Showing papers on "High-bit-rate digital subscriber line published in 1997"

Cable services security system

Abstract: A cable television services security system includes a two-way communication system for transmitting a broadcast signal from a headend to subscribers and subscriber viewing information from a channel identifier located within a subscriber's home back to the headend. An addressable switch located outside of the subscriber's home compares the channel being viewed by the subscriber with a subscriber privilege code. If the subscriber is not authorized to view the channel, the broadcast signal being transmitted to the subscriber is interrupted.

Integrated circuits for data transmission over twisted-pair channels

Abstract: This paper discusses typical architectures and challenges in designing integrated circuits for data transmission over twisted-pair wire channels. To highlight the various architectural approaches, two main applications are discussed-high-bit-rate digital subscriber loop (HDSL) and fast-Ethernet. Although these two applications have orders of magnitude difference in their bit rates, they share many common building blocks including line-drivers, 24 wire hybrids, echo cancellation, digital equalization, and clock recovery. Typical integrated circuit approaches for realizing each of these blocks are presented as well as possible tradeoffs. Finally, future challenges facing integrated circuit designers are presented.

Constant envelope modulation for splitterless DSL transmission

Abstract: A digital subscriber line (DSL) communication system that utilizes the high frequency band of a standard telephone line does not require the use of a plain old telephone service (POTS) splitter in the resident's home, which provided isolation between the POTS frequency band (0 to 4 kHz) and the DSL frequency band. Digital signal processing techniques are utilized to adapt to varying subscriber line conditions due to POTS telephone equipment. The digital signal processing techniques eliminate the need for a splitter by reducing susceptibility to distortion due to varying subscriber line characteristics. The digital subscriber line modem utilizes constant envelope modulated signals and frequency division multiplexing, where the constant envelope modulations lessens the intermodulation distortion products due to DSL signals that are transmitted by the modem and which may result in audible noise at the POTS telephone equipment due to non-linearities of the POTS telephone equipment.

Hdsl and pots carrier system

Abstract: High-speed digital transmission is achieved with existing phone lines and HDSL chipsets while retaining plain old telephone service (POTS) with full failsafe capability One original digital data signal (4) at a rate of at least 352 kbps and one POTS channel (10) digitized at 64 kbps are multiplexed by a HPCS card (6) of a signal provider (1) The resulting digital signal is transported over a twisted cable pair (2) which is approximately 16 kft based on the current technology At a receiving end, the signal is demultiplexed and regenerated by a subscriber's HPCS card (7) The subscriber's HPCS card is line-powered via the cable (2) to avoid dependence upon local power The regenerated signals are transmitted over one POTS line (42) and one data line (8) to or within a remote premise Both HPCS cards have bypass relays for the POTS line to ensure the subscriber's POTS access in the event of a local power outage or electronic failure

Adaptive voice and data bandwidth management system for multiple-line digital subscriber loop data communications

Abstract: An adaptive voice and data bandwidth management system is implemented in a subscriber loop to permit higher data rates and adaptive allocation of this increased capacity between multiple applications. The management system communicates digital data across multiple-lines when these lines are not in use by other communication equipment. However, when a request for use of a line by another device is detected, a modem clears down a subscriber line and connects the subscriber line to the appropriate communication device. As a result, simultaneous use of a modem and other communication devices is allowed. Once the other communication device ends its communication session, the system adapts to once again communicate digital data over multiple lines in order to increase the speed and efficiency of the data communication.

Telecommunications system for accessing subscriber premises equipment using ring suppression

Abstract: A no-ring access telecommunications system (10) is connected to a subscriber's telephone line (14), at the demarcation point (20) between the public switched telephone network and the telephone line (14). The system (10) comprises a processor (48) and a normally open switch (50) which is selectively closed by the processor (48) to connect the telephone line (14) to another line servicing the subscriber's telecommunications equipment (17). The system (10) suppresses the first power ring signal of an incoming call. The ring signal is analyzed for caller-id or distinctive ringing. If a valid Caller ID, distinctive ring signal or other special tone is provided, the switch (50) is closed. The Caller ID is then regenerated on the line servicing the subscriber telecommunications equipment. The subscriber telecommunication equipment (17) is configured to monitor the line servicing it and establish a connection when an incoming is directed to it.

Low-cost phaselocked local oscillator for millimeter wave transceivers

Abstract: An LMDS system including a base station, subscriber units and subscriber modems. Transmission frequencies between the base station and the subscriber units are specified by the Federal Frequency Commission. Signal frequencies between the subscriber units and the subscriber modems are specified by industry standards. The subscriber units couple and frequency translate modulated signals between the base stations and the subscriber modems. The frequency translation requires an intermediate transmit oscillator and a local oscillator. The intermediate transmit oscillator, however, can also be used to frequency translate a local oscillator signal within each subscriber unit down to a lower frequency which allows a low cost phase locked loop chip to be used to phase lock the local oscillator in each subscriber unit to a reference source. A pilot tone can be coupled onto modulated signals transmitted from the base station to the subscriber units. The pilot tone can be summed into the local oscillator phase locked loop within each subscriber unit to reduce the effects of signal transmission on the phase noise of the modulated signals. Furthermore, dual pilot tones can be coupled onto the modulated signal transmitted from the base station to the subscriber units. The dual pilot tones can be used to generate a reference signal within each subscriber unit.

Systems considerations for the use of xDSL technology for data access

Abstract: A variety of signal processing techniques have been developed over the past 10 years to increase the bit rate of digital transmission through telephone loop twisted pairs. The ISDN basic rate access 2B1Q digital subscriber line (DSL) was the first technology of this type to be deployed commercially at 160 kb/s full-duplex transmission on a single twisted pair. Other transmitter/receiver circuits have been developed over the years that support symmetric and asymmetric data transmission from several hundreds of kilobits per second to several megabits per second using the 2B1Q line code in the case of HDSL and various modulation techniques (QAM, CAP, and DMT) in the case of ADSL. These more recent forms of xDSL circuitry have begun to be used to provide commercial Internet access. This article analyzes the system level considerations for using these technologies in the increasing complex loop network of telephone companies. A "next generation" of xDSL access system is proposed, and the requirements for such a system are discussed.

Joint equalization and coding for intersymbol interference channels

Abstract: We present a novel scheme that combines decision feedback equalization (DFE) with high-rate error-detection coding in an efficient manner. The proposed scheme is shown to considerably outperform the conventional practice on channels with high SNR, such as those encountered in twisted-pair telephony systems. In order to analyze the performance of our method, we introduce an approximate mathematical model taking into account the error propagation phenomenon. Based on this model, upper and lower bounds on the overall probability of error are developed. These show that a simple low-redundancy error-detecting code, when properly integrated with the equalizer, can make the overall probability of error several orders of magnitude lower than that obtained with the conventional DFE, or with a DFE followed by an error-correcting code. Computer simulations of the proposed method have been performed for several channels, including the so-called high-bit-rate digital subscriber line (HDSL) test-loop 4, which is known to have a considerable amount of intersymbol interference. For all these channels, our results show that a reduction in the probability of error by more than three orders of magnitude can be obtained using codes of rate 0.96 and above. This, in turn, translates into power savings (coding gain) of 2.5 to 3 dB.

Multiple ISDN carrier system

Abstract: High-speed digital transmission can be achieved with existing phone lines and HDSL chipsets. Two original ISDN signals (4, 5) at a rate of 160 kbps are multiplexed by a MICS card (6) of a signal provider (1). The resulting digital signal is transported over a twisted cable pair (2) which has an approximate maximum length of 16 kft. At a receiving end, the signal is demultiplexed and regenerated by a subscriber's MICS card (7). The subscriber's MICS card is line-powered via the cable (2) to avoid dependence upon local power. The regenerated signals are transmitted over two ISDN cables to remote premises which can be as far as 18 kft away.

High speed data interface using tdm serial bus

Abstract: A split-architecture audio codec providing an interface to a high speed broad band modem or other data source device capable of multi-megabit data rates. A plurality of time slots are utilized by the broad band modem in a time division multiplexed (TDM) data bus between the controller and analog sub-systems of the audio codec. Current examples of such high speed broad band modems include HDSL, SDSL, and ADSL, collectively referred to as xDSL. An interleaver in the analog sub-system rate adapts between the data rate of the broad band modem and the fixed rate of the TDM data bus between the sub-systems based on the number of time slots assigned to the broad band modem interface. Interface capability is provided for broad band modems having data rates up to 6.72 Mb/s for split-architecture audio codecs which conform to the AC '97 specification, and higher if non-conformance is acceptable. A programmable clock in the analog sub-system has the capability to operate in several modes including a conventional AC '97 conforming mode with the clock set to divide the frequency of the external crystal in half, and an AC '97 non-conforming mode wherein the frequency of an external crystal oscillator is multiplied by one or more to correspondingly increase the speed of the TDM data bus and the capacity of the interface to the broad band modem.

Three-dimensional carrierless AM/PM line code for the unshielded twisted pair cables

Abstract: The Carrierless AM/PM (CAP) modulation scheme is a viable alternative for high speed digital transmission for the HDSL/ADSL/VHDSL environments. In this paper, the conventional 2-D CAP system is expanded to a 3-D space. A 50% increase in the system throughput is achieved at the expense of added receiver complexity and some performance degradation. The 3-D signaling is obtained through a minimax optimization process to match the characteristics of the original 2-D system and to achieve perfect reconstruction (PR) condition. The 3-D CAP system is simulated over unshielded twisted pair (UTP) cable environment for baud rate of 150 Mbps.

Simulation of ADSL over ISDN on German subscriber lines

Abstract: The shortcomings of the existing asymmetric digital subscriber line (ADSL) standard ANSI T1.413 for application with the integrated services digital network (ISDN) are explained. An ADSL system modified by increasing the high-pass cutoff frequency of the splitter to about 140 kHz and, therefore, moving also the pilots, has been simulated under noise conditions and the ISDN requirements of the German subscriber line network. The reach reduction due to ISDN compared with the "plain old telephone service" (POTS) application is shown to he between 10% and 15%. It is proposed to apply ISDN ADSL rather than POTS ADSL.

Subscriber loop extension system for ISDN basic rate interfaces

Abstract: A system and method for reducing signal attenuation of integrated services digital network (ISDN) digital transmissions at the subscriber loop, thereby increasing the available subscriber loop range, is provided. An ISDN digital transmission system is used for transmitting and receiving digital information via a line termination at a central office. Customer premises equipment is coupled to a network termination (NT-1) within the customer premises, which is in turn coupled to interface the line termination at the central office. A plurality of inductive load coils are coupled in series with the two-wire subscriber loop ISDN BRI at predetermined distance intervals, which are calibrated to resonate the two-wire bus.

Apparatus and method for selecting different communication speeds on a data signal line

Abstract: An apparatus and method for automatically selecting different data rates for communicating data over a high bit rate, digital signal line (HDSL) line such as a dry pair line (16). In one embodiment master/slave interface circuits (fig. 5) at opposite ends of a line attempt to establish communications at a higher frequency. If this fails, communications are attempted at a lower frequency. If communications are successful at the higher frequency and communications continue for a predetermined period of time at the higher frequency and then communications fail, an attempt is made to reestablish communications at the higher frequency. An algorithm is set forth for enabling selecting among a plurality of different speeds.

Achievable rates vs. operating characteristics of local loop transmission: HDSL, HDSL2, ADSL and VDSL

Abstract: Prior work has focused on achievable rates for digital subscriber lines, only to have future technology surpass the "achievable" bounds. This paper focuses on how achievable rates vary under different operating characteristics. We show how the achievable rates change as transmission moves from echo-cancelled symmetric transport (HDSL), to frequency-division transport (original ADSL), partially overlapped transport without bandwidth coordination (echo-cancelled ADSL), to partially-overlapped, frequency-coordinated transmission (HDSL2). The limitations of spectral compatibility and crosstalk from existing services are discussed as they effect the fundamental limits and deployable services. The lessons learned are related to higher rate services in a next-generation network employing VDSL.

Method for transmitting information signals in a subscriber terminal network

Abstract: A method for transmitting information signals in a subscriber terminal network wherein the network is between an exchange and the individual subscribers and which is used in the course of the worldwide expansion of the digital telecommunication networks for the transmission of digital signals In order to be able to guarantee optimal transmission rates, measurements of the transmission parameters of the subscriber terminal lines are carried out and, according to the standard provided by these measurements, a maximum bit rate is determined for each subscriber terminal line

Subscriber line termination circuit

Abstract: The circuit terminates a subscriber line in form of a copper conductor, on which telephone signals in a voice band are exchanged between the telecommunications terminal of a subscriber arrangement and a telecommunications exchange. A high bit-rate and a low bit-rate data signal streams are transferred in a direction from a central arrangement to the subscriber arrangement, and from the subscriber arrangement to the central arrangement, respectively, whereby the data signal stream lies in a frequency range above the voice band. The arrangement necessary for separating and combining data signals and telephone signals, as well as the necessary modem for the data signals are integrated in such way in the subscriber connection circuit, that they are protected through a provided over-voltage protection circuit against excessive voltages appearing on the subscriber line.

Data transmission method

Abstract: PROBLEM TO BE SOLVED: To optimize current consumption and the range by changing a clock frequency so as to maintain frame constitution, etc., while varying the amount of data collected for each block and depending on the amount of data in the case of transmitting discrete data integrated into the frame constitution for each block. SOLUTION: Transmitters/receivers 2 and 3 connected through a transmission medium (transmission line) 1 respectively receive data 4 and 5 made into binary codes under clock control and respectively transmit these data through the transmission medium 1 after adjustment. In this case, the transmitters/receivers 2 and 3 are provided with echo compensators 8 and 8', equalizers 9 and 9' and means 10 and 10' for generating HDSL frames from the provided data 4 and 5 every time and when transmitting the discrete data integrated into the frame constitution for each block, the clock frequency of the transmitters 2 and 3 is changed so as to maintain the frame constitution and frame length while varying the amount of data collected for each block and depending on the amount of data.

Digital Subscriber line (HDSL and ADSL) Capacity

Abstract: The fundamental limits of the outside loop plant to carry high-speed digital (bidirectional HDSL and ADSL) data are reported in this Chapter. This Chapter also focuses on the copper wire-pairs, drop lengths, and interconnects that convey the data over the “last mile” to almost all businesses and residences in the United States. 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 to distance and spectral constraints. The signal-to-noise ratio can thus be estimated to ascertain the transmission quality through the plant. Accordingly, this Chapter reports losses, bandwidths, and bit rates in the first half, and major bottlenecks and their implication in the second half.

Radio system forming a wireless subscriber interface

Abstract: A radio system providing a wireless subscriber interface comprising subscriber stations (1, 2, MS) and a network element (4) comprising means for transmitting telecommunication signals between the subscriber stations and a fixed telephone network exchange (3), whereby the system comprises a subscriber station (1, 2) consisting of a radio unit (6) and a fixed telephone network telecommunication terminal (5) connected to the radio unit. In order to route a local call correctly even when the subscriber does not dial an area code, the network element (4) comprises a register (10) including the fixed telephone network area code corresponding to the location (A, B) of the subscriber station (1, 2). In addition, the network element (4) comprises means for retrieving an area code from the register (10) and for adding it as a prefix to the number dial transmitted from the subscriber station (1, 2) in connection with call set-up if the number dial transmitted from the subscriber station (1, 2) does not include an area code.

Method of changing the telecommunication of a subscriber station in a radio system

Abstract: The present invention relates to a method of changing the telecommunication settings of a subscriber station (1) in a radio system providing a wireless subscriber interface. For easy and swift changing of the telecommunication settings the subscriber station (1) is equipped with means (13) for changing its telecommunication settings as a response to a message received by the subscriber station over the radio path, a message (S1) is transmitted to the subscriber station including new telecommunication settings, and an acknowledgement (S2) of the implementation of the new telecommunication settings is awaited from the subscriber station (1).

Computer Based Optimization Techniques for HDSL Design

Abstract: The design and optimization of the high-speed digital subscriber line (HDSL) need powerful computational strategies. Traditional techniques of distributing poles and zeros on Smith charts generally do not work. In the past, such approaches have lead to suboptimal designs for applications where the data capacity sought is considerably less than the Shannon capacity of the lines. Typical subscriber loops are less than perfect and for the current demands on the HDSL at T1/T2 and El rates every possible venue for the HDSL design needs to be investigated, if not exploited. In this Chapter, flexible computational techniques are presented that explore and optimize system components in view of the operating environment of the HDSL and/or the asymmetric digital subscriber line (ADSL) and inherent limitations of system components. The optimization occurs automatically by forcing the computer to track the effects of incremental changes of the subsystem performance (e.g., echo cancelers or equalizers), or the component values (Rs and Cs in the matching circuits) in context to the functional constraints of the (HDSL, ADSL, duplex, dual-duplex, triplex, etc.) line in conjunction with various subscriber loop environments (CSA loops, loops <18 kft., American, Australian, European, ANSI, ETSI, etc.)

Method for communication with no power feed and exchange for realizing the method

Abstract: Disclosed is a method for communication with no power feed in an exchange. (1) A calling subscriber unit transmits a special service code designating the disuse of a direct current loop together with the numeric information on the called subscriber unit to the exchange after formation of a direct current loop. (2) When the special service code is received, an on-hook transmission state in which the transmission and reception of an alternating current signal is possible between the subscriber line interface circuit and the calling subscriber unit even if no direct current loop is formed is established in the subscriber line interface circuit to which the calling subscriber unit which has transmitted the special service code is connected. (3) The calling subscriber unit disconnects the direct current loop, and the exchange maintains the speech path between the calling subscriber unit and the called subscriber unit even after the direct current loop is disconnected. (4) An alternating current signal is transmitted and received between the subscriber line interface circuit and the calling subscriber unit in the state in which no direct current loop is formed.

Operational Environment for the HDSL

Abstract: The DSL and HDSL environments depend upon the physical and electrical constraints of the loops and their ultimate digital capacity. Some of the typical subscriber loop environments are presented in Chapter 5. The BRISDN services are expected to be made available over all telephone lines (without load coils and range extension devices) and their statistics are presented in Chapter 5. The PRISDN services are expected to be available to all CSA type of customers and their loop statistics are also presented in Chapter 5. Even though the simulations indicate that a single wire-pair is not able to carry T1 and E1 rate data over every HDSL CSA type (US) loops in the presence of crosstalk (typical of current Central Offices), there is good reason to believe that the dual duplex systems (i.e., two wire-pairs carrying half rate data in the duplex mode) will be satisfactory even for the most adverse loops. In this Chapter, the total operating environments for the DSL and HDSL including the electrical aspects in the design considerations are presented.

Simulation and CAD Aspects

Abstract: In this Chapter, an overview of the analysis, numerical and simulation aspects of the high-speed digital subscriber line (HDSL) is presented. The analytical techniques for generation and processing of the ABCD matrices are included. Computational data and file handling aspects are addressed. For the physical environment of the HDSL, the typical subscriber loop makeup, the overall topology and its physical distances over which the HDSL data transmission occurs are presented. The important features of the subscriber loops around the world are summarized. This Chapter covers two significant aspects of the organization of HDSL: (a) computational environment and (b) actual physical HDSL environments. The typical features necessary for a flexible approach to the yet evolving HDSL systems are retained in the software design. The evolving integrated network services to the subscribers open a variety of fundamental questions regarding their digital capabilities so far considered unimportant for the loop environments around the world. This software organization permits the designers to probe different national telecommunication environments regarding their status and compatibility to carry ISDN data.

Data Bases and Their Management for DSL Design Studies

Abstract: The performance evaluation of the high-speed digital subscriber line (HDSL) depends upon the design, linkages, and cooperative role of the extensive data bases during simulation studies. Such data bases are necessary during component design, performance evaluation and the overall feasibility studies of the HDSL at the basic data rate (144 kbps) or at the primary data rate (1.544 Mbps in the United States and 2.048 Mbps in Europe). In this Chapter, the design and procedures to build these interoperable data bases are presented. The need, consistency and interdependence of the data bases that actually supply the simulation programs are presented. The input data to the simulation programs is derived from large national Loop Surveys, the cable characteristics and surveys of noise in the loop plant. The output of the simulation programs generates interdependent and consistent data bases that are essential to evaluate the overall performance of the entire subscriber Loop Survey population at various rates (such as 144, 384, 768 kbps, 1.544 and 2.048 Mbps) in different telecommunication networks of various countries, regions, or even in premises distribution systems. In this Chapter, the success and frustrations in organizing and working with such interdependent and interoperable data bases are also presented.

Subscriber circuit for connecting an analog subscriber line to a digital time multiplex telephone exchange

Abstract: The circuit introduced between the line (TL) and the Subscriber Line Interface Circuit (SLIC 2) of the exchange is a multi-functional relay (MR) having two changeover contacts (u1,u2). These transfer the Subscriber Line Interface Circuit connection from the two wires (a,b) of the line to a test circuit (TS). The simplest instance of a test circuit is a single resistor, in which the input terminals (a1,b1) of the Subscriber Line Interface Circuit are connected by the relay contacts. More generally it is a passive network with a complex impedance.