Communication systems and methods in accordance with various embodiments of the invention utilize modulation on zeros. Carrier frequency offsets (CFO) can result in an unknown rotation of all zeros of a received signal's z-transform. Therefore, a binary MOCZ scheme (BMOCZ) can be utilized in which the modulated binary data is encoded using a cycling register code (e.g. CPC or ACPC), enabling receivers to determine cyclic shifts in the BMOCZ symbol resulting from a CFO. Receivers in accordance with several embodiments of the invention include decoders capable of decoding information bits from received discrete-time baseband signals by: estimating a timing offset for the received signal; determining a plurality of zeros of a z-transform of the received symbol; identifying zeros from the plurality of zeros that encode received bits by correcting fractional rotations resulting from the CFO; and decoding information bits based upon the received bits using a cycling register code.

Systems and methods are disclosed herein for modifying modulated signals for transmission. The system receives a modulated signal comprising a speech signal and a carrier wave and generates first and second spectral signals by converting the modulation signal and carrier wave from the time domain to the frequency domain respectively. The system then determines spectral bands for the first and second spectral signals. For each spectral band, the system calculates a weighted spectral band value based on a magnitude of the first spectral signal within the spectral band and generates a modified spectral signal by modifying the second spectral signal with the weighted spectral band value. The system then converts the modified spectral signal from the frequency domain to the time domain and transmits the converted modified spectral signal to a server.

System for generating a constant envelope and suppressed cyclic feature signal may include a transmission security (TRANSEC) function, a spread spectrum chip, an M-ary continuous phase modulator, and a pulse-shaped filter. The TRANSEC may generate a pseudorandom symbol by M-ary symbol generation selects a symbol with a signal phase, and the spread spectrum chip corresponding to the generated pseudorandom symbol or a phase rotation of the pseudorandom symbol. The M-ary continuous phase modulator with a delta-phase mapper maps the signal phase based at least in part on the selected symbol. The pulse-shaped filter of the M-ary modulator introduces inter-symbol interference from a previous and a subsequent symbol into a current symbol; the inter-symbol interference may be introduced by the main lobe of the signal phase being contained within a bandwidth of a chip rate of the spread spectrum chip for frequency modulation signal transmission of information by the generated signal.

Methods, systems, and apparatus, including computer programs encoded on a computer storage medium, for communicating signals using a multi-dimensional symbol constellation. In one example, a process for modulating a carrier signal includes the actions of mapping data to symbols of a multi-dimensional symbol constellation that includes at least three dimensions, each dimension of the constellation represented by a respective modulation signal. The dimensions of the constellation include first and second dimensions each of which are represented by respective in-phase modulation values and quadrature phase modulation values of a quadrature amplitude modulation (QAM) signal, and a third dimension represented by a transpositional modulation (TM) signal. The method further includes modulating a carrier signal with the TM signal and the QAM signal.

Communication systems and methods in accordance with various embodiments of the invention utilize modulation on zeros. Carrier frequency offsets (CFO) can result in an unknown rotation of all zeros of a received signal's z-transform. Therefore, a binary MOCZ scheme (BMOCZ) can be utilized in which the modulated binary data is encoded using a cycling register code (e.g. CPC or ACPC), enabling receivers to determine cyclic shifts in the BMOCZ symbol resulting from a CFO. Receivers in accordance with several embodiments of the invention include decoders capable of decoding information bits from received discrete-time baseband signals by: estimating a timing offset for the received signal; determining a plurality of zeros of a z-transform of the received symbol; identifying zeros from the plurality of zeros that encode received bits by correcting fractional rotations resulting from the CFO; and decoding information bits based upon the received bits using a cycling register code.

In general, techniques are described for limiters used in wireless transmitters. A transmitter comprising a frontend circuit and a backend circuit may perform various aspects of the limiter techniques. The frontend circuit may obtain a data symbol of a plurality of data symbols representative of data to be transmitted wirelessly, and determine an amplitude and a phase representative of the data symbol. The frontend circuit may also transform the phase to a frequency, compare the frequency to a threshold frequency, and adjust, based on the comparison of the frequency to the threshold frequency, the frequency to obtain an adjusted frequency. The backend circuit configured may obtain, based on the amplitude and the adjusted frequency, a wireless signal, and transmit the wireless signal.

A communication system using an increased sampling rate includes a baseband signal generator and a PLL that generates an LO signal and an inverted LO signal. An interpolator generates an interpolated/delayed data stream from a baseband original data stream, and a cell control circuit generate control signals based on the interpolated data stream and the baseband original data stream. An RFDAC generates an RF output signal from the baseband signal using an increased sampling rate, the LO signal, the inverted LO signal, and the control signals.

A method and system are herein provided. According to one embodiment, a method includes receiving, by a transceiver including a digital intermediate frequency (IF) modulator, an I baseband signal and a Q baseband signal, cancelling, by the digital IF modulator, an image in the I and Q baseband signals, and generating, by the digital IF modulator, a digital IF signal and a Hilbert transform of the digital IF signal.

Systems and methods are disclosed herein for modifying modulated signals for transmission. The system receives a modulated signal comprising a speech signal and a carrier wave and generates first and second spectral signals by converting the modulation signal and carrier wave from the time domain to the frequency domain respectively. The system then determines spectral bands for the first and second spectral signals. For each spectral band, the system calculates a weighted spectral band value based on a magnitude of the first spectral signal within the spectral band and generates a modified spectral signal by modifying the second spectral signal with the weighted spectral band value. The system then converts the modified spectral signal from the frequency domain to the time domain and transmits the converted modified spectral signal to a server.

In a signal generating device 2, first signal generation means 12 for generating a most significant bit signal stream MSB, second signal generation means 13 for generating a least significant bit signal stream LSB, a mask generation means 14 for defining a bit that allows error insertion and a bit that prohibits error insertion with different pieces of bit information, and generating a mask pattern of each of the most significant bit signal stream MSB and the least significant bit signal stream LSB, based on symbol transition information indicating a transition destination of four PAM4 symbols of a PAM4 signal; and error insertion means 15 for inserting an error, based on bit information of the mask pattern corresponding to each bit of the most significant bit signal stream and the least significant bit signal stream designated according to a symbol error rate.