A method includes accessing a network graph including: a set of nodes, each representing a transceiver; and a set of edges, each edge connecting two nodes and representing a communication channel between a pair of transceivers. The method also includes: accessing a network state comprising a set of edge values for the set of edges; and identifying a set of triangle graphs in the network graph. The method further includes, for each triangle graph in the network graph: calculating a component diagnostic score based on a subset of edge values; and for each node in the triangle graph, updating a cumulative diagnostic score for the node based on the component diagnostic score. The method additionally includes, in response to detecting a cumulative diagnostic score for a node exceeding a threshold cumulative diagnostic score, triggering a corrective action at a transceiver represented by the node.

A communications waveform schema integrates security at the physical layer and has many desirable features of traditional LPI/LPD waveforms. To provide additional covert aspects in communications a single-carrier base waveform is divided up in frequency and/or time and redistributed pseudo-randomly among subcarriers and channel assignment. Multiple matched polyphase filterbank channelizers are used so that each individual channel has a bandwidth well below a Nyquist rate for information carried by the base waveform, thereby making full data extraction from any individual channels a theoretic impossibility. The individual channels do not carry enough information from the base waveform to be useful and only in the aggregate can the entire base waveform be reconstructed. Individual channels are up-converted onto pseudo-randomly chosen carrier frequencies within the bandwidth of the high rate hardware IF in such a way as to obfuscate the order in which they occur in the base waveform.

In a mobile communication system using a mobile-type radio relay apparatus that forms a plurality of cells toward the ground or the sea while moving in an upper airspace, a deterioration in communication quality, which is caused by a Doppler shift of a reception signal due to a relative movement of a radio relay apparatus with respect to a terminal apparatus of each of a plurality of cells or a feeder station on the ground or on the sea, is suppressed. The communication system comprises a mobile-type radio relay apparatus that is disposed movably by flying in an upper airspace, forms a plurality of cells from an antenna at a predetermined altitude toward the ground or the sea, and performs a radio communication with a terminal apparatus located in each of the plurality of cells. The communication system comprises an estimation section for estimating a Doppler shift in at least one of a radio communication of a service link between the terminal apparatus located in the cell and the radio relay apparatus and a radio communication of a feeder link between the radio relay apparatus and a feeder station on the ground or on the sea, and a correction section for correcting a frequency of the at least one radio communication based on an estimation result of the Doppler shift.

Systems and methods are described, and one method includes acquiring a frequency offset for a demodulator receiving one symbol rate in combination with acquiring another frequency offset for another demodulator, based on sweeping the other frequency offset until detecting a qualifying symbol pattern or acquiring the frequency offset for the demodulator receiving one symbol rate, whichever occurs first. Associated with acquiring the other frequency offset based on acquiring the frequency offset for the demodulator receiving one symbol rate, setting the other frequency offset includes adjusting the frequency offset for the demodulator receiving one symbol rate.

Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may receive a synchronization signal block (SSB) transmitted by a base station. The UE may receive system information that includes reconfigurable intelligent surface (RIS) or repeater assisted initial access information that identifies a set of SSBs that are associated with an RIS or a repeater and a modulation signature associated with the RIS or the repeater. The UE may selectively perform initial access using the SSB or search for another SSB based at least in part on the RIS or repeater assisted initial access information. Numerous other aspects are described.

A node of a multi-node network (e.g., a transmitter (Tx) node or receiver (Rx) node) is disclosed. The node may include a communications interface with antenna elements and a controller. The controller may include one or more processors and have information of own-node velocity and own-node orientation relative to a common reference frame. The node may be time synchronized to apply Doppler corrections associated with the node’s own motions relative to the common reference frame. The node may receive an input sequence via a zero or near-zero Doppler path from a source node, the input sequence one of a set possible correlation sequence uniquely identifying the source node. The controller includes a correlator with sub-correlator blocks for breaking the input sequence into a set of N sub-sequences. Based on sequence processing by the sub-correlators, the correlator outputs the decoded input sequence and associated delay metrics.

A system is disclosed. The system may be a directional communications network (e.g., MANET) including at least a receiver or transmitter node. The receiver or transmitter node may include a communications interface with an omnidirectional antenna element and a controller. The controller may include one or more processors and have information of own node velocity and own node orientation relative to a common reference frame known to the receiver or transmitter node prior to the receiver or transmitter node receiving signals from a source. The receiver or transmitter node may be time synchronized to apply Doppler corrections associated with the receiver or transmitter node's own motions relative to the common reference frame. The transmitter and receiver nodes may exchange medium access control (MAC) packets prior to establishing directional communications links, determining bearings to each other via Doppler corrections with respect to the packet exchanges.

A system includes a transmitter node and a receiver node. Each node of the transmitter node and the receiver node are time synchronized to apply Doppler corrections associated with said node’s own motions relative to a stationary common inertial reference frame. The stationary common inertial reference frame is known to the transmitter node and the receiver node prior to the transmitter node transmitting a plurality of packets to the receiver node and prior to the receiver node receiving the plurality of packets from the transmitter node. The plurality of packets each comprise at least a preamble and a body payload. The body payload comprises a plurality of symbols. The plurality of symbols are separated into a plurality of blocks. The plurality of blocks are scanned at separate null directions.

In at least one embodiment, a method for measuring a distance between a first communications device including a first local oscillator and a second communications device including a second local oscillator includes unwrapping N phase values to generate N unwrapped phase values. N is an integer greater than one. Each of the N phase values indicate an instantaneous phase of a received signal. The method includes averaging the N unwrapped phase values to generate an average phase value. The method includes wrapping the average phase value to generate a final phase measurement of the first local oscillator with respect to the second local oscillator.

The present disclosure relates to: a communication technique merging IoT technology with a 5G communication system for supporting a data transmission rate higher than that of a 4G system; and a system therefor. The present disclosure can be applied to intelligent services (for example, smart homes, smart buildings, smart cities, smart cars or connected cars, healthcare, digital education, retail, security- and safety-related services, and the like), emergency communication services (emergency rescue signal transmission services), and the like on the basis of 5G communication technology, IoT-related technology and satellite communication. Proposed in the present disclosure is a method for performing a correlation operation on the basis of a reception signal and a PRACH preamble, and estimating a frequency offset on the basis of a first peak value and/or a second peak value in accordance with the correlation operation result.