyclic shift corresponding to the combination of the small cyclic shift for the at least one transmit antenna and half of an orthogonal frequency division multiplexed (OFDM) symbol post guard removal.

27. The system of claim 26 , further comprising the plurality of transmit antennas.

28. The system of claim 27 , wherein the plurality of transmit antennas comprise four transmit antennas.

29. A system, comprising:

a transmit processor, comprising:

waveshape logic, comprising at least one application specific integrated circuit (ASIC), the waveshape logic configured to:

generate long training symbols (LTSs) in each legacy portion of packets corresponding to a plurality of transmit antennas,

generate a plurality of copies of legacy portion LTSs in each spatially multiplexed portion of the packets,

invert and impose a small cyclic shift to at least one copy of the plurality of copies of legacy portion LTSs for at least one transmit antenna of the plurality of transmit antennas, and

invert and impose a large cyclic shift to at least one copy of the plurality of copies of legacy portion LTSs for the at least one transmit antenna of the plurality of transmit antennas, the large cyclic shift corresponding to the combination of the small cyclic shift associated with the at least one transmit antenna and half of an orthogonal frequency division multiplexed (OFDM) symbol post guard removal, thereby generating a packet structure; and

a radio, configured to transmit the packet structure.

30. The system of claim 29 , further comprising the plurality of transmit antennas.

31. The system of claim 30 , wherein the plurality of transmit antennas comprises four transmit antennas.