Method and apparatus for performing channel estimation and equalization based on a signal field of a received packet

1. A network device comprising:

a receiver module configured to receive a packet wirelessly transmitted over a channel to the network device, wherein the packet comprises a signal field, and wherein the signal field (i) comprises a plurality of bits, or (ii) has a corresponding plurality of sub-carriers;

a first channel estimate module configured to, (i) based on the signal field, perform a plurality of determinations, wherein each of the plurality of determinations indicates whether a respective one of the plurality of bits or a respective one of the plurality of sub-carriers has been modulated with a first predetermined value or a second predetermined value, and (ii) based on the plurality of determinations, output a first channel estimate of the channel; and

a frequency equalizer configured to (i) receive a first signal comprising the packet, and (ii) equalize the first signal based on the first channel estimate.

2. The network device of claim 1 , wherein:

the packet comprises legacy fields and high throughput fields;

the high throughput fields include the signal field; and

the signal field indicates a length of data in the packet or a type of modulation and coding method of the packet.

3. The network device of claim 1 , wherein:

the first channel estimate module comprises a slicer module; and

the slicer module is configured to slice constellation points of the signal field to determine (i) which of the plurality of bits or which of the plurality of sub-carriers has been modulated with the first predetermined value, and (ii) which of the plurality of bits or which of the plurality of sub-carriers has been modulated with the second predetermined value.

4. The network device of claim 3 , further comprising a common phase error module configured to correct a common phase error of the signal field to generate a corrected signal, wherein:

the slicer module is configured to (i) monitor a real part of the corrected signal, and (ii) based on the real part of the corrected signal, determine (a) which of the plurality of sub-carriers has been modulated with the first predetermined value, and (b) which of the plurality of sub-carriers has been modulated with the second predetermined value;

the first predetermined value is a +1; and

the second predetermined value is a −1.

5. The network device of claim 3 , further comprising:

a second channel estimation module configured to generate a second estimate of the channel based on a training field, wherein the packet comprises the training field;

an averaging module configured to generate a third estimate of the channel based on an average of the first estimate of the channel and the second estimate of the channel; and

a multiplexer configured to select the second estimate of the channel or the third estimate of the channel,

wherein the frequency equalizer is configured to equalize the first signal based on the third estimate of the channel.

6. The network device of claim 5 , wherein the multiplexer is configured to select the second estimate of the channel or the third estimate of the channel based on whether a signal strength value is greater than a predetermined threshold.

7. The network device of claim 1 , further comprising a smoothing module configured to perform channel smoothing on the first estimate of the channel,

wherein the frequency equalizer is configured to equalize the first signal based on a result of the channel smoothing.

8. The network device of claim 1 , further comprising:

a second channel estimation module configured to generate a second estimate of the channel based on a training field, wherein the packet comprises the training field;

an averaging module configured to generate a third estimate of the channel based on an average of the first estimate of the channel and the second estimate of the channel; and

a multiplexer configured to select the second estimate of the channel or the third estimate of the channel,

wherein the frequency equalizer is configured to equalize the first signal based on the third estimate of the channel.

9. The network device of claim 8 , further comprising:

a first smoothing module configured to perform channel smoothing on the first estimate of the channel; and

a second smoothing module configured to perform channel smoothing on the second estimate of the channel,

wherein

the averaging module is configured to generate the third estimate of the channel based on (i) a result of channel smoothing the first estimate of the channel, and (ii) a result of smoothing the second estimate of the channel, and

the frequency equalizer is configured to equalize the first signal based on the result of smoothing the second estimate of the channel.

10. The network device of claim 1 , further comprising a second channel estimate module configured to generate a second estimate of the channel based on a training field, wherein:

the packet comprises the training field; and

the first channel estimate module is configured to (i) generate a log likelihood ratio based on the signal field and the second estimate of the channel, (ii) decode data of the signal field based on the log likelihood ratio, and (iii) encode the data of the signal field to determine (a) which of the plurality of bits or which of the plurality of sub-carriers has been modulated with the first predetermined value, and (b) which of the plurality of bits or which of the plurality of sub-carriers has been modulated with the second predetermined value.

11. The network device of claim 10 , further comprising:

an averaging module configured to generate a third estimate of the channel based on an average of the first estimate of the channel and the second estimate of the channel; and

a multiplexer configured to select the second estimate of the channel or the third estimate of the channel,

wherein the frequency equalizer is configured to equalize the first signal based on the third estimate of the channel.

12. The network device of claim 11 , wherein the multiplexer is configured to select the second estimate of the channel or the third estimate of the channel based on whether a signal strength value is greater than a predetermined threshold.

13. A method comprising:

receiving a packet wirelessly transmitted over a channel at a network device, wherein the packet comprises a signal field, and wherein the signal field (i) comprises a plurality of bits, and (ii) has a corresponding plurality of sub-carriers;

based on the signal field, performing a plurality of determinations, wherein each of the plurality of determinations indicates whether a respective one of the plurality of bits or a respective one of the plurality of sub-carriers has been modulated with a first predetermined value or a second predetermined value, and (ii) based on the plurality of determinations, output a first channel estimate of the channel;

receiving a first signal comprising the packet at a frequency equalizer; and

equalizing, via the frequency equalizer, the first signal based on the first estimate of the channel.

14. The method of claim 13 , further comprising slicing constellation points of the signal field to determine (i) which of the plurality of bits or which of the plurality of sub-carriers has been modulated with the first predetermined value, and (ii) which of the plurality of bits or which of the plurality of sub-carriers has been modulated with the second predetermined value.

15. The method of claim 14 , further comprising:

correcting a common phase error of the signal field to generate a corrected signal;

monitoring a real part of the corrected signal; and

based on the real part of the corrected signal, determining (a) which of the plurality of sub-carriers has been modulated with the first predetermined value, and (b) which of the plurality of sub-carriers has been modulated with the second predetermined value,

wherein

the first predetermined value is a +1, and

the second predetermined value is a −1.

16. The method of claim 14 , further comprising:

generating a second estimate of the channel based on a training field, wherein the packet comprises the training field;

averaging the first estimate of the channel and the second estimate of the channel to generate a third estimate of the channel; and

selecting the second estimate of the channel or the third estimate of the channel,

wherein the equalizing of the first signal is based on the third estimate of the channel.

17. The method of claim 13 , further comprising performing channel smoothing on the first estimate of the channel,

wherein the equalizing of the first signal is based on a result of the channel smoothing.

18. The method of claim 13 , further comprising:

generating a second estimate of the channel based on a training field, wherein the packet comprises the training field;

averaging the first estimate of the channel and the second estimate of the channel to generate a third estimate of the channel; and

selecting the second estimate of the channel or the third estimate of the channel,

wherein the equalizing of the first signal is based on the third estimate of the channel.

19. The method of claim 18 , further comprising:

performing channel smoothing on the first estimate of the channel; and

performing channel smoothing on the second estimate of the channel,

wherein

the third estimate of the channel is generated based on (i) a result of channel smoothing the first estimate of the channel, and (ii) a result of smoothing the second estimate of the channel, and

the equalizing of the first signal is based on the result of smoothing the second estimate of the channel.

20. The method of claim 13 , further comprising:

generating a second estimate of the channel based on a training field,

wherein the packet comprises the training field;

generating a log likelihood ratio based on the signal field and the second estimate of the channel;

decoding data of the signal field based on the log likelihood ratio; and

encoding the data of the signal field to determine (a) which of the plurality of bits or which of the plurality of sub-carriers has been modulated with the first predetermined value, and (b) which of the plurality of bits or which of the plurality of sub-carriers has been modulated with the second predetermined value.

21. The method of claim 20 , further comprising:

averaging the first estimate of the channel and the second estimate of the channel to generate a third estimate of the channel; and

selecting the second estimate of the channel or the third estimate of the channel,

wherein the equalizing of the first signal is based on the third estimate of the channel.