An abnormality detection device 1 includes: a vibration acquisition unit 11 configured to acquire an acoustic signal generated during passage of a vehicle on a road; a frequency domain conversion unit 12 configured to convert the acquired acoustic signal into a frequency domain signal; an unexpectedness determination unit 13 configured to determine whether there is unexpectedness at each predetermined frequency using the frequency domain signal; and an abnormality determination unit 14 configured to determine whether there is an abnormality in the road based on the number of frequencies at which it is determined that there is the unexpectedness.

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.

A method for determining and compensating for residual phase noise in a 5G NR DL signal includes converting a block of 5G NR DL time domain signal samples into a block of frequency domain samples for one OFDM data symbol and equalizing and combining the frequency domain samples that fall in an outermost sample accumulation region of each quadrant to form a first composite sample for each quadrant, selecting a signal constellation point belonging to one of the four outermost constellation point decision region as a reference constellation point, rotating at least some of the first composite samples so that the first composite samples are in the same quadrant as the reference constellation point, combining the rotated first composite samples to produce a second composite sample, calculating a phase error between the second composite sample and the reference constellation point, applying phase correction corresponding to the phase error to all subcarriers of the OFDM data symbol, and generating output data from the phase-error-corrected OFDM symbol.

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.

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 1× 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.

Systems, methods and computer software are disclosed for providing high resolution timing advance estimation based on Physical Random Access Channel (PRACH). An example method includes receiving a preamble signal r(n) having a predetermined sampling frequency and a predetermined length; correlating a down sampled version of the received preamble with a reference preamble sequence c(n) using an FFT method to provide correlation output Ryc; using a peak value P of the correlation output Ryc to detect a preamble ID and a timing advance at a resolution of 24Ts; zero padding sequences Y(k) and C(k) so that they have a predetermined length resulting in sequences Y_hat(k) and C_hat(k), which are 1024-point FFT of y(n) and c(n); performing a maximum likelihood estimation (MLE) to estimate a timing offset; and detecting a peak value out of the R_hat(m) and using a corresponding index Q to provide a timing advance with an accuracy of 2Ts.

The invention provides a frequency offset estimation method for an OFDM-IM system. The method includes: S1. performing preliminary frequency offset compensation on a received signal subjected to non-uniform frequency offset by using a two-step method of: (1) resampling and down conversion; and (2) unified compensation for residual frequency offset ε, wherein in the step (2), a sum of energy of null sub-carriers is used as a cost function, an initial estimation value of ε is obtained by one-dimensional search, and the preliminary compensation is performed; S2. estimating positions of non-activated sub-carriers in the OFDM-IM system by using the signal subjected to the preliminary compensation; and S3. assigning certain weights to the estimated sub-carriers, adding energy of the estimated sub-carriers into the cost function according to different weights, obtaining a final estimation value of ε by the one-dimensional search performed on ε, and performing secondary compensation.

A transmitter for transmitting data to communications devices via a wireless access. The transmitter including modulator circuitry configured to receive modulation symbols of a segment and to rotate each modulation symbol by an angle dependent on a choice of modulation scheme, and receive each of the segments of rotated modulation symbols and for each segment to separate real and imaginary components of the rotated modulation symbols for the segment and to interleave the real components of the rotated modulation symbols of the segment differently to the imaginary components of the rotated modulation symbols of the segment. The circuitry also is configured to recombine the real and imaginary interleaved components of the rotated modulation symbols of each segment and to form from the real and imaginary components modulation cells.

According to an embodiment of the present invention, a method is disclosed for transmitting a signal on the basis of a competition-based non-orthogonal multiple access scheme, by means of a terminal in a wireless communication system. At this time, the method for transmitting a signal comprises: a step of transmitting a first codeword on the basis of the competition-based NoMA scheme; a step of receiving a negative response to the first codeword transmission from a base station; a step of selecting a second codeword, taking into account a magnitude vector and a correlation of the first codeword; and a step of transmitting the selected second codeword on the basis of the competition-based NoMA scheme.