The present disclosure provides a method for detecting a random access signal. The method includes: determining a temporary peak detection sequence according to a received time domain random access signal; determining an interference cancellation weight for a frequency domain cyclic shift sequence corresponding to a search window in the temporary peak detection sequence, and performing interference cancellation on the temporary peak detection sequence according to the interference cancellation weight, obtaining a final peak detection sequence; and performing peak detection on the final peak detection sequence. The present disclosure discloses an apparatus and system for detecting a random access signal at the same time. According to the method, the present disclosure can eliminate the deterioration of the leak detection performance and the false detection performance caused by the interference during the random access signal detection, improve the detection accuracy and save resources.

Methods and OFDM receivers for decoding an OFDM signal include estimating a channel impulse response from a pilot-dense symbol of the OFDM signal for each of a plurality of potential FFT window positions; determining a noise floor of each of the channel impulse responses; selecting the potential window position corresponding to the channel impulse response with the lowest noise floor as an optimum FFT window position; and decoding symbols of the OFDM signal using the optimum FFT window position.

Disclosed are a method and an apparatus for sounding in a wireless communication system. A method for sounding in a wireless local area network (WLAN) may comprise: a step of receiving, by an STA, an NDPA frame from an AP; a step of receiving, by the STA, an NDP frame on the basis of identification information included in the NDPA frame; and a step of transmitting, by the STA, channel state information determined on the basis of the NDP frame to the AP, wherein the NDPA frame may be demodulated on the basis of a first FFT and the NDP frame may be demodulated on the basis of a second FFT.

Frame formatting for communications within single user, multiple user, multiple access, and/or MIMO wireless communications. A signal is processed within a communication device using at least two respective downclocking ratios (e.g., a first downclocking ratio applied to a first portion of the signal such as a frame or packet extracted there from, a second downclocking ratio applied to a second portion of the signal). Alternatively, a signal is divided into more than two respective portions, and different respective downclocking ratios are applied to those different respective portions (e.g., a first downclocking ratio applied to a first portion of the signal, and so on up to an n-th downclocking ratio applied to an n-th portion of the signal). Some implementations apply a singular or common downclocking ratio to more than one portion of the signal (which may be contiguous/adjacent or non-contiguous/non-adjacent within the signal).

An optical transmitter transmits an orthogonal frequency division multiplexing symbol in which only one-half of available subcarriers are modulated with data and the remaining subcarriers are suppressed by not modulating with data. The transmission is of duration equal to half the symbol period of the OFDM symbol, resulting in a half-cycle transmission. An optical receiver receives the half-cycle transmission OFDM symbol, regenerates the full time domain representation and recovers data modulated on the one-half of available subcarriers. The modulated subcarriers and the suppressed subcarriers alternate in the frequency domain.

Methods and systems are provided that enable an OFDM transmitter to be used for transmitting conventional OFDM or a form of transformed OFDM. A technique is provided for transforming a coded and modulated sequence of samples prior to an IFFT that enables the transformed sequence of samples to be transmitted using conventional OFDM or transformed OFDM. The selection of a transform function for transforming the coded and modulated sequence of samples may be based on optimizing the transform function for particular operating conditions between the transmitter and receiver. In some embodiments of the invention OFDM and time transformed OFDM are multiplexed in time and/or frequency in a transmission frame. In some embodiments of the invention a pilot pattern is provided in which the pilot are sent using OFDM and data is sent using OFDM and/or transformed OFDM.

A method includes receiving a signal at a receiver device via a channel from a transmitter device and determining a frequency domain representation of the signal. The signal includes multiple modulation symbols. The method further includes detecting a first symbol of the signal and determining a time domain representation of a distortion estimate associated with the first symbol using a distortion recovery receiver (DRR) technique. The method further includes subtracting the distortion estimate from the first symbol to generate an updated estimate of the first symbol. The method further includes determining a frequency domain representation of a second symbol using a value that is based on a frequency domain representation of the distortion estimate and that is further based on a frequency domain representation of a quantized version of the updated estimate of the first symbol.

In 60 GHz WiGig/IEEE 802.11ad, Orthogonal Frequency Division Multiplexing (OFDM) is used to achieve higher throughput. However, OFDM has one problem of high Peak-to-Average Power Ratio (PAPR) caused by the summing up of the large number of subcarriers. A high PAPR signal degrades the efficiency of power amplifier (PA) and may cause spurious emissions because of the PA non linearity. In order to reduce PAPR, Generalized Frequency Division Multiplexing (GFDM) which has the characteristics of both single carrier and multi carrier transmission has been studied. By introducing GFDM, the number of subcarriers can be decreased while still maintaining a high throughput.

The invention relates to a method for reducing the PAPR in FRFT-OFDM systems, which belongs to the field of broadband wireless digital communications technology. The method is based on fractional random phase sequence and fractional circular convolution theorem, which can effectively reduce the PAPR of the system. The method of the invention has the advantages of simple system implementation and low computational complexity. In this method, the PAPR of the system can be effectively reduced while maintaining the reliability of the system. When the number of candidate signals is the same, the PAPR performance of the present method was found to be almost the same as that of SLM and better than that of PTS. More importantly, the present method has lower computational complexity than that of SLM and PTS methods.

Methods and OFDM receivers for decoding an OFDM signal include estimating a channel impulse response from a pilot-dense symbol of the OFDM signal for each of a plurality of potential FFT window positions; determining a noise floor of each of the channel impulse responses; selecting the potential window position corresponding to the channel impulse response with the lowest noise floor as an optimum FFT window position; and decoding symbols of the OFDM signal using the optimum FFT window position.