Abstract: Data at a transmitter is modulated, in accordance with instructions from a receiver, to provide M different modulations in successive sequences. N spreading codes are also provided in successive sequences at the transmitter, in accordance with instructions from the receiver, alternately with the M data modulations. The alternate sequences of the M data modulations and the N spreading codes are paired and individual ones of the M data modulations and the N spreading codes in the paired sequences are combined (e.g. multiplied). Alternatively, an individual one of the M data modulations is combined (e.g. multiplied) with an individual one of the N spreading codes in the adjacent sequence. The modulator and the spreader may be included at the transmitter with (a) a channel encoder which provides channel coding in accordance with instructions from the receiver, (b) a puncturer which removes particular data in accordance with instructions from the receiver and (c) an interleaver.

Abstract: A circuit and method reduces noise signals coupled to a reference voltage used by a digital differential input receiver having an input that is coupled to an input/output terminal. The circuit and method selectively isolates the reference voltage from the input/output terminal to which output signals are selectively applied. The isolation occurs responsive to detecting that an output signal is being applied to the input/output terminal so that transitions of the output signal are not coupled through the input receiver to generate noise in the reference voltage. In one embodiment, the isolation is provided by placing an isolation circuit between the input receiver and either the input/output terminal or a source of the reference voltage. In another embodiment, the isolation is provided by selectively biasing the input receiver so that coupling of output signal transitions through the input receiver is substantially reduced.

Abstract: Symbol timing recovery employs a blind cost criterion from the Bussgang class of functions, and its stochastic gradient, to generate a timing phase error used to adjust sampling of received symbols. For one implementation, the estimate is derived in accordance with the Constant Modulus (CM) criterion and its gradient via the CM algorithm (CMA), and the estimate is calculated from a sequence of samples. This estimate is then used to adjust the period and phase of the sample sequence toward the period and phase of the transmitted symbols, driving the timing phase error to zero. The values used may be either i) samples themselves, ii) processed (e.g., interpolated) samples, or iii) equalized and processed samples. In addition, timing phase error estimates for other cost criteria, including the least mean squares algorithm, may be generated. These timing phase error estimates are selected either alone or in combination for deriving the timing phase error used to adjust the period and phase of the sample sequence.

Abstract: In order to provide a simple and reliable means of frame synchronization in a serial data communication system, which avoids the problem of ‘bit-stuffing’ in known HDLC systems, the data communication system comprises a transmitter arranged to transmit data as a sequence of frames, each frame comprising a synchronization section and a payload section of data, and the transmitter including in the synchronization section of each frame a count value of a sequence of count values (a part of a predetermined code sequence), wherein successive frames contain successive count values (other parts of the predetermined code sequence) The receiver includes a FIFO buffer for storing three successively received frames, and a processor for assessing the stored data within the frames in order to locate and recognize the count values, whereby to synchronize to the received frames.

Abstract: A system for suppressing ambient signals from a signal containing radiated emissions of a electronic device and ambient signals. The system comprises a first receiver operative to receive the ambient signals and the radiated emissions from the electronic device. The first receiver is operative to demodulate and digitize the ambient signals and the radiated emissions. The system further comprises a second receiver operative to receive primarily the ambient signals wherein the second receiver is time and frequency synchronized to the first receiver and operative to demodulate and digitize the ambient signals. A central computer is in electrical communication with the first and second receivers and is operative to store and process the ambient signals and the radiated emissions from respective ones of the first and second receivers. Accordingly, the central computer is configured as an adaptive filter operative to suppress the ambient signals correlated between the first and second receivers.

Abstract: A digital VSB transmission system in disclosed. The system is compatible with the existing ATSC 8T-VSB receiver and able to transmit additional supplemental data as well as MPEG image/sound data. It initially encodes the information bit of the supplemental data with a ½ encoding rate in order to produce a parity bit and sends the parity bit together with the information bit. Therefore, both of the MPEG image/sound data and the supplemental data can be transmitted properly even through a channel having a high ghost and/or noise level. Particularly, it can significantly improve performances of the slicer predictor and trellis decoder of the VSB receiver.

Abstract: A base station receives a signal resulting from multiplexing a communication signal spread using a signal-specific spreading code and sent by mobile station apparatus and a calibration (CAL) signal spread using a signal-specific spreading code and sent for each unit frame for a predetermined time by a CAL radio signal generator in a same frequency band. An A/D conversion/despreading section and an A/D conversion/despreading section extract the communication signal and CAL signal from the received signal. A calibration processing section carries out calibration processing using the CAL signal in parallel with a communication using the communication signal. An array combining/signal processing section carries out demodulation processing on the communication signal using the calibration processing result.

Abstract: A UWB communication system and method for fast synchronization of one transceiver with another using the incoming UWB signal, where synchronization is achieved in less than a full code wheel spin. An exemplary embodiment includes a UWB waveform correlator, a timing generator, and a controller wherein the controller examines the correlator outputs as the code-wheel spins, and generates control signals to cause the timing generator to stop and track the incoming UWB signal whenever the incoming signal is received with sufficient SNR to provide a predetermined quality of service such as bit-error rate (BER). This embodiment will in any case determine when the receiver has been substantially synchronized with an incoming signal, yet without an exhaustive search of the entire code-wheel.

Abstract: A digital PLL device in accordance with the present invention comprises a selector for selecting one of a first synchronous timing signal and a second synchronous timing signal, and a comparator for outputting a phase correction value corresponding to phase difference between the synchronous timing signal selected by the selector and an internal synchronous timing signal. The digital PLL device stores the phase correction value from the comparator at a stable operation. The digital PLL device also performs a hold over operation accompanied by high accurate phase correction based on the phase correction value, since a fault occurs in the first synchronous timing signal until the timing signal is switched to the second synchronous timing signal.

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: An apparatus for digitally processing signals within wireless communications base-stations which includes a channel pooling signal processor and a digital signal processor. The channel pooling signal processor includes a plurality of computation units typically realized in a heterogeneous multiprocessing architecture, a test interface for testing the function of the plurality of the computation units, a general-purpose microprocessor for managing the dataflow into and out of the channel pooling signal processor as well as effecting the control and configuration of the computation units, and an interconnect mechanism for connecting the plurality of computation units to the input, output, test interface, and the general-purpose microprocessor.

Abstract: A method and apparatus for substantially reducing or eliminating the timing skew caused by delay elements in a delay locked loop. A method and apparatus is disclosed wherein a rising edge of a local timing signal is established and phase-locked to a rising edge of a system clock signal by delaying the system clock signal. A falling edge of the local timing signal is established and phase-locked to a falling edge of the system clock signal by further delaying only a portion of a signal representative of the delayed clock signal. By separately delaying different portions of the system clock signal and using the separately delayed portions to establish a local timing signal, a local timing signal may be established which is compensated for the varied effects of delay elements in a delay locked loop.

Abstract: A digital communications system with a built-in apparatus for improving receive path performance in the presence of noise. An analog datastream is provided to a hardware receive filter that rejects signals lying outside a frequency spectrum of interest, while a hardware equalizer flattens the channel response. An analog-to-digital converter digitizes the filtered and equalized analog datastream into a digital bitstream, which is then filtered, further channel-equalized and demodulated. The system also includes a memory, an estimator unit, having a first input coupled to the memory and a second input coupled to a data input, and an output coupled to a compute unit. The estimator unit is adapted to providing estimates of signal power, channel noise and channel response. The compute unit, has an input coupled the estimator unit and an output coupled to the memory, and is adapted to computing a channel capacity based the selected combination of modem parameters.

Abstract: A base station having the strongest downlink signal is identified by utilizing a unique slope of a pilot tone hopping sequence being transmitted by a base station. Specifically, base station identification is realized by determining the slope of the strongest received pilot signal, i.e., the received pilot signal having the maximum energy. In an embodiment of the invention, the pilot tone hopping sequence is based on a Latin Squares sequence. With a Latin Squares based pilot tone hopping sequence, all a mobile user unit needs is to locate the frequency of the pilot tones at one time because the pilot tone locations at subsequent times can be determined from the slope of the Latin Squares pilot tone hopping sequence. The slope and initial frequency shift of the pilot tone hopping sequence with the strongest received power is determined by employing a unique maximum energy detector.

Abstract: A method and a system for providing an input signal from a multiple decision feedback equalizer to a decoder based on a tail value and a subset of coefficient values received from a decision-feedback equalizer. A set of pre-computed values based on the subset of coefficient values is generated. Each of the pre-computed values is combined with the tail value to generate a tentative sample. One of the tentative samples is selected as the input signal to the decoder. In one aspect of the system, tentative samples are saturated and then stored in a set of registers before being outputted to a multiplexer which selects one of the tentative samples as the input signal to the decoder.

Abstract: A differential encoder is designed to correct for any phase invariance. Without differential encoding defined for the V.92 upstream, undetectable errors are possible in a modem due to an inversion in the upstream channel. Immunity to channel inversions is provided by differentially encoding a combined preceding and modulus conversion system. A frame of a constellations is attributed a sign and the frame and the sign are differentially encoded. The frame and the sign are differentially decoded after the multiple modulus decoder, ensuring phase shift immunity.

Abstract: Base station identification and downlink synchronization are realized by employing pilots including known symbols transmitted at prescribed frequency tones in individual ones of prescribed time intervals. Specifically, the symbols used in the pilots are uniquely located in a time-frequency grid, where the locations are specified by periodic pilot tone hopping sequences. In a specific embodiment of the invention, a period of a pilot tone hopping sequence is constructed by starting with a Latin-square based hopping sequence, truncating it over time, and possibly offsetting and permuting it over frequency. Particular examples of pilot tone hopping sequences are parallel slope hopping sequences in which the periodicity of the sequences is chosen to be a prime number of symbol time intervals. In another embodiment of the invention, a notion of phantom pilots is employed to facilitate use of various system parameters while accommodating the above noted pilot tone hopping sequences.

Abstract: In a radio receiver, an equalizer generates reliability information in the form of soft decision information indicating probabilities that a data symbol received by the radio receiver is based on a specific transmitted value. A bit error rate estimator obtains bit error rate information regarding the bit error rate of the received signal, corresponding to the received data symbols, by evaluating the reliability information.

Abstract: Data at a transmitter is modulated, in accordance with instructions from a receiver, to provide M different modulations in successive sequences. N spreading codes are also provided in successive sequences at the transmitter, in accordance with instructions from the receiver, alternately with the M data modulations. The alternate sequences of the M data modulations and the N spreading codes are paired and individual ones of the M data modulations and the N spreading codes in the paired sequences are combined (e.g. multiplied). The paired combinations of the individual ones of the M data modulations and the N spreading codes are transmitted to the receiver, which uses correlation or matched filter techniques to recover each combination of the individual one of the data modulations and the individual one of the spreading codes. A single spreading code may be used instead of the N spreading codes.

Abstract: A transmitter generates a pair of test weight vectors, each vector comprised of a plurality of complex entries, with each entry corresponding a different one of a plurality of antennae. The first and second complex weight vectors are applied to a dedicated pilot signal during alternate time intervals. During each time interval, the average of the first and second complex weight vectors is applied to the data traffic transmitted by the transmitter. A receiver alternately receives the pilot signal as multiplied by the first and second weight vectors as described above. The receiver determines which of the weighted pilot signals resulted in a stronger signal received at the mobile and, based upon this determination, transmits feedback.