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: Modified branch metrics for processing bit-soft decisions to account for phase noise impact on cluster variance (CV). The present invention is able to partition a modulation scheme's constellation into two or more regions, so that the bit-soft decision branch metrics may be adjusted based on the CV of the various constellation points. A confidence level may be attached to the various constellation points based on their particular CVs. There are a number of methods to ascertain the CV of the constellation's points, including finding characteristics of various components in a communication system (transmitter, communication channel and receiver), and any method may be used within various embodiments. The modification of the branch metrics/confidence level may be performed in a communication receiver; the communication receiver may be implemented in a communication system employing the vector orthogonal frequency division multiplexing (VOFDM) portion of the broadband wireless internet forum (BWIF).

Abstract: Characterizing channel response in a single upstream burst using redundant information from training tones (TTs). The invention is operable to utilize inserted TTs, contained within a transmitted data frame, to provide for an improved estimate of a communication channel's actual response and an improved estimate of the noise of the communication channel. The invention determines a maximum allowable delay spread of the many communication paths within a multi-path communication channel. Using the redundant TTs information then a portion of the finite impulse response of the communication channel, within the time domain, may be zeroed, thereby providing a much improved channel estimate and noise estimate. Using the redundant TTs, less noise is introduced onto the data tones (DTs) within a data frame. The present invention is also able to identify those portions of the TTs that are attributable to the actual channel and those that are attributable to the channel's noise.

Abstract: A communication system includes a supervisory node (e.g., a headend) and one or more remote nodes (e.g., cable modems). The supervisory node or a remote node monitors a characteristic associated with the communication system. Remote node transmits an upstream communication among a plurality of physical upstream channels based on the characteristic. The average transmit power used to transmit the upstream communication among the plurality of physical upstream channels is no greater than the average transmit power that would be necessary to transmit the upstream communication using a single physical upstream channel at a lower data rate.

Abstract: Cancellation of interference in a communication system with application to S-CDMA. A relatively straight-forward implemented and computationally efficient approach of selecting a predetermined number of unused codes is used to perform weighted linear combination selectively with each of the input spread signals in a multiple access communication system. If desired, the predetermined number of unused codes is always the same in each implementation. Alternatively, the predetermined number of unused codes is selected from within a reordered code matrix using knowledge that is shared between the two ends of a communication system, such as between the CMs and a CMTS. While the context of an S-CDMA communication system having CMs and a CMTS is used, the solution is generally applicable to any communication system that seeks to cancel narrowband interference. Several embodiments are also described that show the generic applicability of the solution across a wide variety of systems.

Abstract: Cancellation of interference in a communication system with application to S-CDMA. A relatively straight-forward implemented and computationally efficient approach of selecting a predetermined number of unused codes is used to perform weighted linear combination selectively with each of the input spread signals in a multiple access communication system. If desired, the predetermined number of unused codes is always the same in each implementation. Alternatively, the predetermined number of unused codes is selected from within a reordered code matrix using knowledge that is shared between the two ends of a communication system, such as between the CMs and a CMTS. While the context of an S-CDMA communication system having CMs and a CMTS is used, the solution is generally applicable to any communication system that seeks to cancel narrowband interference. Several embodiments are also described that show the generic applicability of the solution across a wide variety of systems.

Abstract: A distributed cable modem termination system of the present invention includes a downstream transmitter hub, an upstream receiver hub, and a head end that communicatively couples to the downstream transmitter hub and to the upstream receiver hub via a packet data network. The head end and the downstream transmitter hub are operable to synchronize a clock of the downstream transmitter hub with a clock of the head end. Further, the upstream receiver hub and the downstream transmitter hub are operable to synchronize a clock of the upstream receiver hub with the clock of the downstream transmitter hub. Clock synchronization between the upstream receiver hub and the downstream transmitter hub are performed using ranging operations supported by at least one cable modem communicatively coupled to both the upstream receiver hub and the downstream transmitter hub via cable modem network plant.

Abstract: Signal processing under attenuated transmission conditions. Within an orthogonal signal space, the number of orthogonal signals that are used to transmit information from a transmitter to a receiver is reduced and the transmitted power of each of the now remaining orthogonal signals is modified; this may involve increasing the power of all of the remaining orthogonal signals equally or alternatively modifying them individually. The same modulation used before the reduction may also be used afterwards; within communication systems having multiple transmitter-receiver paths, this will ensure that the communication system's throughput and efficiency will remain unchanged even when one (or more) transmitter-receiver paths are highly attenuated. In addition, robust mode operation is provided for ranging and registering of transmitter devices when entering the communication system.

Abstract: Provided is a method and system for estimating distortion in a communications channel including an adaptive equalizer. The method includes determining one or more adaptive filter coefficients associated with a signal passed through the equalizer. The method also includes estimating un-equalized channel distortion based upon the determined adaptive filter coefficients.

Abstract: Vector orthogonal frequency division multiplexing (VOFDM) receiver correlation matrix processing using factorization. Efficient correlation matrix processing is used to combine multiple signals into a single combined signal. This single combined signal may be viewed as being a beam form soft decision. An efficient square root factorization system and method provides for computational resource savings while, at the same time, providing for greater precision of the overall computational results. By reducing intermediate variable calculation dynamic ranges, the overall calculation becomes more precise. Particularly within fixed-point arithmetic applications, a reduction in dynamic range of the intermediate variable calculations provides for a significant increase in final calculation precision.

Abstract: Equalization is provided in a high speed communication receiver that includes in various aspects an automatic gain control input stage, a decision feedback equalizer, a clock and data recovery circuit and equalization control circuits. The automatic gain control stage may include a continuous time filter with an adjustable bandwidth. A threshold adjust signal may be applied to the output of the automatic gain control stage. The equalization control circuits may be implemented in the digital domain and operate at a lower clock speed than the data path.

Abstract: Data error such as mean square error may be reduced in a system such as a communication receiver using a dithering algorithm that adjusts one or more parameters in the system. The dithering algorithm may be applied to more than one parameter in a nested manner. The dithering algorithm may be modified to immediately check the MSE after a parameter has been adjusted.

Abstract: A communication system performs burst noise cancellation. A transmitter produces and transmits a spread signal that comprises at least one known-value symbol spread by a plurality of non data-carrying orthogonal codes and data symbols spread by at least one data-carrying orthogonal code. The transmitter transmits the spread signal across a communication link that introduces burst noise. A burst noise detector determines burst noise affected chips of the orthogonal codes. A weight computation functional block calculates a plurality of complex-valued combining weights based upon the burst noise affected chips. A vector de-spreader and a linear combiner operate in combination to use the plurality of non data-carrying orthogonal codes, the at least one data-carrying orthogonal code, and the plurality of complex-valued combining weights to de-spread the received spread signal to produce the data symbols with the burst noise substantially removed.

Abstract: Cancellation of interference in a communication system with application to S-CDMA. A relatively straight-forward implemented, and computationally efficient approach of selecting a predetermined number of unused codes is used to perform weighted linear combination selectively with each of the input spread signals in a multiple access communication system. If desired, the predetermined number of unused codes is always the same in each implementation. Alternatively, the predetermined number of unused codes are selected from within a reordered code matrix using knowledge that is shared between the two ends of a communication system, such as between the CMs and a CMTS. While the context of an S-CDMA communication system having CMs and a CMTS is used, the solution is generally applicable to any communication system that seeks to cancel narrowband interference. Several embodiments are also described that show the generic applicability of the solution across a wide variety of systems.

Abstract: A cable modem communication system includes a plurality of Cable Modems (CMs), a CM network segment, and a Cable Modem Termination System (CMTS). The CMTS segregates the plurality of CMs into a first group of CMs with which standard registering and ranging operations are performed and a second group of CMs with which attenuated transmission registering and ranging operations are performed. Each CM of the first group of CMs operable to perform registering and ranging operations by transmitting a ranging burst of a first format. Each CM of the second group of CMs operable to perform registering and ranging operations by transmitting a ranging burst of a second format that differs from the ranging burst of the first format. The CMTS may include a rake receiver that receives and demodulates a plurality of multi-path copies of the ranging burst of the second format.

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 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 central entity and/or a remote device in a communication system are designed to address the problem of maintaining upstream synchronization in the remote device after loss of the downstream signal. One issue of particular importance is maintaining upstream transmissions from the remote device in an S-CDMA (or perhaps S-TDMA) mode that do not degrade performance of the communication system via poor upstream timing or a need for re-ranging. By providing novel functionality at the central entity for synchronizing first and second downstream signals and/or by providing novel functionality at the remote device for determining a symbol clock offset between a first terminated downstream signal and a second re-acquired downstream signal, embodiments of the present invention facilitate maintenance of synchronization through the loss of the downstream signal, thereby minimizing the need for re-ranging and avoiding poorly timed upstream bursts.

Abstract: A central entity and/or a remote device in a communication system are designed to address the problem of maintaining upstream synchronization in the remote device after loss of the downstream signal. One issue of particular importance is maintaining upstream transmissions from the remote device in an S-CDMA (or perhaps S-TDMA) mode that do not degrade performance of the communication system via poor upstream timing or a need for re-ranging. By providing novel functionality at the central entity for synchronizing first and second downstream signals and/or by providing novel functionality at the remote device for determining a symbol clock offset between a first terminated downstream signal and a second re-acquired downstream signal, embodiments of the present invention facilitate maintenance of synchronization through the loss of the downstream signal, thereby minimizing the need for re-ranging and avoiding poorly timed upstream bursts.

Abstract: Systems and methods are disclosed for detecting temporary high level impairments, such as noise or interference, for example, in a communications channel, and subsequently, mitigating the deleterious effects of the dynamic impairments. In one embodiment, the method not only performs dynamic characterization of channel fidelity against impairments, but also uses this dynamic characterization of the channel fidelity to adapt the receiver processing and to affect an improvement in the performance of the receiver. For example, in this embodiment, the method increases the accuracy of the estimation of the transmitted information, or similarly, increases the probability of making the correct estimates of the transmitted information, even in the presence of temporary severe levels of impairment. The channel fidelity history may also be stored and catalogued for use in, for example, future optimization of the transmit waveform.