Abstract: A frequency-domain based echo and NEXT canceller is claimed. The canceller uses log2 encoding to precondition the error signal representing the echo. An improved gradient constraint is applied on at least a portion of a full weight vector in the least-means-square algorithm. The gradient constraint on the portion of the full weight vector and the log2 encoding improves system complexity with less hardware and power consumption than previous technologies.

Abstract: In at least some embodiments, a communication system includes a receiver having a local oscillator (LO) for each of a plurality of frequency bands. Each LO is controlled by a separate phase-locked loop (PLL) that tracks carrier frequency offset (CFO) using a common phase error (CPE). The CPE is selectively weighted based on at least one inter-band frequency correlation (IFC) coefficient.

Abstract: A method of determining when cable modems in a distributed digital data delivery service over cable TV hybrid fiber coaxial cable network have a headroom problem and resolving said problem. The method involves measuring the burst power from each cable modem, and if the burst power is too low, requesting the cable modem whose burst power is too low to increase its transmit power, and keeping track of which modems have been requested to increase their power. If a predetermined number of requests to increase power have not resulted in the cable modem transmitting with sufficient power for reliable reception, the cable modem is listed as having a headroom problem. Subsequent requests for upstream bandwidth from all modems with headroom problems are analyzed to determine if the requested burst size is too large and will result in a headroom problem. If so, a calculation as to the maximum number of spreading codes that each modem with a headroom problem can simultaneously transmit on without a headroom problem.

Abstract: A cable modem termination system is disclosed with flexible mapping of upstreams to downstreams and flexible mapping of downstreams to optical nodes and optical nodes to upstream receivers and the ability to add singe upstreams or downstreams as needed for load balancing. Multiple downstreams can share the same upstream. Multiple receivers can be coupled to the same upstream. Monitoring of upstream performance for overperforming or underperforming modems can be carried out, and new upstreams with higher and/or lower throughtput can be created to service the overperformers and/or underperformers. Modems can be grouped into logical groups with different performance levels and serviced by different upstreams or different upstream logical channels on the same upstream physical channel. An upstream linecard with a digital crosspoint switch is disclosed with the switch operated during contention intervals to allow reception with or without aggregation of noise where multiple upstream share the same receiver.

Abstract: Systems and methods for digital communication using an inexpensive reference crystal are described herein. Some illustrative embodiments include a method that includes setting a center frequency of a local oscillator used by a radio frequency (RF) transceiver, sequentially applying each of a plurality of predetermined offsets to the center frequency of the local oscillator, determining a plurality of metrics indicative of the quality of a received signal (each of the plurality of metrics corresponding to a different predetermined offset of the plurality of predetermined offsets), and selecting a predetermined offset of the plurality of predetermined offsets that results in a metric indicating a received signal that is higher in quality than the received signal that results when applying each of the remaining predetermined offsets of the plurality of offsets.

Abstract: Systems and methods for improving data throughput in an interference-rich wireless environment are described herein. Some illustrative embodiments include a method including receiving a modulated radio frequency (RF) signal including a message packet, identifying a preamble of the message packet generating a correlated preamble by combining the message packet preamble with a correlation sequence corresponding to an expected preamble, determining a characteristic of a correlated signal representing the correlated preamble, comparing the determined characteristic of the correlated signal to a first threshold value, and discarding the message packet if the determined characteristic of the correlated signal is below the first threshold value.

Abstract: A headend transmitter that transmits 1024 QAM including a 256 QAM modulator which has been modified to have more aggressive forward error correction processing. The 256 QAM modulator outputs 256 QAM points to a summer. Another data modulator receives additional data to be transmitted in a separate, substantially less complex constellation. This modulator processes the additional data to do forward error correction thereon and then maps the encoded data into a less complex constellation such as QPSK, 16 QAM etc. The additional data constellation points are then amplified in a variable gain amplifier and fed to a summer where each additional data point is added by vector summation to one 256 QAM point. The output 1024 QAM point is filtered and shifted to the desired transmission frequency. Legacy cable modem receivers can still receive the 256 QAM point since the addition of the new data just appears to be noise which they can overcome using the parity bits encoded in the transmitted symbols.

Abstract: One or more upstream line cards each include a digital or analog multiplexer front end circuit for a Cable Modem Termination System. Each upstream line card has only upstream receivers and allows a CMTS to share one or more receiver chips to receive and recover data from a larger number of input cables coupled to the front end multiplexer. A control circuit for the multiplexer uses MAP data and burst assignment data and upstream mini-slot counts for each of the input cables to determine when a burst is about to arrive on a cable and cause appropriate switching by the multiplexer or crossbar switch. In some embodiments, there is only one RF channel circuit coupled to the output of the multiplexer, so the multiplexer is controlled to couple the input cable upon which the burst is expected to the single RF channel.

Abstract: A method of adjusting overlap-and-add length for zero-padded suffixes. The method includes, based on a channel impulse response, estimating an effective channel length. When the effective channel length is less than a default overlap-and-add length and greater than a minimum length, the method includes setting the overlap-and-add length to the effective channel length. When the effective channel length is less than the minimum length, the method includes setting the overlap-and-add length to the minimum length. When the effective channel length is greater than the default overlap-and-add length, the method includes setting the overlap-and-add length to the default overlap-and-add length.

Abstract: A method and appartus for converting FFE and FBE coefficients from a DOCSIS compatible cable modem termination system upstream equalizer into FFE only coefficients to be sent down to the cable modem which transmitted the training burst which resulted in convergence on the FFE and FBE coefficients. The method involves programming an FBE like conversion structure comprised of an FFE filter and an FBE filter whose outputs are summed with the FFE and FBE coefficients from the CMTS equalizer. The FFE coefficients are stored in the FFE filter of the conversion structure. The FBE coefficients are stored in an FBE filter of the conversion structure. Then, an input vector which simulates the Dirac function (an impulse) is input to the conversion structure to derive coefficients at its output which define the impulse response and transfer function of the conversion structure. These coefficients are the FFE only coefficients which may be used to select a subset of 24 for sending to the cable modem.

Abstract: A cable modem termination system is disclosed with flexible mapping of upstreams to downstreams and flexible mapping of downstreams to optical nodes and optical nodes to upstream receivers and the ability to add singe upstreams or downstreams as needed for load balancing. Multiple downstreams can share the same upstream. Multiple receivers can be coupled to the same upstream. Monitoring of upstream performance for overperforming or underperforming modems can be carried out, and new upstreams with higher and/or lower throughtput can be created to service the overperformers and/or underperformers. Modems can be grouped into logical groups with different performance levels and serviced by different upstreams or different upstream logical channels on the same upstream physical channel. An upstream linecard with a digital crosspoint switch is disclosed with the switch operated during contention intervals to allow reception with or without aggregation of noise where multiple upstream share the same receiver.

Abstract: Automatic channel selection in a wireless network includes measuring throughput influencing factors for a plurality of wireless channels. A channel capacity metric is calculated for each of the plurality of wireless channels based on the measured throughput influencing factors. A serving channel is determined from the plurality of channels according to which channel capacity metric indicates a maximum channel capacity. Operation occurs in a normal operating mode using the determined serving channel for communication in the wireless network.

Abstract: A system and method of flexible channel allocation in an ultra wideband frequency hopping communication system is disclosed. In one embodiment, a method includes communicating radio signals through rapidly switching among a band group 6 according to a hopping pattern. The method also includes scanning the ultra wideband spectra to determine the band group 6 based on the hopping pattern of the radio signals. In another embodiment, a method includes scanning ultra wideband spectra to eliminate any frequency band of the ultra wideband spectra from a list of available frequency bands when the any frequency band is currently used, selecting a band group in combination of two or more frequency bands to communicate radio signals with an optimal transmission power and/or maximum range, and communicating the radio signals through rapidly switching among the band group.

Abstract: A novel and useful apparatus for and method of packet detection and carrier frequency offset estimation. The packet detection mechanism is robust to channels and sustains reasonable miss-detect (and false alarm) rates at low SNR values. The mechanism uses a modified combined cross correlation and delay and correlate scheme. A delay and correlate scheme is used in order to handle the effects of multipath while swapping integration and multiplication to increase cross-correlation factors resulting in improved sensitivity in low SNR conditions. Correlation is divided into multiple chains to generate a plurality of partial correlations to observe short patterns in the spread sequence resulting in improved performance in long multipath channels.

Abstract: A system for bidirectional communication of digital data between a central unit and a remote unit wherein the need for tracking loops in the central unit has been eliminated. The central unit transmitter generates a master carrier and a master clock signal which are used to transmit downstream data to the remote units. The remote units recover the master carrier and master clock and synchronize local oscillators in each remote unit to these master carrier and master clock signals to generate reference carrier and clock signals for use by the remote unit receiver. These reference carrier and clock signals are also used by the remote unit transmitters to transmit upstream data to the central unit. The central unit receiver detects the phase difference between the reference carrier and clock signals from the remote units periodically and adjusts the phase of the master carrier and master clock signals for use by the central unit receiver to receive the upstream data.

Abstract: A system for bidirectional communication of digital data between a central unit and a remote unit wherein the need for tracking loops in the central unit has been eliminated. The central unit transmitter generates a master carrier and a master clock signal which are used to transmit downstream data to the remote units. The remote units recover the master carrier and master clock and synchronize local oscillators in each remote unit to these master carrier and master clock signals to generate reference carrier and clock signals for use by the remote unit receiver. These reference carrier and clock signals are also used by the remote unit transmitters to transmit upstream data to the central unit. The central unit receiver detects the phase difference between the reference carrier and clock signals from the remote units periodically and adjusts the phase of the master carrier and master clock signals for use by the central unit receiver to receive the upstream data.

Abstract: A method of determining when cable modems in a distributed digital data delivery service over cable TV hybrid fiber coaxial cable network have a headroom problem and resolving said problem. The method involves measuring the burst power from each cable modem, and if the burst power is too low, requesting the cable modem whose burst power is too low to increase its transmit power, and keeping track of which modems have been requested to increase their power. If a predetermined number of requests to increase power have not resulted in the cable modem transmitting with sufficient power for reliable reception, the cable modem is listed as having a headroom problem. Subsequent requests for upstream bandwidth from all modems with headroom problems are analyzed to determine if the requested burst size is too large and will result in a headroom problem. If so, a calculation as to the maximum number of spreading codes that each modem with a headroom problem can simultaneously transmit on without a headroom problem.

Abstract: A pipelined digital data receiver for a cable TV headend which is capable of receiving DOCSIS 1.0 or 1.1 or advanced PHY TDMA or SCDMA bursts having programmable symbol rates and programmable modulation types as well as a host of other burst parameters such at Trellis code modulation on or off, scrambling on or off, various values for Reed-Solomon T number and codeword length. The receiver has an RF section to filter and digitize incoming RF signals. It also has an input section to detect impulse noise and do match filtering and despread SCDMA bursts. A timing recovery section recovers the symbol clock and detects the start of bursts and collisions. A rotational amplifier and equalizer calculate and track gain, phase and frequency offsets and correct symbols and calculates equalization coefficients. A decoder section decodes TCM and non TCM bursts, and a Reed-Solomon decoder section reconstructs RS codewords and uses them to error correct the payload data.

Abstract: A method and appartus for converting FFE and FBE coefficients from a DOCSIS compatible cable modem termination system upstream equalizer into FFE only coefficients to be sent down to the cable modem which transmitted the training burst which resulted in convergence on the FFE and FFE coefficients. The method involves programming an FBE like conversion structure comprised of an FFE filter and an FBE filter whose outputs are summed with the FFE and FFE coefficients from the CMTS equalizer. The FFE coefficients are stored in the FFE filter of the conversion structure. The FBE coefficients are stored in an FBE filter of the conversion structure. Then, an input vector which simulates the Dirac function (an impulse) is input to the conversion structure to derive coefficients at its output which define the impulse response and transfer function of the conversion structure. These coefficients are the FFE only coefficients which may be used to select a subset of 24 for sending to the cable modem.

Abstract: A headend transmitter that transmits 1024 QAM including a 256 QAM modulator which has been modified to have more aggressive forward error correction processing. The 256 QAM modulator outputs 256 QAM points to a summer. Another data modulator receives additional data to be transmitted in a separate, substantially less complex constellation. This modulator processes the additional data to do forward error correction thereon and then maps the encoded data into a less complex constellation such as QPSK, 16 QAM etc. The additional data constellation points are then amplified in a variable gain amplifier and fed to a summer where each additional data point is added by vector summation to one 256 QAM point. The output 1024 QAM point is filtered and shifted to the desired transmission frequency. Legacy cable modem receivers can still receive the 256 QAM point since the addition of the new data just appears to be noise which they can overcome using the parity bits encoded in the transmitted symbols.