Wi-lan Inc.

General Instrument Corporation

Other

Ensemble Communications, Inc.

Harington Valve, LLC

Stephen C Pollmann

Frederick Wales Price

Timothy Leo Gallagher

Yair Bourlas

Sheldon I Gilbert

Eli Arviv

John Wiss

Blaine Clifford Readler

Pranesh Sinha

Sharon Akler

Jacques Behar

Kenneth L Stanwood

David Gazelle

Timothy L Gallagher

Paul Moroney

Edward A Krause

Paul Shen

Woo H Paik

Serdar Yilmaz

Moti Kabelly

Yossi Keren

Frederick W Price

Ell Arviv

Apparatus, system and method for synchronizing one or more clocks across a communication link. A slave clock may be synchronized to a master clock by means of a synchronization signal sent from the master to the slave clock side of the link. The synchronization signal may be an expected signal pattern sent at intervals expected by the slave side. The slave clock may correlate received signals with a representation of the expected synchronization signal to produce a correlation sample sequence at a first sample rate which is related as n times the slave clock rate. The synchronization signal receipt time indicated by the correlation sample sequence may be refined by interpolating the correlation sample sequence around a best correlation sample to locate a best interpolation at an interpolation resolution smaller than the sample resolution. The best interpolation may in turn be further refined by estimating between interpolator outputs adjacent to the best interpolation output. The synchronization signal receipt time thus determined is compared to the expected time based upon the slave clock, which is adjusted until the times match. After initialization, all slave clock errors are preferably accumulated to prevent long-term slip between the slave and master clocks. Formerly independent master and slave clocks synchronized across the communication link constitute a noncommon clock which may be compared on each side of the link to secondary independent clocks, and the secondary independent clocks may then be separately synchronized by adjusting one to have the same difference from its local noncommon clock as the secondary clock on the other side of the link has from its local noncommon clock.

Synchronizing clocks across a communication link

A slave clock may be synchronized to a master clock by means of a synchronization signal sent from the master to the slave clock side of the link. The synchronization signal may be an expected signal pattern sent at intervals expected by the slave side. The slave clock may correlate received signals with a representation of the expected synchronization signal to produce a correlation sample sequence at a first sample rate which is related as n times the slave clock rate. A best interpolation may in turn be further refined by estimating between interpolator outputs adjacent to the best interpolation output. The synchronization signal receipt time thus determined is compared to the expected time based upon the slave clock, which is adjusted until the times match. The best interpolation may in turn be further refined by estimating between interpolator outputs adjacent to the best interpolation output.

A system that provides a wireless broadband connection between base stations and customer sites is described. The system includes indoor units within the base stations and customer sites and communicate across cables to outdoor units. The indoor units link to routers, switches and other devices and services. The outdoor units transmit and receive wireless data and send it to the indoor units. The indoor units control the timing of detector measurements in the outdoor unit by transmitting a regular, repeating control message at a predetermined time. Once the outdoor unit receives the control message, it samples its detectors and reports measurements back to the indoor unit.

System and method for timing detector measurements in a wireless communication system

A system and method for enhancing the performance of an equalizer in a modem. Multiple techniques are disclosed which improve the modem performance. A first technique uses stored parameters for each burst from each remote site to demodulate a received data stream. A second technique compensates for the gain droop caused by storing parameters across each burst. A third technique minimizes errors caused by adapting the equalizer coefficients for each data burst by analyzing the SN ratio and error rate of the received burst. A fourth technique improves the convergence of the equalizer by using a two-part preamble, whereby both parts are transmitted using different modulation techniques. A fifth technique is provided which performs a soft reset of the modem without performing a complete reset of the modem. A sixth technique determines a modem adaptation factor based on the expected modulation type of an incoming burst transmission. A seventh technique calculates a phase correction value for the stored tap values and applies the value to the incoming signal.

Equalizer performance enhancements for broadband wireless applications

One or more clocks are synchronized across a communication link using a synchronization signal sent from a master to a slave clock. The synchronization signal may be an expected signal pattern sent at intervals expected by the slave. The slave clock may correlate received signals with a representation of the expected synchronization signal to produce a correlation sample sequence at a first sample rate. The synchronization signal receipt time is compared to the expected time and the slave clock is adjusted until the times match. Master and slave clocks synchronized across the communication link constitute a noncommon clock which may be compared on each side of the link to secondary independent clocks. The secondary independent clocks may be separately synchronized by adjusting one to have the same difference from its local noncommon clock as the secondary clock on the other side of the link has from its local noncommon clock.

The system and method optimizes a SNR calculation for a signal received during a downlink burst even in the absence of a node's preferred modulation. This system and method are used in communication systems that include a multi-modulation modem. An adaptation factor is selected whereby its use during portions of the downlink burst, which were not modulated using the preferred modulation, provides the SNR. The selected adaptation factor is used by an equalizer to perform channel inversion to the signal. The system and method can be used in, for example, an FDD or TDD communication system. Such communication systems can be, for example, symmetric, asymmetric, and/or adaptive in their operation.

System and method for measuring signal to noise values in an adaptive wireless communication system

A memory control and management system efficiently multiplexes access to a dynamic random access memory (DRAM) among several client processes in an MPEG or similar digital television delivery system or the like. These processes can include, for example, an on-screen display (OSD) graphics processor, a microprocessor interface, graphics accelerator functions, and audio and data processors. An arbiter receives packetized data from an MPEG transport layer for distribution to an associated DRAM. The arbiter sequentially time-multiplexes access to the DRAM by the client processes according to priority criteria, including the bandwidth requirements of the client processes, and whether a client process is requesting access. Access is granted for a predetermined period as long as the client is requesting access. Access can be terminated early if the client no longer requests access, or if a new row in the DRAM must be addressed, and the re-addressing period will consume the remainder of the available data transfer cycles in the access period. The invention is particularly applicable to a digital video decoder where an on-screen display graphics processor consumes a large portion of the DRAM interface bandwidth.

DRAM arbiter for video decoder

Apparatus is provided for decoding variable length code words to recover transform coefficients, such as DCT transform coefficients provided by a high definition television encoder. A first category of the code words has a length of no more than n bits. A second category has a length of greater than n bits. A feedback ROM is used to decode the code words. Code words from the first category are processed by directly addressing a lookup table in the ROM. Code words from the second category are processed using multiple passes through the ROM, wherein a portion of the data output during a prior pass is fed back to address the memory during a subsequent pass.

Variable length code word decoder for use in digital communication

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Santee, CA, United States of America

Stephen C Pollmann