8 results about "Doppler rate" patented technology

Embodiments of this application provide a wireless communication method and an apparatus. The method includes: A first communication apparatus receives first information, where the first information indicates a determining threshold of a parameter in a first parameter set, and the first parameter set includes at least one of the following parameters: location information, delay information, a timing advance rate, a rate of the timing advance rate, a Doppler value, a Doppler rate, and remaining coverage time. The first communication apparatus determines, based on the first information, whether an access condition is met, and performs random access when the access condition is met. This avoids a random access failure in a current cell and re-access in a next cell due to random access performed when the condition is not met.

This invention discloses a secure transmission method for satellite constellation communication based on post-quantum cryptography, relating to the fields of satellite communication and information security technology. The method includes: analyzing the satellite constellation topology to determine the latency sensitivity level of the secure handshake; pre-screening a set of candidate PQC algorithms based on the sensitivity level; sensing the channel and extracting non-stationary features such as fading depth, duration, and Doppler rate of change; constructing a multi-dimensional joint optimization model with algorithm identifier, fragmentation granularity, redundancy, and modulation and coding scheme as joint decision variables, aiming to maximize the handshake probability within the expected duration; solving the model to generate an adaptive transmission strategy, and performing adaptive non-uniform fragmentation and fountain code encoding on PQC protocol data units; predicting link trends based on Doppler rate of change and dynamically scheduling symbol transmission. This invention achieves deep coupling optimization of network topology, cryptographic algorithms, and channel characteristics, improving the transmission reliability of PQC in dynamic satellite networks.

The invention belongs to the field of satellite navigation, and particularly relates to a space-frequency anti-interference method based on self-adaptive null broadening, which comprises the following steps: converting a digital intermediate frequency signal into a frequency domain signal through windowing and discrete Fourier transform, and calculating a covariance matrix in a conventional operation scene; the Doppler change rate is adopted to identify a current motion scene, so that whether matrix reconstruction is carried out or not is judged, and an adaptive null broadening function is realized; and performing spatial filtering on each narrow sub-band, and transforming a frequency domain signal back to a time domain signal by using inverse discrete Fourier transform and inverse window to obtain anti-interference data. According to the method, the Doppler change rate is innovatively introduced into null broadening for self-adaptive judgment, the problem of mismatching of the null depth and the interference coming direction in special motion scenes such as a large off-axis attitude is solved, meanwhile, the anti-interference limit performance in a conventional operation scene is not affected, and the self-adaptive capacity of the anti-interference navigation terminal is effectively improved.

The application relates to the technical field of satellite navigation, and discloses a low-orbit satellite and medium-orbit satellite acquisition tracking method, which comprises the following steps: acquiring the orbital height of a satellite and the Doppler rate of a satellite signal; determining the type of the satellite based on the orbital height and the Doppler rate; determining the acquisition parameters and the tracking loop parameters corresponding to the satellite based on the type of the satellite; acquiring the satellite according to the acquisition parameters, wherein the acquisition parameters comprise a Doppler search step and a coherent integration time; and setting a tracking loop according to the tracking loop parameters to track the satellite, wherein the tracking loop parameters comprise Kalman filter weights, a phase-locked loop bandwidth and a frequency-locked loop bandwidth. The application adjusts the acquisition parameters of a receiver according to the type of the satellite to quickly acquire a low-orbit satellite signal and reduce the acquisition time of a medium-orbit satellite signal, and adjusts the tracking loop parameters of the receiver according to the type of the satellite to ensure the tracking accuracy of the medium-orbit satellite signal and improve the tracking stability of the low-orbit satellite signal.

The application relates to a method of estimating a location of a source of an electromagnetic signal. Also disclosed is a system comprising apparatus for carrying out the method, and a computer-readable medium storing a computer program for carrying out the method. The method includes: obtaining a first set of equations that, for each of a plurality of receivers of the electromagnetic signal, relate time of arrival (TOA), frequency of arrival (FOA), and Doppler rate of arrival (DROA), to a range between the source and the particular one of the plurality of receivers; selecting a candidate source location in three-dimensional space; obtaining a second set of equations by transforming each of the first set of equations based on a displacement vector; based on the second set of equations, obtaining a set of difference equations comprising, for each of a number of pairs of the receivers, respective equations representing a time difference of arrival (TDOA) between the pair, a frequency difference of arrival (FDOA) between the pair, and a Doppler rate difference of arrival (DRDOA) between the pair; obtaining a plurality of datasets, each dataset comprising successive data samples representative of the electromagnetic signal as received at a respective one of the receivers; comparing pairs of the datasets to determine respective measured TDOA, FDOA and DRDOA values; solving the set of difference equations by searching for a displacement vector that minimises a cost function; and iteratively arriving at an estimate of the location of the signal source.

The invention relates to the technical field of satellite navigation, and discloses a low-orbit satellite and medium-orbit satellite capturing and tracking method, which comprises the following steps: acquiring the orbit height of a satellite and the Doppler change rate of a satellite signal; determining the type of the satellite based on the orbit height and the Doppler change rate; determining capture parameters and tracking loop parameters corresponding to the satellites based on the types of the satellites; the satellite is captured according to capture parameters, and the capture parameters comprise Doppler search step length and coherent integration time; a tracking loop and a tracking satellite are set according to tracking loop parameters, and the tracking loop parameters comprise the Kalman filter weight, the phase-locked loop bandwidth and the frequency-locked loop bandwidth. The acquisition parameters of the receiver are adjusted according to the types of the satellites so as to quickly acquire the low-orbit satellite signals and reduce the acquisition time of the medium-orbit satellite signals, and the tracking loop parameters of the receiver are adjusted according to the types of the satellites so as to ensure the tracking precision of the medium-orbit satellite signals and improve the tracking stability of the low-orbit satellite signals.

The application relates to a Doppler rate calculation method in a low-orbit satellite communication system and belongs to the field of mobile communication. In view of a low-orbit satellite communication system of a non-ground communication network (NTN), the application aims to solve the problem of Doppler rate calculation without ephemeris information and frequency and timing precision synchronization conditions. By utilizing the OFDM data frame structure features, the cyclic prefix data and the symbol tail data of the OFDM symbol are extracted, the phase offset is obtained through correlation calculation, the Doppler rate is calculated in combination with the OFDM symbol interval time, and the calculation precision is improved through multiple averaging. The application does not need to analyze the data frame content, has low calculation complexity, is convenient for engineering implementation, is suitable for estimation and compensation of the Doppler frequency shift rate in the low-orbit satellite communication, and effectively improves the communication system performance.

A method for the transmission to a non-geostationary satellite of data stored by a ground-based device being carried out by the device, includes entering an awaken mode, performing successive Doppler shift estimations: receiving, by the device during the awaken mode, a signal from the satellite including a frequency parameter and an elevation emission criterion, performing a Doppler shift estimation based on the frequency of the received signal; estimating a Doppler rate of frequency change to obtain a relative position of the device, defining a transmission window during which the position of the device relative to position of the satellite verifies the elevation emission criterion, and if the position of the device relative to the position of the satellite verifies the elevation emission criterion: emitting at the frequency parameter a signal including the data stored by the device.