Example synchronization signal sending and receiving methods and apparatus are described. In one example method, a terminal device determines a target frequency resource. A frequency domain position of the target frequency resource is determined based on a frequency domain position offset and a frequency interval of synchronization channels. The terminal device receives a synchronization signal by using the target frequency resource.

An HE-LTF transmission method is provided, including: determining, based on a total number N.sub.STS of space-time streams, a number N.sub.HELTF of OFDM symbols included in an HE-LTF field; determining a HE-LTF sequence in frequency domain according to a transmission bandwidth and a mode of the HE-LTF field, where the HE-LTF sequence in frequency domain includes but is not limited to a mode of the HE-LTF field sequence that is in a 1x mode and that is mentioned in implementations; and sending a time-domain signal according to the number N.sub.HELTF of OFDM symbols and the determined HE-LTF sequence in frequency domain. In the foregoing solution, a PAPR value is relatively low.

Methods, systems, and devices for wireless communications are described. A device (e.g., a base station or a user equipment (UE)) may identify a sequence length corresponding to a number of resource blocks, and select a modulation scheme based on the sequence length. The device may select, from a set of sequences associated with the modulation scheme, a sequence having the sequence length. In some examples, the set of sequences may include at least one of a set of time domain phase shift keying computer-generated sequences or a set of frequency domain phase shift keying computer-generated sequences. The device may generate a reference signal for a data transmission based on the sequence and transmit the reference signal within the number of resource blocks.

Techniques are described for carrier frequency offset (CFO) and channel estimation of orthogonal frequency division multiplexing (OFDM) transmissions over multiple-input multiple-output (MIMO) frequency-selective fading channels. A wireless transmitter forms blocks of symbols by inserting training symbols within two or more blocks of information-bearing symbols. The transmitter applies a hopping code to each of the blocks of symbols to insert a null subcarrier at a different position within each of the blocks of symbols, and a modulator outputs a wireless signal in accordance with the blocks of symbols. A receiver receives the wireless signal and estimates the CFO, and outputs a stream of estimated symbols based on the estimated CFO.

According to embodiments described herein, a long delay-detector improves delay estimation performance for PRACH for many practical deployment scenarios. This, for example, reduces the risk that the timing advance of the UE is set incorrectly and hence reduces the risk that subsequent communication fails and that the UE spreads unnecessary interference to other communication in the system.

Systems and methods for enabling pre-compensation of timing offsets in OFDM receivers without invalidating channel estimates are described. Timing offset estimations may be sent along with the received OFDM symbols for FFT computation and generating a de-rotated signal output. The timing offset estimation may provide a reference point for dynamic tracking of timing for an OFDM signal and estimated based on an integral value associated with the OFDM signal.

This document discloses a solution for reducing a frequency offset. According to an aspect, a method comprises: acquiring a signal distorted by the frequency offset; estimating a frequency offset estimate describing the frequency offset; computing coefficients for a frequency-domain filter on the basis of a relation between the frequency offset estimate and a combination of the frequency offset estimate and an index of the frequency-domain filter; and performing frequency-domain filtering of the signal by using the computed coefficients.

This application provides a synchronization signal sending method and receiving method, and an apparatus. In the method, a base station determines a frequency domain position of a target frequency resource based on a frequency interval of synchronization channels, wherein the frequency interval of synchronization channels is 2.sup.m times a predefined frequency resource of a physical resource block, and m is a preset nonnegative integer. The base station sends a synchronization signal by using the target frequency resource.

The invention discloses a data processing method and an intelligent terminal based on an orthogonal frequency division multiplexing (OFDM) system. The method comprises: a communication base station inserting equally spaced frequency domain reference signals to frequency domain data; obtaining frequency domain signals by equivalently transforming the frequency domain data being inserted with the frequency domain reference signals, wherein the frequency domain signals comprise the frequency domain reference signals superimposed with the frequency domain data; obtaining time domain signals by performing inverse Fast Fourier Transform (IFFT) on the frequency domain signals, wherein the time domain signals comprise time domain reference signals superimposed with the time domain data; and transmitting the time domain signals to the intelligent terminal.

According to one embodiment of the present invention, a method by which a first wireless device receives a reference signal for distance measurement in a wireless communication system can comprise the steps of: receiving, from a second wireless device, a first reference signal including a first sinusoidal signal having a first angular frequency and a second sinusoidal signal having a second angular frequency; performing fast Fourier transform (FFT) on the first reference signal; acquiring a phase difference between the first sinusoidal signal and the second sinusoidal signal on the basis of the FFT result; and transmitting, to the second wireless device, a second reference signal for the distance measurement and a third reference signal indicating information on the phase difference. The first wireless device is capable of communicating with at least one of another wireless device, a wireless device related to an autonomous driving vehicle, a base station or a network.