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Showing papers on "High-bit-rate digital subscriber line published in 1991"


Journal ArticleDOI
TL;DR: A discrete multitone (DMT) transceiver design for high bit rate digital subscriber line (HDSL) access is presented and analyzed and is an excellent candidate for HDSL implementation.
Abstract: A discrete multitone (DMT) transceiver design for high bit rate digital subscriber line (HDSL) access is presented and analyzed. The DMT transmitter and receiver structure and algorithms are detailed, and the computational requirements of DMT for HDSL are estimated. At a sampling rate of 640 kHz, using an appropriate combination of a short finite-impulse-response (FIR) equalizer and a length-512 DMT system, 1.6 Mb/s data transmission is possible within the carrier serving area (CSA) at an error rate of 10/sup -7/ on a single twisted pair. A significant performance margin can be achieved when two coordinated twisted pairs are used to deliver a total data rate of 1.6 Mb/s. In terms of a performance-per-computation figure of merit, the DMT system is an excellent candidate for HDSL implementation. >

549 citations


Journal ArticleDOI
J.-J. Werner1
TL;DR: A tutorial on the physical environment in which high bit rate digital subscriber line (HDSL) transceivers will have to evolve and succeed is presented, with special attention given to the most damaging impairments that are encountered in subscriber lines.
Abstract: The author presents a tutorial on the physical environment in which high bit rate digital subscriber line (HDSL) transceivers will have to evolve and succeed. Special attention is given to the most damaging impairments that are encountered in subscriber lines, such as propagation loss, linear distortion, crosstalk, bridged taps, and impulse noise. Somewhat less important impairments, such as change of gauge, temperature variation, and thermal noise, are also briefly described. The author concludes with a discussion of the capacity of a twisted-pair channel in a crosstalk-dominated environment. >

207 citations


Journal ArticleDOI
TL;DR: The authors study the performance of a multichannel modulation method for asymmetric digital subscriber lines (ADSLs) and very high-speed digital subscriber Lines (VHDSLs) to find out whether data rates in excess of 100 Mb/s can be transmitted reliably.
Abstract: The authors study the performance of a multichannel modulation method for asymmetric digital subscriber lines (ADSLs) and very high-speed digital subscriber lines (VHDSLs). In the ADSL case, over all unloaded North American subscriber lines in the test set, a unidirectional 1.536 Mb/s data rate service from the end office to the customer premises is possible on a single twisted pair at an error rate of 10/sup -7/ with at least a 6 dB margin used coded multichannel modulation with sufficient transmit power. In the VHDSL case, data rates in excess of 100 Mb/s can be transmitted reliably, at an error rate of 10/sup -7/, using uncoded multichannel modulation on a single twisted pair over a distance >

204 citations


Journal ArticleDOI
TL;DR: 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.
Abstract: 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. >

84 citations


Journal ArticleDOI
TL;DR: 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, and the advantages of coordination in an optimal way are quantified.
Abstract: 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. >

73 citations


Journal ArticleDOI
TL;DR: The authors explore the issues of complexity, precision, and dynamic range and practical implementation issues such as nonlinearities in high bit rate digital subscriber line (HDSL) echo cancelers using computer simulations and verifying simulation results with laboratory prototyping.
Abstract: The authors explore the issues of complexity, precision, and dynamic range and practical implementation issues such as nonlinearities in high bit rate digital subscriber line (HDSL) echo cancelers. The approach taken is to study these issues analytically using computer simulations, and then to verify simulation results with laboratory prototyping. One of the objectives was to determine whether HDSL echo cancellation will be practical and cost effective within the next several years, consistent with the desire to develop and deploy a repeaterless T1 capability by 1993. Thus, attention is given to practical design issues. >

49 citations


Proceedings ArticleDOI
02 Dec 1991
TL;DR: A brief overview of asymmetrical digital subscriber line (ADSL) technology is provided, describing important technology considerations, including noise impairments, spectral compatibility, and data-over-voice design challenges.
Abstract: A brief overview of asymmetrical digital subscriber line (ADSL) technology is provided, describing important technology considerations, including noise impairments, spectral compatibility, and data-over-voice design challenges. Potential service applications utilizing the unique advantages of the ADSL are discussed, including advanced videotext, compressed video, and education applications. Network architecture and interface issues are addressed. Physical configurations at the customer premises and associated interfaces are discussed, along with a high-level view of possible network switching and control architectures. >

49 citations


Journal ArticleDOI
TL;DR: The digital subscriber line (DSL), which applies adaptive filtering to yield significant performance and administrative advantages, is introduced and 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.
Abstract: 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. >

44 citations


Journal ArticleDOI
TL;DR: 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.
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. >

41 citations


Journal ArticleDOI
TL;DR: A 60-MHz 64-tap adaptive finite-impulse-response (FIR) filter chip was fabricated in 1.2- mu m CMOS to implement either an echo canceler or a decision feedback equalizer for 2B1Q high bit rate digital subscriber line (HDSL) transceivers.
Abstract: A 60-MHz 64-tap adaptive finite-impulse-response (FIR) filter chip was fabricated in 1.2- mu m CMOS. It can implement either an echo canceler or a decision feedback equalizer for 2B1Q high bit rate digital subscriber line (HDSL) transceivers. The 4.3*4.3 mm/sup 2/, 30000 transistor chip is a completely self-contained adaptive filter which incorporates the least mean square (LMS) algorithm for coefficient updating. The device can be cascaded to implement very long filter lengths, which are often required in high bit rate transceivers. At a 60-MHz clock rate, the echo canceler/decision feedback equalizer chip can accommodate symbol rates in excess of 800 kbaud. >

27 citations


Journal ArticleDOI
TL;DR: The recent growth in the use of digital radio is reviewed, and the technology used to implement low-power digital radio in the local exchange loop plant is discussed and the integration of digitalRadio subscriber loops with network intelligence is explored.
Abstract: The recent growth in the use of digital radio is reviewed. The technology used to implement low-power digital radio in the local exchange loop plant is discussed. The integration of digital radio subscriber loops withnetwork intelligence is explored. The relationship between low-power digital radio loops and broadband fiber loops is briefly examined, and standards and frequency allocation activities are summarized. >

Journal ArticleDOI
TL;DR: It is argued that the high bit rate digital subscriber line (HDSL), permitting low-cost 1.5 Mb/s copper access, will ease the transition to fiber access by accelerating the use of higher speed services.
Abstract: It is argued that the high bit rate digital subscriber line (HDSL), permitting low-cost 1.5 Mb/s copper access, will ease the transition to fiber access by accelerating the use of higher speed services. Copper will dominate over fiber customer access for at least the next ten years. During this period, the success of high-speed switched services will depend on the connectivity provided by both fiber and copper access. HDSL will initially be used to serve private-line DS 1, ISDN primary rate access, and digital loop carrier feeders. Later, the HDSL will be applied to switched services such as metropolitan area networks (MANs) and circuit switched DS1s. >

Journal ArticleDOI
TL;DR: It was found that the near-end crosstalk (NEXT) loss of Taiwan's subscriber loops is about 10 dB worse than that of US local loops, and a corresponding new foam-skin PIC cable is proposed to reduce the NEXT loss.
Abstract: About 2800 lines out of a total of 8,500,000 subscriber lines in Taiwan have been sampled and characterized. Various kinds of physical compositions and transmission characteristics were investigated and measured. It was found that the near-end crosstalk (NEXT) loss of Taiwan's subscriber loops is about 10 dB worse than that of US local loops. A corresponding new foam-skin PIC cable is proposed to reduce the NEXT loss. The new type of cable will be used to replace the paper cable and old foam-skin PIC cable step-by-step. Based on the measured data, the feasibility of HDSL (high bit rate digital subscriber line) service in Taiwan is studied. To improve the HDSL service distance via the existing subscriber lines, several cable models are discussed and suggested. >

Proceedings ArticleDOI
02 Dec 1991
TL;DR: The results of an analysis of the spectral compatibility of asymmetrical digital subscriber lines (ADSLs) with other digital transport technologies that might coexist in the same binder group are presented and it is concluded that a 16-point QAM ADSL system is a potentially viable transport scheme.
Abstract: The results of an analysis of the spectral compatibility of asymmetrical digital subscriber lines (ADSLs) with other digital transport technologies that might coexist in the same binder group are presented. The near-end crosstalk and far-end crosstalk effects of digital subscriber line (DSL)-based transport schemes, such as basic-rate and high-bit-rate DSL (HDSL) and T1 lines, are investigated. Two categories of loop environment design rules are considered. The ADSL transceiver is assumed to be based on either a 16- or 64-point quadrature amplitude modulation (QAM) symbol constellation for a data rate of 1.6 Mb/s. The guardband of the transmit spectrum is assumed to fall within the range of 20 to 110 kHz. The receiver is assumed to be an ideal decision feedback equalizer with a quarter-baud spaced fractionally spaced feedforward equalizer. It is concluded that a 16-point QAM ADSL system, with the carrier frequency at 250 kHz, is a potentially viable transport scheme. >

Journal ArticleDOI
H. Bauch1
01 Aug 1991-IEEE Lts
TL;DR: The subscription access capacity corresponding to the first level of the synchronous digital hierarchy (SDH), which has been agreed upon as an international standard for broadband ISDN, is discussed and suggested transmission systems or systems already implemented are examined.
Abstract: Subscriber access capacity corresponding to the first level of the synchronous digital hierarchy (SDH), which has been agreed upon as an international standard for broadband ISDN, is discussed. The subscriber access reference configuration defined by the International Consultative Committee for Telephone and Telegraph (CCITT) is described, as is the structure of the transmission network. Suggested transmission systems or systems already implemented are then examined. The discussion covers asynchronous transfer mode, multiplexing and framing, trunk line systems, subscriber line systems, optical transmission, and TV distribution. >

01 Jan 1991
TL;DR: An analytical comparison of various recursive and nonrecursive subtractive equalization techniques which may be used to remove intersymbol interference is presented.
Abstract: The experience gained with pulse amplitude mod- ulation (PAM) for basic rate ISDN transmission makes this baseband coding scheme a strong contender for early HDSL transceiver implementations. After near-end crosstalk (NEXT), the principal problem with PAM is intersymbol interference (ISI). This paper presents an analytical comparison of various recursive and nonrecursive subtractive equalization techniques which may be used to remove ISI. Properties of subscriber loop responses which may be used in the design of simple and effi- cient equalizers are also explored. For early HDSL transceiver implementations with limited processing power, the best over- all equalization strategy may well be a conventional FIR-filter- based decision feedback equalizer with a distributed partial lin- ear equalizer allowing the best compromise between filter length, residual ISI, NEXT enhancement, and implementation complexity.

Proceedings ArticleDOI
02 Dec 1991
TL;DR: The authors study the performance of a multichannel modulation technique for the contemplated data service known as asymmetric digital subscriber lines (ADSLs) and found that the proposed ADSL service can coexist with the previously existing baseband service on the same twisted pair.
Abstract: The authors study the performance of a multichannel modulation technique for the contemplated data service known as asymmetric digital subscriber lines (ADSLs). It was found that over all unloaded North American subscriber lines in the test set, a unidirectional 1.536-Mb/s data rate service from the end-office to the customer premises can be easily achieved on a single twisted pair at an error rate of 10/sup -7/. The dominant line impairments studied include far-end crosstalk from basic-rate access integrated services digital network (ISDN), spill-over basic rate access ISDN signal, and additive white Gaussian noise (AWGN). It was found that the proposed ADSL service can coexist with the previously existing baseband service on the same twisted pair. >

Proceedings ArticleDOI
12 May 1991
TL;DR: In this paper, a 60MHz 64-tap adaptive FIR filter chip has been fabricated in 1.2- mu m CMOS which can implement either an echo canceller or decision-feedback equalizer for 2B1Q high bit-rate digital subscriber line (HDSL) transceivers.
Abstract: A 60-MHz 64-tap adaptive FIR filter chip has been fabricated in 1.2- mu m CMOS which can implement either an echo canceller or decision-feedback equalizer for 2B1Q high bit-rate digital subscriber line (HDSL) transceivers. The 4.3-mm*4.3-mm, 30000-transistor chip is a complete self-contained adaptive filter which incorporates the LMS algorithm for coefficient updating. The device can be cascaded to implement very long filter lengths which are often required in high-bit-rate transceivers. At a 60-MHz clock rate the echo canceller/decision feedback equalizer chip can accommodate symbol rates in excess of 800 kbaud. >

Journal ArticleDOI
TL;DR: A simulation study evaluating the performance of trellis-coded modulation with combined code/ISI sequence estimation for high bit rate transmission on subscriber loops shows that the receiver contains a fractionally spaced forward filter of a decision feedback equalizer as a front end to suppress phase synchronized crosstalk very effectively.
Abstract: The authors present a simulation study evaluating the performance of trellis-coded modulation with combined code/ISI sequence estimation for high bit rate (800 kb/s) transmission on subscriber loops. The receiver contains a fractionally spaced forward filter of a decision feedback equalizer (DFE) as a front end. This is shown to suppress phase synchronized crosstalk very effectively. The performance is further enhanced by the use of trellis code with a large number of states received with an M algorithm sequence-estimating receiver with a smaller number of states. >

Proceedings ArticleDOI
02 Dec 1991
TL;DR: A new adaptive digital filter architecture for parallel output and update computations and its application to a high-speed digital subscriber line (HDSL) equalizer prototype are described.
Abstract: A new adaptive digital filter architecture for parallel output and update computations and its application to a high-speed digital subscriber line (HDSL) equalizer prototype are described. This architecture uses an output/update multiply-accumulate (MAC) pair to compute a finite impulse response (FIR) filter output in parallel with the updating of the filter taps via the leaky LMS algorithm. The MAC pair architecture provides a more efficient structure for adaptive filtering than would the use of its two processors in a normal serial LMS implementation. A second level of parallelism allows the use of multiple MAC pairs to implement long adaptive FIR filters. The viability of this architecture is demonstrated through experimental results obtained for a 800-kb/s HDSL equalizer research prototype. >

Patent
Lechner Robert Dipl Ing1
18 Jul 1991
TL;DR: In this paper, a programmable filter (Z, B) which connects the four-wire transmit branch to the fourwire receive branch in a chip (SICOFI) connected together with the interface circuit (SLIC1) and also ensures that the two-wire impedance is provided with a complex value is provided.
Abstract: The subscriber line is coupled capacitively (C, K). In the subscriber line interface circuit (SLIC) of the line circuit, a positive feedback path leading from the four-wire transmit output to the four-wire receive input and containing filter elements (F) is formed, by means of which a basic setting of the two-wire impedance is effected which is higher than the impedance of the feed bridge, this basic setting is complemented to form the required exact value with the aid of a programmable filter (Z, B) which connects the four-wire transmit branch to the four-wire receive branch in a chip (SICOFI) connected together with the interface circuit (SLIC1) and also ensures that the two-wire impedance is provided with a complex value.


01 Jan 1991
TL;DR: A 60-MHz 64-tap adaptive FIR filter chip has been fabricated in 1.2 pm CMOS which can implement either an echo canceller or decision feedback equalizer for 2B1Q high bit rate digital subscriber line (HDSL) transceivers.
Abstract: A 60-MHz 64-tap adaptive FIR filter chip has been fabricated in 1.2 pm CMOS which can implement either an echo canceller or decision feedback equalizer for 2B1Q high bit rate digital subscriber line (HDSL) transceivers. The 4.3 x 4.3 mm2, 30 000 transistor chip is a completely self-contained adaptive filter which incorporates the LMS algorithm for coefficient up- dating. The device can be cascaded to implement very long fil- ter lengths, which are often required in high bit rate trans- ceivers. At a 60 MHz clock rate, the echo canceller/decision feedback equalizer chip can accommodate symbol rates in ex- cess of 800 kbaud.

Proceedings ArticleDOI
29 May 1991
TL;DR: To improve multiparty telephone services, a four-channel digital subscriber loop carrier system is proposed, with Adaptive differential pulse code modulation bipolar 6-zero substitution line coding, and time-compression multiplexing of speech packets under microprocessor control.
Abstract: To improve multiparty telephone services, a four-channel digital subscriber loop carrier system is proposed. Adaptive differential pulse code modulation bipolar 6-zero substitution line coding, and time-compression multiplexing of speech packets under microprocessor control are novel features of the proposed system. It is believed the design for a digital subscriber loop carrier system outlined will meet the requirements for providing private line service on multiparty lines. The cost of such a system is expected to be less than that required for reinforcement with metallic cables, while providing a comparable level of service. >

Proceedings ArticleDOI
11 Jun 1991
TL;DR: The author presents some of the simulation results when the transmission rate is enhanced to the primary rate, indicating the degradation of the 16 and 64 point quadrature amplitude modulation (QAM) constellations as the echo cancellation is reduced from 60 dB to 40 dB.
Abstract: The author presents some of the simulation results when the transmission rate is enhanced to the primary rate. A series of results indicating the degradation of the 16 and 64 point quadrature amplitude modulation (QAM) constellations as the echo cancellation is reduced from 60 dB to 40 dB is given. The improvements as the loop configuration is altered to conform to the shorter carrier serving area (CSA) loops in the US are summarized. The results presented are indicative of typical CSA loop performance in US and Canada, and those of Australia, where fewer loop discontinuities and bridged taps are encountered. In Europe, the loops are also short with fewer discontinuities and few, if any, bridged taps. >