Methods and apparatus for WLAN transmission
A modulation coding scheme (MCS) is selected i) from a first set of MCSs when the PHY data unit is to be transmitted using a first channel bandwidth, and ii) from a second set of MCSs when the PHY data unit is to be transmitted using a second channel bandwidth. The first set of MCSs corresponds to i) a number of spatial streams, and ii) the first channel bandwidth, the second set of MCSs corresponds to i) the number of spatial streams, and ii) the second channel bandwidth. The second set of MCSs excludes one or more MCSs in the first set of MCSs that will result in a padding-related constraint not being met when the second channel bandwidth is to be used. Information bits are encoded according to the selected MCS, and modulated according to the selected MCS.
1. A method for generating a physical layer (PHY) data unit for transmission via a communication channel, the method comprising:
selecting, at a communication device, a modulation coding scheme (MCS) i) from a first set of MCSs when the PHY data unit is to be transmitted using a channel having a first channel bandwidth, and ii) from a second set of MCSs when the PHY data unit is to be transmitted using a channel having a second channel bandwidth, wherein
the first set of MCSs corresponds to i) a number of spatial streams, and ii) the first channel bandwidth,
the second set of MCSs corresponds to i) the number of spatial streams, and ii) the second channel bandwidth,
the first set of MCSs is different than the second set of MCSs, and
the second set of MCSs excludes one or more MCSs in the first set of MCSs that will result in a padding-related constraint not being met when the second channel bandwidth is to be used;
encoding, at the communication device, information bits using one or more encoders and according to the selected MCS;
parsing, at the communication device, the encoded information bits into the number of spatial streams;
modulating, at the communication device, the encoded information bits according to the selected MCS; and
generating, at the communication device, a plurality of Orthogonal Frequency Division Multiplexing (OFDM) symbols based on the modulated encoded information bits.
2. The method of claim 1 , wherein:
the number of spatial streams is three;
the second channel bandwidth is 80 MHz;
the first set of MCSs includes an MCS corresponding to 64-QAM modulation and rate 3/4 encoding; and
the second set of MCSs excludes the MCS corresponding to 64-QAM modulation and rate 3/4 encoding.
3. The method of claim 1 , wherein the first set of MCSs excludes one or more MCSs in the second set of MCSs that will result in the padding-related constraint not being met when the first channel bandwidth is to be used.
4. The method of claim 3 , wherein:
the number of spatial streams is three;
the first channel bandwidth is 160 MHz;
the second channel bandwidth is 80 MHz;
the first set of MCSs includes an MCS corresponding to 64-QAM modulation and rate 3/4 encoding;
the second set of MCSs excludes the MCS corresponding to 64-QAM modulation and rate 3/4 encoding;
the second set of MCSs includes an MCS corresponding to 256-QAM modulation and rate 5/6 encoding; and
the first set of MCSs excludes the MCS corresponding to 256-QAM modulation and rate 5/6 encoding.
5. The method of claim 1 , wherein selecting the MCS comprises:
selecting the MCS i) from a first MCS table corresponding to i) the number of spatial streams, and ii) the first channel bandwidth when the PHY data unit is to be transmitted using a channel having the first channel bandwidth and using the number of spatial streams; and
selecting the MCS i) from a second MCS table corresponding to i) the number of spatial streams, and ii) the second channel bandwidth when the PHY data unit is to be transmitted using a channel having the second channel bandwidth and using the number of spatial streams;
wherein the second table excludes the one or more MCSs in the first set of MCSs that will result in the padding-related constraint not being met when the second channel bandwidth is to be used.
6. The method of claim 1 , wherein selecting the MCS comprises:
selecting the MCS from an MCS table; and
interpreting the MCS table differently when the PHY data unit is to be transmitted using the first channel bandwidth as compared to when the PHY data unit is to be transmitted using the second channel bandwidth.
7. The method of claim 1 , further comprising:
adding, at a media access control (MAC) unit of the communication device, padding delimiters to an end of a MAC data unit to be included in the PHY data unit; and
adding, at a PHY unit of the communication device, PHY padding to the PHY data unit.
8. The method of claim 1 , wherein:
the second channel bandwidth is 80 MHz; and
when the second channel bandwidth is to be used, generating the plurality of OFDM symbols comprises generating OFDM symbols having 256 subcarriers, with data tones and pilot tones i) at subcarrier indices −122 to −2 and ii) at subcarrier indices 2 to 122.
9. The method of claim 8 , wherein:
when the second channel bandwidth is to be used, generating the plurality of OFDM symbols comprises generating OFDM symbols with
guard tones only at subcarrier indices i) −128 to −123 and ii)+123 to +127, and DC tones only at subcarrier indices −1 to +1.
10. The method of claim 8 , wherein:
when the second channel bandwidth is to be used, generating the plurality of OFDM symbols comprises generating OFDM symbols with pilot tones at subcarrier indices −103, −75, −39, −11, 11, 39, 75, and 103.
11. An apparatus, comprising:
a network interface device including:
a memory to store indicators of a first set of modulation coding schemes (MCSs) and a second set of MCSs, wherein
the first set of MCSs corresponds to i) a number of spatial streams, and ii) the first channel bandwidth,
the second set of MCSs corresponds to i) the number of spatial streams, and ii) the second channel bandwidth,
the first set of MCSs is different than the second set of MCSs, and
the second set of MCSs excludes one or more MCSs in the first set of MCSs that will result in a padding-related constraint not being met when the second channel bandwidth is to be used;
wherein the network interface device is configured to select an MCS i) from the first set of MCSs when a physical layer (PHY) data unit is to be transmitted using a channel having a first channel bandwidth, and ii) from the second set of MCSs when the PHY data unit is to be transmitted using a channel having a second channel bandwidth;
wherein the network interface device further includes:
one or more encoders configured to encode information bits according to the selected MCS,
a parser configured to parse the encoded information bits into the number of spatial streams, and
a modulator configured to modulate the encoded information bits according to the selected MCS; and
wherein the network interface device is further configured to generate a plurality of Orthogonal Frequency Division Multiplexing (OFDM) symbols based on the modulated encoded information bits.
12. The apparatus of claim 11 , wherein:
the number of spatial streams is three;
the second channel bandwidth is 80 MHz;
the first set of MCSs includes an MCS corresponding to 64-QAM modulation and rate 3/4 encoding; and
the second set of MCSs excludes the MCS corresponding to 64-QAM modulation and rate 3/4 encoding.
13. The apparatus of claim 11 , wherein the first set of MCSs excludes one or more MCSs in the second set of MCSs that will result in the padding-related constraint not being met when the first channel bandwidth is to be used.
14. The apparatus of claim 13 , wherein:
the number of spatial streams is three;
the first channel bandwidth is 160 MHz;
the second channel bandwidth is 80 MHz;
the first set of MCSs includes an MCS corresponding to 64-QAM modulation and rate 3/4 encoding;
the second set of MCSs excludes the MCS corresponding to 64-QAM modulation and rate 3/4 encoding.
the second set of MCSs includes an MCS corresponding to 256-QAM modulation and rate 5/6 encoding.
the first set of MCSs excludes the MCS corresponding to 256-QAM modulation and rate 5/6 encoding.
15. The apparatus of claim 11 , wherein:
the memory is configured to store:
a first MCS table corresponding to i) the number of spatial streams, and ii) the first channel bandwidth, the first MCS table storing indicators of the first set of MCSs, and
a second MCS table corresponding to i) the number of spatial streams, and ii) the second channel bandwidth, the second MCS table storing indicators of the second set of MCSs;
the network interface device is configured to:
select the MCS from the first MCS table when the PHY data unit is to be transmitted using a channel having the first channel bandwidth and using the number of spatial streams, and
select the MCS from the second MCS table when the PHY data unit is to be transmitted using a channel having the second channel bandwidth and using the number of spatial streams;
the second MCS table excludes one or more indicators of the one or more MCSs in the first set of MCSs that will result in the padding-related constraint not being met when the second channel bandwidth is to be used.
16. The apparatus of claim 11 , wherein:
the memory is configured to store an MCS table storing indicators of MCSs; and
the network interface device is configured to:
selecting the MCS from the MCS table, and
interpret the MCS table differently when the PHY data unit is to be transmitted using the first channel bandwidth as compared to when the PHY data unit is to be transmitted using the second channel bandwidth.
17. The apparatus of claim 11 , wherein the network interface device includes:
a media access control (MAC) unit configured to add padding delimiters to an end of a MAC data unit to be included in the PHY data unit; and
a PHY unit configured to add PHY padding to the PHY data unit.
18. The apparatus of claim 11 , wherein:
the second channel bandwidth is 80 MHz; and
the network interface device is configured to, when the second channel bandwidth is to be used, generate the plurality of OFDM symbols to have 256 subcarriers, with data tones and pilot tones i) at subcarrier indices −122 to −2 and ii) at subcarrier indices 2 to 122.
19. The apparatus of claim 18 , wherein the network interface device is configured to:
when the second channel bandwidth is to be used, generate the OFDM symbols with
guard tones only at subcarrier indices i) −128 to −123 and ii)+123 to +127, and DC tones only at subcarrier indices −1 to +1.
20. The apparatus of claim 18 , wherein the network interface device is configured to:
when the second channel bandwidth is to be used, generate the OFDM symbols with pilot tones at subcarrier indices −103, −75, −39, −11, 11, 39, 75, and 103.