| 摘要 |
A method includes generating first and second preambles for first and second data units corresponding to first and second PHY modes, respectively. Generating the first preamble includes generating a first STF, LTF, and SIG field. The first SIG field includes an OFDM symbol modulated according to a first modulation technique. The OFDM symbol begins a first time interval, and ends a second time interval, after the first LTF begins. Generating the second preamble includes generating a second STF and LTF. The second STF has a greater duration, and different repeating sequence, than the first STF. The second LTF includes a second OFDM symbol modulated according to a second modulation technique, and at least partially occupying a location beginning a third time interval, and ending a fourth time interval, after the second LTF begins. The third and fourth time intervals are equal to the first and second time intervals, respectively.
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