Method and apparatus for transmitting PLCP frame in wireless local area network system

A method of receiving a data unit comprising first, second, and third orthogonal frequency-division multiplexing (OFDM) symbols, the third OFDM symbol immediately following the second OFDM symbol, the method comprising:

• demodulating the first OFDM symbol using a first binary phase shift keying (BPSK) constellation;
• demodulating the second OFDM symbol using the first BPSK constellation and obtaining, from the demodulated second OFDM symbol, an indication of whether the data unit is a Single User-Multiple Input Multiple Output (SU-MIMO) data unit or a multi user-MIMO (MU-MIMO) data unit;
• and
• demodulating the third OFDM symbol using a second BPSK constellation, rotated by 90 degrees relative to the first BPSK constellation, and obtaining, from the demodulated third OFDM symbol, a cyclic redundancy check (CRC) for at least the second OFDM symbol.

An apparatus configured to transmit data, the apparatus comprising transmitting circuitry, a processing circuit and memory operatively coupled to the processing circuit, the memory storing program instructions for execution by the processing circuit whereby the apparatus is configured to:

• map a first orthogonal frequency-division multiplexing (OFDM) symbol to a first binary phase shift keying (BPSK) constellation;
• map a second OFDM symbol to the first BPSK constellation, the second OFDM symbol comprising an indication of whether the data unit is a Single User-Multiple Input Multiple Output (SU-MIMO) data unit or a multi user-MIMO (MU-MIMO) data unit;
• map a third OFDM symbol to a second BPSK constellation, rotated by 90 degrees relative to the first BPSK constellation, the third OFDM symbol comprising a cyclic redundancy check (CRC) for at least the second OFDM symbol;
• and
• transmit a data unit comprising the first, second, and third OFDM symbols, the third OFDM symbol being transmitted immediately following the second OFDM symbol.

An apparatus configured to receive a data unit comprising first, second, and third orthogonal frequency-division multiplexing (OFDM) symbols, the third OFDM symbol immediately following the second OFDM symbol, the apparatus comprising a processing circuit and memory operatively coupled to the processing circuit, the memory storing program instructions for execution by the processing circuit whereby the apparatus is configured to:

• demodulate the first OFDM symbol using a first binary phase shift keying (BPSK) constellation;
• demodulate the second OFDM symbol using the first BPSK constellation and obtaining, from the demodulated second OFDM symbol, an indication of whether the data unit is a Single User-Multiple Input Multiple Output (SU-MIMO) data unit or a multi user-MIMO (MU-MIMO) data unit;
• and
• demodulate the third OFDM symbol using a second BPSK constellation, rotated by 90 degrees relative to the first BPSK constellation, and obtain, from the demodulated third OFDM symbol, a cyclic redundancy check (CRC) for at least the second OFDM symbol.