Disclosed are method and device for indicating a PLCP header transmission mode. A method for generating a physical layer convergence protocol (PLCP) of a data frame can comprise the following steps: demodulating PLCP header mode information based on a scrambling sequence of the received frame or information elements included in the received frame; and generating a data frame including the PLCP header generated based on the PCLP header mode information. The PLCP header mode information comprises at least one indication from a space time block coding mode indication, a guard interval mode indication, and a repetition mode indication. The invention is capable of improving data transmission efficiency by adaptively determining a transmission mode of a PCLP header to a channel situation.

In a multi-user communication system, a pre-coder in a transmitter comprises a Discrete Fourier Transform (DFT) spreader provides data symbols spread with Fourier coefficients to generate DFT-spread data symbols. An OFDM modulator, such as an inverse-DFT, modulates the DFT-spread data symbols onto OFDM subcarriers to produce a pre-coded OFDM transmission signal. The Fourier coefficients reduce the transmission signal's peak to average power.

A method and system for compensating for a doubly selective channel, and a related apparatus are applied to the field of communications technologies. In embodiments of the present invention, a receive end obtains, based on a minimum mean square error between a transmit pilot sequence and a receive pilot sequence, an optimal parameter used in a process of channel compensation and signal modulation, that is, a modulation order and a channel compensation parameter such as a channel compensation matrix. Therefore, according to the embodiments of the present invention, an optimization method is used to apply a banded equalization channel compensation method and a partial FFT transform to a communications system, thereby improving system performance.

An apparatus includes a receiver to receive a first signal from at least one additional apparatus including a data frame including a FACK request in a signal (SIG) field. A baseband processor generates feedback information for use to perform channel estimation. A transmitter transmits a second signal that includes the feedback information to the at least one additional apparatus.

A device configured to communicate in a wireless network modulates data symbols onto a sequence of code symbols to produce a transmit signal comprising linear combinations of the data symbols. Modulation includes performing a block transform on the data symbols to produce coded data symbols. The block transform multiplies each of the data symbols with one of a set of code vectors, wherein each of the code vectors comprises a different frequency. Subcarrier modulation is employed to modulate each coded data symbol onto a different subcarrier frequency to produce modulated subcarriers. The transmit signal comprises a sum of the modulated subcarriers. The block transform has dimension NN, whereas the subcarrier modulation employs a transform having dimension KN, where K>N.