Design Philosophy and Hardware Implementation for Digital Subscriber Loops

This paper presents various requirements and configurations in the information network system (INS) NTT's version of the integrated services digital network (ISDN)- such as field trials, and technologies and equipment design of the digital subscriber loop using balanced wire pairs. The main aspects characterizing digital subscriber loops, are a customer access structure, a digital transmission system on existing subscriber loops, and customer interface. A configuration of two-wire digital subscriber loops with two customer access channels, which is adopted in the field trials, will be described. The time-shared two-wire digital transmission and power feeding methods on subscriber loops are discussed. The common mode rejection ratio (CMRR) is discussed in detail, since CMRR is one of the main factors which affects the transmission ability of balanced wire pairs. A proposed self-clocked four-wire customer interface utilizes time division multiplexing technique. The digital subscriber loop operates on a call-by-call basis for link establishment to avoid excessive power dissipations as well as to avoid impairments caused by crosstalk from other lines within a cable. Its design objectives and implementation are also discussed.     

Video communications and services in the copper loop

There are several technologies available for providing access using the embedded copper loop plant. However, none of these technologies can provide a high-bit-rate digital transport capability (1.544 Mb/s) over the existing loop plant. The authors describe continuing advances in both VLSI implementation and signal processing algorithms that are making it possible to provide the high-bit-rate digital subscriber line (HDSL) for a repeaterless T1 capability within carrier serving areas (CSAs); asymmetric digital subscriber lines (ADSL) for a 1.5-Mb/s transport capability over the nonloaded copper loop plant; and the next-generation ADSL-II for a 3 to 4 Mb/s transmission rate over CSA ranges. It is argued that, coupled with advances in video compression techniques and recent standards activities in CCITT, these bit rates will allow local exchange carriers (LECs) to provide video communication and services using highly compressed digital video by allowing the LECs to use their existing embedded loop plant to enter the video market and establish a base of customers     

Video on phone lines: technology and applications

This paper reviews the telephone loop plant characteristics, current DSL (digital subscriber line) technologies, recent efforts in video coding standards, and the interrelationship between DSL technologies and visual communications over subscriber lines. In overview of the loop plant characteristics we examine its physical makeup and transmission properties, where for the latter we discuss frequency and time responses of wire-pair lines and the impairments of echo, crosstalk, impulse noise, and radio frequency interference. We trace the historical development of various DSL technologies and comment on possible future evolution. Transmission technologies used in the ISDN basic-access DSL, the high bit-rate DSL, and the asymmetric DSL are portrayed. And the issue of spectrum compatibility among different transmission systems is explained. Several important video coding standards are briefly described, including ITU-T's H.261 and ISO's JPEG and MPEG series, which are either completed or emerging. The synergistic relationship between these standards and the DSL technologies is elucidated. As a result, DSL technologies provide the potential of delivering certain broadband services well in advance of direct fiber access for telephone subscribers     

Communications [technology analysis and forecast]

Several spectacular changes in the communications scene over the past few years will have a still stronger impact in 1997. Most obviously, the World Wide Web has been expanding. Showing a nice mixture of optimism and concern, the telecommunications establishment is mulling how best to exploit the Web commercially while deploying such packet-switched networks as the integrated services digital network (ISDN) and such subscriber access technologies as asymmetric digital subscriber line (ADSL) to keep the telecom infrastructure from being overwhelmed. Amid the competitive pressures generated by deregulation, telecom companies have more incentive than ever to squeeze as much performance as possible out of their existing infrastructure. Hence the attraction of local-access technologies like ADSL for boosting the capacity of installed copper subscriber loops, and long-haul technologies like wavelength division multiplexing (WDM) for boosting the capacity of installed optical fiber. Wireless local-area networks (LANs) are benefiting from spread-spectrum technology, just as cellular telephony is. Also planned is provision of satellite-based, global mobile voice and datacom services to pocketsized, hand-held devices     

EV-DO Rev A快速寻呼接入研究

DO Rev A在前向链路采用多种包传输格式、子同步控制信道（SSCC）、动态寻呼周期等关键技术实现了前向快速寻呼;在反向链路采用高速接入信道、短接入包前导等关键技术实现了反向快速接入,从而改善了对时延敏感业务的支持。DO Rev A通过DOS协议实现了在控制信道和接入信道传送用户数据,从而支持PTT业务。本文介绍了DO Rev A上述关键技术,并分析它们对用户接入和寻呼的性能影响。     

Fiber Optic Transport Systems for Present and Future Local Networks

This paper describes fiber optic transport systems for present and future local networks. The present most important fiber optic system in a local network emerges as a broad-band video distribution system, because large-scale system introduction might be attained only for distributed video services. The system architecture and system parameters are presented. As for future integrated services, a highspeed digital transmission system and local network architecture are very important. The network architecture should be constructed to meet the demands for increased flexibility, capacity, reliability, and economy. Considering expected future demands and technologies, a new fiber optic local network architecture is proposed. The architecture's main features are the use of transmission processing nodes and a multilane-ring structure in subscriber transfer networks in combination with star-shaped subscriber access lines.     

基于HFC的宽带接入网关键技术

随着通信的发展和“信息高速公路”概念的提出,网络运营商越来越倾向集视频、话音、数据于一体的宽带综合业务,如今世界各国相继开发了基于现有铜缆的接入网技术高比特率数字用户环路(HDSL)和不对称数字用户环路(ADSL)、基于光缆接入技术的光接入网(OAN)、混合光纤同轴电缆(HFC)网络以及无线接入技术等宽带用户接入网技术,文章详细分析了HFC宽带接入网的网络结构及其关键技术。     

The fiber-optic subscriber network in Japan

Nippon Telegraph and Telephone Corporation (NTT) has two primary aims regarding the installation of optical fiber cables for subscriber networks as the access network: to provide high-speed broadband services, and to provide narrowband services through optical fiber cables with subscriber-line multiplex technology. Thus, NTT is preparing an infrastructure to support the forthcoming B-ISDN subscriber networks. NTT has been developing technologies for implementing the full-scale construction of fiber-optic subscriber networks. The present article describes the deployment methodology for these networks, their current status, and plans for their future development     

Evolutionary architecture for an all-services ATM access network

This paper presents a flexible concept for a broadband subscriber access network which minimizes investment costs by predominantly using the existing network infrastructure. The target network may consist of either a coaxial tree-and-branch structure or symmetrical copper pairs to the subscriber, and is connected to the central head station with the aid of optical feeder lines which can be implemented or enhanced by a passive optical network (PON). In the event of an increase in bit rate requirements, the coaxial network can be expanded by dividing it into smaller, optically fed subnetworks or by supplementing it with optical overlay systems. Flexibility, expandability and low costs are achieved through the standard ATM format implemented for the signals of all interactive services down to the network termination units on the subscriber side. Those signals are transmitted in the coaxial network in frequency bands above the CATV band in accordance with a multiple of the CATV channel width to ensure that the modulation and demodulation is implemented in a cost-efficient manner while providing ‘bit rate on demand’ for a suitably high number of subscribers. Separation of the network termination unit from the customer premises equipment enables a flexible, cost-efficient subscriber configuration to be selected, existing domestic wiring to be used and several completely different subscriber terminals to be simultaneously connected.     

High-speed copper access: a tutorial overview

Telecommunication companies (telcos) are beginning to exploit further their existing access networks by using new technologies capable of delivering data at up to 30 Mbit/s over unshielded twisted copper wire pairs. This tutorial paper provides a high-level overview of the key issues related to these digital subscriber line (DSL) technologies, including the environment in which they must operate, line codes, standards, and the current state of the market     

通信用户接入设施的发展前途

概括说明数字用户线（xDSL)、无源光纤网络（PON）和光纤到路边（FTTC）、有线电视（CATV）和光纤同轴电缆混合（HFC）网、无线本地环路（WLL）和固定宽带无线接入（FBWA）4种用户接入方式。     

A consideration of ADSL service under NTT's network

NTT is aggressively promoting the deployment of fiber to the home in Japan in order to deploy broadband services. The demand for high-speed Internet access has been increasing rapidly. Until migration from metallic cables to optical fiber is complete, NTT needs to develop technology that can provide high-speed access over the existing metallic cable. We believe that high-speed subscriber transmission systems operating on the existing phone lines, in addition to fiber optic lines, will accelerate the deployment of broadband services. This article discusses the technical issues of deploying ADSL in Japan     

Wireless Internet access for mobile subscribers based on theGPRS/UMTS network

With the advent of IP technologies and the tremendous growth in data traffic, the wireless industry is evolving its core networks toward IP technology. Enabling wireless Internet access is one of the upcoming challenges for mobile radio network operators. The General Packet Radio Service is the packet-switched extension of GSM and was developed to facilitate access to IP-based services better than existing circuit-switched services provided by GSM. We illustrate how a visited mobile subscriber on a GPRS/UMTS network can access his/her home network via the gateway GPRS support node (GGSN). We also propose some implementation ideas on wireless Internet access for a remote mobile subscriber based on a GPRS/UMTS network     

Ethernet PONs: a survey of dynamic bandwidth allocation (DBA) algorithms

Optical networks are poised to dominate the access network space in coming years. Ethernet passive optical networks, which leverage the ubiquity of Ethernet at subscriber locations, seem destined for success in the optical access network. In this article we first provide a brief introduction to Ethernet passive optical networks, followed by a discussion of the problem of dynamic bandwidth allocation. We then introduce a framework for classifying dynamic bandwidth allocation schemes and provide a comprehensive survey of the dynamic bandwidth allocation methods proposed to date. We conclude with a side by side comparison of the schemes based on their most prominent characteristics, and outline future developments of dynamic bandwidth allocation schemes.     

Optical broadband access using ATM on a passive optical network

Within the framework of the ‘FITL (fibre in the loop) evolution’, Siemens is developing a prototype based on a passive optical network (PON) for the economic provision of BISDN services in the subscriber access area. It provides 32 subscribers with BISDN access up to a maximum user data rate of 45 Mbit/s per subscriber. The information is transferred via ATM cells and PON-specific overhead in both directions on the PON at a data rate of 155.52 Mbit/s. For transmission to the subscribers, the time division multiplex procedure (TDM) is used. For transmission in the opposite direction, a highly flexible time division multiple access procedure (TDMA) controls the access to PON for the subscriber-side line terminations. In order to keep the transmission system inexpensive emphasis is placed on a digital calibration of the fibre loop delay, a burst transmitter at the subscriber side without amplitude recovery and a burst receiver at the exchange side with purely digital bit synchronization. However, to achieve these features a small part of data rate must be used as a PON specific overhead.     

Toward management systems for emerging hybrid fiber-coax accessnetworks

Advances in networking and hardware are motivating the development of high bandwidth local access networks that connect subscriber communities to the Information Superhighway. Hybrid fiber-coaxial (HFC) technology is emerging as one of the few economical viable technologies for designing new local access networks. These HFC local access networks are expected to support a variety of services in different spheres in an integrated manner, by drawing upon diverse technologies from the cable, computer, and telecommunications industries: the tree-and-branch network topology is typical of the cable network; intelligence in the end devices is a characteristic of the computer industry; and addressability, global interconnectivity, and quality of service (QoS) are characteristic of the telecommunications industry. It is this combination of diverse services and technologies that poses fundamental challenges in architecting a management system for HFC networks. The design of a management framework for HFC access networks is discussed     

Novel algorithm for time division multiple access in broadband ISDN passive optical networks

For shared access to a broadband communication network using the asynchronous transfer mode (ATM) a passive optical network (PON) has previously been proposed. A novel algorithm to evaluate the time division multiple access (TDMA) protocol which controls the traffic from the various subscribers towards the shared access equipment (upstream direction) is proposed. It uses counters to estimate the moment of a data packet arrival at the subscriber side. By this ‘look-ahead’ technique no extra upstream channels are needed to initiate the polling by the subscriber. The algorithm guarantees fair access for all subscribers and minimizes the necessary overhead. Both the maximum access delay and overhead may be readily calculated, and the obtained results were supported by numerical simulation. Applicability in the standard broadband network environment has been proved by hardware design simulation.     

A Field Trial of Fiber Optic Subscriber Loop Systems Utilizing Wavelength-Division Multiplexers

Future subscriber loops will provide various services including broad-band video. Fiber optic technology is the key for introducing these services. The Electrical Communication Laboratories (ECL) of Nippon Telegraph and Telephone Public Corporation (NTT) have been promoting research and development on basic technology of fiber optic subscriber loops, and studying the ways to use fiber optic subscriber loops for new services. As one of the programs, a field trial of fiber optic subscriber loops was planned and conducted in the Yokosuka area from April 1980 until May 1981. This paper first describes fiber optic transmission technologies for subscriber loops. Then, the system configuration and experimental results of the Yokosuka field trial are presented.     

Broadband access using subcarrier multiplexing and asymmetric digital subscriber lines

A broadband access system using subcarrier multiplexing on optical fibre and asymmetric digital subscriber lines (ADSL) or very high‐speed digital subscriber lines (VDSL) on unshielded twisted‐pair is proposed to provide broadband access. In this hybrid‐fibre/twisted‐pair (HFTP) system, the digital multiplexing/demultiplexing process is moved back to the central office by using subcarrier multiplexing for fibre transmission. Instead of installing in remote node, ADSL/VDSL transceivers are installed at the central office to greatly reduce the remote node complexity. The local node simply down‐converts the subcarrier multiplexed ADSL/VDSL signal to the baseband, suitable to send directly into the twisted‐pair. The reduction of complexity could result in a lower initial installation cost, especially for a low service penetration rate. Copyright © 2000 John Wiley & Sons, Ltd.     

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