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Проблематика. Сучасних мережах доступу, що використовують мідний кабель, поширена технологія EFM. Ця технологія у режимі агрегації пар використовує функцію PAF, яка дозволяє нерівномірно розподіляти потік даних між парами у залежності від їх якості. Однак, функція PAF знижує перепускну здатність системи передачі внаслідок службових полів у форматі фрейму, що використовується. Додатково, істотну роль в зниженні перепускної здатності відіграють перехідні завади. Таким чином, дослідження впливу цих двох факторів на перепускну здатність системи SHDSL EFM є актуальною задачею. Мета досліджень. Теоретичні дослідження перепускної здатності для багатопарного з’єднання SHDSL EFM у залежності від кількості пар, що агрегуються, та відстані. Методика реалізації. Аналіз всіх відомих публікацій та стандартів, присвячених технології EFM. Аналіз форматів фреймів протоколів, що використовуються в SHDSL системах з EFM, з метою вирахування співвідношення між корисними та службовими даними. Дослідження впливу перехідних завад на перепускну здатність лінії SHDSL EFM. Результати досліджень. Теоретичні результати відносно перепускної здатності лінії, які можуть бути досягнуті у багатопарному режимі. Висновки. Методика досліджень та одержані результати можуть бути використані для оцінки реальної перепускної здатності ліній SHDSL з EFM у процесі планування та проектування мереж доступу. Background. In modern access networks based on copper cable, EFM is widely used. This technology, using the PAF function, allows you to unevenly distribute data stream between pairs of cables depending on their quality. However, the function of PAF decreases the throughput of the transmission system due to the additional fields in PAF data frame. In addition, there is crosstalk interference between pairs, which also reduces the throughput of the connection. Therefore, research of impact of these two factors on EFM transmission systems throughput is the actual task. Objective. The purpose of the paper is theoretical research of the throughput for multipair SHDSL EFM connection depending on number of aggregated pairs and distance. Methods. Study all known publications and standards concerning EFM technology. Analyzing frames’ format for protocols used for SHDSL systems with EFM to calculate relation between payload and special data. Research of crosstalk interference impaction on SHDSL EFM link throughput. Results. The theoretical results concerning the throughput which can be achieved in multipair mode. Conclusions. Methods of research and their results may be used for estimation of the real throughput of SHDSL EFM links during the planning and project process. Проблематика. В современных сетях доступа, использующих медный кабель, широко используется технология EFM. Эта технология в режиме агрегации пар использует функцию PAF, которая позволяет неравномерно распределять поток данных между парами в зависимости от их качества. Однако, функция PAF снижает пропускную способность системы передачи вследствие служебных полей, содержащихся в формате используемого фрейма. Дополнительно, существенную роль в снижении пропускной способности линии играют переходные помехи. Таким образом, исследование влияния этих двух факторов на пропускную способность системы SHDSL EFM является актуальной задачей. Цель исследований. Теоретические исследования пропускной способности для многопарного соединения SHDSL EFM в зависимости от количества агрегируемых пар и расстояния. Методика реализации. Анализ всех известных публикаций и стандартов, посвященных технологии EFM. Анализ форматов фреймов протоколов, которые используются в SHDSL-системах c EFM, с целью вычисления соотношений между полезными и служебными данными. Исследование влияния переходных помех на пропускную способность линии SHDSL EFM. Результаты исследований. Теоретические результаты относительно пропускной способности линии, которые могут быть достигнуты в многопарном режиме. Выводы. Методика исследований и полученные результаты могут быть использованы для оценки реальной пропускной способности линий SHDSL EFM в процессе планирования и проектирования сетей доступа.

This paper describes the preliminary design and simulation towards a gigabit digital subscriber line modem that provides multi-user interference-free communication in a far-end crosstalk dominated environment by incorporating super orthogonal complete complementary spreading into the existing xDSL modem architecture. This is in contrast to existing vectoring and dynamic spectral management techniques that use joint processing and pre-processing of each user's signal to mitigate far-end crosstalk. A novel code allocation algorithm is introduced to provide all users with equal data rate ratios, even with bad line profiles and high-required data rates. Preliminary simulation results show that 1i¾źGbps aggregate throughput can be obtained for the system over a single pair of 0.5i¾źmm copper wire over a distance from 180 to 150i¾źm, depending on whether ADSL2+ or VDSL2 Profile 30a service bands are avoided, if present. Copyright © 2016 John Wiley & Sons, Ltd.

A new approach for inference based on treating sampled functions is presented. Sampled functions can be transformed into only a few points by wavelet analysis, thus the complete function is represented by these several discrete points. The finiteness of the teaching samples and the resulting sparse rule bases can be handled by fuzzy rule interpolation methods, like KH interpolation. Using SHDSL transmission performance prediction as an example, the simplification of inference problems based on large, sampled vectors by wavelet transformation and fuzzy rule interpolation applied on these vectors are introduced in this paper.

Digital Subscriber Line technology has democratized broadband access, and over the past several decades, telecommunications providers have evolved from providing plain old telephone service (POTS) over a copper loop plant to providing broadband access and high-definition video over hybrid fiber-copper networks. This article focuses on three revolutionary copper technologies in different stages of development that will enable hybrid networks to continue to increase data rates over orders of magnitude for many years to come. The first of the three, vectoring, is a mature technology with massive ongoing rollout that provides end user speeds above 100 Mb/s across typical distances of 500m. The second, G.fast, is the first ultrabroadband technology offering 1 Gb/s speeds, across typical distances of 100m. It has recently gained approval in the standards bodies and is currently undergoing trials both in research labs and in the field by numerous telecom operators. Finally, we discuss Bell Labs' XG-FAST technology, now in proof of concept, which can deliver 10 Gb/s across a 30 meter copper drop cable. XG-FAST paves the way for a homes-passed fiber network, leveraging high speed copper to the premises to increase its homes-connected.

The world is connected by a core network of long-haul optical communication systems that link countries and continents, enabling long-distance phone calls, data-center communications, and the Internet. The demands on information rates have been constantly driven up by applications such as online gaming, high-definition video, and cloud computing. All over the world, end-user connection speeds are being increased by replacing conventional digital subscriber line (DSL) and asymmetric DSL (ADSL) with fiber to the home. Clearly, the capacity of the core network must also increase proportionally.

Проблематика. Технологія EFM, яка поширена на мережах доступу по мідним кабельним лініям, передбачає низку перетворень Ethernet-сигналу для його розподілення та передачі по багатьом парам кабелю з метою підвищення перепускної спроможності з’єднання. Так як пари кабелю можуть мати різні передаточні характеристики, то застосовуються методи нерівномірного розподілу Ethernet-потоку між парами. Це призводить до потреби передавати певні ідентифікатори параметрів передачі, що викликає зниження перепускної спроможності багатопарного з’єднання. Мета досліджень. Аналітичне та практичне дослідження коефіцієнту використання перепускної спроможності багатопарного з’єднання SHDSL з EFM у залежності від виду трафіку, що передається. Методика реалізації. Аналіз всіх відомих публікацій та стандартів, присвячених технології EFM. Аналіз форматів фреймів протоколів, що використовуються в SHDSL системах з EFM, з метою вирахування співвідношення між корисними та службовими даними. Побудова натуральної моделі лінії з SHDSL EFM та практичні дослідження її перепускної спроможності. Результати досліджень. Одержані теоретичні та практичні результати щодо коефіцієнту використання Перепускної спроможності у багатопарному з’єднані SHDSL з EFM. Висновки. Методика досліджень та одержані результати можуть бути використані для оцінки реальної перепускної здатності ліній SHDSL з EFM у процесі укладання угод про якість надання послуг користувачу. Background. The EFM technology is widely used in access network and assumes transformations chain of the Ethernetsignal for its distribution and further transmission through multiple copper lines named pairs. Multipairs mode is used in order to increase the capacity of the link. But copper pairs may have a different parameters and therefore different throughput. In this case non-equal distribution of the Ethernet traffic is used between pairs. But this approach requires transmitting some identificators in order to create original Ethernet frames at the receiving side. These identificators will impact on bandwidth utilization for multipairs connection. Objective. The aim of the paper is theoretical and practical researches of bandwidth utilization for multipairs SHDSL/EFM connection in depending on traffic type. Methods. Study all known publications and standards concerning EFM technology. Analyzing frames format for protocols which are used for SHDSL systems with EFM in order to calculate relation between payload and special data. Installation of the SHDSL link with EFM for practical researches. Results. The theoretical and practical results concerning the bandwidth utilization for multipairs mode are achieved. Conclusions. Methods of researches and their results may be used for estimation of the real throughput of SHDSL/EFM links during service level agreement (SLA) conclusion with customers. Проблематика. Технология EFM, широко используемая в сетях доступа по медным кабельным линиям, предполагает цепочку преобразований Ethernet-сигнала для его распределения и передачи по многим парам кабеля с целью увеличения пропускной способности соединения. Так как пары кабеля могут иметь разные передаточные характеристики, то используются методы неравномерного распределения Ethernet-потока между парами. Это приводит к потребности передавать определенные идентификаторы параметров передачи, что вызывает снижение пропускной способности многопарного соединения. Цель исследований. Аналитические и практические исследования коэффициента использования пропускной способности многопарного соединения SHDSL с EFM в зависимости от вида передаваемого трафика. Методика реализации. Анализ всех известных публикаций и стандартов, посвященных технологии EFM. Анализ форматов фреймов протоколов, которые используются в SHDSL-системах c EFM, с целью вычисления соотношений между полезными и служебными данными. Построение натуральной модели линии с SHDSL EFM и практические исследования ее пропускной способности. Результаты исследований. Получены теоретические и практические результаты относительно коэффициента использования пропускной способности многопарного соединения SHDSL с EFM. Выводы. Методика исследований и полученные результаты могут быть использованы для оценки реальной Пропускной способности линий SHDSL с EFM в процессе заключения договоров о качестве предоставления услуг пользователю.

The continued growth of broadband traffic pushes wireline access network operators to continuously offer better service. Due to the large investments needed to upgrade to an all-fiber network, operators seek to boost performance over their existing copper-based infrastructure, while gradually evolving to a fiber network. As a result, Digital Subscriber Line (DSL) technology, which offers broadband over copper, has been drastically improving. The next generation of DSL will enable the continued cost-effective deployment of fiber in the access network by providing aggregate data rates up to 1 Gb/s. To keep operational costs down, this new DSL generation should enable self-installation. Therefore, it should be robust and adaptive to a wide range of time-varying channels. In this paper, we propose a novel technique based on hierarchical modulation to achieve this robustness. It adapts quickly to noise and interference dynamics in frequency and in time and allows the transmitter to select its preferred configuration without the need for an explicit communication of this configuration to the receiver. We present an overview of hierarchical modulation and how we aim to use these concepts in DSL. We further show with simulations that the receiver is able to blindly track the changes introduced by the transmitter and discuss how this protocol can be easily introduced in state-of-the-art systems.

Three fixed‐line media are of main interest to broadband telecommunications: twisted pair copper wires traditionally used for the telephony system; coaxial copper cables used for inter‐exchange links and cable TV broadcasting; and optical fibre systems used for international and long‐distance telephony and telecommunications backhaul. This chapter presents a chronological account of major milestones in fixed‐line data and digital voice systems. The performance of twisted pair copper wire systems is affected by interference from other telephone connections. This interference is generally known as crosstalk, and exists in two main types: near end crosstalk (NEXT) far end crosstalk (FEXT). While much of additive noise is random and therefore difficult to remove, the crosstalk interference signals are deterministic and therefore it is possible to calculate and remove them from the received signal. Asymmetric digital subscriber line (ADSL)/very‐high‐bit‐rate DSL (VDSL) standards have evolved to deliver higher transmission rates in both upstream and downstream.

In order to meet the ever-increasing bandwidth demand of the users, new "digital subscriber line" (DSL) technologies are being developed. In addition to the traditional differential mode of the telephone line, telecom operators are now looking in to the exploitation of the phantom-mode signal. New transmission line models, using the multiconductor transmission lines theory, were developed to support this extended use. In this paper, it is shown that the phantom mode is an eigenmode of the quad cable system, and hence, according to the theory, there is no crosstalk between this mode and the differential mode.

The paper presents a structure of the hardware-software complex for investigating the wiretap channels of wire segments of local communication systems. In addition, it also presents new experimental data on the estimation of hiding and noise immunity of multimedia digital data transmission systems based on SHDSL technologies.

Digital subscriber lines (xDSL) belong to a family of technologies that provide the ability to transmit digital data over local telephone (copper) infrastructure. As the second most popular broadband platform in the United States, it is estimated that over twenty-five million xDSL lines are in service, capturing nearly 30 percent of the U.S. broadband market. While the service range of xDSL is somewhat limited, often extending to a maximum of 18,000 feet from a central office (CO), available bandwidth also decays as distance increases from the CO. As a result, there are often marked disparities in the quality of xDSL service within market areas. This article proposes a bi-objective location model for maximizing both service coverage and quality of coverage in siting digital subscriber line access multiplexers (DSLAMs). An application of the developed model highlights important implications for telecommunication policy.

Digital subscriber line (DSL) technology allows copper access network operators to offer high-speed links at a reasonable cost. The optimization of the DSL network is a cumbersome task due to the abundance of physical layer configuration parameters and significant differences between lines with respect to interference and attenuation. This paper discusses concepts for dynamic optimization techniques that trade off rate, latency, stability, and power usage in an automated and transparent fashion. The techniques use an initial configuration selection to swiftly obtain a near-optimal configuration and then proceed to acquire additional statistics on noise and interference in order to be able to fine-tune the configuration and gradually increase performance. Optimization results for a DSL network that is carrying video services are presented by aid of the Dynamic Line Management module in the Alcatel-Lucent 5530 Network Analyzer.

An echo-cancelling duplex transmission system is described for the digital subscriber loop which uses a 4-level zero redundancy line code (2B1Q) to give very long reach in the presence of crosstalk. Novel digital signal processing algorithms are used to simplify the analogue line interface circuitry. All the digital signal processing, along with sophisticated maintenance and interfacing circuitry, can be contained on a single LSI circuit. Measured performance results are presented.

This paper provides an overview of digital subscriber line (DSL) technology and describes some of the key technical issues facing BT‘s DSL engineering team. The factors which determine the theoretical information-carrying capacity of BT‘s access network cables are discussed to give the reader a feel for the potential of the existing access network to deliver broadband services. Transmission on this network will be subject to impairments which will limit the achievable capacity, and there is an urgent need to ensure that all DSL systems are spectrally compatible if the capacity of the network is to be fully realised.

This paper investigates the dynamic spectrum management problem for digital subscriber lines. Two new distributed dynamic spectrum management algorithms, which improve upon the existing iterative water-filling algorithm, are proposed. Unlike the iterative water-filling algorithm, in which crosstalk interference is reduced by using adaptive power backoff, the new algorithms employ full power and mitigate crosstalk interference by shifting one user's spectrum away from the other's. Simulation results show that the new algorithms achieve significant performance gains over the iterative water-filling algorithm in mixed central office/remote terminal (CO/RT) deployment asymmetric digital subscriber line (ADSL) and upstream very-high bit-rate digital subscriber line (VDSL).

The capabilities of today's digital subscriber line (DSL) technology are being stretched to the limit. Residential and business subscribers need more and more bandwidth, especially for applications such as interactive personalised TV, high definition TV (HDTV) and video-on-demand, which are growing in popularity. Ultimately the answer may lie in running fibre out to the building, or at least to the kerb, to deliver virtually unlimited bandwidth. In the meantime, most operators must look for new cost-effective ways of exploiting their existing copper infrastructure to deliver the speeds that subscribers need. The very high bitrate DSL 2 standard (VDSL2) offers looks set to fill the gap neatly.

Aiming at the problems in G.SHDSL application and main methods of building G.SHDSL system, this paper describes the characteristics of G.SHDSL access technology, and designs G.SHDSL signal reconfigurable system based on FPGA because of its reprogrammable ability and strong flexibility, which improves flexibility and capacity of reuse of the G.SHDSL reconfigurable system, and greatly reduces the cost of building system.

High-Definition (HD) information is the consumed bandwidth application in Telecommunication network. The quality of service (QoS) on uncompressed High-Definition content transmission with Paralleled Digital Subscriber Lines is needed in smooth information transmission and most tasks on QoS are served by each telecommunication network operator. The Adaptive Rate Control (ARC) is introduced and deployed on High-Definition (HD) contents transmitting on Paralleled Digital Subscriber Lines and compare with classical mechanism to provide more reliability, utilization, and throughput before served in telecommunication network. In this paper we simulated the application of the paralleled Digital Subscriber Lines (DSLs) to deliver the HD information, As results, the performances of communication are evaluated base on throughputs, utilization, and queue performance matrices. Finally results were impressive to support by ARC.

Next-generation communication services will be driven by increasingly rich and distributed subscriber information. Current wireless networks have evolved such that subscriber information now resides in various elements e.g., home location register [HLR], prepay, voice mail, short message, and location determination systems). Convergence with the Internet promises significantly more personal information, such as presence, calendars, address books, buddy lists, pictures, and video. The home subscriber server (HSS) in the IP Multimedia Subsystem (IMS) architecture provides centralized storage for subscriber data. However, some application servers will also have their own subscriber data. As the quantity and variety of applications grow, it will become increasingly useful to provide unified views of subscriber data both within a network and across networks. The Lucent Datagrid™ software provides a telecom-targeted data integration capability, so that applications can use a logical “single-point-of-access” for user profile information inside a service provider's network.

G.fast is the next-generation digital subscriber line (DSL) technology targeting bit-rates of up to 1 Gbps. Very high speed digital subscriber line 2 (VDSL2) is the the latest DSL technology delivering bit-rates of up to 100 Mbps. Replacement of VDSL2 by G.fast modems will be gradual, which implies coexistence of these two systems. G.fast and VDSL2 use different symbol durations, carrier frequency spacings, and sampling rates, which results in inter-carrier and inter-symbol interference (ICSI). We derive an analytical model of ICSI capturing these differences in modulation. Furthermore, through simulations we show that for particular network topologies coexistence of the two systems results in significant bit-rate losses compared to an interference-free scenario.

QoS is an important requirement of the FTTH (Fiber To The Home) subscriber in access network using E-PON (Ethernet Passive Optical Network). In this research, we describe the structure of the access network and propose a bandwidth guarantee scheme for subscriber and service according to the requirements of the subscriber, service and system. This scheme uses two kinds of the classification table, which are called `service classification table` and `subscriber classification table.` Using the classification table, we can identify the flow of the subscriber and service. Also, we compute the number of hash table entry to minimize the loss ratio of flows using the M/G/k/k queueing model. Finally, we apply the DRR scheduling through virtual queueing per subscriber instead of the aggregated class.

There exist several types of distributed subscriber networks using Asymmetric Digital Subscriber Line(ADSL), Very high -bit rate Digital subscriber Line(VDSL), and Data Oner Cable Service Interface Specifications(DOCSIS). The efficient and concentrated network management of those several distributed subscribers networks and resources requires the general management information model of network, which has abstract and conceptual managed objects of the heterogeneous networks and its equipment to manage the integrated subscriber network. This paper presents the general Internet subscribers network modeling framework using RM-ODP to manage that network in the form of integrated hierarchy. This paper adopts the object-oriented development methodology with UML and designs and implements the HFC network of DOCSIS as an example of the subscriber network.

DSL (digital subscriber line) systems are strongly driving the broadband Internet in Asia because they are less costly. The spectrum management of metallic subscriber loop cables is needed so that multiple DSL technologies may be deployed without impaired operation due to crosstalk. Spectrum management standards are described here and Japanese standard is presented in some detail.

Digital subscriber line (DSL) is a service that offers much faster Internet connection than a standard dial up connection. Crosstalk is a major impairment in DSL telecommunication networks. It degrades the upstream and downstream data rates and risks the DSL service providers ability to meet their service level agreement requirements. A novel approach to solve the upstream and downstream data rate problems is presented in this paper. The approach considered is to control the power spectral density and aggregate power level of the DSL access multiplexer.

Today's digital subscriber line deployments are often conservatively engineered to function in a statistically worst case environment. Crosstalk is treated as unknown and uncontrollable random noise, even though it is manmade. Other impairments are often treated by simply adding margin to crosstalk. While this simplistic practice currently suffices, it often provisions unnecessarily low bit rates. This article shows methods that can increase these bit rates and decrease DSL failure rates. Data can be collected about individual telephone lines and cables from loop databases, by automated test equipment, or from DSL modems. This data may then be fed into an advanced DSL management system with a database of DSL loop and noise characteristics, and an analysis engine that tailors DSL deployments to the actual individual line characteristics, to increase provisioned DSL bitrates while simultaneously increasing reliability and lowering maintenance costs. The maximum service can be provisioned with high accuracy, eliminating many service activation failures. Automated maintenance routines can even isolate faults before a customer experiences them. Dynamic spectrum management (DSM) treats crosstalk as the manmade noise it is, and jointly optimizes DSL transmit spectra and signals to minimize crosstalk and maximize received signals, allowing substantially higher DSL speeds than current practice. This opens the door for new services, including symmetric enterprise services and full video service, with minimal physical plant upgrade.

In this paper, we propose the system architecture and implementation of a medium-size Digital Subscriber Line Access Multiplexer (DSLAM). When designing a DSLAM system, the UNI signaling capability, the ATM layer OAM function, the VPI/VCI translation, and the cell multiplexing should be considered. A novel backplane architecture is designed for traffic concentration in the DSLAM, which provides a platform for function integration of other access technologies. On each circuit board, FPGA is designed to provide cell header translation, buffering, and routing functions, thus fast prototyping can be achieved. An experimental Asymmetric Digital Subscriber Line-based access network is setup to perform the integration test and some results are shown in this paper.

Different digital subscriber lines transmitting on loops in the same telephone cable generate crosstalk into each other. Two different DSLs are spectrally compatible if they can both use the same cable with low probability of significant degradation from crosstalk. Spectrum management is the process of ensuring spectral compatibility while optimizing the loop plant. Spectrum management requires knowledge of cable plant characteristics extending into higher frequency spectra (/spl sim/1 MHz), the different DSL types, and how to compute the impact of crosstalk. Also, definitions of the level of crosstalk from one DSL type that significantly degrades another DSL type is needed, which can only reach broad acceptance through industry-wide agreements. In the United States, DSL Access Standards Committee T1E1.4 has created a technical definition of spectral compatibility, the Spectrum Management Standard T1.417-2001. The details of DSL spectral compatibility and compliance with the standard are presented, as well as a history of the standard and some possibilities for the future.

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.

Increasing deployment of digital subscriber line (DSL) technology operating in the long wave, medium wave and sometimes short wave frequency ranges, has raised the question of how such systems interact with rival radio frequency sources and equipment. Two of the major standards bodies in the field, ITU and ETSI, imposed by the standardization of such promising technologies like ADSL, SHDSL and VDSL, have begun to elaborate performance tests for radio frequency interference (RFI) scenarios for inclusion into their standards documents. Existing out-door loops of the copper telephone network can have large dimensions, are often unshielded and sometimes not even twisted, thus, they can act like antennas for both RFI egress and ingress. The RFI egress issue requires basic knowledge of the relationship between a given current distribution I(l) on a twisted pair communication cable and the electromagnetic fleld E, H generated by that current distribution at a given distance d. This problem is reciprocal to the RFI ingress issue, which requires knowledge of the relationship between a disturbing high-frequency electric field E in the surroundings of a twisted pair cable, and the terminal voltage of that cable across a load impedance. This contribution provides the theoretical background to the field theoretical problem and supplies simple yet accurate approximation formulae for the prediction of RFI egress and RFI ingress.

This paper presents a study of the effects of bridged taps on very high-speed digital subscriber line (VDSL) transmission systems. It is shown that the short bridged taps, which affect VDSL signals, are much more damaging than the longer bridged taps, which affect other xDSL signals, such as high-rate digital subscriber line (HDSL) and asymmetric digital subscriber line (ADSL). Specifically, short bridged taps introduce a lot of linear distortion in the loop's transfer function. In addition, they also tend to introduce more overall propagation loss than longer bridged taps. The peak-power-to-average-power ratio (PAR) of the signal increases for the loop with short bridged taps, and thus more A/D bits are needed in the implementation of a digital VDSL transceiver as compared to the loop with long bridged taps. The performance of various equalizer structures is discussed in the presence of a severe channel distortion caused by the bridged tap.

The ongoing developments in the field of high-speed data transmission over twisted-pair cables (DSL-Digital Subscriber Line) leads to methods that can exploit the transmission media with increased efficiency. MIMO (Multiple-Input Multiple-Output) transmission, i.e., the coordinated use of many pairs within a bundle, is such an emering DSL technology. A further goal is to maintain a certain transmission quality in the presence of non-DSL noise. For example, cancellation techniques to combat narrowband radio interference, which is generated by radio amateur transmitters and may be picked up by the wire close to the subscriber or by the in-hourse wiring, become important.

Different technologies for subscriber access are put side by side. Starting from the various transmission media characteristics of all systems, the well-known twisted pair lines with their corresponding digital subscriber line services are evaluated against wireless local loops, communications over ubiquitous power lines, high-bandwidth cable modems, and mobile radio. Each technology has its advantages and disadvantages. The different technologies will find their fields of applications. Most networks will have to provide a mixture of solutions for individual subscribers and customer segments to meet their boundary conditions. As a result, the future of subscriber access is a hybrid solution.

DSL (Digital Subscriber Line) is the technology that enables high-speed data transfer and rapid access to the Internet via telephone lines, with a secure connection straight into the high-speed network. DSL has raised its importance in the data communication industry. This article identifies the importance of DSL in Internet age, illustrates DSL's analysis and development frameworks, and delineates future development of the DSL technology.

This article describes the near-far problem in the upstream direction of VDSL, which results when the lengths of VDSL loops in a binder vary significantly. Methods of upstream power backoff to mitigate the near-far problem are then described. Simulation results are presented, and the performances of the methods are discussed.

This paper provides an overview of the evolution of digital transmission in the copper access network from voice-band modems to Digital Subscriber Line (DSL) technologies. The various types of DSL technology are described. Copyright © 2001 John Wiley & Sons, Ltd.

In Digital Subscriber Line (DSL) systems, the noise perceived by a DSL line fluctuates when DSL lines sharing the same bundle are switched on/off. The concept of Seamless Rate Adaptation (SRA) was introduced to seamlessly adapt the data rate of a connection to the changing channel while in operation without any service interruption. Interleavers in communication paths impose a constraint on the amount of data rate that can be changed by an SRA procedure. In the case of large changes in the channel, multiple consecutive SRA procedures have to be executed. Moreover, to keep an equal signal-to-noise-ratio margin over all tones, it is very likely that the bit loadings of all tones have to be modified in each SRA procedure. Hence, the state of the art SRA is too slow and provides means of adaptation only to slowly changing channels and will not prevent reinitializations under certain conditions such as large rapid changes in noise. In this paper, we optimize the rate adaptation procedure in terms of adaptation time and average bit error rate. We present an algorithm that solves the stated problem optimally and a sub-optimal low complex algorithm that can be used in practice by modems with limited computing power. Both algorithms lead to significant gains in terms of adaptation time and average bit error rate.

We study the problem of designing an efficient resource allocation scheme in the application of providing integrated multimedia services over a digital subscriber line. For a predefined quality of service (QoS) requirement and data throughput, we show that the transmitted power consumption can be reduced by applying the parallel transmission framework previously proposed. Data streams are recognized as a set of layers with different data rate and bit error rate requirements. The characteristics of the telephone channel can be utilized to provide unequal error protection naturally and thus efficiently. Simulation results provide comparison of the proposed parallel transmission framework to the existing schemes designed for general data, and demonstrate significant performance improvement, such as a 0.5-2 dB power gain.

Broadcast digital subscriber lines (BDSL) can provide a cost-effective architecture to deploy digital broadcast services in the near future by utilizing the in-place unshielded twisted-pairs. In the BDSL system, all broadcasting channels can share the same transmitter to reduce the cost. Because all twisted-pairs transmit the same BDSL signal in the downstream direction, both near- and far-end crosstalk can be eliminated. While HDSL and Asymmetrical Digital Subscriber Lines (ADSL) signals are carried at low frequency band, BDSL signals can be transmitted at higher frequency band. A discrete multitone based modulation method is used to increase the efficiency of BDSL. Compared to scheme employing identical modulation for all subchannels, the channel though-put of low frequency subchannels can be increased because of their smaller channel losses and the high frequency subchannels can be utilized even if their signal-to-noise ratios are small. The combination of HDSL, ADSL, and BDSL can provide subscribers many digital one-to-one and broadcasting broadband services.

VDSL services are overviewed with an emphasis on the basic architecture, applications, and data rates, as well as the technological challenges of design. Discussions of the telephone line environment, radio-band interference ingress and egress, impulse noise, and symmetric and asymmetric multiplexing are included, along with brief descriptions of two popular implementations.

This letter presents the method useful in subscriber line qualification for asymmetric digital subscriber line service. It is based on the results of the line frequency response measurement in the voice band by V.34 modems. The response is related to the line attenuation at 300 kHz. The measurement results are also presented.

Digital subscriber lines seemed to have reached the last stage of its development. Further development of the fixed access network is a matter of optical fibers. However, the upcoming ITU-T recommendation with working title g.fast gives to metallic line another chance. The very high speed digital subscriber line (VDSL2) is standardized for the frequency bands to 12, 18 and 30 MHz. In next stage digital subscriber lines with gigabit rates will use in the frequency bands to 100, 200 and possibly up to 300 MHz. This paper describes model of the local telecommunication cable and achievable bit rates for gigabit DSL under different conditions, which will be offered to subscribers. The resulting bit rates are calculated depending on the length of the line with a copper core diameter of 0.4 mm.

Japan has caught up in the competitive high-speed Internet technologies thanks to the efforts of billionaire entrepreneur Masayoshi Son and his Softbank Corp, by deploying ADSL (asymmetric digital subscriber line) technology in its fixed-line telephone networks. Though Japan still lags far behind some other countries in broadband penetration, it now tops the world in providing the cheapest DSL services. Through the years, Son has made advancement in the technology introducing Internet protocol-based telephone service (IP phone), fixed-line services, broadband and mobile services, but because of competition in the technology market his telecom strategy is still to be erect, at a maximum speed to a little lower price compared to the competition.

Dual-ended line testing (DELT) is a common capability in most current modems and can be used for digital subscriber line (DSL) qualification and monitoring purposes. In spite of that, this feature remains largely unexplored in the literature. This paper proposes a new method based on wavelets and DELT measurements for estimating the total length of the line under test and identification of bridged-taps, two important line parameters that affect the maximum bit rate reached by a DSL line. The proposed method was tested with measurements employing real twisted-pair cables and obtained reasonably accurate results for the analyzed cases.

Digital Subscriber Line (DSL) combines the advantages of providing fast means of internet access with the usage of an existent infrastructure known as the plain old telephone service (POTS). Transmissions that use higher frequencies are more subject to attenuation and to crosstalk. Crosstalk is the undesired radiation of energy among wires. It is more likely to occur among/between similar frequencies and results in a received wave form that differs from the original wave form that was sent. In this article we analysis the crosstalk in various DSL systems by evaluating power spectral density function, i.e. functional principles of DSL and impairment caused by crosstalk. It is performed by the analysis of the results obtained from the Matlab program.

This paper describes the error performance of the ISDN basic access digital subscriber line (DSL), the high bit rate digital subscriber line (HDSL), and the asymmetric digital subscriber line (ADSL) in the presence of impulse noise. Results are found by using data from the 1986 NYNEX impulse noise survey in simulations. It is shown that a simple uncoded ADSL would have an order of magnitude more errored seconds than DSL and HDSL. >

The asymmetric digital subscriber line (ADSL) takes advantage of the existing twisted-pair copper loop that currently provides customer access to the telephone network. An ADSL modem is placed at each end of the loop to create a high speed access link above the existing telephone service. Since ADSL makes use of the existing copper telephone line, its application in the telephone network can conceivably be nearly as ubiquitous as the public telephone network itself. With ADSL, it is possible to connect small numbers of customers to broadband services in areas where full upgrade to hybrid fiber coaxial or fiber facilities is not economical in the near term. ADSL systems offer a means to introduce broadband services using the embedded base of metallic loops in areas where optic fiber-based, hybrid fiber-coaxial radio systems or other broadband transport systems may not be scheduled for deployment in time to meet business needs and customer demand. The article concentrates on ADSL systems capable of at least a nominal 6 Mb/s payload transport toward the customer, in addition to associated upstream channels and symmetrical "telephony" services via nonloaded loops that comply with carrier serving area design guidelines. >

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. >