Abstract: A method is disclosed for synchronization, comprising obtaining baseband signal samples of a baseband information signal having an in-phase signal sample and a quadrature signal sample, the baseband information signal having been generated by mixing a received modulated carrier signal with a local oscillator (LO) signal having an LO frequency, the modulated carrier signal being an in-phase signal and quadrature signal having a substantially uncorrelated nature and derived from different input data sets; determining an offset frequency rotation based on an estimated residual correlation between the in-phase signal samples and the quadrature signal samples; and, deriving synchronization information from the offset frequency rotation, wherein the received modulated carrier signal is a quadrature-modulated signal with arbitrary orthogonal in-phase and quadrature signal components.

Abstract: Systems and methods for canceling carrier frequency offset (CFO) and sampling frequency offset (SFO) in a radio receive chain are disclosed. In one embodiment, a method is disclosed, comprising: receiving a sub-frame via a radio receive chain in a time domain; performing per-user filtering on the sub-frame to obtain a signal for a particular user; obtaining a CFO correction signal; adding the CFO correction signal in the time domain to perform a CFO correction step on the signal for the particular user; performing an FFT on the output of the CFO correction step to obtain samples in a frequency domain; adding an SFO correction signal in the frequency domain to perform an SFO correction to the output of FFT step; and demodulating the output of SFO correction step, thereby performing CFO and SFO correction while reducing inter-carrier interference (ICI).

Abstract: A synchronizing radio receiver is disclosed, comprising: an analog baseband receive chain and a digital baseband receive chain. The digital baseband receive chain may comprise an analog to digital converter, a frame synchronization module, a frequency synchronization module, and an orthogonal frequency division multiplexing (OFDM) demodulator, wherein the frequency synchronization module is configured to cross-correlate a plurality of in-phase and quadrature samples to generate a synchronization signal and output the synchronization signal to a local oscillator in the analog baseband receive chain. The digital baseband receive chain may also further comprise a carrier frequency offset (CFO)/sampling frequency offset (SFO) correction module coupled to a frequency synchronization module configured to cross-correlate a plurality of in-phase and quadrature samples, with the CFO/SFO correction module configured to apply correction in a digital domain before outputting a corrected signal to the OFDM demodulator.

Abstract: A method is disclosed for synchronization, comprising obtaining baseband signal samples of a baseband information signal having an in-phase signal sample and a quadrature signal sample, the baseband information signal having been generated by mixing a received modulated carrier signal with a local oscillator (LO) signal having an LO frequency, the modulated carrier signal being an in-phase signal and quadrature signal having a substantially uncorrelated nature and derived from different input data sets; determining an offset frequency rotation based on an estimated residual correlation between the in-phase signal samples and the quadrature signal samples; and, deriving synchronization information from the offset frequency rotation, wherein the received modulated carrier signal is a quadrature-modulated signal with arbitrary orthogonal in-phase and quadrature signal components.

Abstract: Systems and methods for canceling carrier frequency offset (CFO) and sampling frequency offset (SFO) in a radio receive chain are disclosed. In one embodiment, a method is disclosed, comprising: receiving a sub-frame via a radio receive chain in a time domain; performing per-user filtering on the sub-frame to obtain a signal for a particular user; obtaining a CFO correction signal; adding the CFO correction signal in the time domain to perform a CFO correction step on the signal for the particular user; performing an FFT on the output of the CFO correction step to obtain samples in a frequency domain; adding an SFO correction signal in the frequency domain to perform an SFO correction to the output of FFT step; and demodulating the output of SFO correction step, thereby performing CFO and SFO correction while reducing inter-carrier interference (ICI).

Abstract: A method is disclosed for synchronization, comprising obtaining baseband signal samples of a baseband information signal having an in-phase signal sample and a quadrature signal sample, the baseband information signal having been generated by mixing a received modulated carrier signal with a local oscillator (LO) signal having an LO frequency, the modulated carrier signal being an in-phase signal and quadrature signal having a substantially uncorrelated nature and derived from different input data sets; determining an offset frequency rotation based on an estimated residual correlation between the in-phase signal samples and the quadrature signal samples; and, deriving synchronization information from the offset frequency rotation, wherein the received modulated carrier signal is a quadrature-modulated signal with arbitrary orthogonal in-phase and quadrature signal components.

Abstract: Described in this document are ways to accomplish high resolution and high dynamic range Doppler-Effect measurements for use in wireless communications and other applications such as positioning. Doppler Effect (interchangeably called Doppler shift or Doppler frequency shift) measurements have traditionally been done with purpose-built devices, such as pulse-based radars. Presented in this document are alternative ways to incorporate Doppler frequency shift measurement using modulated carrier signals with a conventional radio, without additional hardware.

Abstract: Systems and methods for wireless synchronization are disclosed. In one embodiment, a method is disclosed for synchronizing a slave device to a master device, comprising: receiving, at a local device, a master device reference signal in the form of a modulated radio frequency (RF) signal from a master device; receiving, at the local device, a master device time stamp from the master device; computing a time offset of the master device reference signal relative to a local reference oscillator signal of a local oscillator, using the master device time stamp; computing a frequency offset of the master device reference signal relative to the local reference oscillator signal; generating a local reference oscillator control signal based on the computed time offset and the computer frequency offset; and adjusting the local reference oscillator to maintain a frequency and time lock with the master device reference signal at the local device.

Abstract: A method comprising generating a baseband information signal by mixing a received modulated carrier signal with a local oscillator (LO) signal having an LO frequency; obtaining baseband signal samples of the baseband information signal having a baseband signal magnitude and a baseband signal phase; determining a cumulative phase measurement associated with baseband signal samples having a baseband signal magnitude greater than a threshold; and, applying a correction signal to compensate for an LO frequency offset of the LO frequency based on the cumulative phase.

Abstract: Systems and methods for canceling carrier frequency offset (CFO) and sampling frequency offset (SFO) in a radio receive chain are disclosed. In one embodiment, a method is disclosed, comprising: receiving a sub-frame via a radio receive chain in a time domain; performing per-user filtering on the sub-frame to obtain a signal for a particular user; obtaining a CFO correction signal; adding the CFO correction signal in the time domain to perform a CFO correction step on the signal for the particular user; performing an FFT on the output of the CFO correction step to obtain samples in a frequency domain; adding an SFO correction signal in the frequency domain to perform an SFO correction to the output of FFT step; and demodulating the output of SFO correction step, thereby performing CFO and SFO correction while reducing inter-carrier interference (ICI).

Abstract: A method for determining an angle of arrival (AOA) of a received signal is disclosed, comprising: generating a baseband information signal by mixing a received signal with a local oscillator (LO) signal, the received signal being an in-phase signal and quadrature signal uncorrelated with each other and derived from different input data sets; obtaining baseband signal samples of the baseband information signal having an in-phase signal sample and a quadrature signal sample; determining a transmitter phase offset based on an estimated correlation between the in-phase signal samples and the quadrature signal samples; performing a plurality of phase measurements using a plurality of antennas to obtain a plurality of phase measurements; correcting the plurality of phase measurements based on the transmitter phase offset to produce a plurality of corrected phase measurement; and calculating an AOA of the received signal based on the difference between the plurality of corrected phase measurements.

Abstract: A synchronizing radio receiver is disclosed, comprising: an analog baseband receive chain and a digital baseband receive chain. The digital baseband receive chain may comprise an analog to digital converter, a frame synchronization module, a frequency synchronization module, and an orthogonal frequency division multiplexing (OFDM) demodulator, wherein the frequency synchronization module is configured to cross-correlate a plurality of in-phase and quadrature samples to generate a synchronization signal and output the synchronization signal to a local oscillator in the analog baseband receive chain. The digital baseband receive chain may also further comprise a carrier frequency offset (CFO)/sampling frequency offset (SFO) correction module coupled to a frequency synchronization module configured to cross-correlate a plurality of in-phase and quadrature samples, with the CFO/SFO correction module configured to apply correction in a digital domain before outputting a corrected signal to the OFDM demodulator.

Abstract: A method comprising generating a baseband information signal by mixing a received modulated carrier signal with a local oscillator (LO) signal having an LO frequency; obtaining baseband signal samples of the baseband information signal having a baseband signal magnitude and a baseband signal phase; determining a cumulative phase measurement associated with baseband signal samples having a baseband signal magnitude greater than a threshold; and, applying a correction signal to compensate for an LO frequency offset of the LO frequency based on the cumulative phase.

Abstract: Methods and systems are described for frequency domain correction, time domain correction, and combinations thereof. Each Long Term Evolution (LTE) uplink residual frequency offset can be determined with less than 1 part per billion accuracy simultaneously and used for frequency offset correction. The disclosed method utilizes the same modulated signals for data and control as the 3GPP LTE wireless standard and can be embedded directly into the base station (downlink) PHY without additional hardware. The use of the disclosed methods provide multiple ways to simultaneously improve the uplink data throughput for every user in an LTE multiple access wireless system.

Abstract: Systems and methods are disclosed for synchronization and positioning, one of which comprises determining a first phase offset for a known signal received at a first antenna by plotting a first arbitrary set of phase corrections and finding a phase offset corresponding to a greatest reflectional symmetry within the first arbitrary set of phase corrections, determining a second phase offset for a known signal received at a second antenna by plotting a second arbitrary set of phase corrections and finding a phase offset corresponding to a greatest reflectional symmetry within the second arbitrary set of phase corrections, calculating an angle of arrival for the known signal from the transmitter based on the first and the second phase offset for the known signal as received at the first antenna and the second antenna, and calculating a positioning vector for a direction of the transmitter.

Abstract: Systems and methods are disclosed herein for blind frequency synchronization. In one embodiment, a method is disclosed, comprising: downconverting a received orthogonal frequency division multiplexed (OFDM) signal to baseband; identifying, from the downconverted received signal, a series of OFDM symbols in the time domain; performing a fast Fourier transform (FFT) on a block of several time domain samples to turn the time domain OFDM symbols into frequency domain OFDM symbols, one sample per subcarrier in the received OFDM signal; computing a cross-correlation between in-phase and quadrature samples in each subcarrier and for each frequency domain OFDM symbol, wherein the cross-correlation may be computed as a sum of products of either squares or absolute values of the in-phase and quadrature samples; and summing the computed cross-correlation across the series of symbols and across all subcarriers to determine a frequency offset for the received OFDM signal.

Abstract: Systems and methods are disclosed for synchronization and positioning, one of which comprises determining a first phase offset for a known signal received at a first antenna by plotting a first arbitrary set of phase corrections and finding a phase offset corresponding to a greatest reflectional symmetry within the first arbitrary set of phase corrections, determining a second phase offset for a known signal received at a second antenna by plotting a second arbitrary set of phase corrections and finding a phase offset corresponding to a greatest reflectional symmetry within the second arbitrary set of phase corrections, calculating an angle of arrival for the known signal from the transmitter based on the first and the second phase offset for the known signal as received at the first antenna and the second antenna, and calculating a positioning vector for a direction of the transmitter.

Abstract: A method comprising generating a baseband information signal by mixing a received modulated carrier signal with a local oscillator (LO) signal having an LO frequency; obtaining baseband signal samples of the baseband information signal having a baseband signal magnitude and a baseband signal phase; determining a cumulative phase measurement associated with baseband signal samples having a baseband signal magnitude greater than a threshold; and, applying a correction signal to compensate for an LO frequency offset of the LO frequency based on the cumulative phase.

Abstract: A method comprising generating a baseband information signal by mixing a received modulated carrier signal with a local oscillator (LO) signal having an LO frequency; obtaining baseband signal samples of the baseband information signal having a baseband signal magnitude and a baseband signal phase; determining a cumulative phase measurement associated with baseband signal samples having a baseband signal magnitude greater than a threshold; and, applying a correction signal to compensate for an LO frequency offset of the LO frequency based on the cumulative phase.

Abstract: A method comprising generating a baseband information signal by mixing a received modulated carrier signal with a local oscillator (LO) signal having an LO frequency; obtaining baseband signal samples of the baseband information signal having a baseband signal magnitude and a baseband signal phase; determining a cumulative phase measurement associated with baseband signal samples having a baseband signal magnitude greater than a threshold; and, applying a correction signal to compensate for an LO frequency offset of the LO frequency based on the cumulative phase.