Abstract: Method and apparatus that compensates for overestimation of channel SINR due to overfitting of an adaptive equalizer to the pilot portion of a received frame. The SINR of a wireless channel is estimated by adapting an adaptive equalizer using the pilot portion of the frame, applying the adaptive equalizer to a non-pilot portion of the frame, determining a parameter using the adaptive equalizer output, and estimating the SINR of the wireless channel using the parameter. The parameter can include, for example, the mean square error (MSE) or the bias of the equalizer output. The accuracy of the SINR estimate according to this aspect of the present invention is thereby improved (as compared to a SINR estimate based on parameters calculated during the pilot interval) because the adaptive equalizer is not overfit to the control or data portions of the frame.

Abstract: A method of communications channel coding gain optimization using combined ISI cancellation and turbo decoding is provided. Log-likelihood ratio probabilities with extrinsic values are computed from previous iterations of turbo decoding and used to compute the soft-decision values of channel symbols. The soft-decision values are then used to perform intersymbol interference cancellation and generate refined channel log-likelihood ratio probabilities for the next iteration of turbo decoding.

Abstract: In wireless communications, it is necessary to monitor the transmission quality of communications channels to maintain system performance and operation. The invention provides a way of measuring bit error rates in channels at the receiver, without diminishing channel throughput by inserting quality monitoring data into the signal at the transmitter.

Abstract: A method and apparatus for adjusting an oscillator in a network for correcting frequency drift is disclosed. Nodes in the network exchange time stamp messages with each other. The time stamp messages contain the time the stamp message is transmitted, node measurement value of an interval and an uncertainty value for the nodes estimation of the interval. By exchanging measurements of common intervals, nodes can determine how far their oscillators have drifted from the correct oscillating frequency.

Abstract: A digital VSB transmission system that is able to send supplemental data along with MPEG image/sound data is enclosed. The system initially encodes the supplemental data symbol to generate a parity bit, and it multiplexes the parity bit with a predefined sequence and transmits the multiplexed data to a receiver. The system is compatible with the existing ATSC 8T-VSB receivers that are already on the market. It can have advantages over the other type of VSB transmission systems that transmit only the predefined sequence. In addition, the system according the to the present invention results a improved robustness against ghost and noise signals in a channel compared to systems using only the ½ rate convolutional encoding.

Abstract: A clock generator includes input circuitry for receiving an input signal and generating a memory address therefrom. A memory stores digital data indexed by the memory address which represents at least a portion of an analog clock. A digital to analog converter converts data retrieved from the memory to generate the analog clock which is then filtered by a filter and then converted into digital output clock.

Abstract: A system and method for encoding/decoding data channels in a CDMA system having data channel interference cancellation, wherein data channel interference cancellation is used to remove unwanted non-orthogonal pilot signal components which are present within a demodulated data signal. This is accomplished by regenerating interference terms with respect to the non-orthogonal pilot signal and subtracting them from the demodulated data signal.

Abstract: A polyphase receiver comprises an RF front end (10 to 28) for receiving a wanted data signal modulated on a carrier signal and for producing quadrature related low IF signals, an image rejection filter formed by a polyphase filter (30) for filtering the quadrature related low IF signals, soft limiting means (36,38) for compressing the dynamic range of the filtered quadrature related IF signals and a signal demodulator (41) for recovering the data signal. The soft limiting means (36,38) has a characteristic which is substantially linear at signal levels 10 dB below a predetermined minimum wanted signal level, moves into compression for higher signal levels and hard limits at substantially 10 dB above the desired receiver sensitivity which avoids degrading the sensitivity of the receiver.

Abstract: The present invention includes path delay difference comparator 14 for receiving path delay amounts ?1 to ?K detected from a reception signal and extracting each pair of paths satisfying first condition (|?1??j|??th), de-spreaders 111 to 11K for performing de-spreading according to the path delay amounts, estimator 121 to 12K for estimating an SIR value every path, estimators 131 to 13K for estimating the carrier phase every path, phase difference comparator 15 for comparing the carrier phases ?1 to ?k of the paths of each pair satisfying the first condition and extracting each pair of paths satisfying second condition (|?1??j|??th), and comparator 16 for selecting one path having larger SIR from the paths of each pair extracted and using the SIR value of the selected path for SIR combining.

Abstract: An apparatus and method for processing data using the complex quadrature phase shift keying (CQPSK) is disclosed. The present invention includes plurality of multiplying units for multiplying a long pseudo noise (PN) code with an in-phase pseudo noise and quadrature pseudo noise, and a results of multiplying with a pilot channel, a dedicated control channel, a voice channel, a high-speed data transmission channel, a result multiplied with channels with gain, filtering units for eliminating noise, subtracting and adding units for calculating final result, and in-phase/quadrature channel outputting unit for outputting I-channel/Q-channel. The present invention can improve data processing speed of a radio channel, increase capacity of data processing in radio communication and also can be applicable to various kinds of radio communication devices transceiving voice, media contents and high-speed data at a same time.

Abstract: The receiver (1) for radio-frequency signals (SV1, SV2, SV3, SV4), modulated by specific codes of transmitting sources, such as satellites (S1, S2, S3, 54), includes receiving and shaping means with frequency conversion for the radio-frequency signals for generating intermediate signals, a correlation stage formed of several correlation channels for receiving the intermediate signals and microprocessor means connected to the correlation stage in order to process the extracted data after correlation. Each channel includes a correlator in which the intermediate signals are correlated with at least two early and late replicas of the specific code of a visible transmitting source to be searched and tracked. The correlator further includes integrator counters for the correlated signals to provide a first amplitude value of the auto-correlation function of the early signals and a second amplitude value for the late signals.

Abstract: A wireless transceiver includes a Radio Frequency (RF) transceiver, a baseband transmitter section, and a baseband receiver section. The baseband receiver section receives a baseband signal from the RF transceiver, extracts data therefrom, and provides the data to a host system. The baseband receiver section includes a programmable gain amplifier, an Analog-to-Digital Converter (ADC), a symbol timing compensation section, an RF carrier compensation section, a decision feedback equalizer section, and a preamble processor. The symbol timing compensation section modifies the samples of the baseband signal to compensate for symbol timing variations between a symbol clock of the wireless device and a symbol clock of a transmitting wireless device. The RF carrier compensation section modifies the samples of the baseband signal to compensate for RF carrier variations between an RF carrier of the wireless device and an RF carrier of the transmitting wireless device.

Abstract: An apparatus and method is disclosed for estimating timing error in a digital signal receiver from a difference between an arrival time of a first training sequence and an arrival time of a second training sequence in the digital signal receiver. Time domain representations of the timing sequence data are converted into frequency domain representations and used to calculate a complex cross power spectrum. The timing error is obtained by determining an average phase of the complex cross power spectrum. The timing error is then used to calculate an accurate value for the clock rate of the digital signal transmitter.

Abstract: A first detector receives a received signal and extracts the data signals from the received signal. A hard decision converter converts soft symbols outputted by the first detector into hard symbols. An interference canceller extracts the voice signals from the received signal. A second detector is connected to the output of the interference canceller, and extracts the individual voice signals. The second detector is a different detector type than the first detector.

Abstract: A method and apparatus for re-modulating an RF carrier modulated signal using a Nyquist folding frequency modulation technique. The method modulates a digitized RF carrier modulated signal with a digital sequence of {1,?1,1,?1, . . . }, where the center frequency of the RF carrier modulated signal is at a first frequency and the sample rate of the modulating signal is at a second frequency. When the second frequency is four times the first frequency, the output of the digital modulation process is a spectrum-inverted copy of the source RF carrier modulated signal. For all other frequencies, the remodulated RF carrier modulated signal has a center frequency equal to the carrier frequency minus one-half the sample rate of the modulating signal. A spectrum inversion is then performed to recreate the spectrum of the source RF carrier modulated signal, which is now located at a different center frequency. The apparatus comprises a modulating signal source and a digital modulator.

Abstract: A system and method are shown for generation of at least one reference voltage level in a bus system. A reference voltage generator on a current driver includes at least one reference voltage level, at least one control signal, and an active device. The active device is coupled to the at least one control signal, such as a current control signal, and a selected reference voltage of the at least one reference voltage level. The active device is arranged to shift the at least one reference voltage level based on the at least one current control signal such as an equalization signal, a crosstalk signal, or the combination thereof, employed on the current driver.

Abstract: A data communication transceiver comprises an equalizer that is operable to selectively participate in one of several different signal processing functions in the transceiver. In a disclosed embodiment the equalizer operates in an echo canceller when the transceiver is transmitting signals, and operates in a feedback equalizer when the transceiver is not transmitting signals.

Abstract: In a data decision circuit: a clock generation unit generates a clock signal based on a phase difference signal so that the clock signal has an optimum phase with respect to a phase of an input data signal; a data determination unit determines data values carried by the input data signal, by using the clock signal; a phase-difference detection unit detects a rising-side phase difference and a falling-side phase difference, where the rising-side phase difference is a phase difference between a rising of the input data signal and a next transition in the clock signal, and the falling-side phase difference is a phase difference between the transition and a next falling of the input data signal; and a phase-difference-signal generation unit generates the phase difference signal so as to represent a difference between the rising-side phase difference and the falling-side phase difference.

Abstract: An FQPSK-B receiver uses a simplified trellis system which uses combinations of FQPSK-B waveforms to correlate against an input signal. This enables reduction of the number of correlators that are used and the number of comparisons that are made by the correlators.

Abstract: A bi-directional communication link has plural channels with respective masters and slaves at respective ends of respective channels, in which each master issues a Master Tx clock, each slave constructs a Slave Rx clock frequency locked to the Master Tx clock, and a Slave Tx clock frequency locked to the Slave Rx clock. A metric processor for each master produces a metric signal indicative of resolution of a signal received by the master from the corresponding slave. A decision processor responsive to the metric processor changes the phase of the Slave Tx clock relative to the Slave Rx clock so as to maximize the metric signal. In one embodiment, the resolution is a resolution between leading and trailing edges of the received signal. In another embodiment, the resolution is a resolution between allowed amplitude levels of the received signal.