Compressed orthogonal frequency division multiplexing (OFDM) symbols in a wireless communication system
View Patent ↗One or more first padding bits are added to information bits to be included in a data portion of a data unit such that the information bits, after being encoded, fill one or more OFDM symbols up to a boundary within a last OFDM symbol. The information bits and the first padding bits are encoded to generate coded bits. After encoding, coded bits corresponding to the last OFDM symbol are padded, or constellation points generated based on the coded bits corresponding to the last OFDM symbol are padded, such that the padded coded bits or the padded constellation points occupy a remaining portion of the last OFDM symbol after the boundary. The last OFDM symbol of the data portion is generated to include the coded information bits corresponding to the last OFDM symbol, the first padding bits and second padding bits or padding constellation points added after encoding.
1. A method for generating a physical layer (PHY) data unit for transmission via a communication channel, the method comprising:
receiving a plurality of information bits to be included in a data portion of the PHY data unit;
adding one or more first padding bits to the information bits such that the information bits, after being encoded, fill one or more OFDM symbols up to a first portion of a last OFDM symbol, wherein the first portion of the last OFDM symbol is an initial portion of the last OFDM symbol up to a boundary within the last OFDM symbol, and wherein the method includes
determining a number of excess information bits, of the plurality of information bits, to be included in the last OFDM symbol, and
selecting a boundary value of the boundary within the last OFDM symbol based on the determined number of excess information bits;
encoding the information bits and the first padding bits to generate coded bits;
performing one of (i) adding one or more second padding bits to the coded bits corresponding to the last OFDM symbol or (ii) adding one or more padding constellation points to a set of constellation points generated based on the coded bits corresponding to the last OFDM symbol such that the padded coded bits or the padded constellation points occupy a second portion of the last OFDM symbol, wherein the second portion is a remaining portion of the last OFDM symbol after the boundary; and
generating the one or more OFDM symbols, including generating the last OFDM symbol to include (i) the coded information bits corresponding to the last OFDM symbol, (ii) the coded first padding bits in the first portion of the last OFDM symbol to allow a receiving device to stop decoding the one or more OFDM symbols after decoding the first portion of the last OFDM symbol, and (iii) the one or more second padding bits or the one or more padding constellation points in the second portion of the last OFDM symbol; and
generating the PHY data unit to include at least the one or more OFDM symbols.
2. The method of claim 1 , wherein the last OFDM symbol is a long OFDM symbol corresponding to an Inverse Digital Fourier Transform (IDFT) of a first size, and wherein selecting the value of the boundary comprises selecting the value from a set of integer multiples of a number of data bits in a virtual short OFDM symbol, wherein the virtual short OFDM symbol corresponds to an Inverse Digital Fourier Transform (IDFT) of a second size that is a fraction of the first size.
3. The method of claim 1 , wherein generating the PHY data unit further comprises including a signal extension field after the data portion if the selected boundary value exceeds a threshold, wherein a duration of the signal extension field is determined based on the selected boundary value.
4. The method of claim 3 , further comprising
generating a signal field to be included in a preamble of the PHY data unit, wherein the signal field includes an indication of the selected boundary value,
generating the preamble of the PHY data unit to include the signal field, and
generating the PHY data unit to include the preamble.
5. The method of claim 4 , wherein generating the signal field comprises generating the signal field to further include an indication to indicate whether an extension signal field is included in the PHY data unit.
6. The method of claim 1 , wherein encoding the information bits and the first padding bits to generate coded bits comprises encoding the information bits and the first padding bits using one or more binary convolutional code (BCC) encoders.
7. The method of claim 1 , wherein encoding the information bits and the first padding bits to generate coded bits comprises encoding the information bits and the first padding bits using one or more low density parity check (LDPC) encoders.
8. The method of claim 1 , wherein adding the one or more second padding bits to the coded bits comprises repeating Y last coded bits, where Y is a positive integer greater than zero.
9. An apparatus, comprising:
a network interface device having one or more integrated circuits configured to
receive a plurality of information bits to be included in a data portion of a physical layer (PHY) data unit;
add one or more first padding bits to the information bits such that the information bits, after being encoded, fill one or more OFDM symbols up to a first portion of a last OFDM symbol, wherein the first portion of the last OFDM symbol is an initial portion of the last OFDM symbol up to a boundary within the last OFDM symbol, and wherein the one or more integrated circuits are configured to
determine a number of excess information bits, of the plurality of information bits, to be included in the last OFDM symbol, and
select a boundary value of the boundary within the last OFDM symbol based on the determined number of excess information bits;
encode the information bits and the first padding bits to generate coded bits;
perform one of (i) adding one or more second padding bits to the coded bits corresponding to the last OFDM symbol or (ii) adding one or more padding constellation points to a set of constellation points generated based on the coded bits corresponding to the last OFDM symbol such that the padded coded bits or the padded constellation points occupy a second portion of the last OFDM symbol, wherein the second portion is a remaining portion of the last OFDM symbol after the boundary; and
generate the one or more OFDM symbols, including generating the last OFDM symbol to include (i) the coded information bits corresponding to the last OFDM symbol, (ii) the coded first padding bits in the first portion of the last OFDM symbol to allow a receiving device to stop decoding the one or more OFDM symbols after decoding the first portion of the last OFDM symbol, and (iii) the one or more second padding bits or the one or more padding constellation points in the second portion of the last OFDM symbol; and
generate the PHY data unit to include at least the one or more OFDM symbols.
10. The apparatus of claim 9 , wherein the last OFDM symbol is a long OFDM symbol corresponding to an Inverse Digital Fourier Transform (IDFT) of a first size, and wherein the one or more integrated circuits are configured to select the value of the boundary from a set of integer multiples of a number of data bits in a virtual short OFDM symbol, wherein the virtual short OFDM symbol corresponds to an Inverse Digital Fourier Transform (IDFT) of a second size that is a fraction of the first size.
11. The apparatus of claim 9 , wherein the one or more integrated circuits are configured to generate the PHY data unit to further include a signal extension field after the data portion if the selected boundary value exceeds a threshold, wherein a duration of the signal extension field is determined based on the selected boundary value.
12. The apparatus of claim 11 , wherein the one or more integrated circuits are further configured to
generate a signal field to be included in a preamble of the PHY data unit, wherein the signal field includes an indication of the selected boundary value,
generate the preamble of the PHY data unit to include the signal field, and
generate the PHY data unit to further include the preamble.
13. The apparatus of claim 11 , wherein the one or more integrated circuits are further configured to generate the signal field to further include an indication to indicate whether an extension signal field is included in the PHY data unit.
14. The apparatus of claim 9 , wherein the one or more integrated circuits are configured to encode the information bits and the first padding bits using one or more binary convolutional code (BCC) encoders.
15. The apparatus of claim 9 , wherein the one or more integrated circuits are configured to encode the information bits and the first padding bits using one or more low density parity check (LDPC) encoders.
16. The apparatus of claim 9 , wherein adding the one or more second padding bits to the coded bits corresponding to the last OFDM symbol comprises repeating Y last coded bits, where Y is a positive integer greater than zero.