Abstract: A number of features for enhancing the performance of a communication system, in which data is transmitted between a base station and a plurality of subscriber stations located different distances from the base station, are presented. The power transmission level, slot timing, and equalization of the subscriber stations are set by a ranging process. Data is transmitted by the subscriber stations in fragmented form. Various measures are taken to make transmission from the subscriber stations robust. The uplink data transmission is controlled to permit multiple access from the subscriber stations.

Abstract: A method of managing traffic in a communications channel includes the steps of receiving a subscriber ID corresponding to a subscriber, performing a spectral analysis on a signal received from the subscriber within a time interval identified by the subscriber ID, and adjusting transmission characteristics of the subscriber based on the spectral analysis.

Abstract: A system for mitigating impairment in a communication system includes a delay block, a signal level block, a moving average window block, an impulse noise detection block, and a combiner. The delay block receives and delays each chip of a plurality of chips in a spreading interval. The signal level block determines a signal level of each chip of the plurality of chips in the spreading interval. The moving average window block determines a composite signal level for a chip window corresponding to the chip. The impulse noise detection block receives the signal level, receives the composite signal level, and produces an erasure indication for each chip of the plurality of chips of the corresponding chip window. The combiner erases chips of the plurality of chips of the spreading interval based upon the erasure indication.

Abstract: A system and method are used to provide uncorrelated code hopping in a communications system. A shift register receives data. The shift register is clocked to shift the data. A scaler performs a scaling operation on the data with a numerical value of active codes. A truncator truncates the scaled data to its seven most significant bits to produce a pseudo random hop number. A code matrix shifter circularly shifts the active codes in a code matrix based on the pseudo random hop number to produce a circularly shifted code. A transmitter transmits the circularly shifted code.

Abstract: A system and method are used to provide uncorrelated code hopping in a communications system. A multi-bit linear shift register receives data and clocks the data fifteen times. A word assembler receives the shifted data and outputs a fifteen bit word. A mixer mixes the fifteen bit word with an numerical value of active codes to generate a mixed signal. A divider divides the mixed signal to produce a divided signal. A truncator truncates the divided signal to its seven most significant bits to produce a pseudo random hop number. A code matrix shifter circularly shifts the active codes in a code matrix based on the pseudo random hop number to produce a circularly shifted code. A transmitter transmits the circularly shifted code matrix.

Abstract: The present invention provides a system and method for performing ranging operations in a cable modem system. In accordance with embodiments of the present invention, transmission times, transmission power levels, transmission carrier frequencies, and pre-equalization parameters are adjusted to provide for robust operation of the cable modem system. More particularly, iterative processing steps are used to provide coefficient ordering, scaling, and aligning between the multiple cable modems and the cable modem termination system present in a cable modem system.

Abstract: A system for detecting collisions in a shared communications medium, such as a TDMA medium, includes a receive path adapted to generate a first intermediate signal, a second intermediate signal, and a data symbol sequence from an input signal. A preamble detection module generates a correlation metric from the first intermediate signal. A power measurement module generates a power indication signal from the second intermediate signal. A noise measurement module generates a noise indication signal from the second intermediate signal and the data symbol sequence. A processing module is adapted to characterize the input signal as a collision for certain values of correlation metric, power indication signal, and noise indication signal.

Abstract: A filter settings generation operation includes sampling a communication channel to produce a sampled signal. The sampled signal is spectrally characterized across a frequency band of interest to produce a spectral characterization of the sampled signal. This spectral characterization may not include a signal of interest. The spectral characterization is then modified to produce a modified spectral characterization. Filter settings are then generated based upon the modified spectral characterization. Finally, the communication channel is filtered using the filter settings when the signal of interest is present on the communication channel. In modifying the spectral characterization, pluralities of spectral characteristics of the spectral characterization are independently modified to produce the modified spectral characterization. Modifications to the spectral characterization may be performed in the frequency domain and/or the time domain.

Abstract: A system for mitigating impairment in a communication system includes a delay block, a signal level block, a moving average window block, an impulse noise detection block, and a combiner. The delay block receives and delays each chip of a plurality of chips in a spreading interval. The signal level block determines a signal level of each chip of the plurality of chips in the spreading interval. The moving average window block determines a composite signal level for a chip window corresponding to the chip. The impulse noise detection block receives the signal level, receives the composite signal level, and produces an erasure indication for each chip of the plurality of chips of the corresponding chip window. The combiner erases chips of the plurality of chips of the spreading interval based upon the erasure indication.

Abstract: The present invention provides a system and method for performing ranging operations in a cable modem system. In accordance with embodiments of the present invention, transmission times, transmission power levels, transmission carrier frequencies, and pre-equalization parameters are adjusted to provide for robust operation of the cable modem system. More particularly, iterative processing steps are used to provide coefficient ordering, scaling, and aligning between the multiple cable modems and the cable modem termination system present in a cable modem system.

Abstract: A filter settings generation operation includes sampling a communication channel to produce a sampled signal. The sampled signal is spectrally characterized across a frequency band of interest to produce a spectral characterization of the sampled signal. This spectral characterization may not include a signal of interest. The spectral characterization is then modified to produce a modified spectral characterization. Filter settings are then generated based upon the modified spectral characterization. Finally, the communication channel is filtered using the filter settings when the signal of interest is present on the communication channel. In modifying the spectral characterization, pluralities of spectral characteristics of the spectral characterization are independently modified to produce the modified spectral characterization. Modifications to the spectral characterization may be performed in the frequency domain and/or the time domain.

Abstract: A number of features for enhancing the performance of a wireless communication system, in which data is transmitted between a central node and a plurality of subscriber nodes located remotely with respect to the central node, are presented. The power transmission level, slot timing, and equalization of the subscriber nodes are set by a ranging process. Data is transmitted by the subscriber nodes in fragmented form. Various measures are taken to make transmission from the subscriber nodes robust. The uplink data transmission is controlled to permit multiple access from the subscriber nodes.

Abstract: Carrier frequency offset (CFO) estimation from preamble symbols. Any communication receiver may be adapted to perform the CFO estimation. The CFO estimation is performed using a low complexity, high accuracy CFO estimation method. The operation may be described as follows: each element of a received sequence is divided by the corresponding preamble element, the resulting sequence is divided into N subgroups, and each subgroup is then averaged. The phase differential of the resulting sequence is computed, averaged, and used to compute an estimate of the carrier frequency offset. This approach to performing CFO estimation is of relatively high estimation accuracy and of relatively low computational complexity.

Abstract: A number of features for enhancing the performance of a wireless communication system, in which data is transmitted between a central node and a plurality of subscriber nodes located remotely with respect to the central node, are presented. The power transmission level, slot timing, and equalization of the subscriber nodes are set by a ranging process. Data is transmitted by the subscriber nodes in fragmented form. Various measures are taken to make transmission from the subscriber nodes robust. The uplink data transmission is controlled to permit multiple access from the subscriber nodes.

Abstract: A communication device constructed according to the present invention detects impulse noise in a preamble sequence. In detecting impulse noise in the preamble sequence the communication device first receive a preamble sequence that includes a plurality of preamble symbols. The communication device then divides the plurality of preamble symbols by at least one known preamble symbol to produce a plurality of preamble gains and/or a plurality of preamble phases corresponding to the plurality of preamble symbols. Finally, the communication device determines, based upon the plurality of preamble gains and/or the plurality of preamble phases, that at least one preamble symbol has been adversely affected by a impulse noise. The communication device may discard at least one preamble symbol that has been adversely affected by impulse noise from the plurality of preamble symbols.

Abstract: A system for mitigating impairment in a communication system includes a delay block, a signal level block, a moving average window block, an impulse noise detection block, and a combiner. The delay block receives and delays each chip of a plurality of chips in a spreading interval. The signal level block determines a signal level of each chip of the plurality of chips in the spreading interval. The moving average window block determines a composite signal level for a chip window corresponding to the chip. The impulse noise detection block receives the signal level, receives the composite signal level, and produces an erasure indication for each chip of the plurality of chips of the corresponding chip window. The combiner erases chips of the plurality of chips of the spreading interval based upon the erasure indication.

Abstract: A receiver includes a filter stage that receives, filters, and equalizes a received signal, and a decisional feedback loop coupled to the filter stage that receives and processes a signal output from the filter stage using remodulation. The decisional feedback loop includes a converter that generates a baseband signal, a detector that generates a decision signal, a restorative signal generator that generates a restorative signal using remodulation, and a carrier loop that generates a frequency correction signal and provides a frequency-offset estimate. The restorative signal and the frequency correction signal are provided to the converter to compensate for inter-symbol interference. The presented “remodulation” technique decouples interaction between the carrier loop, the pre-filters, and the equalizer of the restorative signal generator, providing an architecture that is more stable and significantly faster than conventional architectures.

Abstract: A method of parameter estimation in a shared channel communications system includes the steps of receiving a preamble including a first sequence corresponding to a sequence having zero autocorrelation, a second sequence having zero autocorrelation, and a third sequence having zero autocorrelation, performing a coarse carrier frequency estimate based on the first sequence, and performing a fine carrier frequency estimate based on the second and third sequences.

Abstract: A system for mitigating impairment in a communication system includes a delay block, a signal level block, a moving average window block, an impulse noise detection block, and a combiner. The delay block receives and delays each chip of a plurality of chips in a spreading interval. The signal level block determines a signal level of each chip of the plurality of chips in the spreading interval. The moving average window block determines a composite signal level for a chip window corresponding to the chip. The impulse noise detection block receives the signal level, receives the composite signal level, and produces an erasure indication for each chip of the plurality of chips of the corresponding chip window. The combiner erases chips of the plurality of chips of the spreading interval based upon the erasure indication.

Abstract: “Multiple approaches are presented herein to perform CFO correction within CDMA systems having multiple users. Any communication receiver may be adapted to perform the CFO correction in this manner CDM. One approach assumes a diagonal CFO matrix to decouple the different codes' soft symbol decisions, and each soft symbol decision is independently corrected to obtain hard decisions. Another approach employs direct CFO matrix inversion and multiplies it by a despread soft symbol decision vector to obtain corrected soft symbol decisions. Another approach first performs a single-user correction on the despread soft symbol decisions so, which are then sliced to obtain initial hard decisions. In the next step of this particular approach the initial hard decisions are multiplied by the CFO coefficients to obtain an estimate for the undesired ICI, which is then subtracted from the despread soft symbol decisions to obtain cleaner soft symbol decisions, which then can undergo slicing.