Showing papers on "High-bit-rate digital subscriber line published in 1993"

Asymmetrical digital subscriber line control system

Abstract: PURPOSE: To increase the number of stored subscriber's private devices and reduce the cost without extending the facilities of the asymmetrical digital subscriber line control system which transmitts a sound signal in two ways and sends an image signal and a control signal unilaterally in the opposite directions. CONSTITUTION: The sound signal from a subscriber private device 1 to a telephone set 4 is sent in both the ways, the image signal to a monitor television set 5 is sent in one direction from the side of an exchange 2, and the control signal from an input operation part 6 is sent in one direction to the side of the exchange 2. An unused image signal line from the subscriber private device 1 to the exchange 2 on a feeder lie FDL between the exchange 2 and a remote station 3 is assigned as the control signal line from the subscriber private device 1 to the exchange 2 to assign two lines corresponding to the subscriber private device 1. Further, the time slot replacement part TSI of the remote station 3 assigns a pair of time slots of the image signal VDS and control signal CNTS to the image requesting subscriber private device 1. COPYRIGHT: (C)1995,JPO

A Multicarrier El‐HDSL Transceiver System with Coded Modulation

Abstract: In this paper, we present a trellis-coded multicarrier transceiver system, known as Discrete Multitone modulation, for the application of transmitting digital data at the El rate of 2.048 Mbit/s over existing copper telephone lines. The service of El-HDSL (El-rate High-speed Digital Subscriber Lines) is currently being studied by ETSI for future deployment in Europe. Because of severe crosstalk and additive white Gaussian noise (AWGN) encountered in El-HDSL, the application of a powerful trellis code is highly desirable to ensure reliable system performance, with a required bit-error-rate (BER) of no more than 10−7, at the desired El data rate. Detailed descriptions of the DMT transmitter and receiver structures are given, and projected performance results, both with and without the addition of a trellis code, are presented. Because of the different transmission environments encountered in the various countries in Europe, we have performed our computer simulation on both British and German (1) copper twisted-pairs. We find that with the addition of Wei's powerful 4-D 16-state trellis code, we can achieve the El rate with a positive margin over all loops tested using either one or two sets of twisted-pairs only, depending on the particular transmission scenario.

Video communications and services in the copper loop

Abstract: 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. >

Constellations for good diversity performance

Abstract: The case in which there are several channels available for transmission, and the additive noise on each channel may have different power, is treated. A signal constellation, called the coordinated code, for the signal space formed by the different channels is presented. The coordinated code has good performance when the noise powers are equal, while simultaneously providing diversity for good performance when the noise powers are unequal, and is relatively simple. The maximum-likelihood receiver is presented; it extracts information from the coded signal in inverse proportion to each channel's noise power. The minimum distance of the code is found, and the coding gain over a system that transmits independent bit streams on each channel is derived as a function of the noise statistics. The gain of the code is also found relative to symbol splitting diversity, which transmits a copy of the same message on each channel; this gain is as high as 9 dB. The code is considered in detail for use with a high rate digital subscriber line (HDSL) comprised of two pairs of a local loop, each pair having different amounts of near end crosstalk (NEXT). >

A 1 Mb/s digital subscriber line transceiver signal processor

Abstract: A monolithic custom digital signal processor which satisfies both the US and the European standards for HDSL (high-bit-rate digital subscriber line) transmission is presented. The architecture of an HDSL transceiver is shown. At the receiver, the ADC (analog-to-digital converter) samples the signal once per symbol period. The transmit energy is removed using an echo canceller. The resulting receive energy is then prefiltered and sent to the feedforward equalizer (FFE). The FFE provides gain and removes any precursor intersymbol interference (ISI). The decision-feedback equalizer then removes the postcursor ISI. The resulting data are sliced into a symbol decision and error value. >

High-bit-rate digital subscriber lines

Abstract: High-bit-rate digital subscriber line (HDSL) technology provides a simple, cost-effective solution for the rapid provision of 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.

Distance-gains by multiple-duplex transmission, coding, and shaping for HDSL

Abstract: The maximum distance over which reliable high rate digital transmission over twisted pair lines is possible can be increased substantially by multiple-duplex transmission, channel coding, and signal shaping. Simple equations are derived to transform SNR (signal to noise ratio)-gains into distance gains. Numerical examples are given for a transmission of 2.048 Mb/s over twisted pairs with line diameters 0.4 mm and 0.6 mm (AWG 26 and AWG 22). A new signal shaping method without scrambling of data bits is proposed, by which a SNR-loss due to error multiplication in the descrambling procedure is avoided. >

Method and system for the transmission of a data signal in a VC-12-container in transmission channels.

Abstract: In this method, a digital signal (DS) is inserted into a VC-12 container (VC-12), differences in the data rates being equalised by stuffing. The container data (VC-D) are divided into three subsignals (TS1, TS2, TS3) and inserted into, in each case, one HDSL pulse frame (HPR1, HPR2, HPR3). The remaining free time slots in the HDSL pulse frame are occupied by fixed stuffing bits (R1, R2,...) or/and supplementary information (Z1). The subsignals (TS1, TS2, TS3) thus supplemented are transmitted via three HDSL data channels (L1, L2, L3) and inserted at the receiving end into a VC-12 container which is transmitted in a synchronous transport module (STM-N).

Simulation environments for the high-speed digital subscriber line (HDSL)

Abstract: An overview is presented of the high-speed digital subscriber line (HDSL) simulation facilities and selected results from recent CAD environments for HDSL. The evolving integrated network services to the subscribers opens a variety of fundamental questions regarding their digital capabilities. Two significant aspects are covered: the organization of the HDSL CAD environment and the typical results comparing the performance of the limited carrier serving area loop population and with a corresponding performance of all the loops that are less than 12 kft in the typical American subscriber loop environment. The question of the design of the simulation environment which evolves, changes and matures as the applications and requirements change and grow is addressed. Dominant physical, spectral and time domain simulation results for HDSL at H1 and E1 rates with 2B1Q and carrierless amplitude and phase (CAP) modulation techniques for the CSA loops and all loops >

Interoperability of multiple databases for the design and simulation of high-speed digital subscriber lines

Abstract: The performance evaluation of the high-speed digital subscriber line (HDSL) depends upon the design, linkages, and the cooperative role of the extensive databases during the simulation studies. Such databases are necessary during component design performance evaluation and the overall feasibility studies ofthe HDSL at the basic data rate (144 kilobits/sec) or at the primary data rate (1.544 Megabits/sec in US and 2.048 Mb/s in Europe). The authors present the design and procedures to build these interoperable databases. They are also present the successes and frustrations in organizing and working with such interdependent and interoperable databases. >

Wide band communication system optical network current supply - supplies electric energy for opto-electric conversion and to devices at subscriber end individually from subscriber

Abstract: Subscribers connected to a common network are connected to a number of optical data transmission lines (LWL) provided from the central exchange (AMT) to the subscribers (TN). The energy supply for the devices (SV) at the subscriber end, such as bells, D/A converters etc., is provided by the subscriber (TN). Each subscriber terminal (TN) may be associated with an opto-electronic converter (O/E). The power for these is provided directly from the respective subscriber end memory devices (SV). ADVANTAGE - System operator only has to supply data lines. Electric energy for devices at subscriber end is supplied by subscriber himself.

Adaptive filtering for HDSL equalizers

Abstract: The main challenges in the high bit-rate digital subscriber line (HDSL) system are the near-end crosstalk (NEXT) from other signals in the same multipair cable and the intersymbol interference. In the present work, the authors use a simulation environment to study the performance of of an HDSL equalizer working under different crosstalk conditions and demonstrate its successful operation. >

Extending the bandwidth of the local loop

Abstract: The authors consider the growth in demand for the delivery of new telecommunication services that require digital rather than analogue delivery. They highlight the problem that the provision of these services often requires the costly installation of new transmission media. For both service providers and end users, this can make the cost of serve provision prohibitive. High-speed digital subscriber line (HDSL) systems have been introduced in Europe, allowing transmission up to 2048 Mbit/s over conventional unscreened copper pairs. These systems combined with appropriate interfaces, will allow the timely and economic provision of a range of services that need up to a bit rate of 2048 Mbit/s. The authors consider the service applications of HDSL and develop a deployment strategy that allows the economic migration to fibre systems when service demands allow.< >

HDSL design issues-optimization and achievable gains

Abstract: The principle design goal for high rate digital subscriber lines (HDSL) is to achieve the maximum field length for a given bit error probability. A transmission system can be decomposed in the functions channel equalization, line coding and channel coding. The largest distance gain compared to an existing, non-optimized system is achieved by channel coding. However, line coding and the optimization of the symbol rate and the number of levels remain important issues. In the paper, optimization criteria for all three areas are discussed and numerical results are given. If a new line coding scheme using trellis shaping is employed, the overall distance gain achieves 20% compared to the systems in use today. >

Application of high bit-rate digital subscriber line (HDSL) technology

Abstract: High bit-rate Digital Subscriber Line (HDSL) technology permits two-way 1.544 or 2.048 Mb/s transport over most existing copper telephone cables without repeaters, cable conditioning, or binder group segregation. Approximately 1000 HDSLs are now in service, and the rate of deployment is accelerating. Compared with traditional high speed copper transport systems, HDSL engineering, installation, and maintenance are simpler. Non-intrusive measurement of Signal-to-Noise Ratio (SNR) and digital performance greatly improves the HDSL's utility. HDSL permits rapid and low-cost service turn-up for private line DS1, fractional DSI rate, switched services, and access to PCS base stations. A strong synergy exists between HDSL and the fiber deployments planned for the next several years.

Performance of interleaved trellis codes in the presence of impulse noise

Abstract: Interleaved trellis coded modulation is described. It utilizes multiple encoder/decoder pairs as a means of mitigating the effects of impulse noise in the high-rate digital subscriber line (HDSL) and related applications such as the asymmetric digital subscriber line (ADSL). The component code for the interleaved scheme is a trellis code coupled with 32-quadrature amplitude modulation (QAM) which has the same spectral efficiency as uncoded 16-QAM. It is found that the interleaved trellis coded modulation scheme is more robust against impulsive noise than the conventional trellis coded modulation. Two trellis codes are considered for the component code for the interleaved scheme: an eight-state code and a simple four-state code. The interleaved scheme using the four-state code performs better than the interleaved scheme using the eight-state code in an impulsive noise environment, even though the asymptotic coding gain for the four-state code in additive white Gaussian noise is less than that of the eight-state code. Computer simulation results are presented for the interleaved and conventional schemes using the two trellis codes for actual impulses with variable durations. >

VLSI design of echo cancelers for the HDSL system

Abstract: A VLSI design of an echo canceler for a high bit-rate digital subscriber line transceiver is presented. The paper begins with the basic architecture and considers the operation of the various units in some detail. It concludes with simulation results which demonstrate that the data clock can be as high as 1.2 MHz. >

Higher order DC-constrained line codes

Abstract: The authors consider the use of multilevel line codes which generate sequences with higher-order spectral nulls at DC for the suppression of low-frequency spectral contents of the digital signal so that a baseband speech signal can be inserted at low frequencies. The use of these line codes is proposed for the asymmetrical digital subscriber line (ADSL). The new line codes exhibit a large dead band at DC, and can thus be considered for use on the control channel of the ADSL. A further advantage of using the block codes is that the additional spectral nulls in the pass band of each of these block codes make it possible to insert pilot tones at these frequencies, to aid with functions such as clock recovery at the receiver. >

Environment study for asymmetrical digital subscriber line in Taiwan

Abstract: The concept of Asymmetrical Digital Subscriber Line (ADSL) is to provide greater than 1.544 Mbps DSI or higher bit rate service from the networking end to the customer end through the ordinary telephone line. For purpose of evaluating the performance of the ADSL within the local loop plant of Taiwan, we utilize quadrature amplitude modulation QAM) passband signaling scheme with 16 point constellation as an example for the present study. In this paper, we present the current loop plant environment and feasibility study of ADSL in Taiwan. The loop survey results show the crosstalk loss is around 10 dB and 15 dB, respectively, worse than the ANSI model. Preliminary simulation results show the transmission coverage range can be achieved at 17 kft for the FS PIC cable and 13.5 kft for the paper cable in the presence of self-FEXT (far-end crosstalk), background noise and up to 99 disturbers NEXT (near-end crosstalk) from Basic Rate DSL. ADSL coverage range can achieve a significant portion of the entire copper loop plant as sharing the same binder group with ISDN Basic Rate Access. Replacing NEXT from Basic Rate DSL by 10-disturber HDSL NEXT, the transmission range will be shorten to be 9.5 Ut and 6.5 kft for the FS PIC and paper cable, respectively. Hence, the engineering rule for HDSL installation should be carefully treated for the future deployment of ADSL in Taiwan's copper loop plant.