1756results about "Transmission control/equlisation" patented technology

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.

In an OFDM system, a transmitter broadcasts a first TDM pilot on a first set of subbands followed by a second TDM pilot on a second set of subbands in each frame. The subbands in each set are selected from among N total subbands such that (1) an OFDM symbol for the first TDM pilot contains at least S1 identical pilot-1 sequences of length L1 and (2) an OFDM symbol for the second TDM pilot contains at least S2 identical pilot-2 sequences of length L2, where L2>L1, S1·L1=N, and S2·L2=N. The transmitter may also broadcast an FDM pilot. A receiver processes the first TDM pilot to obtain frame timing (e.g., by performing correlation between different pilot-1 sequences) and further processes the second TDM pilot to obtain symbol timing (e.g., by detecting for the start of a channel impulse response estimate derived from the second TDM pilot).

Improved approaches to flexibly implementing graphic equalizers on media players are disclosed. These approaches provide dynamic order reduction of a multi-band graphic equalizer so that equalizer effects can be timely performed with only limited computational resources. In one embodiment, a media player receives a media item and associated equalizer settings for a multi-band graphic equalizer. The media player can then automatically (i.e., without user action) approximate the multi-band graphic equalizer with the equalizer settings for the media item using a fewer number of filters. Fewer filters means order reduction, and thus reduction in computational requirements. After the multi-band graphic equalizer is approximated, the media player can present the media item to its user in accordance with the reduced complexity, approximated equalizer.

Multiple passes are executed in the setup of an equalizer, and modification of the equalization is performed after each pass of an analysis phase. After an initial pass, the equalization is adjusted, based upon the location of peaks and valleys in the system response. This initial adjustment of equalization may tend to flatten most of the peaks and valleys to produce the desired uniform linear response. Inexact application of equalization corrections may introduce other artifacts into the system response and / or may not sufficiently normalize equalization. A second pass is then performed to measure the system response using the new equalization settings. The new peaks and valleys are measured, and the equalization adjusted to try to flatten response further. A proximity range may be applied to each pass, to reduce the likelihood that adjustment of one equalizer coefficient will create artifacts in the resulting system response.

An apparatus and method for generating an octal code for identifying cells in a mobile communication system. In the octal code generating apparatus, a binary code generator generates a binary code with a predetermined minimum Hamming distance. A column permutator permutes the order of columns of the binary code in a predetermined interleaving method. A 3-bit combiner generates a plurality of codewords using the column-permuted binary code as a generator matrix and groups the bits of each of the codewords by threes. An octal code generator converts the 3-bit grouped binary codewords to octal code sequences.

A system for monitoring the output of an adaptive channel equalizer in order to determine if convergence has been achieved. A slicer samples data from the equalizer during a predetermined period. The output data from the slicer is forwarded to a microprocessor in order to apply a test standard to the slicer data. For example, if one of every possible transmitted symbol is detected by the microprocessor, convergence is assumed to have occurred. If the test criterion is not met, a reset signal is sent to the equalizer.

Apparatus for suppressing noise and electromagnetic coupling in the printed circuit board of an electronic device includes an upper conductive plate and an array of conductive coplanar patches positioned a distance t2 from the upper conductive plate. The distance t2 is chosen to optimize capacitance between the conductive coplanar patches and the upper conductive plate for suppression of noise or electromagnetic coupling. The apparatus further includes a lower conductive plate a distance t1 from the array of conductive coplanar patches and conductive rods extending from respective patches to the lower conductive plate.

A random access channel transmission method in which a user terminal selects a preamble pattern from among a plurality of known preamble patterns and transmits that preamble pattern to a base station, where that transmission method comprises: a step of dividing a cell into a plurality of areas, and setting one or more preamble patterns and the number of repetitions for transmitting the preamble pattern for each area; and a step wherein a user terminal that exists in an are close to the base station transmits a specified preamble pattern one time, and a user terminal that exists in an area far from the base station transmits another specified preamble pattern a plurality of times.

A transmitting apparatus, receiving apparatus, communication system, and a signal processing method of each applying a suitable modulation method and transmission path estimation method in accordance with characteristics of the transmission information for improving the transmission efficiency operate so that at the transmission side, the ratio of adding transmission path estimation pilot symbols is suitably controlled in accordance with an aspect of the dat transmitted, for example, the size of the packets transmitted and the state of the transmission path, wherein the transmission data is mapped by the selected modulation method, and the signal is processed in accordance with the method of estimation of the transmission path, and the transmission signal is produced by inverse fast Fourier transform processing and transmitted. At the reception side, the received signal is fast Fourier transformed, the transmission path is estimated by the transmission path estimation method selected at the transmission side, the received signal is correct in accordance with result, and the received data is reproduced in accordance with the modulation method. Therefore, it is possible to always adopt the optimum transmission method in accordance with the attribute of the transmission data etc. and possible to realize an improvement of a transmission efficiency and an enhancement of the quality of communication.

Systems and methods are described for long subscriber loops using automatic gain control. A method includes extending a digital subscriber loop including: producing an output signal in a first direction from a variable gain amplifier at a mid-span extender unit responsive to an input signal in the first direction from the digital subscriber loop; monitoring a signal strength of said output signal in the first direction at the mid-span extender unit; generating a gain control signal responsive to the signal strength at the mid-span extender unit; controlling a gain of the variable gain amplifier at the mid-span extender unit responsive to the gain control signal; and controlling a second gain of a second variable gain amplifier at said mid-span extender unit responsive to said gain control signal to produce an output signal in a second direction from said second variable gain amplifier at said mid-span extender unit responsive to a second input signal in said second direction from said digital subscriber loop.

A receiver circuit has an equalizer that equalizes a received signal propagating through a transmission medium; a data detection circuit that detects an analog output signal of the equalizer at a data sample timing and outputs a digital signal; an intersymbol interference detection circuit that detects an intersymbol interference level from the analog output signal of the equalizer at the data sample timing and from the digital signal of the data detection circuit; and an equalization characteristic control unit that controls the characteristic of the equalizer to minimize the detected intersymbol interference level. The receiver circuit further has a data sample timing control unit in which the data sample timing is controlled to a sample timing at which the difference between the amplitude of the analog output waveform of the equalizer with respect to an impulse and the amplitude of an ideal impulse response waveform is minimal.

A tunable receiver is disclosed including a plurality of select filters to perform an initial band selection, a variable-gain low noise amplifier (LNA) whose gain is controlled to prevent its output power level to exceed a predetermined power threshold, a plurality of digitally-tunable tracking filters to pass signals within a selected channel and to reject signals in a corresponding image band, a second LNA to further amplify the received RF signal and to generate differential signal outputs, a down converting stage which converts the received RF signal to an IF signal while rejecting signals in the image band, an IF trap to further reject undesired signals present at the output of the down converting stage, an IF amplifier to amplify the IF signal to compensate for losses, an IF filter to provide channel select and reject undesirable signals, and a variable-gain IF amplifier to amplify the IF signal and maintain its power level within specification.

A method is provided for extracting a sequence of pilot symbols enabling to estimate the transfer function of a transmission channel. At least a radiocommunication device communicates through the channel with a remote station, the latter regularly delivering to the radiocommunication device a reference pattern. The structure of the reference pattern is variable, depending on at least one characteristic of the transmission channel.

A transmitting apparatus, receiving apparatus, communication system, and a signal processing method for each apply a suitable modulation method and transmission path estimation method in accordance with the characteristics of the transmission information and capable of improving the transmission efficiency. At the transmission side, the method of estimation of the transmission path and the modulation method are selected in accordance with an attribute of the data to be transmitted, for example, the size of a packet to be transmitted, the transmission data is mapped by the selected modulation method, the signal is processed in accordance with the transmission path estimation method, and a transmission signal is created by increase fast Fourier transform processing and transmitted. At the reception side, the received signal is fast Fourier transformed, the transmission path is estimated by the transmission path estimation method selected at the transmission side, the received signal is corrected in accordance with the result, and the received data is reproduced in accordance with the modulation method. Therefore, it is possible to always adopt the optimum transmission method in accordance with the attribute of the transmission data etc. and possible to realize an improvement of a transmission efficiency and an enhancement of the quality of communication.

A timing recovery unit detects a phase offset and a frequency offset from a head area of reproduction data and initially corrects them. The timing recovery unit stores data in which a head reproduction signal has been made to be discrete by a fixed clock into a buffer. A phase offset detector detects the phase offset from the data head area in parallel with the operation for writing the data into the buffer. At the same time, a frequency offset detector detects the frequency offset from the data head area in parallel with the operation for writing the data into the buffer. A correction value of the detected phase offset and a correction value of the detected frequency offset are initially set into a digital PLL. While the data is read out from the buffer, a frequency lead-in and a phase lead-in are executed in the head area.

A method and apparatus for a multiple channel communication device training, and processing utilizing a transmit signal power control operation. Multiple channel communication devices utilize inter-channel crosstalk mitigation techniques, such as MIMO processing modules or MIMO precoding systems, to cancel unwanted crosstalk coupling across active and provisioned channels. Upon provisioning and activation of a new channel that connects to the multiple channel communication device the signal on the new channel couples into other channels and the existing MIMO filtering or processing structure is untrained to mitigate the crosstalk from the new channel. A power control training operation prevents crosstalk from hindering operation on other channels during the training operation. During one example training operation, the power level of a transmit signal is incrementally increased as the crosstalk cancellation filter(s) are trained.

Adaptive equalization methods and adaptive equalizers used with precoded systems dominated by intersymbol interference (ISI) monitor the output of a DFE and compare it to a reference for updating a precoder in response to the comparison. To accomplish this, an adaptive equalizer includes a feed forward equalizer receiving a signal from a communication channel, the feed forward equalizer equalizing variations in pre-cursor intersymbol interference resulting from changes in characteristics of the channel and providing an output signal to an error correction decoder, a decision circuit, coupled to the feed forward equalizer, for generating error vectors in response to the output signal of the feed forward equalizer and a decision feedback equalizer, coupled to the decision circuit, the decision feedback equalizer monitoring the pre-cursor intersymbol interference of the channel, determining when the transmitter coefficients to the precoder warrant updating, and generating a signal indicating that an update to the transmitter coefficients to the precoder is warranted. The adaptive equalizer farther includes a comparison circuit, the comparison circuit receiving an output from the decision feedback equalizer and comparing the output from the decision feedback equalizer to a reference, the comparison circuit generating the signal indicating that an update to the transmitter coefficients to the precoder is warranted in response to the comparison.

The present invention provides a method and an apparatus for communicating data over a network between a communication node, for example, an access point having a first and a second antenna and a first and a second mobile station. The method comprises weighting a first data at the access point to transmit the first data using the first and second antennas so that the first mobile station only receives the first data and weighting a second data at the access point to transmit the second data using the first and second antennas so that the second mobile station only receives the second data. A space division multiple access (SDMA) module may cause a transmission protocol to transmit the first data to the first mobile station on the downlink and transmit the second data to the second mobile station in parallel to the transmission of the first data on the downlink. In a telecommunication system, this substantially simultaneous transmission of the first and second data using a similar carrier frequency in a radio frequency communication over a wireless local area network (WLAN) may increase throughput of a downlink, for example, by a factor nominally equal to the number of antennas at an access point.

A tunable filter has a plurality of variable capacitors and a plurality of inductor elements, each being formed on a common substrate, a filter circuit formed by using at least a portion of the plurality of variable capacitors and a portion of the plurality of inductor elements, a monitor circuit formed by using at least a portion of the plurality of variable capacitors and a portion of the plurality of inductor elements, a detecting circuit which detects a prescribed circuit constant of the monitor circuit, a storage which stores information relating to a reference circuit constant of the monitor circuit, and a capacitance control circuit which controls capacitance of the variable capacitors in the monitor circuit and capacitance of the variable capacitors in the filter circuit, based on a result detected by the detecting circuit and information stored in the storage.

An equalizer bank with interference reduction is disclosed. The equalizer bank with interference reduction comprises a front-shelving filter, a plurality of peak filters, a rear-shelving filter and a plurality of compensators. The center frequency and the quality factor of each compensator are designed intentionally to be identical to those of the corresponding peak filter. When a user selects a specific gain level, the corresponding parameters that determine the peak filter and the compensator are retrieved directly and a complex calculation is skipped. Therefore, an audio signal can be equalized more efficiently with lower hardware cost.

An equalization circuit is disclosed that enables high data rate transmission over high loss communications channels. Also disclosed is a set of functional blocks and update criteria that allow for the equalization function to be adapted for a large variety of different communications channels. A fully continuous adaptive equalizer is used in conjunction with a Decision Feedback Equalizer to fully equalize a large number of communications channels.

A training circuit for training a tap coefficient of an adaptive equalizer that performs error calculations in a training process and updating of the tap coefficient in a time area and thereby makes the tap coefficient converge stably in a short time.

A timing recovery unit detects a phase offset and a frequency offset from a head area of reproduction data and initially corrects them. The timing recovery unit stores data in which a head reproduction signal has been made to be discrete by a fixed clock into a buffer. A phase offset detector detects the phase offset from the data head area in parallel with the operation for writing the data into the buffer. At the same time, a frequency offset detector detects the frequency offset from the data head area in parallel with the operation for writing the data into the buffer. A correction value of the detected phase offset and a correction value of the detected frequency offset are initially set into a digital PLL. While the data is read out from the buffer, a frequency lead-in and a phase lead-in are executed in the head area.