High-bit-rate digital subscriber line

About: High-bit-rate digital subscriber line is a research topic. Over the lifetime, 516 publications have been published within this topic receiving 8537 citations. The topic is also known as: HDSL & high-bit-rate DSL.

Mechanism for transporting digital pots signals within framing structure of high bit rate digital local subscriber loop signals

Abstract: A local subscriber loop architecture embeds digitized POTS signals into the framing format of high bit rate digital subscriber loop signals being transported over a local loop for serving both subscriber digital terminal equipment and a POTS telephone. The remote transceiver unit is line-powered from the central office unit, facilitating installation of a reliable (office-powered) POTS interface (containing codec and subscriber line interface circuitry providing BORSHT functions) into the remote unit. The data rate of the added digital POTS signal is relatively small with respect to the data rate of the DSL channels, so that there is only slight increase in the overall data rate. As a consequence, adding the digital POTS signal has negligible impact on transport range. Moreover, the high-complexity analog filters used in an FDM architecture to separate the POTS signal from the DSL signal are not required

Low-cost phaselocked local oscillator for millimeter wave transceivers

Abstract: An LMDS system including a base station, subscriber units and subscriber modems. Transmission frequencies between the base station and the subscriber units are specified by the Federal Frequency Commission. Signal frequencies between the subscriber units and the subscriber modems are specified by industry standards. The subscriber units couple and frequency translate modulated signals between the base stations and the subscriber modems. The frequency translation requires an intermediate transmit oscillator and a local oscillator. The intermediate transmit oscillator, however, can also be used to frequency translate a local oscillator signal within each subscriber unit down to a lower frequency which allows a low cost phase locked loop chip to be used to phase lock the local oscillator in each subscriber unit to a reference source. A pilot tone can be coupled onto modulated signals transmitted from the base station to the subscriber units. The pilot tone can be summed into the local oscillator phase locked loop within each subscriber unit to reduce the effects of signal transmission on the phase noise of the modulated signals. Furthermore, dual pilot tones can be coupled onto the modulated signal transmitted from the base station to the subscriber units. The dual pilot tones can be used to generate a reference signal within each subscriber unit.

Combined coding and precoding for PAM and QAM HDSL systems

Abstract: A system is described for high-speed digital subscriber line (HDSL) applications. It uses trellis coding combined with Tomlinson (1971) precoding. Theoretical performance results are provided for uncoded pulse amplitude modulation (PAM) and quadrature amplitude modulation (QAM) assuming an ideal decision feedback equalizer (DFE) that includes an optimum feedforward filter. The similarities and differences in behavior are explained. It is shown that combined coding and Tomlinson precoding can achieve the equalization performance of the DFE and full coding gain of the trellis code. Simulation results are given to show that about 3.4 dB additional margin is obtained by using a four-dimensional eight-state trellis code. The receiver complexity is increased by it is quite manageable. >

Source adaptive digital subscriber line and method

Abstract: A communication system includes plurality of subscribers (22) having a telephone set (34) and different types of home modems (36) coupled using twisted pairs to a local server (24) that includes plurality of down stream repeaters (44), a central office (30) coupled to a local server using twisted pair subscriber lines (29, 31). The central office includes a telephone switch (54) that provides telephone service to the subscribers and a concentrator (56) that connects a plurality of upstream repeaters (46) with a number of office modems (58) that provide data service to the subscriber. A communication system uses CAP or DMT line signals with time division. The line signal transmits with different time framing. Every subscriber line can work in one of three operation modes: Asymmetrical mode, Half-Asymmetrical mode, Symmetrical mode. An office modem changes the operation mode of subscribers line and downstream/upstream bit rate depending on the type of an information source and the type of the subscriber home modem that is connected to the office modem in the current transmit cycle.

Method of and apparatus for performing line characterization in a non-idle mode in a subscriber line communication system

Abstract: A digital subscriber line communication system does not require the use of a plain old telephone service (POTS) splitter in the resident's home. Digital signal processing techniques are utilized to adapt to varying subscriber line conditions due to POTS telephone equipment. The digital signal processing techniques eliminate the need for a splitter by reducing susceptibility to distortion due to varying subscriber line characteristics. The digital subscriber line modem characterizes the subscriber line under a variety of conditions when the modem is in a non-idle mode. The digital subscriber line modem includes a control circuit which performs rapid retrain operation utilizing line characterization information.