A new interpolation theorem with application to pulse transmission

An interpolation theorem is determined for the case when there are a finite number of arbitrarily placed sampling instants and the interpolation function is the output of a known filter. They are also the interpolation functions with the specified properties that have minimum energy. The theorem is used to determine the input to a communications channel given a finite number of samples of its output. This provides a generalization of matched filters and a perspective on the benefits of fractionally spaced equalization. The theorem is also used to construct masks of a family of pulses that are specified by the range of pulse voltages at a finite number of sampling instants. The theory determines how the pulse masks thus constructed is transformed when the pulse family is transmitted through a filter such as a length of transmission line     

Digital subscriber line technology facilitates a gracefultransition from copper to fiber

The loop environment and the techniques that historically have been used for providing transmission treatment are reviewed. The digital subscriber line (DSL), which applies adaptive filtering to yield significant performance and administrative advantages, is introduced. How this technology will evolve to complement the emerging fiber-based network, providing timely, ubiquitous wire pair transmission capabilities at basic rate, primary rate, and above is examined     

Broad Signal Constraints for the Management of the Spectrum in Telephone Loop Cables: Identical Constraint on All Pairs

A previous paper showed that constraining the total energy transmitted on all pairs in a cable during any time interval of a specified duration limits the maximum instantaneous near-end crosstalk voltage on any pair. This paper determines a constraint on the energy that is the same for each pair and that guarantees the same limit on near-end crosstalk. While the new constraint permits less variation of transmitted power among the pairs, it permits greater average power per pair. Thus, the constraint developed herein would be particularly useful when a cable is used principally for one type of capability, e.g., ISDN basic access.     

Broad Signal Constraints for Management of the Spectrum in Telephone Loop Cables

It is shown that the maximum instantaneous near-end crosstalk interference voltage on a cable pair can be constrained by restricting the energy transmitted in any time interval of a duration determined by the cable properties. The maximum interference is proportional to the sum of the energies in the impulse responses of the equalized near-end crosstalk paths to the disturbed pair.     

Coordinated transmission for two-pair digital subscriber lines

The performance of two-pair dual-duplex systems is substantially improved if the transmission on one pair is coordinated with that on the other, so that the transmitted signals are two-dimensional vector pulses. The advantages of coordination of transmission in an optimal way are quantified. Signal processing gains of 1.8 dB can be achieved in this way by averaging the SNRs on the two pairs constituting the high rate digital subscriber line (HDSL) and by canceling the near-end crosstalk (NEXT) between them. Exploitation of pair-to-pair correlation of NEXT voltages on the constituent pairs provides an additional source of processing gain. Under reasonable assumptions concerning the distribution of NEXT coupling coefficients between cable pairs, there is a better than 50% chance that the signal processing gain achieved by exploiting pair-to-pair NEXT correlation will be greater than 1.5 dB. Coordinated transmission requires the adaptation of four flat gain amplifiers in transmitters to achieve its optimum system configuration     

Detecting moving objects using the rigidity constraint

A method for visually detecting moving objects from a moving camera using point correspondences in two orthographic views is described. The method applies a simple structure-from-motion analysis and then identifies those points inconsistent with the interpretation of the scene as a single rigid object. It is effective even when the actual motion parameters cannot be recovered. Demonstrations are presented using point correspondences automatically determined from real image sequences     

Smad2 transduces common signals from receptor serine-threonine and tyrosine kinases

SMAD proteins mediate signals from receptor serine-threonine kinases (RSKs) of the TGF-beta superfamily. We demonstrate here that HGF and EGF, which signal through RTKs, can also mediate SMAD-dependent reporter gene activation and induce rapid phosphorylation of endogenous SMAD proteins by kinase(s) downstream of MEK1. HGF induces phosphorylation and nuclear translocation of epitope-tagged Smad2 and a mutation that blocks TGF-beta signaling also blocks HGF signal transduction. Smad2 may thus act as a common positive effector of TGF-beta- and HGF-induced signals and serve to modulate cross talk between RTK and RSK signaling pathways.     

Tyrosyl phosphorylation and growth factor receptor association of the human corkscrew homologue, SH-PTP2

The pivotal role of tyrosine kinases in signal transduction is well established, but the role of tyrosine phosphatases remains obscure. The discovery of src homology 2 domain-containing protein tyrosine phosphatases suggested roles for these molecules in growth factor signaling pathways, since src homology 2 domains direct association of downstream signaling molecules with activated growth factor receptors and other phosphotyrosyl proteins. We have found that SH-PTP2, a putative homologue of Drosophila corkscrew, associates in vivo with the ligand-activated epidermal growth factor and platelet-derived growth factor receptors. The N-terminal src homology 2 domain of SH-PTP2 directly associates with activated receptors. SH-PTP2 itself is a phosphoprotein, and it becomes tyrosyl phosphorylated upon growth factor activation. These findings suggest several possible models for SH-PTP2 signaling.     

High bit rate digital subscriber lines: a review of HDSL progress

The author gives an overview of progress made in the evolution of technology to provide DS1 rate telephone access in a restricted segment of the loop plant without intermediate repeaters, loop conditioning, or pair selection in assignment. This technology is called the high bit rate digital subscriber line (HDSL). Discussed are background information on electronics in the loop plant and characterization of the tranmission environment in the relevant frequency band. The progress of HDSL study project of the American National Standards Institute (ANSI) is outlined. Analytical and theoretical studies to determine the limits on the transmission capabilities of the loop plant, motivated by the need to determine the feasibility limits of HDSLs, are reviewed. Also discussed is progress in technical work on suitable transmission formats. The possibility of an asymmetrical digital subscriber line (ADSL), transmitting at the DS1 rate from the central office to a remote distribution point, through the entire nonloaded loop plant is discussed     

Loop Transmission Aspects of ISDN Basic Access

The status of the formulation of standards for loop transmission to provide Basic Access in the North American loop plant is reviewed. The impact of loop plant bridged taps on performance is discussed, the reasons for preferring echo canceller technology over time compression multiplexing are reviewed, and issues involved in the specification of echo canceller requirements are discussed. This includes line code selection and receiver design, including linear and decision feedback equalizer design. Some of the possible methods of timing recovery are reviewed, and future directions for the evolution of Basic loop access are considered.