Digital subscriber lines: network considerations for ISDN BasicAccess standard

The authors review digital subscriber line (DSL) technology features and the key technical factors that have driven the development of the technology. The application of DSL technology to network access and the relevant standards activities that provide a framework for developing DSL performance requirements are considered. The important aspects of the physical and operational characteristics of the US loop plant that influenced critical technology choices are reviewed with an emphasis on the physical characteristics of the embedded loop plant and considerations pertinent to the economic provisioning and operations for ISDN (integrated services digital network) Basic Access. A review of the essentials of DSL technology for ISDN Basic Access is presented     

在"九七工程"上开通ISDN和ADSL业务

介绍了十堰电信分公司在"九七工程"上开通ISDN和ADSL业务的设计思路,并针对不同业务类型说明了业务处理流程.     

Multimedia services over digital subscriber lines

We study the problem of reliable and yet efficient multimedia communications over asymmetric digital subscriber line (ADSL) through joint consideration of compression/coding and channel transmission techniques. The transmission of digital multimedia data requires the existing systems to be augmented with functions that can handle not only ordinary (nonmultimedia) data. In addition, the high volume of multimedia data can be handled efficiently only if all available system resources are carefully optimized. We consider the special characteristics of ADSL channels to formulate optimization criteria. We present a system where the encoder consists of a layer coder that divides and compresses the source data into coded layers of multimedia data with different performance and quality-of-service requirements. The encoded bit streams are then transmitted over a noisy channel, where channel noise may distort the data. The decoder removes all the coding and compression applied in the encoder to obtain as close as possible the original data. It is conceivable that for such a system the loss of information occurs not only during the source compression but also in the channel transmission. The source coding scheme and bit stream arrangement have a direct impact on the channel distortion. Therefore, the joint consideration of source/channel coding design is ideal to reduce the overall information loss     

Line codes for digital subscriber lines [ISDN basic access]

The attributes of the several line codes considered for a North American standard for ISDN basic access are compared. Impairments that affect line code performance are examined, and their performance characteristics are discussed. An intuitive explanation of why the code performs as it does is attempted in each case. Some variations of the codes that were considered and that were intended to improve their performance are also discussed. The codes considered are bi-phase, modified duobinary, alternate mark inversion, 3B2T, 2B1Q and 4B3T     

ADSL and high bandwidth over copper lines

ADSL is a new telecommunications phenomenon. Because it works over the existing copper telephone lines, it will likely become the dominant form of broadband data transmission for at least the next 20 years. © 1997 John Wiley & Sons, Ltd.     

Lightwave subscriber loop systems toward broad-band ISDN

The state-of-the-art of lightwave subscriber loop systems is reviewed. An approach is described for deriving an architecture for subscriber loop systems that can accommodate technological trends in broadband ISDN such as asynchronous transfer mode (ATM) and synchronous digital networks. Key component technology is discussed, namely, optical fibers and cables, splicing and connectors, and switching     

An adaptive line equalizer LSI for ISDN subscriber loops

An adaptive line equalizer LSI applied to a time-compression multiplexing transmission system, which transfers 320-kb/s AMI coded signals to provide the 144-kb/s (2B+D) transmission capacity recommended by CCITT, is described. The √f equalizer can adaptively equalize up to 53-dB cable loss at Nyquist frequency (160 kHz), using switched-capacitor filter (SCF) technology. The equalizer transfer function is optimized in the time domain. The coarse automatic gain control circuit is composed of a fourth-order SCF. A high-speed operational amplifier, with wide output voltage swing and excellent stability against load capacitance variation, has been developed. The equalizer enables 5.5-km transmission over 0.5-mm diameter cable with two bridged taps because of its wide gain dynamic range and the use of decision feedback. A small chip size, 6.2×6.6 mm, and low power consumption, 80 mW (from a 5-V single supply), are achieved in 3-μm CMOS technology     

High-bit-rate digital subscriber lines

High-bit-rate digital subscriber line (HDSL) technology provides a simple, cost-effective solution for the rapid provision of a new digital telecommunication services direct to a customer's premises over existing twisted copper pair telephone lines. It makes full use of the existing network infrastructure and hence removes the need for the costly replacement of copper twisted pairs by alternative transmission media     

Broadcast digital subscriber lines

The adoption of asymmetrical digital subscriber lines (ADSL) technology in conjunction with the broadcast digital subscriber lines (BDSL) proposed in this paper could provide a cost effective solution for the introduction of digital video services in the near term. BDSL provides the same digital broadcast video programs to all subscribers through existing twisted pair telephone loops. In this paper, the basics of telephone loop-based digital subscriber lines are first discussed. Then the potential of BDSL is explored in the twisted pair loop plant near end crosstalk (NEXT), far end crosstalk (FEXT), and white noise environment. The capability of BDSL is examined with different serving areas and transmit power levels. The possibility of using orthogonal quadrature amplitude modulation (QAM) to implement a zero guard-band BDSL system is studied. Computer BDSL performance simulations are then presented. The combination of high-bit-rate digital subscriber lines (HDSL), ADSL, and BDSL can provide telephone subscribers many digital broadband services     

Voice over ADSL技术

在宽带接入技术飞速发展的今天,ADSL等接入方式已经成为用户接入Internet的重要途径。除了宽带上网这一应用外,我们也意识到,通过ADSL承载语音也具有广阔的市场前景,与此同时,Voice over ADSL也将是传统电信网络向下一代网络(NGN)过渡的途径之一。在本文中,根据Voice承载于ADSL中的不同层,Voice over ADSL可以有不同的解决方案,分别是Voice over ATM的BLES解决方案,Voice over IP的MBN解决方案基于IDM的信道化语音(Channelized Voice)解决方案。     

Digital subscriber line (HDSL and ADSL) capacity of the outsideloop plant

The fundamental limits of the outside loop plant to carry high-speed digital (bi-directional HDSL and ADSL) data are reported. The paper focuses on the copper wire pairs, drop lengths, and interconnects that convey data over the “last mile” to almost all businesses and residences in the US. The two major customers, businesses and households, are classified, characterized, and categorized by the distance to the central office or the remote terminal. Their spectral capabilities are computed and their ultimate digital capabilities are reported. The crosstalk limitations inherent in the plant are also computed and verified against the loss of signal due the distance and spectral constraints. The signal to noise ratio can thus be estimated to ascertain the transmission quality through the plant. Accordingly, the paper reports on losses, bandwidths, and bit rates in the first half, and discusses the major bottlenecks in the second half     

Channelized voice over digital subscriber line

This article presents a promising voice over digital subscriber line (VoDSL) solution: an alternative method that uses physical layer transportation to provide channelized VoDSL (CVoDSL). This article also presents the advantages that the CVoDSL provides to the customers in terms of high-quality services and lower cost, and service providers in terms of market growth and success. It also offers a set of requirements, architectural design, and implementation scenarios that provide end-to-end solutions for CVoDSL.     

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     

Comparison of precoding schemes for digital subscriber lines

Precoding at the transmitter side is a practicable method for transmission over intersymbol interference channels. In contrast to decision-feedback equalization no error propagation occurs and coded modulation can be applied as for the intersymbol interference free channel. Tomlinson-Harashima (1971, 1972) precoding and flexible precoding are analyzed and compared. The dualities and differences are discussed. The focus of interest is the application of precoding to fast digital transmission over twisted pair lines, such as high-rate or asymmetric digital subscriber lines. It turns out that flexibility-which is not necessary in the specific application, digital subscriber lines-of flexible precoding is paid with a performance loss compared to Tomlinson-Harashima precoding     

不对称数字用户线上的多播视频传送

集中讨论了基于不对称数字用户线上多播视频业务的特性、体系结构及开发多播业务的几种关键技术，对目前用于传送的几种接入体系结构进行了分析比较。     

Distributed multiuser power control for digital subscriber lines

This paper considers the multiuser power control problem in a frequency-selective interference channel. The interference channel is modeled as a noncooperative game, and the existence and uniqueness of a Nash equilibrium are established for a two-player version of the game. An iterative water-filling algorithm is proposed to efficiently reach the Nash equilibrium. The iterative water-filling algorithm can be implemented distributively without the need for centralized control. It implicitly takes into account the loop transfer functions and cross couplings, and it reaches a competitively optimal power allocation by offering an opportunity for loops to negotiate the best use of power and frequency with each other. When applied to the upstream power backoff problem in very-high bit-rate digital subscriber lines and the downstream spectral compatibility problem in asymmetric digital subscriber lines, the new power control algorithm is found to give a significant performance improvement when compared with existing methods     

Voice over ADSL技术剖析

1 Voice over ADSL技术概述 ADSL作为被广泛应用的宽带接人手段之一,其应用范围拓展得愈来愈宽,Voice over ADSL即是其中一项备受瞩目的应用。Voice over ADSL具有极强的市场前景,其主要原因在于：虽然3G、NGN等新型网络不断涌现,为人们描绘出一张色     

Optimal multiuser spectrum balancing for digital subscriber lines

Crosstalk is a major issue in modern digital subscriber line (DSL) systems such as ADSL and VDSL. Static spectrum management, which is the traditional way of ensuring spectral compatibility, employs spectral masks that can be overly conservative and lead to poor performance. This paper presents a centralized algorithm for optimal spectrum balancing in DSL. The algorithm uses the dual decomposition method to optimize spectra in an efficient and computationally tractable way. The algorithm shows significant performance gains over existing dynamics spectrum management (DSM) techniques, e.g., in one of the cases studied, the proposed centralized algorithm leads to a factor-of-four increase in data rate over the distributed DSM algorithm iterative waterfilling.