Texas Instruments Corporation

Intel Corporation

Libit Signal Processing Inc.

Mordechai Segal

Ofir Shalvi

Zvi Reznic

Naftali Sommer

A method, device and network for compressing cable modem data signals and conserving bandwidth within the network. Cable modems transmit upstream data signals to a fiber node which compresses the data signals and transmits the compressed signals upstream to a headend which decompresses the data signals. The fiber node compression may be by a shaping filter or a fast Fourier transform (FFT) function. The headend decompression may be by an inverse shaping filter or an inverse FFT function.

Signal compression for fiber node

In a cable television (CATV) data communication network, channel throughput and communications robustness are increased in a manner that improves speed of data transmission while maintaining compatibility with existing specifications and equipment. Enhanced throughput can be realized using the return channel of the CATV network. Alternatively, data retransmission and/or diversity techniques can be used to improve throughput.

Method and apparatus for capacity increase and enhanced communications performance in CATV networks

The digital communications receiver receives an analog signal, modulated with digital information. The receiver converts the analogue signal to a digital signal, and demodulates the digital signal to recover the complex valued components of the transmitted digital signal. The complex valued components are low pass filtered and passed through an adaptive pre-equalizer filter, to reduce eigen value spread. The filtered complex valued signal is then subject to a decision feedback equalization, which operates using a series of adaptive filters additionally to remove artifacts of inter-symbol interference. The resulting filtered and equalized complex valued signal is the converted to a digital signal to recover the digital information.

Blind DFE and phase correction

This invention is particularly useful as a system for digital communications over channels that suffer from impulse noise, and particularly over return cable TV channels, downstream cable TV channels, and digital subscriber loops (DSL) channels for high speed communications over twisted pair copper lines.

Method and apparatus for combating impulse noise in digital communications channels

A collision-based multi-access system is described which is capable of recovering collisions by means of jointly detecting the mutually interfering signals, followed by re-transmission of functions of portions of some of the colliding signals. This system reduces the amount of required re-transmission of all of the colliding signals, decreasing the amount of re-transmission in the system, increasing the system throughput. The system is also applicable to non-colliding communications systems to correct interference due to noise.

Multi-access, collision-based communications

An adaptive equalizer capable of tracking rapid channel variations while maintaining high stability and low jitter, and a receiver constructed therefrom. A novel feature of the invention is that is that the equalizer is sectioned, that is constructed from a plurality of feed-forward sections and decision-feedback sections, where these sections comprise a cascade of an adaptive linear filter and an adaptive multiplier. This structure is effective at combating rapid channel variations, which are a result of delay variations of the reflections of the signal, e.g., airplane flutter, without sacrificing the stability and the accuracy of the equalizer even in cases where the equalizer has a large number of taps. The different equalizer sections may have different step size parameters. A controller monitors the channel variations and adjusts the step size parameters of each section accordingly. The controller increases the step sizes of the equalizer sections that are able to compensate for the variation of the channel and does not increase the step sizes of the other sections. This allows the equalizer to combat rapid channel variations without sacrificing stability and accuracy. The present invention is particularly suitable to high speed wireless RF digital communications applications, e.g., to DTV broadcast applications, where the equalizer is characterized by a large number of taps and the signal is subject to rapid time varying reflections due to movement of objects such as cars and airplanes.

High stability fast tracking adaptive equalizer for use with time varying communication channels

An adaptive equalizer capable of tracking rapid channel variations while maintaining high stability and low jitter, and a receiver constructed therefrom. A novel feature of the invention is that is that the equalizer is sectioned, that is constructed from a plurality of feed-forward sections and decision-feedback sections, where these sections comprise a cascade of an adaptive linear filter and an adaptive multiplier. This structure is effective at combating rapid channel variations, which are a result of delay variations of the reflections of the signal, e.g., airplane flutter, without sacrificing the stability and the accuracy of the equalizer even in cases where the equalizer has a large number of taps. The different equalizer sections may have different step size parameters. A controller monitors the channel variations and adjusts the step size parameters of each section accordingly. The controller increases the step size of the equalizer sections that are able to compensate for the variation of the channel and does not increase the step sizes of the other sections. This allows the equalizer to combat rapid channel variations without sacrificing stability and accuracy. The present invention is particularly suitable to high speed wireless RF digital communications applications, e.g., to DTV broadcast applications, where the equalizer is characterized by a large number of taps and the signal is subject to rapid time varying reflections due to movement of objects such as cars and airplanes.

A single transducer digital communication receiver is described which is capable of extracting the data bits of at least one desired signal in the presence of interfering signals of similar type. The present invention also seeks to provide a communication system in which overlapping transmissions are tolerated and allowed. The present invention describes a design for a digital communication system, according to a specific frequency plan, which includes an appropriate digital demodulator that extracts the data bits of the desired signal(s) in the presence of closely spaced signals. The present invention enables reduced channel spacing in digital communication systems and thereby increases the system capacity (i.e. the number of users per bandwidth unit) without incurring any significant loss in system performance (e.g. power margins, BER, and channel availability). It also allows a reduced power margin that is required to maintain a pre-specified performance level without sacrificing system capacity. These two factors, power margin and system capacity, play a central role in the design and construction of state-of-the-art digital communication systems which seek to pack more users on the same frequency band without incurring significant power loss. Thus, the present invention also provides a method and apparatus for upgrading existing systems such as a cellular system for mobile wireless communications that is based on the IS-54 or the GSM standard.

Growing community of inventors

Herzlia, Israel

Mordechai Segal