8 results about "Quadrature amplitude modulation" patented technology

The invention discloses an OFDM (Orthogonal Frequency Division Multiplexing) communication method, device and system, and the method comprises the steps: generating a transmission frame which comprises a plurality of OFDM symbols; a first OFDM symbol of the transmission frame is a synchronous pilot symbol, and a second OFDM symbol is a reference pilot symbol; based on the transmission frame, configuring at least two demodulation modes according to channel conditions or communication requirements; when the first demodulation mode is configured, the receiving end performs differential phase shift keying differential demodulation on subsequent data symbols based on the reference pilot symbols; and when a second demodulation mode is configured, the receiving end performs channel estimation by using the reference pilot symbol, and performs quadrature amplitude modulation equalization and demodulation on subsequent data symbols according to a channel estimation result. According to the invention, ultralow pilot frequency overhead can be realized, the pilot frequency overhead is compressed to only two symbols, a synchronization sequence and a reference pilot frequency sequence in each frame, and the frequency spectrum utilization rate is greatly improved.

The application discloses a kind of optical fiber communication method and system based on anti-pattern gorilla algorithm, comprising: obtaining original bit data to be sent;Original bit data is mapped to constellation diagram by quadrature amplitude modulation mapping algorithm and converted into optical fiber transmission signal;Optical fiber transmission signal is transmitted to receiving end by few-mode channel;The received optical fiber transmission signal is converted into receiving bit data by analog-digital conversion, and receiving bit data is decomposed into leading receiving information and text receiving information;Mode coupling matrix and mode transmission matrix are generated from leading receiving information using anti-pattern gorilla algorithm;Text receiving information is corrected using mode coupling matrix and mode transmission matrix to obtain correction signal, and correction signal is demapped and converted into original bit data again;Reduce the waste of computing resources caused by mode equalization technology and the equalization deviation caused, improve the quality of quadrature mode signal transmission.

The application discloses a layered quadrature amplitude modulation multiple access method without serial interference cancellation. User bits are mapped to constellation points of different levels, and the Euclidean distance between constellation points in each level is set according to the channel gain of the user, that is, the power of each user is adjusted. Finally, after superposition of multi-level constellation points, hierarchical constellation points are formed to carry the bits of multiple users. On this basis, multiple working configuration points are set, and one or more working configuration points are selected to complete the transmission task according to the number of users in the current transmission and the rate requirement of the user. The transmitter sends the corresponding position of each user in the bit string mapped by the constellation point, the Euclidean distance between the constellation points in each level and the corresponding origin in the complete constellation diagram to the receiver, and if multiple working configuration points are selected, the working configuration point matching information can enable the user to achieve the maximum capacity limit of the downlink multi-user transmission service without serial interference cancellation.

A ground-high altitude platform-satellite (G-H-S) laser communication system and method based on anisotropic non-Kolmogorov turbulence are provided, and the system includes a ground transmitting terminal, a HAP, a satellite terminal, a ground-HAP uplink and an HAP-satellite uplink. When laser beams are transmitted upwards from the ground transmitting terminal and through the HAP, the laser beams are affected light intensity scintillation, beam drift, and angle of arrival fluctuation, and are transmitted through vacuum channels and received by receiving antenna of the satellite terminal. The HAP is located at stratosphere, and an anisotropic non-Kolmogorov turbulence model is suitable for analyzing turbulence effect in stratosphere. Thus, the anisotropic non-Kolmogorov turbulence model is used to research transmission characteristics of the laser beams. Meanwhile, a hexagon quadrature amplitude modulation (HQAM) is used in the G-H-S laser communication system, which optimizes system performances on basis of improving communication quality, and enhances stability of communication links.

A sourceless co-packaged optical-electrical chip can include a plurality of different optical transceivers, each of which can transmit to an external destination or internal components. Each of the transceivers can be configured for a different modulation format, such as different pulse amplitude, phase shift key, and quadrature amplitude modulation formats. Different light sources provide light for processing by the transceivers, where the light source and transceivers can be configured for different applications (e.g., different distances) and data rates. An optical coupler can combine the light for the different transceivers for input into the sourceless co-packaged optical-electrical chip via a polarization maintaining media (e.g., polarization maintaining few mode fiber and polarization maintaining single mode fiber), where another coupler operates in splitting mode to separate the different channels of light for the different transceivers according to different co-packaged configurations.

The invention relates to a communication method and device for a cable logging system, equipment and a storage medium. The method comprises the steps that a communication channel is estimated and tracked in real time; determining a target coding mode and a corresponding coding rate according to the signal-to-noise ratio and the bit error rate, wherein the coding rate is in negative correlation with the bit error rate of the communication channel; implementing symbol-level adaptive interleaving on the coded data, wherein the interleaving depth of the adaptive interleaving is positively correlated with the bit error rate of a communication channel; performing quadrature amplitude modulation on the interleaved data, wherein the modulation order of the quadrature amplitude modulation is dynamically adjusted according to the signal-to-noise ratio of a communication channel; and transmitting the modulated data on a communication channel by adopting an orthogonal frequency division multiplexing technology. Various types of errors are coped with through a multi-level error correction mechanism, and parameters are adjusted in real time according to channel conditions, so that the cable logging system can maintain the optimal performance in a complex and changeable long-distance cable communication environment, and the communication requirements between the ground and the underground of a deep well exceeding ten thousand meters and an ultra-deep well are met.

The invention relates to a cascade carrier frequency offset estimation method and device and a storage medium. The method comprises the following steps: generating an initial local carrier signal, and performing coherent demodulation processing on a received quadrature amplitude modulation signal to obtain an initial receiving demodulation signal; performing discrete Fourier transform carrier coarse acquisition with adaptive precision adjustment, regenerating a coarse acquisition local carrier signal, performing coherent demodulation processing and clock synchronization on the quadrature amplitude modulation signal again, and outputting a first demodulation symbol; compensating the first demodulation symbol through a direct judgment phase-locked loop to obtain a second demodulation symbol, finding and outputting an ideal constellation symbol through a direct judgment method, and determining a second phase offset; tracking the phase error through phase integration and loop filtering according to the second phase offset, and determining a phase error tracking result; and determining the residual frequency offset of the first demodulation symbol according to the phase error tracking result. The method is high in anti-noise capability and high in execution efficiency.

In summary, various aspects of this disclosure relate to wireless communications. In some aspects, a user equipment (UE) can receive downlink control information transmissions including resource allocation for downlink services and at least one dedicated table bit indicating whether the UE should decode the downlink service using a first modulation order and a first target code rate corresponding to a first modulation and coding scheme (MCS) table, or a second modulation order and a second target code rate corresponding to a second MCS table (1024 quadrature amplitude modulation table). The UE can decode the downlink service, at least in part, based on at least one value of the at least one dedicated table bit, according to either the first modulation order and the first target code rate or the second modulation order and the second target code rate. Numerous other aspects are described.