This specification is related to a long training field (LTF) symbol of a WLAN. The LTF symbol may be generated based on a first LTF generation sequence used for an odd-numbered stream and a second LTF generation sequence used for an even-numbered stream. An even-numbered element of the first LTF generation sequence may be set to zero (0), and an odd-numbered element of the second LTF generation sequence may be set to zero (0). A plurality of LTF symbols for first and third streams may be generated by applying a P mapping matrix to the first LTF generation sequence. A plurality of LTF symbols for a second stream may be generated by applying the P matrix to the second LTF generation sequence.