Channel description feedback in a communication system
A first communication device receives a plurality of training signal fields in a preamble of a data unit transmitted by a second communication device, the plurality of training signal fields in orthogonal frequency division multiplexing (OFDM) symbols comprising data and pilot tones. The first communication device determines first channel estimate data corresponding to the data tones in the OFDM symbols, and uses pilot tones in the plurality of training signal fields to track at least one of i) a phase offset and ii) a frequency offset while receiving the plurality of training signal fields to improve the first channel estimate data. The first communication device generates feedback data that i) includes data corresponding to the first channel estimate data, and ii) excludes data corresponding to second channel estimate data for the pilot tones in the plurality of training signal fields, and transmits the feedback data to the second communication device.
1. A method, comprising:
receiving, at a first communication device, a plurality of training signal fields in a preamble of a data unit, the plurality of training signal fields having been transmitted by a second communication device in orthogonal frequency division multiplexing (OFDM) symbols comprising data tones and pilot tones;
determining, by the first communication device, first channel estimate data corresponding to the data tones in the OFDM symbols;
using, at the first communication device, pilot tones in the plurality of training signal fields to track at least one of i) a phase offset and ii) a frequency offset while receiving the plurality of training signal fields to improve the first channel estimate data;
generating, by the first communication device, feedback data that i) includes data corresponding to the first channel estimate data, and ii) excludes any channel estimate data corresponding to the pilot tones in the plurality of training signal fields, wherein generating the feedback data includes:
when the first communication device determines that a one tone grouping is to be utilized, generating the feedback data to include feedback data for all data tones in the OFDM symbols,
when the first communication device determines that a two tone grouping is to be utilized, generating the feedback data to include feedback data for only one data tone for each of multiple groups of two data tones in the OFDM symbols, and
when the first communication device determines that a four tone grouping is to be utilized, generating the feedback data to include feedback data for only one data tone for each of multiple groups of four data tones in the OFDM symbols; and
transmitting, with the first communication device, the feedback data to the second communication device.
2. The method of claim 1 , wherein:
the data tones in the OFDM symbols are received via multiple spatial streams; and
the pilot tones in the OFDM symbols are single-stream pilot tones.
3. The method of claim 2 , wherein the first channel estimate data includes multiple input, multiple output (MIMO) channel estimate data for the multiple spatial streams.
4. The method of claim 3 , further comprising:
determining, by the first communication device, second channel estimate data corresponding to the pilot tones in the OFDM symbols;
wherein the second channel estimate data includes multiple input, single output (MISO) channel estimate data.
5. The method of claim 1 , further comprising developing a channel estimate corresponding to i) each of the data tones in the OFDM symbols corresponding to the plurality of training signal fields, and ii) each of the pilot tones in the OFDM symbols corresponding to the plurality of training signal fields.
6. A first communication device, comprising:
a wireless network interface having one or more integrated circuits configured to:
receive a plurality of training signal fields in a preamble of a data unit, the plurality of training signal fields having been transmitted by a second communication device via orthogonal frequency division multiplexing (OFDM) symbols comprising data tones and pilot tones,
determine first channel estimate data corresponding to the data tones in the OFDM symbols corresponding to the plurality of training signal fields,
use pilot tones in the plurality of training signal fields to track at least one of i) a phase offset and ii) a frequency offset while receiving the plurality of training signal fields to improve the first channel estimate data,
generate feedback data that i) includes data corresponding to the first channel estimate data, and ii) excludes any channel estimate data corresponding to the pilot tones in the OFDM symbols corresponding to the plurality of training signal fields, wherein generating the feedback data includes:
when the wireless network interface determines that a one tone grouping is to be utilized, generating the feedback data to include feedback data for all data tones in the OFDM symbols,
when the wireless network interface determines that a two tone grouping is to be utilized, generating the feedback data to include feedback data for only one data tone for each of multiple groups of two data tones in the OFDM symbols, and
when the wireless network interface determines that a four tone grouping is to be utilized, generating the feedback data to include feedback data for only one data tone for each of multiple groups of four data tones in the OFDM symbols; and
wherein the one or more integrated circuits are further configured to cause the first communication device to transmit the feedback data to the second communication device.
7. The first communication device of claim 6 , wherein:
the first channel estimate data includes multiple input, multiple output (MIMO) channel estimate data;
the one or more integrated circuits are configured to determine second channel estimate data corresponding to the pilot tones in the OFDM symbols; and
the second channel estimate data includes multiple input, single output (MISO) channel estimate data.
8. The first communication device of claim 7 , wherein the pilot tones in the OFDM symbols corresponding to the plurality of training signal fields comprise single-stream pilot tones.
9. The first communication device of claim 6 , wherein the one or more integrated circuits are configured to develop a channel estimate corresponding to i) each of the data tones in the OFDM symbols corresponding to the plurality of training signal fields, and ii) each of the pilot tones in the OFDM symbols corresponding to the plurality of training signal fields.
10. The first communication device of claim 6 , wherein:
the data tones in the OFDM symbols are received via multiple spatial streams; and
the pilot tones in the OFDM symbols are single-stream pilot tones.
11. The first communication device of claim 10 , wherein the first channel estimate data includes multiple input, multiple output (MIMO) channel estimate data for the multiple spatial streams.
12. The first communication device of claim 11 , wherein:
the one or more integrated circuits are configured to develop the second channel estimate data corresponding to the pilot tones in the OFDM symbols; and
the second channel estimate data includes multiple input, single output (MISO) channel estimate data.
13. The first communication device of claim 6 , wherein the wireless network interface comprises:
one or more transceivers implemented on the one or more integrated circuits, the one or more transceivers configured to transmit the feedback data.
14. The first communication device of claim 13 , further comprising:
one or more antennas coupled to the one or more transceivers.
15. A tangible, non-transitory medium, or non-transitory media, storing machine readable instructions that, when executed by one or more processors of a first communication device, cause the one or more processors to:
determine first channel estimate data corresponding to data tones in OFDM symbols corresponding to a plurality of training signal fields in a preamble of a data unit received by the first communication device, the plurality of training signal fields having been transmitted by a second communication device via orthogonal frequency division multiplexing (OFDM) symbols comprising data tones and pilot tones;
use pilot tones in the plurality of training signal fields to track at least one of i) a phase offset and ii) a frequency offset while receiving the plurality of training signal fields to improve the first channel estimate data;
generate feedback data that i) includes data corresponding to the first channel estimate data, and ii) excludes any channel estimate data corresponding to the pilot tones in the OFDM symbols corresponding to the plurality of training signal fields, wherein generating the feedback data includes:
when the one or more processors determine that a one tone grouping is to be utilized, generating the feedback data to include feedback data for all data tones in the OFDM symbols,
when the one or more processors determine that a two tone grouping is to be utilized, generating the feedback data to include feedback data for only one data tone for each of multiple groups of two data tones in the OFDM symbols, and
when the one or more processors determine that a four tone grouping is to be utilized, generating the feedback data to include feedback data for only one data tone for each of multiple groups of four data tones in the OFDM symbols; and
cause the first communication device to transmit the feedback data to the second communication device.
16. The tangible, non-transitory medium, or non-transitory media, of claim 15 , wherein:
the first channel estimate data includes multiple input, multiple output (MIMO) channel estimate data;
the tangible, non-transitory medium, or media, further store machine readable instructions that, when executed by the one or more processors, cause the one or more processors to determine second channel estimate data corresponding to the pilot tones in the OFDM symbols; and
the second channel estimate data includes multiple input, single output (MISO) channel estimate data.
17. The tangible, non-transitory medium, or non-transitory media, of claim 16 , wherein the pilot tones in the OFDM symbols corresponding to the plurality of training signal fields comprise single-stream pilot tones.
18. The tangible, non-transitory medium, or non-transitory media, of claim 15 , wherein the tangible, non-transitory medium, or media, further store machine readable instructions that, when executed by the one or more processors, cause the one or more processors to:
develop a channel estimate corresponding to i) each of the data tones in the OFDM symbols corresponding to the plurality of training signal fields, and ii) each of the pilot tones in the OFDM symbols corresponding to the plurality of training signal fields.
19. The tangible, non-transitory medium, or non-transitory media, of claim 15 , wherein:
the data tones in the OFDM symbols are received via multiple spatial streams; and
the pilot tones in the OFDM symbols are single-stream pilot tones.
20. The tangible, non-transitory medium, or non-transitory media, of claim 19 , wherein the first channel estimate data includes multiple input, multiple output (MIMO) channel estimate data for the multiple spatial streams.
21. The tangible, non-transitory medium, or non-transitory media, of claim 20 , wherein the tangible, non-transitory medium, or media, further store machine readable instructions that, when executed by the one or more processors, cause the one or more processors to develop the second channel estimate data corresponding to the pilot tones in the OFDM symbols; and
wherein the second channel estimate data includes multiple input, single output (MISO) channel estimate data.