A method for indicating a frame structure, a method for updating a frame structure, and related devices are provided. The method for indicating a frame structure, performed by a first device, includes: determining a first frame structure based on user data to be transmitted; and when the first frame structure is different from a second frame structure corresponding to a second device, sending indication information, where the indication information is used to indicate the first frame structure.

A method for reducing a peak to average power ratio (PAPR) of an orthogonal frequency division multiplexing (OFDM) signal. A first signal in the frequency domain is processed to generate a second signal by performing a modular permutation on the first signal according to a modular permutation index, and/or by performing a cyclic shift on the first signal according to a cyclic shift parameter. The second signal is then mapped to a number of tones, and transformed into a time-domain signal for transmission. The modular permutation index and/or the cyclic shift parameter are selected so that the signal for transmission has a PAPR that satisfies a predefined PAPR criteria.

Co-existence between an Orthogonal Time Frequency Space (OTFS) modulation system and a Long Term Evolution (LTE) system is achieved by generating a number of transmission beams for a first group of user equipment operating using LTE, and a second group of user equipment operating using the OTFS protocol, and transmitting a first group of data packets formatted according to the LTE protocol to the first group of user equipment and a second group of data packets formatted according to the OTFS protocol to the second group of user equipment. The transmissions are performed by precoding and modulating the first group of data packets according to an LTE modulation scheme, and precoding and modulating the second group of data packets according to an OTFS modulation scheme.

Methods, systems, and devices for wireless communications are described. For example, a wireless device may support physical broadcast channel (PBCH) precoding in high-doppler scenarios. In some cases, a base station may generate a synchronization signal block (SSB) including synchronization signals and PBCH signaling. The base station may transmit, to a UE, the PBCH signaling in accordance with an orthogonal time frequency space (OTFS) precoding and the synchronization signals in accordance with a non-OTFS precoding. The UE may monitor for the SSB and receive the PBCH signaling in accordance with the OTFS precoding and the synchronization signals in accordance with a non-OTFS precoding. The UE may establish or modify a connection with the base station according to the PBCH signaling.

Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may precode a physical sidelink control channel (PSCCH) communication using a first delay-Doppler precoder. The UE may precode a physical sidelink shared channel (PSSCH) communication using one or more second delay-Doppler precoders. The UE may transmit the PSCCH communication and the PSSCH communication in a slot after precoding the PSCCH communication and the PSSCH communication. Numerous other aspects are described.

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 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.

A method includes generating a set of symbols based on an incoming data vector. The set of symbols includes K symbols, K being a positive integer. A first transformation matrix including an equiangular tight frame (ETF) transformation or a nearly equiangular tight frame (NETF) transformation is generated, having dimensions N×K, where N is a positive integer and has a value less than K. A second transformation matrix having dimensions K×K is generated based on the first transformation matrix. A third transformation matrix having dimensions K×K is generated by performing a series of unitary transformations on the second transformation matrix. A first data vector is transformed into a second data vector having a length N based on the third transformation matrix and the set of symbols. A signal representing the second data vector is sent to a transmitter for transmission of a signal representing the second data vector to a receiver.

A discrete Fourier transform spread orthogonal time frequency space modulation method comprises the steps of performing DFT preceding processing and delay-Doppler domain mapping processing on the transmit data symbols, OTFS modulator, and performing delay-Doppler domain demapping processing and IDFT decoding processing on a received signal to realize demodulation; compared with the existing waveforms, including OFDM and DFT-s-OFDM, the proposed DFT-s-OTFS can reduce the bit error rate under high Doppler spread and the peak-to-average power ratio of the transmitted signal at the same time.

Systems and methods for transmitting data using various Modulation on Zeros schemes are described. In many embodiments, a communication system is utilized that includes a transmitter having a modulator that modulates a plurality of information bits to encode the bits in the zeros of the z-transform of a discrete-time baseband signal. In addition, the communication system includes a receiver having a decoder configured to decode a plurality of bits of information from the samples of a received signal by: determining a plurality of zeros of a z-transform of a received discrete-time baseband signal based upon samples from a received continuous-time signal, identifying zeros that encode the plurality of information bits, and outputting a plurality of decoded information bits based upon the identified zeros.