A method for transmitting data to a plurality of Stations (STAs) by an Access Point in a Wireless Local Area Network (WLAN) operating in compliance with Institute of Electrical and Electronics Engineers Standard 802.11ax, the method comprising: generating a High Efficiency-Long Training Field (HE-LTF) for the plurality of STAs; and transmitting a Physical layer Protocol Data Unit (PPDU) frame to the plurality of STAs, the PPDU frame including the HE-LTF field and a data field for the plurality of STAs, wherein the data field includes a plurality of subchannels in a frequency domain, wherein the plurality of subchannels are allocated to the plurality of STAs, and wherein a starting point of the HE-LTF field is same across the plurality of STAs and an end point of the HE-LTF field is same across the plurality of STAs wherein the HE-LTF field includes one or more HE-LTF symbols, wherein the number of the one or more HE-LTF symbols is equal to or greater than the number of spatial streams transmitted in a subchannel having a maximum number of spatial streams across the plurality of subchannels, and characterized in that: when the number of spatial streams transmitted in the subchannel having the maximum number of spatial streams across the plurality of subchannels is one, the number of HE-LTF symbols is equal to one, when the number of spatial streams transmitted in the subchannel having the maximum number of spatial streams across the plurality of subchannels is an even number, the number of HE-LTF symbols is equal to the even number, and when the number of spatial streams transmitted in the subchannel having the maximum number of spatial streams across the plurality of subchannels is an odd number other than one, the number of HE-LTF symbols is equal to the odd number plus one. generating a High Efficiency-Long Training Field (HE-LTF) for the plurality of STAs; and transmitting a Physical layer Protocol Data Unit (PPDU) frame to the plurality of STAs, the PPDU frame including the HE-LTF field and a data field for the plurality of STAs, wherein the data field includes a plurality of subchannels in a frequency domain, wherein the plurality of subchannels are allocated to the plurality of STAs, and wherein a starting point of the HE-LTF field is same across the plurality of STAs and an end point of the HE-LTF field is same across the plurality of STAs wherein the HE-LTF field includes one or more HE-LTF symbols, wherein the number of the one or more HE-LTF symbols is equal to or greater than the number of spatial streams transmitted in a subchannel having a maximum number of spatial streams across the plurality of subchannels, and characterized in that: when the number of spatial streams transmitted in the subchannel having the maximum number of spatial streams across the plurality of subchannels is one, the number of HE-LTF symbols is equal to one, when the number of spatial streams transmitted in the subchannel having the maximum number of spatial streams across the plurality of subchannels is an even number, the number of HE-LTF symbols is equal to the even number, and when the number of spatial streams transmitted in the subchannel having the maximum number of spatial streams across the plurality of subchannels is an odd number other than one, the number of HE-LTF symbols is equal to the odd number plus one. when the number of spatial streams transmitted in the subchannel having the maximum number of spatial streams across the plurality of subchannels is one, the number of HE-LTF symbols is equal to one, when the number of spatial streams transmitted in the subchannel having the maximum number of spatial streams across the plurality of subchannels is an even number, the number of HE-LTF symbols is equal to the even number, and when the number of spatial streams transmitted in the subchannel having the maximum number of spatial streams across the plurality of subchannels is an odd number other than one, the number of HE-LTF symbols is equal to the odd number plus one.