Abstract: A frequency offset estimation apparatus for intersymbol interference channels. A storage area having M elements is provided to shift a received sample sequence by M samples to generate a lagged sample sequence. A sequence of preliminary values is calculated by differential operation between the received sample sequence and the lagged sample sequence. Next, a summation of the power of the preliminary value sequence over M? samples is taken to obtain an accumulative sum. Finally, the angle of the accumulative sum is derived and then scaled by a factor. A frequency offset estimate for the received sample sequence is thus obtained.

Abstract: The invention discloses a cell search method for a CDMA system for a three-stage cell search procedure. The cell search method have the steps of matching of incoming signals by a chip matched filter; over-sampling the incoming signals N times against a chip rate by a sampling device; transmitting the N over-samplers into a serial test unit, selecting a best sample among N over-samples by the serial test unit controlled by a first stage detector; and transmitting the best sample of the N over-samples into a second stage detector and a third stage detector for a trial. The best sample of the N over-samples has a maximum sampling value of the N over-samples. The invention significantly reduces the effects of non-ideal sampling so as to accomplish fast cell search.

Abstract: A method and a circuit arrangement for efficient use of multistage modulation methods using orthogonal base functions for the representation of a signal to be transmitted. Signal points of a signal constellation are selected according to a respective predetermined and/or selected probabilities so as to optimize a respective signal energy and/or a respective signal data rate, the selected signal points each having a defined respective energy. A 16-QAM signal constellation can be used, for example, for transmitting at low data rates. In the circuit arrangement, a source (1) which supplies a data stream (2) and is connected to a code converter (3) for converting the data stream. The output of the code converter (3) is connected to a modulator (4) in which the corresponding signal points are selected according to the respective probabilities. The data stream (2) is then transmitted over a channel (5), and a demodulator (6) situated downstream from a code converter (7) carries out the inverse operation.

Abstract: Provided is a device for improving voice signal in quality by discriminating a radio environment of a signal transmission path and detecting a click noise. The device for improving voice signal in quality calculates an average value for a short interval of a received ADPCM code, identifies from such average value the nature of a radio environment of a signal transmission path, and considers that a click noise is occurred when the average value exceeds a threshold value assigned radio environment. The present invention comprises a click noise detector (22) for outputting a click noise detecting signal, and a click noise suppressing circuit for suppressing the click noise by setting the velocity coefficient of an ADPCM decoder (21) as “0” for a frame in which a frame error detecting signal, which represents the detection of a frame error of the received ADPCM code, and a click noise detecting signal are both detected.

Abstract: A digital communication receiver communicates with a digital communication transmitter across a communication channel and has: a channel estimator, which provide a channel estimate of the communication channel based on a received signal; an equalizer, which estimates a sequence of transmitted symbols and provides a sequence of decided symbols based on the received signal and the channel estimate; and a channel tracker, which produces an updated channel estimate based on the received signal and the decided symbols, and which supplies the updated channel estimate to the equalizer. The digital communication receiver has a controller, which receives channel quality indicative data associated with an output from the equalizer, determines whether these data fail to meet a predetermined criterion, and, if so, supplies an enabling control signal to the channel tracker.

Abstract: Apparatus and methods are disclosed for reducing noise leakage on the upstream channel from a cable modem. Noise leakage from cable modems, such as from a persistently enabled amplifier or other components in the modem, can accumulate on an upstream channel and reduce the overall signal-to-noise ratio of signals sent to the headend. In order to significantly reduce such noise leakage and to provide termination of the cable plant in the modem when the modem is not transmitting data, a cable modem arranged to improve its isolation is disclosed. The modem contains an upstream transmitter having a control line on which the upstream transmitter can emit a control signal. The modem also includes a switch component capable of being enabled and disabled by the control signal on the control line. The control signal from the upstream transmitter to the switch component enables the switch component thereby allowing a data signal to be transmitted on an upstream channel. The switch component includes two switches.

Abstract: A discrete multi-tone (DMT) processor receives predetermined control signals from a digital signal processor (DSP) within an asymmetric digital subscriber line (ADSL) modem, modulates transmission data in response to the control signals, and demodulates reception data. The DMT processor includes a frame synchronization signal generator, a transmitter, and a receiver. The frame synchronization generator generates a transmission frame synchronization signal and a reception frame synchronization signal in response to a cyclic prefix contained in the transmission data or reception data and a reception synchronization shift signal applied from the DSP. The transmitter DMT modulates and gain-controls the transmission data input in response to the transmission frame synchronization signal The receiver gain-controls and DMT demodulates the reception data response to the reception frame synchronization.

Abstract: An adaptive equalizer comprises a decision device; a decision feedback equalizer coupled to the decision device; an FIR filter coupled to the decision device; and a trellis decoder coupled to the decision device, adapted to provide a reliability output and a decoded output. An error signal is generated by subtracting an output of the decision feedback equalizer from an output of the decision device, the error signal being used to update coefficients of the taps of the FIR filter and the decision feedback equalizer. A magnitude of the change to the coefficients is selected based at least in part the reliability output of the trellis decoder.

Abstract: An asynchronous sample rate estimator and a method for generating a rate estimate to track an asynchronous input sampled signal is disclosed. The present invention achieves lock quickly and maintains an optimum input buffer configuration and enhanced signal fidelity by responding quickly and accurately to changes in the incoming frequency. An asynchronous sample rate estimator receives and determines a measured sample period of an asynchronous input signal. Furthermore, a reciprocal frequency error signal and a current rate estimate signal are used to generate a rate estimate for tracking the read pointer to the write pointer of a FIFO buffer, as well as a phase correction signal for centering the write pointer in the FIFO buffer. An asynchronous sample rate estimator might also include an error gain generator for providing an error gain and a lock detector for indicating whether the system has achieved a locked condition.

Abstract: The invention includes a circuit for aligning the phase of a clock derived from a frequency multiplied version of a reference clock used in a computer system. The dynamic phase alignment circuit includes a few logic gates to perform the operation of delaying the derived clock, detecting its phase misalignment, and correcting such misalignment by incrementally aligning the phase of the derived clock to the reference clock. The invention is capable of aligning the phase of a derived clock to a reference clock in a computer system whose CPU operates at as high a frequency as about 500 MHz or higher.

Abstract: A receiver receives spread spectrum signals which include unwanted narrowband signals, for example, radio signals which comprise a mixture of signals from signal sources using the Group Special Mobile (GSM) ETSI standard coding and from signal sources using Code Division Multiple Access (CDMA) coding. Both despreading of the spread spectrum signal and attenuating of predetermined frequencies (corresponding to the narrowband signal) of the spread spectrum signal are performed prior to downconverting. In another approach to decoding a spread spectrum signal in which an unwanted narrowband signal has been coded using a coding scheme with error correction capabilities, the narrowband signal is decoded, regenerated and subtracted prior to despreading of the spread spectrum signal.

Abstract: A crosstalk elimination system allowing the reduced number of cables and a downsizing of transmission equipment is disclosed. A sending equipment includes a detector for detecting a possible crosstalk timing in each of the data signals by comparing phases of the clock signals to transmit it to the receiving equipment. A receiving equipment includes a read timing shifter for shifting a read timing of each of the clock signals associated with a corresponding data signal to a no-crosstalk timing determined based on the possible crosstalk timing.

Abstract: A decision feedback loop for a receiver for channel estimation and de-rotation of complex input symbols derived from a sampled information signal received via a channel which contains data organized into successive time slots, is configured to retrain and reinitialize the loop during each slot in order to mitigate slot to slot propagation of the estimation error.

Abstract: A modulation format identification device capable of realizing a practical receiver capable of identifying a modulation format of a received signal irrespective of its modulation format by a simple configuration, wherein provision is made of a phase lock detector group having a plurality of detectors provided corresponding to a plurality of modulation formats and with the received signals input in parallel thereto, counting a number of symbols in accordance with the modulation format for every detector, making a primary decision that the received signal has been modulated by the related modulation format when the count exceeds a constant threshold value, and outputting the results as lock detection flags and a logic circuit for exclusively selecting one modulation format upon receipt of the plurality of output results of the phase lock detector group, and a method of the same.

Abstract: A system and method for embedding information into digital media and later detecting the embedded information using a unique spread spectrum modulation technique. In general, the present invention removes interference caused by an original signal from the detection process thereby eliminating a major source of detection error. The interference caused by the original signal is removed by using the encoder knowledge about the original signal and modulating the energy of the embedded mark to compensate for the original signal interference. The present invention also includes a novel redundant bit representation technique causes a resulting average over a large sample to tend to zero, thereby reducing the vulnerability of the present invention to malicious collusion attacks.

Abstract: Signals are developed for use in a wireless system with multiple transmit and multiple receive antennas so that even in the face of some correlation the most open-loop capacity that can be achieved using a substantially open-loop system with a channel of that level of correlation is obtained. In accordance with the principles of the invention, the signals transmitted from the various antennas are processed so as to improve their ability to convey the maximum amount of information. More specifically, the data to be transmitted is divided into M+1 substreams, where M is the number of transmit antennas. Each transmit antenna is supplied with a combination signal that is made up of a weighted version of a common one of the substreams and a weighted version of a respective one of the substreams that is supplied uniquely for that antenna, so that there are M transmit signals. A receiver having N antennas receives the M transmit signals as combined by the channel and reconstitutes the original data therefrom.

Abstract: A transmitter of a base station stops a spread modulation so as to transmit a free-line signal and a call-in signal to a mobile station in a wait state. A receiver of a mobile station which is in the wait state stops a despread modulation so as to receive the free-line signal and the call-in signal which are from the base station. The transmitter modulates, spreads, and then transmits and the receiver receives and then despreads and demodulates a control signal for connecting a line after transmitting and receiving the call-in signal are completed, a control signal for connecting the line when a call-out request is sent from the mobile station, and a talk signal and a talk completion control signal which are transmitted and received through the line.

Abstract: The automatic gain control method with little being influenced of the unnecessary electric wave, even if strong unnecessary electric wave is near the frequency of input signal, is offered by carrying out change of the delay point level. The automatic gain control system with a scale of few circuit, having low noise property and high adjacent disturbance oppression property, is offered. When the IF AGC signal 112 is smaller than delay point level, the output agcerr of the signal level detector 614 is provided to the 1st loop filter 105. Since the IF AGC signal 112 provided to the IF AGC amplifier 608 is value responding to signal level of IF signal, output is fed back to this amplifier, and control of IF gain is performed automatically. On the other hand, when output of the 2nd loop filter 106 is “0”, output rfzero of the 2nd comparator 108 is set to 1, and “0” is provided to the 2nd loop filter 106.

Abstract: The invention computes frequency-domain channel gains by compiling a set of estimated channel gains as a function of pilot sequences, a set of analytical channel gains variables, and a set of weighting coefficients variables. A plurality of weighting coefficients are computed as a function of time and frequency correlation functions, a noise correlation matrix, and pilot sequences. A weighting matrix is computed from the weighting coefficients. After receiving a training sequence from at least one transmitter, a received data matrix is computed from the training sequence. The weighting matrix and the received data matrix are used to compute the frequency-domain channel gains. The invention also provides a method for reducing the computational complexity of estimating the time and frequency response of at least one desired signal received by at least one antenna.

Abstract: The process in an xDSL transceiver transfers into a fast retraining sequence when the cause of an error on a telephone circuit is a change from an off hook state to an on hook state of a telephone instrument, a signal indicating an inversion of polarity of a signal on the telephone circuit, a change from an on hook to an off hook and when a handshake waiting time has passed without detecting a predetermined signal on the telephone circuit, or when the predetermined signal is detected within the handshake waiting time. The handshake waiting time can be updated in accordance with a dial pulse width, the maximum number of digits in the dial pulse signal, and the maximum number of pulses in one digit, or depending on whether or not the dial pulse comes from NTT.