A driver circuit of a PAM-N transmitting device transmits a PAM-N signal via a communication channel, wherein N is greater than 2, and the PAM-N signal has N signal levels corresponding to N symbols. A PAM-N receiving device receives the PAM-N signal. The PAM-N receiving device generates distortion information indicative of a level of distortion corresponding to inequalities in voltage differences between the N signal levels. The PAM-N receiving device transmits to the PAM-N transmitting device the distortion information indicative of the level of the distortion. The PAM-N transmitting device receives the distortion information. The PAM-N transmitting device adjusts one or more drive strength parameters of the driver circuit of the PAM-N transmitting device based on the distortion information.

The present disclosure provides a method in a receiver for frequency offset estimation. The method includes: for each of two or more pairs of symbols in a set of symbols from a transmitter: calculating a phase difference between a first symbol and a second symbol in the pair; and removing from the calculated phase difference a phase difference component due to a difference between information carried in the first symbol and information carried in the second symbol, to obtain a residual phase difference component. The method further includes: estimating a frequency offset between the receiver and the transmitter as a function of the respective residual phase difference components obtained for the two or more pairs.

A method is used for frequency offset estimation in a wireless communication network that employs time based scheduling of packets. The method is performed by a packet receiver in the wireless communication network. The method includes receiving a packet from a packet transmitter. The packet includes a preamble that is composed of samples of a single orthogonal frequency-division multiplexing symbol. The preamble has a cyclic prefix (CP) defined by a repetition of samples from an end-portion of the preamble and the preamble, except for the CP, is free from any repeated sequence of samples. The method also includes determining a sequence of similarity measure values between the CP of the preamble and the end-portion of the preamble, applying a low-pass filter to the sequence of similarity measure values, resulting in a filtered sequence of similarity measure values, and performing frequency offset estimation on the filtered sequence of similarity measure values.

Methods and systems are provided for using decision feedback phase error correction during signal processing. When an input signal comprises a plurality of sub-carriers, each of the plurality of sub-carriers may be processed separately, for each one of the plurality sub-carriers error related information may be determined separately, based on the processing of that sub-carrier. Subsequent processing of at least one of the plurality of sub-carriers may then be adjusted based on determined error related information corresponding to one or more sub-carriers. In this regard, the subsequent processing of the at least one sub-carrier may be adjusted based on determined error related information for that sub-carrier, based on determined error related information for at least one other sub-carrier, or based on determined error related information corresponding to all of the sub-carriers. The error related information may comprise phase error related information.

The present disclosure provides a method implemented in a wireless communication device for estimating a frequency offset between a carrier frequency of a received signal and a frequency of a local oscillator as well as the wireless communication device. The method comprises determining a plurality of phase change candidates for a phase change between a data symbol and a first reference symbol in the signal. The method further comprises generating a collection of constellation symbols from the data symbol and rotating the collection of constellation symbols by the plurality of phase change candidates. Then, one of the phase change candidates corresponding to one of the rotated collections of constellation symbols is selected in such a manner that said one of the rotated collections of constellation symbols matches a set of constellation points best. Next, the frequency offset is determined based on the selected phase change candidate.

A driver circuit of a PAM-N transmitting device transmits a PAM-N signal via a communication channel, wherein N is greater than 2, and the PAM-N signal has N signal levels corresponding to N symbols. A PAM-N receiving device receives the PAM-N signal. The PAM-N receiving device generates distortion information indicative of a level of distortion corresponding to inequalities, in voltage differences between the N signal levels. The PAM-N receiving device transmits to the PAM-N transmitting device the distortion information indicative of the level of the distortion. The PAM-N transmitting device receives the distortion information. The PAM-N transmitting device adjusts one or more drive strength parameters of the driver circuit of the PAM-N transmitting device based on the distortion information.

Included are a demodulation unit 20 that demodulates a received OFDM modulation signal to acquire a demodulated constellation signal, an ideal constellation signal generation unit 312 that generates an ideal constellation signal from the demodulated constellation signal, a data extraction unit 313 that extracts signal data corresponding to subcarriers included in a part of an intermediate frequency section among all frequency sections, from the demodulated constellation signal and the ideal constellation signal, a phase error calculation unit 314 that calculates the phase error of the demodulated constellation signal for the ideal constellation signal, with respect to the extracted signal data, a phase error characteristic estimation unit 315 that estimates the frequency characteristic of the phase error, and a phase error correction unit 316 that corrects the phase error of the demodulated constellation signal, based on the frequency characteristic of the phase error.

A digital transmission system includes a transmitter configured to transmit an orthogonal frequency division multiplexing (OFDM) signal along a signal path, a receiver for receiving the OFDM signal from the transmitter and extracting OFDM symbols from the received OFDM signal, and a diagnostic unit configured to (i) demodulate the received OFDM signal to create an ideal signal, (ii) compare the received OFDM signal with the ideal signal to calculate an error signal, (iii) cross-correlate the error signal with the ideal signal, and (iv) determine a level nonlinear distortion from one of the transmitter and the signal path based on the correlation of the error signal with the ideal signal.

Included are a demodulation unit that demodulates a received OFDM modulation signal to acquire a demodulated constellation signal, an ideal constellation signal generation unit that generates an ideal constellation signal from the demodulated constellation signal, a data extraction unit that extracts signal data corresponding to subcarriers included in a part of an intermediate frequency section among all frequency sections, from the demodulated constellation signal and the ideal constellation signal, a phase error calculation unit that calculates the phase error of the demodulated constellation signal for the ideal constellation signal, with respect to the extracted signal data, a phase error characteristic estimation unit that estimates the frequency characteristic of the phase error, and a phase error correction unit that corrects the phase error of the demodulated constellation signal, based on the frequency characteristic of the phase error.

A driver circuit of a PAM-N transmitting device transmits a PAM-N signal via a communication channel, wherein N is greater than 2, and the PAM-N signal has N signal levels corresponding to N symbols. A PAM-N receiving device receives the PAM-N signal. The PAM-N receiving device generates distortion information indicative of a level of distortion corresponding to inequalities in voltage differences between the N signal levels. The PAM-N receiving device transmits to the PAM-N transmitting device the distortion information indicative of the level of the distortion. The PAM-N transmitting device receives the distortion information. The PAM-N transmitting device adjusts one or more drive strength parameters of the driver circuit of the PAM-N transmitting device based on the distortion information.