Showing papers on "High-bit-rate digital subscriber line published in 1996"

Reconfigurable subscriber terminal for a wireless telecommunications system

Abstract: A subscriber station for the wireless connection of user telecommunications equipment to a remote central station of a wireless telecommunications system includes a transmitter/receiver for wireless communication with the central station, at least one telephone line for connection to subscriber telecommunications equipment and a communications controller connected between the transmitter/receiver and the telephone line for processing signals for transmission and/or received signals. The subscriber station is configurable in response to wireless programming signals representative of control code down-loaded from the central station. By enabling the down-loading of software for programming the subscriber station, the flexibility and convenience of configuring the subscriber station, both initially and subsequently, is greatly enhanced.

Concentrated subscriber system for wireless local loop

Abstract: A cellular telephone concentrated subscriber system (113) is described. The concentrated subscriber system includes a set of subscriber units (116) each having a unique electronic serial number that is coupled to a concentrated subscriber system controller that provides a radio frequency (RF) interface to the standard base station transceiver (110) of a cellular telephone system. The concentrated subscriber system controller includes a set of modulator-demodulator systems (modems) and a RF transceiver and antenna system (270, 250) that is configured to transmit sufficient information to conduct multiple telephone calls over both long and short distances. The concentrated subscriber system controller also includes control circuitry (254) for coupling the set of subscriber unit (116) to the set of modems via a multiplexed (266) system using stored information. In the preferred embodiment the number of modems is significantly less than the number of subscriber units which are implemented in a simplified manner so that the per user cost of cellular telephone service is reduced.

Mechanism for transporting digital pots signals within framing structure of high bit rate digital local subscriber loop signals

Abstract: A local subscriber loop architecture embeds digitized POTS signals into the framing format of high bit rate digital subscriber loop signals being transported over a local loop for serving both subscriber digital terminal equipment and a POTS telephone. The remote transceiver unit is line-powered from the central office unit, facilitating installation of a reliable (office-powered) POTS interface (containing codec and subscriber line interface circuitry providing BORSHT functions) into the remote unit. The data rate of the added digital POTS signal is relatively small with respect to the data rate of the DSL channels, so that there is only slight increase in the overall data rate. As a consequence, adding the digital POTS signal has negligible impact on transport range. Moreover, the high-complexity analog filters used in an FDM architecture to separate the POTS signal from the DSL signal are not required

Multiple ISDN and pots carrier system

Abstract: High-speed digital transmission can be achieved with existing phone lines and HDSL chipsets while retaining plain old telephone service (POTS) with full failsafe capability. Two original ISDN signals [4,5] at a rate of 160 kbps and one POTS channel [10] digitized at 64 kbps are multiplexed by a MIPCS 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 based on the current technology. At a receiving end, the signal is demultiplexed and regenerated by a subscriber's MIPCS card [7]. The subscriber's MIPCS 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 two ISDN cables [8,9] to remote premises. Both MIPCS cards have bypass relays for the POTS lines to ensure the subscriber's POTS access in the event of a local power outage or electronic failure.

Adapted optimization criterion for FDM-based DMT-ADSL equalization

Abstract: The ANSI T1E1.4 Committee finalized the standardization of the asymmetric digital subscriber loop system and the usage of discrete multitone modulation as the ADSL line coding scheme. In order to separate the upstream channel from the downstream channel, the committee accepted two approaches as vendor options: echo cancellation and frequency division multiplexing. We illustrate the impact of the FDM approach on the equalization problem. The unsatisfactory performance of formerly known algorithms is described. A new, simple and near-optimal equalization optimization criterion that is an FDM-based DMT-ADSL is proposed.

Multi-channel digital data transmission in a wireless telecommunications system

Abstract: A wireless telecommunications system includes a central station communicates with a plurality of subscriber stations served by the central station. The central station is connectable to a telecommunications network under a multiplexed multi-channel digital data telecommunications protocol having a plural number of data channels. Each subscriber station provides a line connection for carrying a predetermined number of digital data channels, where the plural number is greater than the predetermined number. The central station is connectable to each subscriber station via a wireless link under a wireless link protocol having the predetermined number of data channels. The central station includes a central protocol interface for converting between the multi-channel telecommunications protocol and the wireless link protocol for each wireless link. The subscriber station includes a subscriber protocol interface for converting between the wireless link protocol and the multiplexed multi-channel digital data telecommunications protocol with the predetermined number of digital data channels active. By converting an incoming multi-channel digital data protocol to a wireless link protocol, and then reconverting the wireless link protocol to a multi-channel digital data protocol at the other end, it is possible to provide for selective communication in accordance with the multi-channel digital data protocol, despite the limited bandwidth available.

Subscriber line interface in a telecommunications exchange

Abstract: A TR-8 compatible Remote Terminal (RT) with 96 subscriber line capacity is partially or wholly replaced with one or more D4 channel banks each comprising 24 subscriber line capacity without changing the TR-8 interface module within the servicing telecommunications exchange. The D4 channel bank is connected via a T-1 digital link to any one of the B, C, and D links within the TR-8 interface module. A-B bit pattern data and time slot assignments communicated between the D4 channel bank and the TR-8 interface module are converted to be compatible with each other. Connecting a D4 channel bank to a TR-8 interface module allows small telecommunications service providers to more economically provide line access to sparsely populated customer sites.

Communication system having switchably-coupled subscriber terminals

Abstract: A communication system includes subscriber terminals which can be coupled via at least one switch, and to which subscriber terminals, several call numbers can be assigned for which telecommunication parameters are definable. The subscriber terminals each store respective telecommunication parameters. In the case of a change of assignment of a subscriber call number from a first subscriber terminal to a second subscriber terminal, the telecommunication parameters belonging to the subscriber call number are transmitted to the second subscriber terminal. The communication system is preferably implemented in ISDN switching systems with ISDN telephones as terminals.

Telemessaging connection network for information transmission

Abstract: In the transmission network, 2048 MBit/s information is transmitted between line connection units (LT) near the subscribers and network connection units (NT) individually assigned to subscribers. The information is transmitted on two pairs (a0,b0;a1,b1) of copper line branches using the HDB3 or HDSL method. The line branch pairs also form a virtual circuit. The a,b branches aT/bT of the terminal branches on the subscriber side and the a,b, branches (aZ/bZ) of the subscriber connection lines on the messaging side for transmission of 64 kBit/s information are connected to the virtual circuit.

Transmission capacity and design of a VHDSL-system

Abstract: In a hybrid fiber/twisted-pair architecture the transmission of data rates much higher than the 1.5 or 2 Mbit/s of the high bit-rate digital subscriber line (HDSL) service can be achieved by reducing the loop length of twisted pair cables in the access network. In this paper we present a channel model for twisted-pair cables for frequencies up to 40 MHz, which is derived from measurements and theoretical analyses. Based on the new channel model the transmission capacity for a symmetrical pulse amplitude modulation (PAM) system with adaptive echo cancellation (EC) and for a carrierless AM/PM (CAP) system based on frequency division multiplexing (FDM) is calculated, Up to a table length of 200 m the PAM system achieves higher data rates, whereas for longer distances CAP systems are advantageous, Over 200 m a data rate of about 30 Mbit/s can be transmitted by both systems with 24 identical self-crosstalk disturbers in the 50-pair distribution cable. Whereas the reach of a 25 Mbit/s echo cancellation system can be increased to 360 m by NEXT cancellation, the range of the FDM system can even be improved from 300 m to 610 m for the same data rate. Crosstalk cancellation results in a high hardware complexity but could be realized with gate arrays in 0.5 or 0.35 /spl mu/m technology.

Minimizing crosstalk in twisted pair wires carrying TDD multitone signals

Abstract: A digital transmission system comprises a plurality of wire sets 151, 155, such as twisted-pair wires, for delivering services to subscribers 110, 120, 130, 140. A first wire set 151 carries a time-division duplexed multitone signal VDSL. The system is arranged to individually select the transmitted spectra of the upstream and downstream portions of the duplexed signal so as to minimise cross-talk interference with further signals ADSL, HDSL carried by other wire sets 155. In use the transmitted spectra of the upstream and downstream portions of the duplexed signal may differ in bandwidth.

Wireless telecommunications based subscriber terminal with monitor facility

Abstract: A subscriber station of a wireless telecommunications system includes a transceiver 24 for wireless communication 26 with a central station and for processing signals for transmission and/or received signals. The transceiver is connected via a link 28 to a power supply unit 30 for connection, via network terminal unit 32, to one or more outlets for user telecommunications equipment 34,36,38. The link carries telephone call data for the telecommunication equipment and subscriber station control data in accordance with an internal protocol. The internal protocol control data comprises operational status parameters of the subscriber station. The provision of internal protocol control data on a link between the transmitter/receiver and the supply unit thus provides a point of access for monitoring the operational status of the subscriber station. This access point may also be used to invoke a system installation/configuration routine which may then be effected via the subscriber's telephone keypad.

Bandwidth selection for the very high-rate digital subscriber line (VDSL) system

Abstract: Work is under way to develop a very high-rate digital subscriber line (VDSL) system capable of operating over twisted-pair media at data rates in excess of 10 Mbps. The twisted-pair channel is characterized by both an attenuation and crosstalk susceptibility which increase with frequency and length. The signaling bandwidth for such a channel can be selected to maximize the bit rate. This optimization is carried out for loop lengths in the 1-5 kft range. It is shown that the optimal signal bandwidth is quite sensitive to the loop length. For example, the optimal bandwidth for a 1 kft loop is more than twice that of the 3 kft loop.

Architecture and performance simulation of single pair HDSL

Abstract: The possibility, architecture, and performance of a single pair HDSL (SHDSL) are examined in this paper. Two architectural alternatives, echo canceller (EC) based and frequency division multiplexed (FDM), are studied. The channel capacity and decision feedback equalizer (DFE) based transceiver performance are examined for different self and foreign near end crosstalk (NEXT) and far end crosstalk (FEXT) noise environments. Simulation results show that only a FDM SHDSL is possible for the carrier serving area (CSA) loop with 6 dB of performance margin. This FDM SHDSL can also be deployed in the same loop plant with basic rate ISDN access channel, dual duplex HDSL, or a limited number of FDM asymmetrical digital subscriber line (ADSL) systems. A coding gain of about 4 dB is necessary if ADSL NEXT is to be considered. Otherwise, a simpler FDM SHDSL can also be realized with a wider spectrum bandwidth on a traditional DFE transceiver. Results here can be used as references for the development of a SHDSL system.

Hardware design and performance analysis of VDSL transceivers

Abstract: With a hybrid fiber/twisted-pair architecture, data rates up to about 50 Mbit/s can be transmitted over installed twisted-pair cables in the distribution part of twisted-pair access networks. Based on a channel model for twisted-pair cables for frequencies up to 40 MHz derived from measurements, different transmission formats are compared. It is concluded that frequency division multiplexed VDSL (Very high bit rate Digital Subscriber Line) systems based on QAM (Quadrature Amplitude Modulation) or CAP (Carrierless AM/PM) are a good choice. In this paper, two scalable system proposals are presented. Both systems can transmit 12.5 Mbit/s symmetrically over a distance of about 800 m. System 1 enables as well the asymmetrical transmission of 50/2 Mbit/s over 280 m, whereas system 2 enables the symmetrical transmission of 25 Mbit/s over 300 m. Based on the required filter lengths of the equalizer and the wordlengths of the signals within the adaptive filters, the hardware complexity of the proposed VDSL transceivers is determined.

Mobile communication system

Abstract: PROBLEM TO BE SOLVED: To easily attain system construction not only through a DSL, HDSL, and DSI line (digital transmission line having the data transmitting amounts of 144 kbit/s, 776 kbit/s, and 1.544 Mbit/s in a base station interface) but also through a 2MDTI line (digital transmission line having the data amounts of 2.048 Mbit/s). SOLUTION: A base station interface unified to a 2MDTI line in addition to the other lines is normalized. A base station 200, base station controller 300, and base station interface converter 400 are made correspond to the interface. The converter 400 operates the conversion of the frame constitution of DSL/HDSL/DS1/2MDTI lines. At this point, in the frame constitution of the 2MDTI line, one frame constituted of 32 time slots with 256 bits is defined as a base, 20 frames as one multi-frame, and 0 time slot as a frame synchronizing time slot. Then, 6 time slots constituted of 48 bits are defined as one block unit from the first time slot, and 4 or 5 blocks are assigned until the 31th time slot as necessary.