Certain aspects of the present disclosure provide techniques for hybrid modulation and demodulation, which may include multiplexing and demultiplexing different waveform types. An example method includes receiving a time-domain waveform from a transmitting entity and converting the time-domain waveform to a frequency domain. The method also includes identifying a first set of time and frequency resources associated with converted first information and a second set of time and frequency resources associated with second information in time and frequency resources of an orthogonal frequency domain multiplexing (OFDM) resource grid in a time-frequency domain. The method further includes decoding the first set of time and frequency resources to generate first information from the converted first information. For certain aspects, the first information may be precoded with an orthogonal time frequency space (OTFS) modulation.

A system and method for the efficient compression of the Channel State Information (CSI) in a wireless network with very low complexity and implementation cost. In accordance with the present invention, the CSI can be approximated as the summation of very few sinusoids on constant frequencies and the parameters of the sinusoids can be found efficiently by very simple calculations such as dot products of vectors which are implementable in hardware at very low cost.

An IS-OFDM system for point-to-point wireless communications that suppresses narrow-band interference comprises an IS-OFDM transmitter and an IS-OFDM receiver, wherein a transmitted signal comprises a plurality of subcarriers, and further wherein each subcarrier contains more than one and potentially all symbols transmitted in a given frame. The IS-OFDM transmitted signal is at a data rate that is equal to the data rate of the input data stream via the use of P/S converters.

A transmission method simultaneously transmitting a first modulated signal and a second modulated signal at a common frequency performs precoding on both signals using a fixed precoding matrix and regularly changes the phase of at least one of the signals, thereby improving received data signal quality for a reception device.

A Multiple Input Multiple Output (MIMO) system in a radio access network (RAN) comprises a virtualized baseband unit, an antenna array; and a fronthaul network that connects the virtualized baseband unit to the antenna array. For a first set of antennas in the antenna array, the virtualized baseband unit generates a first MIMO matrix from channel state information (CSI); computes a sparse update matrix corresponding to an update to the first set of antennas; sums the sparse update matrix with the first MIMO matrix to produce a second MIMO matrix corresponding to a second set of antennas in the antenna array; determines which of the MIMO matrices results in a better CSI, MIMO condition number, peak-to-average-power ratio, or quality metric of spatial subchannels; and based on the determination, selects the first set of antennas or the second set of antennas to transmit or receive signals in the RAN.

A communication node included in a multi-antenna multi-carrier system, when precoding matrices corresponding to some subcarriers from among subcarriers allocated to another communication node connected to the communication node are input, obtains precoding matrices for at least some subcarriers from among the allocated subcarriers by performing spherical interpolation on the input precoding matrices, maps the obtained precoding matrices for the at least some subcarriers to the subcarriers allocated to the other communication node, and performs precoding on the plurality of vector signals using the mapped precoding matrices.

Systems and methods for the secure transmission of data and algorithms are disclosed. The coding and modulation schemes meet the need of low signal-to-noise (SNR) ratio applications in areas of high interference. A radio transmitter is used to transmit data signals and a radio receiver is used to receive signals. The new coding algorithms and modulation for wideband communication at very low SNR domains. Systems use orthogonal frequency-division multiplexing modulation and a channel pilot algorithm for timing synchronization and frame alignment. Systems also use an orthogonal code, a super orthogonal convolutional code, and a block code to achieve channel capacity within 80% of the Shannon limit in the subzero decibel (dB) domain with reasonable decoding complexity. In an implementation example given, a 12.5 MHz band radio can transmit at a 108 kbps user data rate at −20 dB SNR and escape adversity detection.

A communication apparatus of the present disclosure includes a receiver which, in operation, receives a signal that includes a non-legacy preamble and a data field, the non-legacy preamble comprising a first field for indicating a number of spatial streams (Nss) in the data field and a second field for indicating one of a plurality of modulation and coding schemes (MCSs), wherein two or more frequency diversity transmission schemes are supported and one of the two or more frequency diversity transmission schemes is applied based on a value of the Nss; and circuitry which, in operation, decodes the signal.

A method and apparatus for underwater acoustic communication are disclosed. A data packet frame structure in the communication transmission includes a preamble, a synchronization code, and a data code. A guard interval is disposed between the preamble and the synchronization code. This method utilizes the different impact response environments of linear frequency modulation signals in different frequency bands to obtain the mapping relationships corresponding to the characteristics of the impulse responses in the frequency band, and adopts the quadrature phase shift keying (QPSK) modulation method to convert four groups of LMF signals with different center frequencies and the same modulation frequency, representing different symbols for signal transmission, where the LFM carrier signal of each center frequency can represent two bits of binary information to improve transmission efficiency. The apparatus for underwater acoustic communication also has the above-mentioned technical effects.

Disclosed techniques for improving computational efficiency can be applied to synthesis and analysis in digital signal processing. A base discrete-time Orthogonal Frequency Division Multiplexing (OFDM) signal is generated by performing at least one linear transform, including an inverse discrete Fourier transform (IDFT), on a first matrix of data symbols. A sparse data matrix is provided as an update to the first matrix of data symbols. The at least one linear transform is performed on the sparse data matrix to generate an update discrete-time OFDM signal. The update discrete-time OFDM signal and the base discrete-time OFDM signal are summed to produce an updated discrete-time OFDM signal.