Method and apparatus for transmitting PPDU in WLAN system

A transmitting device transmitting a Physical Protocol Data Unit (PPDU) in a wireless LAN system, the transmitting device comprising:

• a memory;
• a transceiver;
• and
• a processor coupled operatively to the memory and the transceiver, wherein the processor is configured to:
• generate the PPDU;
• and
• transmit the PPDU to a receiving device,
• wherein the PPDU includes a legacy field and an Extreme High Throughput (EHT) field,
• the legacy field includes a Legacy-Short Training Field (L-STF),
• the EHT field includes a data field,
• the legacy field is composed based on a Cyclic Shift Delay (CSD) value for each transmit chain,
• the CSD value is determined as a candidate CSD value that minimizes a sum of a first absolute value and a second absolute value based on a power ratio,
• the power ratio is a ratio of reception power of the L-STF to reception power of the data field,
• the first absolute value is an absolute value of a value related to 5 percent of a Cumulative Distribution Function (CDF) of the power ratio, and
• the second absolute value is an absolute value of a value related to 95 percent of the CDF of the power ratio.

A method for receiving a Physical Protocol Data Unit (PPDU) in a wireless LAN system, the method comprising:

• receiving, by a receiving device, a PPDU from a transmitting device;
• and
• demodulating, by the receiving device, the PPDU,
• wherein the PPDU includes a legacy field and an Extreme High Throughput (EHT) field,
• the legacy field includes a Legacy-Short Training Field (L-STF),
• the EHT field includes a data field,
• the legacy field is composed based on a Cyclic Shift Delay (CSD) value for each transmit chain,
• the CSD value is determined as a candidate CSD value that minimizes a sum of a first absolute value and a second absolute value based on a power ratio,
• the power ratio is a ratio of reception power of the L-STF to reception power of the data field,
• the first absolute value is an absolute value of a value related to 5 percent of a Cumulative Distribution Function (CDF) of the power ratio, and
• the second absolute value is an absolute value of a value related to 95 percent of the CDF of the power ratio.