WO1991005424A1 - Method for terminating an isdn line - Google Patents

Method for terminating an isdn line Download PDF

Info

Publication number
WO1991005424A1
WO1991005424A1 PCT/NO1990/000141 NO9000141W WO9105424A1 WO 1991005424 A1 WO1991005424 A1 WO 1991005424A1 NO 9000141 W NO9000141 W NO 9000141W WO 9105424 A1 WO9105424 A1 WO 9105424A1
Authority
WO
WIPO (PCT)
Prior art keywords
line
signals
transmitted
isdn
signal
Prior art date
Application number
PCT/NO1990/000141
Other languages
French (fr)
Inventor
Rune Skow
Kjell Hermansen
Original Assignee
Televerket
Alcatel Stk A/S
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Televerket, Alcatel Stk A/S filed Critical Televerket
Publication of WO1991005424A1 publication Critical patent/WO1991005424A1/en

Links

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/04—Selecting arrangements for multiplex systems for time-division multiplexing
    • H04Q11/0428—Integrated services digital network, i.e. systems for transmission of different types of digitised signals, e.g. speech, data, telecentral, television signals
    • H04Q11/0435—Details
    • H04Q11/045—Selection or connection testing arrangements
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/02—Details
    • H04B3/46—Monitoring; Testing
    • H04B3/493—Testing echo effects or singing
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M3/00—Automatic or semi-automatic exchanges
    • H04M3/22—Arrangements for supervision, monitoring or testing
    • H04M3/24—Arrangements for supervision, monitoring or testing with provision for checking the normal operation
    • H04M3/244—Arrangements for supervision, monitoring or testing with provision for checking the normal operation for multiplex systems
    • H04M3/245—Arrangements for supervision, monitoring or testing with provision for checking the normal operation for multiplex systems for ISDN systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/04—Selecting arrangements for multiplex systems for time-division multiplexing
    • H04Q11/0428—Integrated services digital network, i.e. systems for transmission of different types of digitised signals, e.g. speech, data, telecentral, television signals
    • H04Q11/0478—Provisions for broadband connections
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04J—MULTIPLEX COMMUNICATION
    • H04J2203/00—Aspects of optical multiplex systems other than those covered by H04J14/05 and H04J14/07
    • H04J2203/0001—Provisions for broadband connections in integrated services digital network using frames of the Optical Transport Network [OTN] or using synchronous transfer mode [STM], e.g. SONET, SDH
    • H04J2203/0057—Operations, administration and maintenance [OAM]

Definitions

  • the present invention relates to a method for operating and maintaining at least one B-ISDN line between an ISDN exchange and at least one ISDN subscriber.
  • the network provider has to make sure that the signals between the network- and line termination points are trans ⁇ mitted and received correctly. This can be verified in a number of ways and the network usually includes an NTl unit.
  • the reason for having an NTl is to establish a functiona ⁇ lity which allows:
  • Termination of the public network at the subscriber side A standardized interface for the connection of subscriber equipment to the public network. A boundary of responsibility between network and sub ⁇ scriber equipment when these are not provided by the same body.
  • ISDN International Mobile Network
  • VHIth Plenary Assembly Mai aga-Torre ol i nos , 8-19 October 1984, page 126.
  • Reference configurati on for the user-network interface is e.g described in CCITT Blue Book Volume III - Fascicle III.7, 'ISDN, General Structure and Service Capabilities, IX Plenary Assembly, Melbourne, 14-25 November 1988, page 38.
  • the object of the present invention is to simplify the termination network NTl, in particular in connection with single terminal installations.
  • the object is, however, also to simplify larger networks such as those including NT2 units.
  • the main features of the invention are defined in the claims.
  • the present invention is based on the idea that con ⁇ siderable cost savings may be achieved without loss of overall service quality in cases where the U-interface is made identical to the standardized T-interface.
  • the NTl may then be realized as a passive connector. Techniques are described for carrying out all essential maintenance operations from an 0 & M centre at the premises of the network provider. This concept applies equally well for both electrical and optical transmis- sion media.
  • TDR Time Domain Ref1 ectometry
  • Detectable faults may range from short cable sections of higher attenuation than normal, to frayed or even severed cables.
  • 0 _ ⁇ M functions (not yet defined, but referred to as Network Overhead Functions) can be implemented from the premises of the network provider, rather than being dis ⁇ tributed to each individual NTl.
  • the associate test and monitoring equipment may be shared between several subscribers. Performance checking can be done by taking sampled tests of each subscriber's line section at regular intervals. Each user's share of the maintenance costs will hence be just a small fraction of that associated with an active type of NTl.
  • the typical business scenario with a number of terminals sharing a common access to the public network via an NT2, represents a different situation from that found in a single terminal environment, like that of a residential user or a very small business. It is clear that the cost benefit of saving just one NTl unit does not make a major impact upon the total cost for a large business system. However, as regards maintenance costs there will be a significant potential for savi ng. For a single terminal installation the saving may be considerable, because the NTl constitutes a much higher share of the total system cost in this case.
  • Figure 1 schematically illustrates the principles of a known single terminal installation
  • Figure 2 illustrates a known larger installation including a NT2 unit
  • Figure 3 illustrates reflection of signals at the user side in accordance with the invention
  • Figure 4 illustrates an OTDR separate pipe installation.
  • Figure 1 is illustrated a known configuration where a B-ISDN line leads from an exchange 1 through an NTl unit or 20 network terminator 2 to a subscriber terminal 3.
  • FIG. 2 is illustrated a known configuration where a B- ISDN line leads from an exchange 1 through an NTl unit 2 and a NT2 unit 4 (network terminators) to a subscriber 3.
  • Figure 3 illustrates that line-checks can be made by means of reflection of a transmitted signal in an NTl module 5 at user side (bitstream reflection / loop-back).
  • the reflection 30 of the transmitted signal can be continuous, meaning all signals are reflected.
  • the results from the test can be obtained by correlation of transmitted and received signal.
  • Figure 3 illustrates only a mode by which signals are transmitted from an exchange 1 to a receiver terminal 3. The 35 mode of transmission from the subscriber 3 in the direction of the exchange 1 is not shown.
  • the communication signals and test signals may be transmitted from exchange equipment 6 which may include a light emitting diode (LED).
  • the communi- cation signals will reach the terminal equipment 3 which may include a PIN type receiving device 7.
  • the signals transmitte from the exchange 1 are partly passed through NTl module 5 to the subscriber 3, and partly reflected in a reflector 8 back to exchange equipment 9 which may include a PIN type receivin device.
  • FIG. 4 A scheme based on optical TDR and separate pipes is illustrated in Figure 4. The principle is also applicable for single fiber and WDM.
  • the communication signals are trans- mitted at a wavelength of 1500 n , whereas the test signals are at 1300 nm.
  • the tw types of signals can be separated by optical filters, thus allowing for simultaneous data transfer and line supervision.
  • the returned signal may be examined for bit error corruption by means of auto-correlation techniques. This implies that a signal is examined for the degree of correspondence (correlation) with a delayed replica of itself. With no bit errors there will be perfect correlation between the two.
  • the degree of correlation between the returned signal and the one transmitted originally is hence a measure of the bit error rate on the line.
  • FIG. 4 is schematically illustrated a transmitting pipe arrangement 10 with exchange equipment 1 including OTDR equipment 11, a communication signal transmitter 12 (LED
  • the communication signals are passed through an NTl module 15 to terminal equipment 16 which may include a PIN type receiving device (PIN 1500).
  • the receiving channel or pipe 20 includes OTDR equipment
  • test signal transmitting means 24 (LED 1300) and receiving means 23 (PIN 1300).
  • the communication signals are passed through the passive NTl module 25 from the subscriber transmitting equipment 26 which may include a light emitting diode (LED 1500). Test signals are as in the transmitting mode reflected in the NTl module 25.
  • test signals may be transmitted at a frequency different from that of the communication signals as indicated, but the test signals may alternatively be transmitted at the same frequency as that of the communication signals.
  • the passive NTl module may in its simplest form be realized as a connector.

Abstract

This invention relates to a method for operating and maintaining at least one B-ISDN line between an ISDN exchange and at least one ISDN subscriber. The invention is based on the idea that considerable cost savings may be achieved without loss of overall service quality in cases where the U-interface is made identical to the standardized T-interface. The NT1 may then be realized as a passive connector (5, 15, 25). Techniques are described for carrying out all essential maintenance operations from an O & M centre at the premises of the network provider. This concept applies equally well for both electrical and optical transmission media.

Description

Method for terminating an ISDN line
The present invention relates to a method for operating and maintaining at least one B-ISDN line between an ISDN exchange and at least one ISDN subscriber.
The network provider has to make sure that the signals between the network- and line termination points are trans¬ mitted and received correctly. This can be verified in a number of ways and the network usually includes an NTl unit. The reason for having an NTl is to establish a functiona¬ lity which allows:
Termination of the public network at the subscriber side A standardized interface for the connection of subscriber equipment to the public network. A boundary of responsibility between network and sub¬ scriber equipment when these are not provided by the same body.
Operation and maintenance (0 & M) of the public network. This type of layout is described e.g. in CCITT Red Book Volume III - Fascicle III.5, 'Integrated Services Digital
Network (ISDN), VHIth Plenary Assembly, Mai aga-Torre ol i nos , 8-19 October 1984, page 126. Reference configurati on for the user-network interface is e.g described in CCITT Blue Book Volume III - Fascicle III.7, 'ISDN, General Structure and Service Capabilities, IX Plenary Assembly, Melbourne, 14-25 November 1988, page 38.
Until now it has been considered necessary to include at least part of the 0 & M functionality inside the NTl itself, and hence complicated the issue more than strictly necessary. The object of the present invention is to simplify the termination network NTl, in particular in connection with single terminal installations. The object is, however, also to simplify larger networks such as those including NT2 units. The main features of the invention are defined in the claims. The present invention is based on the idea that con¬ siderable cost savings may be achieved without loss of overall service quality in cases where the U-interface is made identical to the standardized T-interface. The NTl may then be realized as a passive connector. Techniques are described for carrying out all essential maintenance operations from an 0 & M centre at the premises of the network provider. This concept applies equally well for both electrical and optical transmis- sion media.
If the T and U interfaces are made equal, then no protocol translation between these will be necessary. This will be so, irrespective of the interfaces being optical or electrical. If this can be done, without a loss of overall 0 & M func- tionality, then there is potential for considerable cost savings and simplification.
Of all the NTl-functi ons listed above, it is really only the last one which at first seems to demand more from the NTl than that afforded by a simple passive connector. However, considerations below will show that even this function may be compatible with such a simple device, as it is possible to realize all the required 0 & M functions externally, without active intervention from the NTl.
The concept of "Time Domain Ref1 ectometry" (TDR), whether performed electrically or optically, may provide an efficient tracing of the most likely sources of operational irregulari¬ ties.
It is recognized that optical cables are extremely robust as regards burst errors, usually caused by electric equipment or atmospheric disturbances. Physical damage is however, not uncommon, and it is believed that this will be one of the most frequent reasons for reported problems also in the future. TDR-measurements performed remotely from an 0 & M centre will effectively detect any physical defects of the network medium, and even pinpoint the exact location of the discontinuity relative to the 0 & M centre. In this way it can be established whether the fault is within the responsibility of the network provider or not.
Detectable faults may range from short cable sections of higher attenuation than normal, to frayed or even severed cables.
Tracing of other types of faults is also possible. Using correlation techniques upon the signal reflected or branched back to the 0 & M centre, measurements like bit error detection and long-term assessment of transmission quality is possible. In this way, the slow deter oration of laser efficiency may be detected and corrective measures taken. The information gathered may provide background material for network-related statistics.
Through signal processing of the reflected signals, more sophisticated 0 _< M functions (not yet defined, but referred to as Network Overhead Functions) can be implemented from the premises of the network provider, rather than being dis¬ tributed to each individual NTl.
With the 0 & M functions located centrally, the associate test and monitoring equipment may be shared between several subscribers. Performance checking can be done by taking sampled tests of each subscriber's line section at regular intervals. Each user's share of the maintenance costs will hence be just a small fraction of that associated with an active type of NTl.
For more complicated analyses, there must be stringent demands on the test equipment to avoid that the reliability o the analyzer itself is inferior to the system being tested. This is another case that speaks in favour of having all 0 & functions located centrally. Investing in high quality test equipment can then be justified in a way that would be prohibited in a distributed test scenario.
The typical business scenario, with a number of terminals sharing a common access to the public network via an NT2, represents a different situation from that found in a single terminal environment, like that of a residential user or a very small business. It is clear that the cost benefit of saving just one NTl unit does not make a major impact upon the total cost for a large business system. However, as regards maintenance costs there will be a significant potential for savi ng. For a single terminal installation the saving may be considerable, because the NTl constitutes a much higher share of the total system cost in this case.
It may be impossible to link the S-interface directly to the T-interface if such a simplified NTl is used.
In a business environment all protocol conversion will take place within the NT2. However, for a single terminal installation, the use of a medium adapter may be required to 5 ensure adequate transmission range from the standardized S- interface.
Above mentioned and other features and objects of the present invention will clearly appear from the following detailed description of embodiments of the invention taken in 10 conjunction with the drawings, where
Figure 1 schematically illustrates the principles of a known single terminal installation,
Figure 2 illustrates a known larger installation including a NT2 unit, 15 Figure 3 illustrates reflection of signals at the user side in accordance with the invention, and
Figure 4 illustrates an OTDR separate pipe installation.
In Figure 1 is illustrated a known configuration where a B-ISDN line leads from an exchange 1 through an NTl unit or 20 network terminator 2 to a subscriber terminal 3.
Figure 2 is illustrated a known configuration where a B- ISDN line leads from an exchange 1 through an NTl unit 2 and a NT2 unit 4 (network terminators) to a subscriber 3.
In principle, there are two different ways of checking the 25 line between a passive NTl module and the exchange; either by TDR or by inspection of a looped-back signal.
Figure 3 illustrates that line-checks can be made by means of reflection of a transmitted signal in an NTl module 5 at user side (bitstream reflection / loop-back). The reflection 30 of the transmitted signal can be continuous, meaning all signals are reflected. The results from the test can be obtained by correlation of transmitted and received signal. Figure 3 illustrates only a mode by which signals are transmitted from an exchange 1 to a receiver terminal 3. The 35 mode of transmission from the subscriber 3 in the direction of the exchange 1 is not shown. The communication signals and test signals may be transmitted from exchange equipment 6 which may include a light emitting diode (LED). The communi- cation signals will reach the terminal equipment 3 which may include a PIN type receiving device 7. The signals transmitte from the exchange 1 are partly passed through NTl module 5 to the subscriber 3, and partly reflected in a reflector 8 back to exchange equipment 9 which may include a PIN type receivin device.
A scheme based on optical TDR and separate pipes is illustrated in Figure 4. The principle is also applicable for single fiber and WDM. The communication signals are trans- mitted at a wavelength of 1500 n , whereas the test signals are at 1300 nm. By operating at different wavelengths, the tw types of signals can be separated by optical filters, thus allowing for simultaneous data transfer and line supervision. By comparing the (known) transmitted signal with the one returned; either through reflection or loop-back, the returned signal may be examined for bit error corruption by means of auto-correlation techniques. This implies that a signal is examined for the degree of correspondence (correlation) with a delayed replica of itself. With no bit errors there will be perfect correlation between the two. The degree of correlation between the returned signal and the one transmitted originally is hence a measure of the bit error rate on the line.
In Figure 4 is schematically illustrated a transmitting pipe arrangement 10 with exchange equipment 1 including OTDR equipment 11, a communication signal transmitter 12 (LED
1500), a test signal transmitter 13 (LED 1300) and a receiver 14 (PIN 1300). The communication signals are passed through an NTl module 15 to terminal equipment 16 which may include a PIN type receiving device (PIN 1500). The receiving channel or pipe 20 includes OTDR equipment
21 as well as a communication signal PIN type receiving device
22 (PIN 1500), test signal transmitting means 24 (LED 1300) and receiving means 23 (PIN 1300). The communication signals are passed through the passive NTl module 25 from the subscriber transmitting equipment 26 which may include a light emitting diode (LED 1500). Test signals are as in the transmitting mode reflected in the NTl module 25.
The test signals may be transmitted at a frequency different from that of the communication signals as indicated, but the test signals may alternatively be transmitted at the same frequency as that of the communication signals.
The passive NTl module may in its simplest form be realized as a connector.
As will be understood separate "pipes" may be used for upstream as well as downstream transmission which requires means for receiving the downstream signals at the transmitter side. The upstream and downstream signals may, however, alternatively be transmitted in the same pipe - meaning that the reflected signal will be added to the received signal.

Claims

Patent Claims
1. Method for operating and maintaining at least one B-ISDN line between an ISDN exchange and an ISDN subscriber, c h a r a c t e i z e d i n t h i s t h a t the line operation and maintenance functions are performed by equipment in the exchange.
2. Method according to claim 1, c h a r a c t e r i z e d i n t h i s t h a t the line operation and maintenance functions are shared by a number of lines.
3. Method according to claim 1, c h a r a c t e r i z e d i n t h i s t h a t the operation and maintenance functions which gives indication on physical parameters regarding the line (disruption, as well as bit error rates), are performed without disconnecting the line.
4. Method according to claim 1, c h a r a c t e r i z e d i n t h i s t h a t the operation and maintenance functions which gives indication on physical parameters regarding the line (disruption, as well as bit error rates), are performed simultaneously with normal traffic on the line.
5. Method according to claim 4, c h a r a c t e r i z e d i n t h i s t h a t test signals are transmitted at a frequency different from that of the communication signals.
6. Method according to claim 4, c h a r a c t e r i z e d i n t h i s t h a t test signals are transmitted at the same frequency as that of the communication signals.
7. Method according to claim 1, c h a r a c t e r z e d i n t h i s t h a t line-checks are made by means of reflection of a transmitted signal in the NTl module at user side (bitstream reflection / loop-back).
8. Method according to claim 7, c h a r a c t e r i z e d i n t h i s t h a t the reflection of the transmitted signal is continuous, meaning all signals are reflected.
9. Method according to claim 7, c h a r a c t e r z e d i n t h i s t h a t results from the test are obtained by correlation of transmitted and received signal.
10. Method according to claim 1, c h a r a c t e r i z e d i n t h i s t h a t the line parameters are checked by means of Time Domain Ref1 ectometry (TDR).
11. Method according to claim 10, c h a r a c t e r i z e d i n t h i s t h a t the line parameters are checked by means of Optical Time Domain Ref1 ectometry (OTDR).
12. Method according to claim 1, c h a r a c t e r i z e d i n t h i s t h a t for transmission, separate "pipes" are used upstream and downstream, requiring means for receiving the downstream signals at the transmitter side.
13. Method according to claim 1, c h a r a c t e r i z e d i n t h i s t h a t the upstream and downstream signals are transmitted in the same pipe - meaning that the reflected signal will be added to the received signal.
PCT/NO1990/000141 1989-09-29 1990-09-13 Method for terminating an isdn line WO1991005424A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NO89893901A NO893901L (en) 1989-09-29 1989-09-29 PROCEDURE FOR ISDN LINE TERMINATION.
NO893901 1989-09-29

Publications (1)

Publication Number Publication Date
WO1991005424A1 true WO1991005424A1 (en) 1991-04-18

Family

ID=19892438

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/NO1990/000141 WO1991005424A1 (en) 1989-09-29 1990-09-13 Method for terminating an isdn line

Country Status (3)

Country Link
AU (1) AU6406690A (en)
NO (1) NO893901L (en)
WO (1) WO1991005424A1 (en)

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
INTERNATIONAL SWITCHING SYMPOSIUM 1987: "Inovations in Switching Technology", Proceedings (Cat. No. 87CH2431-5), Phoenix, Arizona, 1987, P 149-153, Vol. 1, BRANDMAIER K, AXE M: "O&M Concepts for Public Networks using ISDN, CCS7 and Personal Computers". *
PROCEEDINGS OF THE SPIE-THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING, Vol. 1179, 1990, P 198-209, YONEDA S, ROBE T.J.: "Sonet (SDH) Framer Chip Application for the B-ISDN User Network Interface; Operations and Maintenance Functional Requirements". *

Also Published As

Publication number Publication date
NO893901L (en) 1991-04-02
NO893901D0 (en) 1989-09-29
AU6406690A (en) 1991-04-28

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