A modulation apparatus capable of performing highly efficient multiplexing of pilot signals used for equalization and estimation of phase noises for LOS-MIMO (Line Of Sight-Multiple Input Multiple Output) using a single-carrier signal is provided. The modulation apparatus (10) includes means (11) for transforming a time-domain pilot signal sequence into a first number of frequency-domain signals corresponding to a sequence length of the pilot signal sequence, means (12) for mapping the first number of frequency-domain signals at the same number of subcarrier intervals as a number of transmitting antennas of the modulation apparatus by shifting mapping positions of heads of the frequency-domain signals one after another by an amount equivalent to one subcarrier so that the frequency-domain signals do not overlap each other, and means (13) for transforming the mapped frequency-domain signals into time-domain signals.

This application provides example channel measurement methods and example communication apparatuses. One example method includes determining L weighting coefficients for determining channels of K moments based on channels of M moments, where L, M, and K are all positive integers. Information about the L weighting coefficients can then be sent.

Methods, systems, and devices for wireless communications are described. Generally, a transmitting device may send transmissions using a first numerology for a first type of user equipment (UE). The transmitting device may partition a stream of modulated data symbol tones into one or more contiguous subsets of modulated data symbol tones that result in a roughly frequency-flat channel for a second type of UE. The transmitting device may then perform precoding on individual subsets of the one or more contiguous subsets of modulated data symbol tones, and may insert a frequency-domain cyclic prefix, cyclic postfix, or guard interval after each precoded subset. Thus, the first type of UE may communicate using the first numerology and the second type of UE may communicate using the first numerology but with the frequency-domain cyclic prefixes to address doppler spread experienced by the second type of UE.

Systems and techniques are described that are directed to filter frequency response shift compensation, including attenuation compensation. Attenuation compensation can apply a pre-distortion to compensate for the magnitude of attenuated resource units (RUs). Additionally, filter frequency response shift can involve applying PHY Protocol Data Unit (PPDU) scheduling schemes. For example, a PPDU scheduling scheme can reduce bandwidth in the channel, thereby dropping the affected RUs. The attenuation compensation is implemented using front ends that provide feedback to a respective radio, which allows that radio to apply the appropriate pre-distortion. The front end can include one or more filters enabling frequency domain coexistence between collocated radios operating in the differing Wi-Fi bands, and a coupler that provides the feedback indicating the frequency response shift to a radio. The radio then applying a digital pre-distortion to a signal input into the one or more filters to compensate for the attenuated RUs.

Provided are a multipath separation method and device, and a storage medium. The multipath separation method includes: extracting frequency domain response characteristics of received reference signals in at least two different frequency bands; for each of the at least two different frequency bands, constructing a Toeplitz matrix; combining Toeplitz matrixes corresponding to the at least two different frequency bands; performing singular value decomposition on the synthesized Toeplitz matrix; determining a signal space matrix and a noise space matrix according to the decomposed matrix; constructing a plurality of frequency domain response vectors according to frequency domain response characteristics of local signals having different delays and are the same as the received reference signals; and comparing a first preset threshold with inner products between each of the plurality of frequency domain response vectors and the noise space matrix respectively, and determining a delay corresponding to each of a plurality of frequency domain response vectors in which inner products satisfy the first preset threshold to be a delay of one path in the multipath.

In a general aspect, a set of observed frequency-domain channel responses is filtered to remove noise or distortions that are not related to changes in the physical environment. In some aspects, for each frequency-domain channel response, a time-domain channel response is generated based on the frequency-domain channel response; and a filtered time-domain channel response is generated based on a constraint applied to the time-domain channel response. Additionally, a reconstructed frequency-domain channel response is generated based on the filtered time-domain channel response. An error signal is also generated, and a determination is made as to whether the error signal satisfies a criterion. The error signal can be indicative of a difference between the frequency-domain channel response and the reconstructed frequency-domain channel response. In response to each of the error signals satisfying the criterion, motion of an object in a space is detected based on the set of frequency-domain channel responses.

In one example aspect, a method of determining a channel estimate of an optical communications channel between at least one optical transmitting component and at least one optical receiving component is provided, the method comprising determining a location of at least one optical transmitting component, determining an orientation of the at least one optical transmitting component, determining a transmission characteristic of the at least one optical transmitting component, determining a location of at least one optical receiving component, determining an orientation of the at least one optical receiving component, determining a reception characteristic of the at least one optical receiving component, and calculating the channel estimate of the optical communications channel based on the location of the at least one optical transmitting component, the orientation of the at least one optical transmitting component, the transmission characteristic of the at least one optical transmitting component, the location of the at least one optical receiving component, the orientation of the at least one optical receiving component and the reception characteristic of at least one optical receiving component.

Systems and methods for generating a microwave signal using two millimeter-wave frequencies. A first millimeter-wave up-conversion frequency, which is generated from a lower frequency source, is used to up-convert a baseband and/or intermediate signal into a first millimeter-wave signal, which is then down-converted into a microwave signal using a second millimeter-wave down-conversion frequency generated from the same lower frequency source. Each of the first and second millimeter-wave frequencies is associated with a phase noise that is higher than a phase noise associated with the lower frequency source, however, the frequency differential between the first millimeter-wave frequency and the second millimeter-wave frequency is free of the higher phase noise, as a result of the two millimeter-wave signal being generated from the single lower frequency source, thereby causing the resultant microwave signal to be free of the higher phase noise as well.

A signal detection method for a MIMO-OFDM wireless communication system includes obtaining a channel matrix of each subcarrier through channel estimation for each MIMO-OFDM data packet in a plurality of MIMO-OFDM data packets; receiving a reception vector of each subcarrier; performing channel matrix preprocessing for the channel matrix of each subcarrier to generate a global dynamic K-value table, in which the global dynamic K-value table includes a global dynamic K-value corresponding to each search layer of each subcarrier; performing MIMO detection for each OFDM symbol in the MIMO-OFDM data packet, in which the MIMO detection includes performing the following steps for each subcarrier of a current OFDM symbol: reading channel matrix preprocessing results and reception vector of the current subcarrier; transforming the reception vector of the current subcarrier into an LR search domain; and performing K-best search for the current subcarrier to obtain an LR domain candidate transmission vector of the current subcarrier, in which a K-value applied to each search layer of the current subcarrier during the K-best search is a global dynamic K-value in the global dynamic K-value table corresponding to the search layer.

A receiver comprising: a processing module configured to: receive a first portion of a packet of received signalling from a first antenna; receive a carrier estimate signal; adjust the first portion based on the carrier estimate signal and correlate the signal with an expected code sequence to provide a first correlated signal; a tracking module configured to: receive the first correlated signal and update the carrier estimate signal, wherein the processing module is further configured to: receive a second portion of the packet from a second antenna; adjust the second portion based on the carrier estimate signal and correlate the signal to provide a second correlated signal, and wherein the receive path further comprises a phase calculation module configured to: receive the first and second correlated signals and determine a respective first and second carrier phase and an angle of arrival of the received signalling.