A communication apparatus includes circuitry and a transmitter. The circuitry generates a signal including one or more non-legacy long training field (LTF) symbols. Each of the one or more non-legacy LTF symbols has a plurality of data tones and a plurality of pilot tones. The circuitry maps a non-legacy LTF sequence to the plurality of data tones and the plurality of pilot tones, and groups the plurality of data tones with nonzero non-legacy LTF sequence values into a first tone group and a second tone group.
The signal includes information on a number Nsrs of space-time streams, wherein a total number of the one or more non-legacy LTF symbols is [NSTS/2] when the NSTS is 2, 3, 4, 7, 8, 11, 12, 15 or 16; and [NSTS/2] +1 when the NSTS is 5, 6, 9, 10, 13 or 14. The transmitter, in operation, transmits the generated signal.