In accordance with an embodiment of the present invention, a method for receiving a signal, comprising the estimation step for estimating time and frequency shifts that are embedded in the received signal, to cancel-out shifts, wherein the method refers to the non-commutative shift parameter space of co-dimension 2.

A method for determining coarse carrier phase and frequency offsets of an initial block of received M-QAM symbols includes creating a grid of discrete candidate phase offset values and for each candidate value: applying the candidate value to each symbol, applying a respective hard decision to each applied symbol, and computing a figure of merit based thereon. The candidate value having the best figure of merit is selected as an initial phase offset estimate. An initial frequency offset estimate is computed using the symbols updated with the initial phase offset estimate, their respective hard decisions, and an approximation of the complex exponential function. To track carrier phase and frequency offsets associated with a series of symbol blocks, for each symbol of a current block, set a binary trust weight based on comparison of a computed parameter with a threshold and use the binary trust weights to compute a phase offset error and a frequency offset error for the current block.

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.

Examples of wireless OFDM communication systems are described herein which replace pilot subcarriers having known modulation with lower dual subcarriers. At the transmitter, for each resource block, the bits that modulate a few payload subcarriers are selected and then encoded with a short dual code thereby forming dual systematic bits and dual check bits. Such selected payload subcarriers are designated as upper dual subcarriers and the dual check bits modulate the lower dual subcarriers, At the receiver, for each resource block, the dual subcarriers are phase adjusted, demodulated, decoded using the short dual code, and re-modulated thereby forming the original dual subcarrier modulation without phase noise nor channel impairments. The re-modulated dual subcarriers are compared against the received dual subcarriers for channel estimation or carrier phase-locked-loop purposes. For example, prior-art OFDM systems with 4 pilots per resource block could be replaced with 8 dual subcarriers for a rate 1/2 short dual code. An increase in the number of subcarriers used for channel estimation or carrier phase-locked-loop tracking has less error in the channel estimate or phase estimate. Lower error permits lower payload BER, lower transmit power, or wider PLL bandwidth to track higher Doppler frequency shifts.

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.

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.

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.

In accordance with an embodiment of the present invention, a method for receiving a signal, comprising the estimation step for estimating time and frequency shifts that are embedded in the received signal, to cancel-out shifts, wherein the method refers to the non-commutative shift parameter space of co-dimension 2.

In accordance with an embodiment of the present invention, a method for receiving a signal, comprising the estimation step for estimating time and frequency shifts that are embedded in the received signal, to cancel-out shifts, wherein the method refers to the non-commutative shift parameter space of co-dimension 2.

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.