Abstract: A novel mechanism for sharing filter taps across a plurality of interference cancellers. Each interference canceller may be directed to impairment, such as Ethernet impairments, including Ethernet 1000Base-T impairments. Various interference impairments include echo cancellation, NEXT cancellation and/or other interference detection or cancellation, etc. The hardware requirements of the interference impairment cancellers are reduced by sharing filter taps among the cancellers. In a first embodiment, the taps from a unified filter tap bank are shared across all the interference impairment cancellers for all four channels and over all ports. In a second embodiment, a portion of the taps of each filter are shared wherein each canceller comprises a fixed filter tap portion and a shared filter tap portion. A tap allocation algorithm assigns taps to those cancellers that need them the most. A canceller configuration is selected that yields maximal interference mitigation and the taps are allocated accordingly.

Abstract: A novel and useful mechanism for the detection and estimation of far-end cross talk (FEXT) caused by transmissions over adjacent wire pairs or cables. The detection and estimation technique of the invention can be used to identify FET impairments in Ethernet and DSL systems. The detection and estimation scheme is performed utilizing an adaptive FEXT canceller filter for detection purposes during normal operation of the system. FEXT filter tap coefficients are determined one at a time using a mechanism shared amongst all taps. Once adapted, the filter coefficients can be used to estimate FEXT strength and to determine spectral measurements of the FEXT impairment noise.

Abstract: A novel apparatus for and method of estimating the cable length of an active network link. The cable diagnostics mechanism of the invention is particularly suited for use in estimating the length of Ethernet network between two edges when the link is active, i.e. data is being transmitted in both directions simultaneously and the transmission of test pulses is not possible. The cable length estimation mechanism of the present invention is based on a well-known property of the spectrum of the insertion loss of the cable, namely, the linear relationship between the attenuation of the cable at a given frequency in decibels and the cable length. Information characterizing this relationship is extracted and used to determine the length of the cable.

Abstract: A method is provided to provide data to automatically estimate channel performance in a communication system if a different order constellation is used comprising the steps of: receiving an input signal from the channel; passing the input signal to a slicer having an output signal; determining signal noise by taking the difference between the input signal and output signal; identifying a beginning of a noise event when the signal noise is greater than a predefined first threshold; identifying an end of a noise event when the signal noise is less than a predefined second threshold; and providing for output the beginning of the noise event and the end of the noise event. Other systems and methods are disclosed.

Abstract: A method provides frequency and phase offset estimation in a SCDMA burst receiver (such as a DOCSIS 2.0 SCDMA burst receiver) by application of the known Least Square (LS) parameter estimation algorithm to a pre-known transmitted sequence, called preamble, in order to optimally characterize the phase and frequency offsets affecting the transmitted data. The LS parameter estimation algorithm is adapted to SCDMA burst receiver specifications by changing index calculations to fit according to SCDMA preamble locations. Improved estimation accuracy can be achieved by using weighted least squares that disregard symbols affected by impulse and burst noise. Weighted least squares can further impart more weight to last symbols to more accurately estimate contemporary impairments. The method is particularly useful for communication systems having large frequency and phase offsets as in the DOCSIS 2.0 SCDMA burst receiver.

Abstract: A method and apparatus provide phase, frequency and gain characterization and mitigation in a synchronized code division multiple access (SCDMA) burst receiver via use of dedicated phase and frequency correction loops that implemented to deal with the unique characteristics of a SCDMA signal. The way coded and un-coded bits are interleaved within a given frame requires that all symbols related to that frame be captured in a dedicated storage medium such as a RAM prior to the beginning of the data processing. The method and apparatus substantially eliminate gain, phase, and frequency, among other impairments caused by the transmitter, channel and analog parts of the SCDMA burst receiver.

Abstract: A method is provided for automatically optimizing parameter selection in a communication system having one or more channels for transmitting and receiving signals by the steps of: receiving a signal from a channel; characterizing impairments in the channel while gathering statistics using the received signal; analyzing the impairments to obtain recommendations for parameter modifications for improved performance; and modifying the parameters based on the recommendations. Other systems and methods are disclosed.

Abstract: A method is provided to automatically identify noise events in a channel of a communication system comprising the steps of: receiving an input signal from the channel; determining the mean energy of the input signal; determining the recent energy of the input signal; identifying a beginning of the noise event when the recent energy is greater than the product of the mean energy and a predefined first threshold; identifying an end of a noise event when the recent energy is less that the product of the mean energy and a predefined second threshold; and providing for output the beginning of the noise event and the end of the noise event. Other systems and methods are disclosed.

Abstract: Systems and methods for automatic gain control are disclosed. In one aspect of the invention, a system is provided that comprises a programmable gain amplifier that amplifies an input signal based on a gain signal. The system further comprises an analog-to-digital converter that generates at least one digital output signal from the amplified input signal, and an automatic gain control component that determines an adjustment of the gain signal based on a comparison of the at least one digital output signal to a predetermined maximum amplitude reference level.

Abstract: The present application describes a method of implementing a Viterbi algorithm (VA) for trellis coded modulation (TCM) decoding in communication equipment. According to an embodiment, a branch metric is calculated by adding the absolute value of the real and imaginary parts of a complex vector resulting from the subtraction of a received symbol and a constellation point that is the closest to the symbol in each subset.

Abstract: A method is disclosed for providing data for automatically estimating channel performance if different parameters of a Reed-Solomon (RS) code are used in a communication system while transmission is occurring in the communication system without changing the current Reed-Solomon (RS) code parameters.

Abstract: A method of implementing a Viterbi algorithm (VA) is provided for trellis coded modulation (TCM) decoding, optionally in association with a digital signal processor (DSP) or other data processor.

Abstract: A method provides frequency and phase offset estimation in a SCDMA burst receiver (such as a DOCSIS 2.0 SCDMA burst receiver) by application of the known Least Square (LS) parameter estimation algorithm to a pre-known transmitted sequence, called preamble, in order to optimally characterize the phase and frequency offsets affecting the transmitted data. The LS parameter estimation algorithm is adapted to SCDMA burst receiver specifications by changing index calculations to fit according to SCDMA preamble locations. Improved estimation accuracy can be achieved by using weighted least squares that disregard symbols affected by impulse and burst noise. Weighted least squares can further impart more weight to last symbols to more accurately estimate contemporary impairments. The method is particularly useful for communication systems having large frequency and phase offsets as in the DOCSIS 2.0 SCDMA burst receiver.

Abstract: A method and apparatus provide phase, frequency and gain characterization and mitigation in a synchronized code division multiple access (SCDMA) burst receiver via use of dedicated phase and frequency correction loops that implemented to deal with the unique characteristics of a SCDMA signal. The way coded and un-coded bits are interleaved within a given frame requires that all symbols related to that frame be captured in a dedicated storage medium such as a RAM prior to the beginning of the data processing. The method and apparatus substantially eliminate gain, phase, and frequency, among other impairments caused by the transmitter, channel and analog parts of the SCDMA burst receiver.

Abstract: A bit-interleaved encoder for a CATV upstream channel is provided having a convolutional encoder for receiving data values, a bit-interleaver interconnected with said encoder, and a symbol mapper interconnected with said bit-interleaver.

Abstract: A system is provided to automatically estimate performance of a receiver for receiving input signals, the input signals having a carrier frequency and a baud rate, from a channel in a communication system and the effect of highly correlated noise cancellation on performance of the receiver, while no active transmission is occurring on the channel, comprising: a digital front end in the receiver for receiving samples of the input signals; a predictor coupled to the digital front end for predicting highly correlated noise in a second sample of the input signal; and a subtraction unit coupled to the predictor for subtracting the predictor output from the second sample to determine residual noise in the second sample. Other systems and methods are disclosed.

Abstract: A method is disclosed for providing data for automatically estimating channel performance if different parameters of a Reed-Solomon (RS) code are used in a communication system while transmission is occurring in the communication system without changing the current Reed-Solomon (RS) code parameters comprising the steps of: receiving an input signal from the channel; processing the input signal in a receiver in the communication system, the receiver having a Reed Solomon decoder having an output of RS symbols; choosing a virtual RS block code size; determining a RS number of errors data by determining how many RS symbols in a sequence of RS symbols the size of the virtual RS block code size are erred RS symbols; determining a RS sequence of errors data by determining how many occurrences there are of erred RS symbols that occur sequentially in the sample and the number of sequential erred RS symbols in each occurrence; and outputting the RS number of errors data and RS sequence of errors data.

Abstract: A method is provided to provide data to automatically estimate channel performance in a communication system if a different order constellation is used comprising the steps of: receiving an input signal from the channel; passing the input signal to a slicer having an output signal; determining signal noise by taking the difference between the input signal and output signal; identifying a beginning of a noise event when the signal noise is greater than a predefined first threshold; identifying an end of a noise event when the signal noise is less than a predefined second threshold; and providing for output the beginning of the noise event and the end of the noise event. Other systems and methods are disclosed.

Abstract: A method is provided to automatically identify noise events in a channel of a communication system comprising the steps of: receiving an input signal from the channel; determining the mean energy of the input signal; determining the recent energy of the input signal; identifying a beginning of the noise event when the recent energy is greater than the product of the mean energy and a predefined first threshold; identifying an end of a noise event when the recent energy is less that the product of the mean energy and a predefined second threshold; and providing for output the beginning of the noise event and the end of the noise event. Other systems and methods are disclosed.

Abstract: A method is provided for automatically allocating a channel, in a communication system, having a total data rate for transmitting and receiving signals, each of the signals having a carrier frequency, a baud rate and a constellation size, the channel comprising a frequency band comprising a plurality of carrier frequencies, comprising the steps of: receiving a noise sample from the channel; determining a channel noise estimate for the noise sample; receiving a parameter indicating a maximum allowed bit error rate; scanning one or more possible combinations of carrier frequency and baud rate for the channel; determining the bit error rate for each combination based on the channel noise estimate; determining what constellation sizes can be used for each combination such that the bit error rate for that combination does not exceed the maximum allowed bit error rate; determining a data rate for one or more of the combinations; and allocating the channel such that the total data rate is maximized.