Abstract: Methods, systems, and computer program products for reconfiguring a modem. In an embodiment, fast reconfiguration of a modem occurs when a first modem determines there is a need for fast reconfiguration. The first modem signals its transition from showtime to fast reconfiguration. The first modem waits for acknowledgement from a second modem before transitioning to showtime. Once transitioned from showtime, the first modem estimates a signal to noise ratio and then exchanges parameters with the second modem. The first and second modems then transition to showtime.

Abstract: A circuit is provided for transferring a signal from a fast clock domain to a slow clock domain. The circuit includes a fast clock domain configured to receive an input signal and, responsively, transfer an intermediate signal. The circuit also a slow clock domain configured to receive the transferred intermediate signal from the fast clock domain and, responsively, generate an output signal. The circuit further includes a first synchronizer disposed in the slow clock domain and a second synchronizer disposed in the fast clock domain. The first synchronizer, operating with a slow clock, is configured to receive the intermediate signal and, responsively, provide the output signal as a transferred signal which is synchronized to the input signal. The second synchronizer, operating with a fast clock, is configured to receive a feedback signal from the first synchronizer for acknowledging synchronization of the output signal to the input signal.

Abstract: A multi-branch OFDM receiver combines diversity signals received over different receiver branches using interference rejection combining. The receiver generates first channel estimates associated with a serving base station, second channel estimates associated with at least one non-serving base station, and a time offset between the serving base station and non-serving base station. The receiver computes a noise covariance matrix based on the second channel estimates and the time offset, and then combines the diversity signals received over different branches using the first channel estimates and the noise covariance matrix.

Abstract: A digital broadcast receiver is presented. The digital broadcast receiver includes a tuner for receiving a DTV signal, a known data detector for detecting position information of the known data sequences from the DTV signal, an equalizer for compensating a channel distortion of the DTV signal according to at least one of the detected position information of the known data sequences, a first decoder for turbo-decoding, via a block unit, mobile service data in the channel distortion compensated DTV signal, and a second decoder for generating a Reed-Solomon (RS) frame including the turbo-decoded mobile service data and for correcting at least one error of the generated RS frame by performing cyclic redundancy check (CRC) decoding and RS decoding on the generated RS frame.

Abstract: A transmitter and method include a LDPC encoder configured to encode source data, and a mapper configured to generate three coordinates in accordance with a 3D signal constellation where the coordinates include an amplitude coordinate and two phase coordinates. A laser source is modulated in accordance with each of the three coordinates to provide a transmission signal. A receiver, includes a demapper receives an input signal from three branches to demap the input signal using a three-dimensional signal constellation having three coordinates. The three branches include a direct detection branch, and two coherent detection branches such that the direct detection branch detects an amplitude coordinate of the input signal and the two coherent detection branches detect in-phase and quadrature coordinates of the input signal. A bit prediction module and at least one LDPC decoder are configured to iteratively decode bits by feeding back extrinsic LLRs to the demapper.

Abstract: A time-domain IQ mismatch detection apparatus for detecting mismatch between an I-channel signal and a Q-channel signal in unit of a sample included in a symbol of an OFDM signal comprises: a first delayer which delays an input I-channel signal by one sample interval; a second delayer which delays an input Q-channel signal by one sample interval; a first phase mismatch detector which multiplies a currently-input I-channel signal with a currently-input Q-channel signal and output a result thereof; a second phase mismatch detector which multiplies the currently-input I-channel signal and the delayed Q-channel signal and output a result thereof; a third phase mismatch detector which multiplies the delayed I-channel signal with the currently-input Q-channel signal and output a result thereof; and a phase error arithmetic unit which outputs a phase error value calculated using the outputs of the first, second and third phase mismatch detectors.

Abstract: A clock data recovery circuit has a good jitter tolerance characteristic and a broad data recovery range in the event of a wander, that is, a good wander-tracking characteristic of a recovered clock signal. The clock data recovery circuit executes control to compare the position of the edge of data with the position of the edge of a data recovery clock signal (a recovered clock signal) and keeps the clock edge away from the data edge if a gap between the edges becomes smaller than a reference value. A cycle of a reference clock signal is divided into N portions to generate N clock signals (pl ) with phases different from each other in composition circuits. By executing control to turn on 2 of the N selector control signals supplied to each 2 adjacent pins of the N?1 selectors at the same time, the N?1 selectors are capable of generating a middle phase between first and second phases and, hence, generating one of N×2 phases from N input phases as the phase of the data recovery clock signal.

Abstract: A method and apparatus for measuring the phase noise of an low noise block (LNB) and other devices while the device under test is on line is disclosed. Using a signal processing procedure over a short duration of a received signal, the technique demodulates the signal to expose the phase history of the underlying carrier for measurement. In an exemplary apparatus timing and carrier recovery on A/D samples are performed conventionally, a linear phase is estimated from minimum mean square fitting to the recovered carrier phase history, the single tone carrier is removed from the recovered phase to yield a residual phase. A fast Fourier transform (FFT) can be performed on the residual phase to produce a phase noise spectral measurement at an input of the demodulator.

Abstract: Methods and apparatus are provided for spread spectrum signal processing in a wireless communication system. The apparatus includes a control processor to generate commands for processing spread spectrum signal components and a reconfigurable coprocessor to process the spread spectrum signal components based on the commands and to provide reports to the control processor based on results of processing the signal components.

Abstract: A method and system for determining at least one DC offset compensation value used to suppress carrier leakage occurring on real and imaginary signal paths in an analog radio transmitter when a significant temperature change in the transmitter is detected. At least one DC offset signal having a level that corresponds to the at least one DC offset compensation value is provided to a digital DC offset compensation module which adjusts the DC level of at least one of the real and imaginary signal paths.

Abstract: A method and system of the present inventions are directed to selecting an optimal mode for ADSL operation based near/far end modem capability, loop length and capacity in the upper bands of modes of operation. A method for switching among a plurality of modes for ADSL modem operation may include the steps of determining a far end modem's capability for supporting one or more of a base mode, a first mode and a second mode; determining a loop length between a near end modem and the far end modem; determining a capacity in an upper band of the first mode and the second mode; and selecting an appropriate mode based on a combination of the far end modem's capability, the loop length and the capacity in the upper band.

Abstract: A fast Walsh transform (FWT) demodulator and a method are provided. The FWT demodulator includes a FWT correlator for receiving and transforming a first information based on a FWT method to output third information; power approximation devices (PAD) for receiving and calculating one of the third information to output an approximating power value respectively. Wherein, the approximating power values are divided into subgroups. A first unit of comparators selects subgroup-max-values from each subgroup. A plurality of power calculation devices (PCD) are for receiving and calculating one of the subgroup-max-value to output a precise power value respectively. A second unit of comparators is for selecting max power value from each precise power value to output a second information. By applying “PAD” to replace “PCD” into “pre-selection” subgroups with “max-and-zero” property, the invention can reduce the implementation cost without performance degradation.

Abstract: Noise and signal-to-noise ratio (SNR) estimation are relatively straightforward tasks. However, when SNR is small, systematic errors in measurement may result in over-estimation of SNR, which also occurs during runtime monitoring of SNR. Here, sufficient numbers of bits have been preassigned to each channel using QAM modulation scheme. Therefore, SNR relative to QAM lattice size depends on the noise margin and the desired (bit error rate) BER. If a relatively small margin is desired, similar measurement errors may result in over-estimation of SNR. Another problem that arises is that the variance of the noise estimator is relatively high. Therefore, SNR estimates may vary by several dB, and there is only 50% confidence in the usual estimators that the actual SNR value will not be worse than that estimated. Thus, a computationally efficient method for SNR estimation that also allows for specification of a confidence level in the estimates is provided.

Abstract: A digital wireless communication apparatus includes a first modulator that modulates a pilot symbol according to a first modulation scheme, and a second modulator that modulates specific symbols according to a second modulation scheme, the second modulation scheme being different than the first modulation scheme. A third modulator modulates symbols other than the pilot symbol and the specific symbols according to a third modulation scheme, the third modulation scheme being different than the first and second modulation schemes. A timing controller controls timing such that the specific symbols are inserted immediately before and after the pilot symbol. The signal points of the specific symbols are allocated on an imaginary line that connects the origin point and a signal point of the pilot symbol on a signal space diagram.

Abstract: An apparatus uses transmission antenna diversity to compensate for fading. An encoder according to a first embodiment forms 4 combinations each including 3 symbols so that 4 input symbols should be transmitted only once at each antenna and each time interval, and delivers the combinations to the 3 transmission antennas for 4 time intervals, and two or more symbols selected from the 4 input symbols are phase-rotated by predetermined phase values before being transmitted via the transmission antennas. An encoder according to a second embodiment forms 3 combinations each including 3 symbols so that 3 input symbols should be transmitted only once at each antenna and each time interval, and delivers the combinations to the 3 transmission antennas for 3 time intervals, and two or more symbols selected from the 3 input symbols are phase-rotated by predetermined phase values before being transmitted via the transmission antennas.

Abstract: The present invention relates to a system for communicating between two integrated circuits (ICs) or within an IC. The ICs are either on the same circuit boards or on different circuit boards with a common backplane. A first integrated circuit has transmitter circuit that generates frequency shift keying signals using digital data and a second integrated circuit has a receiver circuit for recovering the digital data from the frequency shift keying signals.

Abstract: A timing and carrier error detector module (127) of a communication receiver (111). The timing and carrier error detector module uses phase information of a correlated signal (e.g. a Barker de-spread signal) to generate a timing signal and carrier error signal. In one example, the phase information includes a phase error signal of the correlated signal. In one example, the timing and carrier error detector module calculates an indication of the variance of the phase error signal for a plurality of sample positions over a plurality of Barker symbol intervals. The timing signal is based upon the sample position having a minimum indication of a variance.

Abstract: A matrix {circumflex over (V)} of eigenvectors is derived using an iterative procedure. For the procedure, an eigenmode matrix Vi is first initialized, e.g., to an identity matrix. The eigenmode matrix Vi is then updated based on a channel response matrix ? for a MIMO channel to obtain an updated eigenmode matrix Vi+1. The eigenmode matrix may be updated for a fixed or variable number of iterations. The columns of the updated eigenmode matrix may be orthogonalized periodically to improve performance and ensure stability of the iterative procedure. In one embodiment, after completion of all iterations, the updated eigenmode matrix for the last iteration is provided as the matrix {circumflex over (V)}.

Abstract: Systems and methods are disclosed to provide channel monitoring and/or performance monitoring for a communication channel. For example, in accordance with an embodiment of the present invention, an equalizer is disclosed that equalizes for channel distortions and also provides channel and performance monitoring information, such as for example bandwidth estimation, channel identification, signal-to-noise ratio, chromatic dispersion, and/or polarization-mode dispersion.

Abstract: A signal reception method including method and apparatus for receiving a signal, down converting the received signal through multi-tone down conversion to form an intermediate signal, and decoding the intermediate signal to extract data. In an embodiment, the received signal may include multiple transmission bands of a multi-code (MC)-CDMA signal, each of which occupies a different spectrum. Each of the transmission bands also includes an information channel signal. When the received MC-CDMA signal is down converted through multi-tone down conversion, the intermediate signal is formed. The intermediate signal includes a common spectrum that includes an information channel from a plurality of transmission bands. When the intermediate signal is decoded, data from a plurality of information channel bands is extracted. The method and apparatus may be implemented in a multi-mode MC-CDMA/CDMA receiver.