Systems and methods for adjusting timing in a communication system, such as an OFDM system are described. In one implementation an error signal is generated to adjust the timing of a variable rate interpolator so as to adjust FFT timing. The error signal may be based on detection of significant peaks in an estimate of the impulse response of the channel, with the peak locations being tracked over subsequent symbols and the system timing adjusted in response to changes in the peaks.

The propagation channel in a wireless communication system may be characterized as a multipath fading model wherein the multiple delayed and attenuated versions of the transmitted signal are received. In the receiver's processing chain, the impairments introduced by this propagation channel may be equalized using the channel estimates. The channel estimation is mainly performed using the known reference signals by conventional methods. The estimation of delay spread profile may be crucial for high performance channel estimation. The conventional methods may be appropriate for high operating channel bandwidths. In the case of low channel bandwidth, limited number of reference signals may be available which may not be adequate for accurate delay spread estimation. A method and apparatus are disclosed that improve the delay spread estimation for low channel bandwidth scenarios.

This disclosure relates to techniques for selecting operational modes of a wireless device. The operational mode may be selected based on determining the presence or absence of reference symbols. A low power mode may be selected when the presence or absence of reference symbols suggests that a control channel used by the wireless device may not be present.

Techniques are described for wireless communication. One method includes identifying a plurality of channel responses corresponding to a plurality of channels. Each channel of the plurality of channels corresponds to a pairing of a transmit antenna with a receive antenna. Each channel response of the plurality of channel responses corresponds to a plurality of tone subsets. The method also includes selecting, for each channel of the plurality of channels, a subset of non-frequency domain components of the channel response for the channel, and transmitting, for at least one channel of the plurality of channels, at least one subset of channel state information (CSI). The at least one subset of CSI is based at least in part on at least one of the selected subsets of non-frequency domain components.

This disclosure provides systems, methods and apparatus for wireless communication. In one aspect, a method of wireless communication includes utilizing a sounding procedure to obtain compressed beamforming (CBF) information. The sounding procedure may be a single-user or multi-user sounding procedure. The CBF information may contain various information regarding a particular channel that an access point may use for transmission. The information may include per-tone SNR information which may be processed to determine characteristics of the channel. Various techniques may be utilized to determine the further characteristics of the channel. The determined characteristics of the channel may then be used to determine an appropriate guard interval (GI) between symbols that are to be transmitted. Appropriate GI selection in wireless communications may facilitate higher throughput while decreasing overhead due to unnecessary idle time.

An inter-carrier interference (ICI) mitigation circuit associated with an orthogonal frequency division multiplexing (OFDM) receiver is disclosed. The ICI mitigation circuit comprises an ICI cancellation circuit configured to receive an OFDM symbol associated with an OFDM signal and determine an ICI associated with one or more OFDM subcarriers within the OFDM symbol. The ICI cancellation circuit is further configured to cancel the ICI from the one or more OFDM subcarriers associated with the OFDM symbol, in order to generate a desired OFDM symbol. In some embodiments, the ICI is determined and cancelled at the ICI cancellation circuit, in accordance with a predetermined ICI mitigation algorithm.

This disclosure provides systems, methods and apparatus for wireless communication. In one aspect, a method of wireless communication includes utilizing a sounding procedure to obtain compressed beamforming (CBF) information. The sounding procedure may be a single-user or multi-user sounding procedure. The CBF information may contain various information regarding a particular channel that an access point may use for transmission. The information may include per-tone SNR information which may be processed to determine characteristics of the channel. Various techniques may be utilized to determine the further characteristics of the channel. The determined characteristics of the channel may then be used to determine an appropriate guard interval (GI) between symbols that are to be transmitted. Appropriate GI selection in wireless communications may facilitate higher throughput while decreasing overhead due to unnecessary idle time.

A transmitting device includes: a transmission signal generation circuit that generates a transmission signal using a frame format including a legacy short training field (STF), a legacy channel estimation field (CEF), a legacy header field, an enhanced directional multi-gigabit (EDMG) header field, an EDMG-STF, an EDMG-CEF, and a data field; and a transmission circuit that transmits the generated transmission signal using one or more channels, wherein the legacy header field includes a data length field expressed by multiple bits, and the data length field indicates, to a legacy terminal, information related to a data length using all of the multiple bits, and indicates, to an EDMG terminal, information related to a data length using a subset of the multiple bits, and uses the remaining bit or bits to indicate information related to the one or more channels in which the transmission signal is transmitted.

This disclosure provides systems, methods and apparatuses for selecting a guard interval for transmission of orthogonal frequency-division multiplexing (OFDM) symbols on an uplink (UL) channel and on a downlink (DL) channel. In some implementations, a transmitting device and a receiving device can estimate channel delay spread (CDS) information for each other's transmit channels, exchange the estimated CDS information with each other, and select a guard interval based on the estimated CDS information exchanged with each other. The transmitting device can transmit a number of OFDM symbols separated by the selected guard interval to the receiving device on the UL channel, and the receiving device can transmit a number of OFDM symbols separated by the selected guard interval to the transmitting device on the DL channel.

Precoding, a symbol permutation operation, or pulse shaping may be used to suppress or cancel a tail or head of a symbol. Precoding may include utilization of a suppression vector. A unique word (UW) may be added to the suppression vector before spreading. The symbol and values of the suppression vector may be spread by a spreading function(s) and may be shaped prior to transmission.