Abstract: A digital subscriber line (DSL) communication system that utilizes the high frequency band of a standard telephone line does not require the use of a plain old telephone service (POTS) splitter in the resident's home, which provided isolation between the POTS frequency band (0 to 4 kHz) and the DSL frequency band. A digital subscriber line modem utilizes either constant envelope modulation or quadrature amplitude modulation for outputting DSL signals upstream to a central office. When a telephone in the resident's home is detected as being off-hook, then the constant envelope modulation is used by the DSL modem in order to lessen the intermodulation product distortion that results in audible noise heard by a user of the telephone. When the telephone is on-hook, then another type of modulation, such as QAM, is used to maximize the upstream data rate capability in the DSL frequency band, since any noise generated by the QAM is not a problem due to the non-use of the POTS frequency band.

Abstract: A device, such as an interleaver, a de-interleaver, or other devices, for interleaving or de-interleaving a signal within a wireless communication system. The device may interleave or de-interleave the signal spontaneously using a pseudo-random logic. Interleaving or de-interleaving the signal spontaneously may enable one or more features of the device to be enhanced. For example, less RAM may be required to interleave or de-interleave the signal, a die size of the device may be decreased, or other features may be enhanced. The device may receive a signal including a plurality of symbols. The plurality of symbols may be organized into one or more symbol blocks. While a number of symbols in the symbol blocks may vary from block to block, all (or substantially all) of the symbol blocks may be augmented to be of a fixed block length. Dummy bits may be used to augment the symbol blocks.

Abstract: A detector for detecting a received signal according to a Gaussian shift keying (“GFSK/GMSK”) modulation scheme. The detector may enhance a detection performance of the receiver while limiting one or more implementation impacts. An implementation impact may include an implementation complexity impact, an implementation cost impact, or other impacts. The detection performance of the detector may be enhanced in relation to one or more performance aspects, such as, an ISI aspect, an AWGN aspect, a co-channel interference aspect, a sensitivity aspect, an error propagation aspect, or other aspects. The detector may be configured or reconfigured to enhance one or more particular performance aspects. The enhancement of the particular performance aspects may affect, adversely or otherwise, one or more related performance aspects that may be related to the particular performance aspects. The detector may be configured or reconfigured according to a current application of the detector.

Abstract: A system for detecting a burst in a wireless communications system. A signal strength indicator indicates the strength of an incoming signal representative of incoming packets. A signal strength change detector detects changes in the signal strength of the incoming signal. Signal strength detection logic determines if a change in signal strength of a predetermined magnitude has occurred. A pattern detector detects patterns of symbols, or symbol estimates, in the incoming signal to determine if a predetermined pattern of symbols is present. Burst detection logic signals detection of a burst if the signal strength detection logic determines that a change in signal strength of predetermined magnitude has occurred, and the pattern detector determines that a predetermined pattern of symbols is present.

Abstract: A channel estimation system is disclosed. The channel estimation system comprises a first memory element having a write function and a plurality of read functions, a pilot signal extraction element adapted to receive a first output of the first memory element, a programmable averaging element adapted to receive the output of the pilot signal extraction element, and a combiner adapted to receive a second output of the memory element and the output of the programmable averaging element, wherein the second output of the first memory element is delayed with respect to the first output of the first memory element.

Abstract: A multiple stage matched filter for a wireless receiver comprises a receiver configured to develop a received signal, the received signal comprising a bit stream of signal samples, and a multiple stage matched filter configured to parallel process the received signal such that multiple codes are analyzed simultaneously to determine a frequency offset and code location.

Abstract: A digital phase/frequency detector capable of being implemented with on-chip components and configured to detect signals having small modulation indices. Transition points within the signal are detected and the width between successive transition points measured and averaged. The average width measurements may be converted to width deviation values by subtracting out the width due to the carrier frequency. An interpolation may be performed between the current and previous values of the width deviation values to reduce quantization error. The interpolated values may be converted to frequency deviation values, and a predetermined number of the frequency deviation values may be averaged. The average frequency deviation values may then be equalized in order to reduce intersymbol interference. The resulting equalized values form soft estimates of the underlying source bits. Hard estimates of the source bits may then be derived from the soft estimates.

Abstract: A system is provided for controlling amplification in a receiver. The receiver amplifies a signal in accordance with a controlled gain to enhance the reliability of demodulating the received signal. A lower frequency signal is derived by down-converting the received signal. The derived lower frequency signal is converted into a digital baseband signal. A compensatory direct current offset is determined by evaluation of one of trailing symbols and a defined sequence of a data packet of the received signal. A compensatory direct current offset is manipulated with respect to a digital baseband signal to compensate for an unwanted direct current offset of the digital baseband signal, indicative of a frequency difference between the received signal and the transmitted signal.

Abstract: A demodulation system capable of configuring itself responsive to channel conditions. A plurality of detectors may be provided, one or more of which may be better able to handle a particular form of interference than one or more of the other detectors. The detectors estimate source bits from a common signal. One or more signal quality estimators receive the estimated bits for the detectors, and provide performance metrics for each of the detectors. A selector selects or continues the pre-selection of one of the detectors responsive to the performance metrics. A multiplexor outputs the estimated bits from the selected or pre-selected detector.

Abstract: A bidirectional communication device for transmitting and receiving communications signals in a system which presents a transmission path for conducting a communications signal from the device, a reception path for conducting a communications signal to the device, and an echo path which conducts echo signals from the transmission path to the reception path, the device having an echo canceler connected between the transmission path and the reception path for minimizing echo signals in the transmission path, the echo canceler comprising an adaptive filter for filtering the communications signals from the device according to a filter characteristic having a plurality of filter coefficients, wherein a first group of the coefficients, constituting less than all of the coefficients, has finite filter coefficient values and the remaining ones of the plurality of coefficients have values of zero.

Abstract: A system for detecting a burst in a wireless communications system. A signal strength indicator indicates the strength of an incoming signal representative of incoming packets. A signal strength change detector detects changes in the signal strength of the incoming signal. Signal strength detection logic determines if a change in signal strength of a predetermined magnitude has occurred. A pattern detector detects patterns of symbols, or symbol estimates, in the incoming signal to determine if a predetermined pattern of symbols is present. Burst detection logic signals detection of a burst if the signal strength detection logic determines that a change in signal strength of predetermined magnitude has occurred, and the pattern detector determines that a predetermined pattern of symbols is present.

Abstract: The present invention relates to a method and apparatus that uses cyclic redundancy check (CRC) bits to detect errors and correct particular four-bit error patterns in an information burst. The present invention is particularly suited for relatively simple systems that use differential encoding and either differential or coherent demodulation with no error correction capabilities, such as the Personal Handy Phone System (PHS), DECT, PACS and some digital cordless phones systems. The apparatus also adjusts its error-correction capability to accommodate different types of information bursts and channel qualities. The present invention may be used in a number of wireless, digital communication systems.

Abstract: The present invention relates to a method and apparatus that uses cyclic redundancy check (CRC) bits to detect errors and correct particular four-bit error patterns in an information burst. The present invention is particularly suited for relatively simple systems that use differential encoding and either differential or coherent demodulation with no error correction capabilities, such as the Personal Handy Phone System (PHS), DECT, PACS and some digital cordless phones systems. The apparatus also adjusts its error-correction capability to accommodate different types of information bursts and channel qualities. The present invention may be used in a number of wireless, digital communication systems.

Abstract: A method and apparatus for estimating signal quality in a direct sequence spread spectrum communication system such as a digital cordless telephone. The method and apparatus beneficially uses data that already available from a window-tracking function used to maintain a demodulation window around the correlation data coming from the system's matched filters. The window-tracking function outputs an in-window peak value and out-window peak value for each bit interval. The signal quality is rapidly and effectively estimated by accumulating the difference between the in-window peak correlation value and the out-window peak correlation value over a period time, preferably for one frame.

Abstract: A system for digital-to-analog conversion and up-conversion (frequency multiplication) that reduces the distortion and attenuation caused by the sinc effect is described. The shape of the sinc function that gives rise to the sinc effect is altered in a manner such that the distortion produced by the sinc effect is reduced. The output of a digital-to-analog converter is provided with a return-to-zero (RTZ) output such that the digital-to-analog converter produces output pulses rather than output levels as would be expected from a conventional sample-and-hold output. The use of output pulses pushes the first null of the sinc function to a relatively higher frequency and thus the sinc function does not produce as much distortion in the harmonics of the sampled signal. Since the harmonics are less distorted, a bandpass filter or other filter can be used to extract harmonics of the sampled signal rather than the fundamental frequency.

Abstract: A modulator is configured with a first multiplexer having a first data signal input coupled to receive the first digital baseband signal and a second data signal input coupled to receive the second digital baseband signal. The first multiplexer provides a multiplexed output signal including components of the first and second digital baseband signals. The modulator also includes a source of alternating samples of first and second carrier signals and a multiplier having a first input coupled to the output of the first multiplexer and a second input coupled to the source of carrier signal samples. The multiplier is thereby coupled to provide a digital modulated output signal. The source of alternating samples of first and second baseband signals may include a second multiplexer having a first signal input coupled to receive a first carrier signal and a second signal input coupled to receive a second carrier signal.

Abstract: A digital subscriber line (DSL) communication system that utilizes the high frequency band of a standard telephone line does not require the use of a plain old telephone service (POTS) splitter in the resident's home, which provided isolation between the POTS frequency band (0 to 4 kHz) and the DSL frequency band. Digital signal processing techniques are utilized to adapt to varying subscriber line conditions due to POTS telephone equipment. The digital signal processing techniques eliminate the need for a splitter by reducing susceptibility to distortion due to varying subscriber line characteristics. The digital subscriber line modem utilizes constant envelope modulated signals and frequency division multiplexing, where the constant envelope modulations lessens the intermodulation distortion products due to DSL signals that are transmitted by the modem and which may result in audible noise at the POTS telephone equipment due to non-linearities of the POTS telephone equipment.

Abstract: The invention comprises a method and apparatus for decoding an incoming symbol stream comprised of a plurality of known missing symbols. Within the incoming symbol stream, those symbols corresponding the known missing symbols are replaced with a first set of values to create a modified symbol stream. The modified symbol stream is convolutionally decoded to produce a first decoded information bit stream. An error detection mechanism is performed on the first decoded information bit stream to determine a “pass” or “fail” indication. If the error detection mechanism produces a “fail” indication, a second set of values replaces the known missing symbols to produce a second modified symbol stream. The second modified symbol stream is convolutionally decoded to produce a second decoded information bit stream. The error detection mechanism is performed on the second decoded information bit stream.

Abstract: A unique system for efficiently implementing filtered, phase shifted channels is disclosed. Instead of using separate transmit shaping filters for each channel, and modulating the filtered signals with phase-shifted carrier and one might suppose, the system phase rotates the signals for each channel and modulates such phase rotated signals with a single carrier. In addition, the system decomposes the phase rotations into 90° pre-filter portions and a post-filter portion of, for example, 45°. In an 8 channel system, such as proposed in the IS-95B standard, the channels are divided into two groups and the 90° phase rotations for each group are done at the input of the transmit shaping filters. A 45° phase rotation is then done for one of the groups at the output of the transmit shaping filter. Significantly, no multiplication is required.

Abstract: A digital subscriber line (DSL) communication system that utilizes the high frequency band of a standard telephone line does not require the use of a plain old telephone service (POTS) splitter in the resident's home, which provided isolation between the POTS frequency band (0 to 4 kHz) and the DSL frequency band. A digital subscriber line modem utilizes either constant envelope modulation or quadrature amplitude modulation for outputting DSL signals upstream to a central office. When a telephone in the resident's home is detected as being off-hook, then the constant envelope modulation is used by the DSL modem in order to lessen the intermodulation product distortion that results in audible noise heard by a user of the telephone. When the telephone is on-hook, then another type of modulation, such as QAM, is used to maximize the upstream data rate capability in the DSL frequency band, since any noise generated by the QAM is not a problem due to the non-use of the POTS frequency band.