LDPC coding in a communication system

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 the PHY data unit;
• determining a number of orthogonal frequency division multiplexing (OFDM) symbols that are needed to transmit the plurality of information bits after encoding with a low density parity check (LDPC) encoder;
• performing one or more of a, b, c, d, e, and f according to a set of rules so that a receiving device can determine a number of information bits in the PHY data unit based on i) an indication of the number of OFDM symbols, and ii) the set rules:
• a) adding padding bits prior to encoding with the LDPC encoder,
• b) adding shortening bits prior to encoding with the LDPC encoder,
• c) removing the shortening bits after encoding with the LDPC encoder,
• d) performing puncturing,
• e) repeating information bits after encoding with the LDPC encoder, and
• f) repeating parity bits after encoding with the LDPC encoder;
• encoding the plurality of information bits using the LDPC encoder;
• and
• generating the PHY data unit i) to include the LDPC encoded information bits in OFDM symbols and ii) to include an indication of the number of OFDM symbols in the PHY data unit,
• wherein performing one or more of a, b, c, d, e, and f according to the set of rules comprises:
• determining a number of extra encoded bits needed to reach a last OFDM symbol boundary according to:
• y=NSYMNCBPS−NCWminLCW−(x+Lparity);
• determining a number of additional codewords according to
• N
• CW
• extra
• =
• ⌊
• x
• +
• L
• parity
• +
• y
• L
• CW
• ⌋
• ;
• determining a number of padding bits to be added before encoding according to:
• p1=NCWextraLCWR−x;
• and
• adding p1 padding bits to the plurality of information before encoding.