Abstract: A transceiver which keeps circuitry associated with a receiver in a powered down state during periods when a Received Signal Strength Indicator (RSSI) indicates that a signal being received is below a pre-determined threshold level, and which begins to power up the transmitter as soon as it is determined that a packet being received requires a response. The RSSI signal represents the strength of any signal current being received, and if the RSSI signal falls below a given threshold level, digital circuitry associated with the back-end circuitry of the receiver system is disabled. If the RSSI signal rises above the threshold level, the digital circuitry of the receiver is enabled. A control circuit within the transceiver processes the packet as it is received to determine whether the packet requires a response.

Abstract: When a multiplier receives data transmitted from a transmitting equipment in a spread spectrum communications system, it multiplies the received data by the periodic wave output from a crystal oscillator. The output data from the multiplier is filtered by a low-pass filter, and then binarized by a limiter. The multiplier and a delay circuit differential-decodes the binarized data. A correlation circuit obtains correlation between the decoded data and the PN code generated by the PN code generation circuit, and outputs the data as transfer data when the correlation is obtained. In another aspect, an input signal is divided, and then one is multiplied by an I-phase wave. Similarly, another is multiplied by a Q-phase wave. Each signal is individually processed and input to a correlation value/data value determination circuit.

Abstract: This invention reduces near-end crosstalk between identical discrete multi-tone (DMT-type) modems by introducing the following modifications to modems at a central office or a subscriber premises. The modifications include: a mechanism for aligning the frames of all modems at the central office (CO), a mechanism for aligning the frames transmitted by the subscribers' modems with the frames received by those modems, and lengthening the DMT frame to include a cyclic prefix. The cyclic prefix to a frame has been made longer than twice the maximum round-trip delay, that is, the delay between the central office and the most distant subscriber to be served. By making adjacent DMT carrier frequencies be orthogonal to each other, the aforementioned modifications will reduce both Near End Cross-Talk (NEXT) and Leakage-Excited Cross-Talk (LEXT). These benefits apply to modems at both the central office (CO) and subscriber ends of the communication path (for example, a high capacity twisted-pair wire).

Abstract: The present invention includes a method and system for improving performance of a receiver at a low signal-to-noise ratio. According to a first aspect, an encoded signal is received. The encoded signal is decoded to recover information in the encoded signal. Next, a threshold is ascertained in response to the recovered information, the threshold indicating a maximum number of acceptable errors in the recovered information. It is determined if the errors in the recovered information are in excess of the ascertained threshold. Information is then extracted from the encoded signal without decoding. The extracted information is output when the errors in the recovered information are in excess of the ascertained threshold. In all other instances, the recovered information is output. According to a second aspect, recovered signal data is output, the recovered signal data being either the recovered information or the extracted information.

Abstract: Techniques for more accurately detecting the data rate of a frame of data in a cellular telephone system are described. Data is preferably received at one of four rates: full, half, quarter and eighth. A correlation is performed between the incoming soft data and the data generated by re-encoding and re-repeating the data. Variations on the approach make it readily possible to accurately perform rateset 1 or rateset 2 rate detection.

Abstract: An improved system and method for maximum likelihood sequence detection where an incoming stream of symbols subjected to intersymbol interference (ISI) are decoded without knowledge of channel coefficients. Through use of improved metrics, the Fano and stack algorithms may be employed to determine the maximum likelihood sequence detection for a given input data stream during blind equalization, offering improved performance over the Viterbi algorithm which requires foreknowledge of the channel coefficients to operate effectively.

Abstract: The present invention provides for a receiver addressable AM compatible digital broadcast system and method. The digital broadcast signal includes a plurality of digitally modulated signals and an analog signal. A transmitter useable within the system includes a data combiner for generating an aggregate digital data signal, and a waveform generator for forming the digital broadcast signal. A receiver useable within the system comprises a waveform detector for separating the signals and a data parser for separating the digitally modulated signals. The present invention further provides for a method of selectively transmitting data via a digital broadcast signal. The method includes forming the digital broadcast signal from an analog signal and a plurality of digitally modulated signals, transmitting and receiving the digital broadcast signal.

Abstract: An adaptable, variable rate symbol timing recovery system for a digital sal receiver comprises an analog to digital (A-D) signal converter having analog signal input and digital data signal output terminals. A source of selectable, substantially fixed rate, data sampling clock signals is coupled to the A-D signal converter for sampling a signal received at the input at a predetermined, substantially fixed clock rate, depending on data rate and modulation of the received signal. A digital signal processing loop is coupled to the digital data signal output terminal for adjustably producing interdependent signals in synchronism with the data signals at the output terminal which are asynchronous with respect to the fixed rate clock signals. A Controller is provided for selectively configuring the data sampling clock signal source and the digital signal processing loop according to the data rate and modulation characteristics of the received signal.

Abstract: The disclosure describes a multi-stage phase comparator and a phase-locked loop incorporating such a comparator. The comparator measures a phase difference between a reference signal and an output signal using a periodic clock. The comparator is a two stage comparator comprising a fine and coarse comparator. The coarse comparator measures the number of full clock periods between a transition of the reference signal and the output signal. The fine comparator comprises a delay line generator that generates a plurality of delayed clocks. The delayed clocks are used to over sample the reference signal to determine a fine phase difference representing a remaining fraction of the clock period, between transitions of the reference and output signals. A phase locked loop using the multi-stage comparator allows for more accurate phase locking.

Abstract: A method of demodulating voice or data and control information in systems that support multiple modulation schemes modulates voice or data using a first linear modulation scheme, such as 16QAM modulation scheme, and modulates control information using a second linear modulation scheme, for example, QPSK modulation scheme, that has the same symbol rate as that of the first modulation scheme. The first linear modulation scheme has a higher modulation level than the second linear modulation scheme. Information modulated using the second linear modulation scheme, which uses a reduced signal set of the first linear modulation scheme, are demodulated using the same demodulator that is used for demodulating information modulated using the first linear modulation scheme. Also, in-band signalling information within a traffic channel, such as stealing flags, are modulated using the second modulation scheme.

Abstract: The invention relates to a communication system (300) having a receiver (304) that is capable of performing targeted interference suppression. An interference classifier (314) within the receiver (304) analyzes a signal received from a channel (306) and identifies and classifies interference components within the signal. An interference suppressor (316) then suppresses the interference components in the signal based on interference type. The interference suppressor (316) includes a plurality of interference suppression modules that are each optimal for suppressing certain interference types. In one embodiment, one or more of the interference suppression modules perform interference suppression using modal moment estimates to identify different modes within the signal.

Abstract: The present invention is an apparatus and method thereof for performing frequency hopping communication with another party over a subset of hopping frequencies from available frequencies. The spectrum is arranged into a plurality of segments, with each segment corresponding to a subset of the spectrum of frequencies, preferably a contiguous subset of the spectrum. The apparatus includes a communication device for communicating with another party. The communication device receives data over a used segment from a plurality of the segments and signal strength data indicating a current reception power level for the hopping frequency from the other party. A processing unit analyzes the received data to determine an occurrence or non-occurrence of an error over the used segment and notifies the other party to modify the current transmission power level for that used segment according to the occurrence or non-occurrence of an error, via said communication means.

Abstract: The present invention is an apparatus and method thereof for performing frequency hopping (FH) communication with another party over an available spectrum of frequencies. The spectrum is arranged into a plurality of segments, with each segment corresponding to a subset of the frequencies, preferably a contiguous subset of the frequencies. The FH communication apparatus includes a communication device for communicating with another party. The communication device receives data over a sequence of hopping frequencies from the other party, with each of the hopping frequencies being part of a used segment from the plurality of segments. A storage device stores an error value for each used segment. A processing unit identifies a reception error in the received data and an erred segment in which the reception error occurred. The processing unit modifies the error value associated with the erred segment accordingly.

Abstract: A data symbol sequence detector for choosing data symbol sequences likely to be represented by corresponding sequences of samples received by the detector with these sample sequences formed by sampling data signals obtained from magnetically stored data through a data retrieval channel which asymmetrically affects the magnitudes of the data signals. An expected sample value estimator provides estimated expected magnitude values for a selected set of samples in the sequence, and a magnitude difference determiner is used for obtaining representations of differences between values of the samples in the sequence and the corresponding estimated expected values. These differences representations can be limited in algebraic form.

Abstract: A method, system, and computer program product for spread spectrum communication is provided using circular waveform shift-keying (CWSK). Circular waveform shift-keying is a modulation technique for conveying data over a spread spectrum channel. Data symbols are encoded in a circular time shift and/or circular frequency shift of a spread spectrum waveform. In a receiver, a CWSK synchronization stage and demodulator stage can be combined on a single fast convolution ASIC chip. Using CWSK modulation and demodulation, a secure, low-cost terminal is realized that can process calls on multiple spread spectrum channels in a hubless wireless network linking large numbers of low data rate users.

Abstract: A system for spread spectrum power line communications employs a harmonic modulation (HM) transmitter coupled to the power line for transmitting message bits to an HM receiver. The spread spectrum accommodates a plurality of HM transmitters simultaneously occupying the same bandwidth. The spectrum of HM, in a frequency range above 60 Hz but below the maximum frequency that will carry through a distribution transformer, is ideal in combating carrier synchronous noise since it can be interleaved with the noise harmonics and therefore be effectively spectrally disjoint with the synchronous noise process spectrum.

Abstract: An adaptive gain algorithm allows the maximization of gain of an audio signal that is transmitted with a digital data signal by allowing a trellis decoder to compensate for occasional excursions of the audio and noise signal across a signal space boundary. By measuring the short term energy present in an audio signal, the algorithm of the present invention allows the maximum power to be used to transmit an analog signal without overloading the trellis decoder.

Abstract: A clock generating system used to generate a clock signal which compensates for chip operating conditions. The system includes a delay line oscillator and a reference clock which determines the actual propagation time of delay elements on the chip. A clock generator which includes a number of serially connected delay units uses this information to generate a clock signal for the chip logic functions. The output clock rums the chip logic functions at the proper frequency for the current chip conditions.

Abstract: An apparatus and methods for tracking a power level of a signal received at a base station of a code division multiple access (CDMA) digital cellular communication system. The apparatus comprises a storage unit for storing a first table comprising automatic gain control voltages corresponding to a series of received signal levels and a second table comprising variable attenuation control voltages corresponding to the automatic gain control voltages.

Abstract: Circuit and method for generating a signal for use in locking a second signal on a first signal. The first and second signals have an associated frequency. A first beat note signal and a second beat note signal are generated from the first and second signals, respectively, when the frequencies of the first and second signals are not equal. The circuit includes a first and second flip-flop and detector circuitry. The first flip-flop is configured to receive the first and second beat note signals for generating a first state signal. The first flip-flop generates the first state signal by sampling the second beat note signal at a first periodic interval of the first beat note signal. The second flip-flop is configured to receive the first and second beat note signals for generating a second state signal. The second flip-flop generates the second state signal by sampling the second beat note signal at a second periodic interval of the first beat note signal.