1、Problem Solvers to the Telecommunications IndustryCommittee T1 -TelecommunicationsTechnical Report No. 60July 1999Unbundled VoicegradeAnalog LoopsPrepared by T1A1.7Working Group onSignal Processing and NetworkPerformance for Voiceband ServicesCopyright 1999 by Alliance for Telecommunications Industr
2、ySolutionsAll rights reserved.Committee T1 is sponsored by the Alliance for TelecommunicationsIndustry Solutions (ATIS) and accredited by the American NationalStandards Institute (ANSI)No part of this publication may be reproduced in any form,in an electronic retrieval system or otherwise, without t
3、heprior written permission of the publisher.A Technical Report onUnbundled Voicegrade Analog LoopsAbstractThis T1 technical report discusses the transmission performance of unbundledvoicegrade analog loops and is intended to help the telecommunications industry planquality voicegrade local networks.
4、 The report provides performance information forunbundled subscriber access wherein the unbundled subscriber loop is connected to acompetitive/incumbent local exchange carrier (CLEC/ILEC) inter-network interface (INI).This connection takes place when the CLEC is collocated and the ILEC distributionf
5、rame (DF) terminates the loop. Furthermore, the technical report reviews local accesslines by discussing ANSI IEEE 820-1992, loop design methodologies, signal levels, andbridged taps. Finally, the document considers treated lines by reviewing ANSI T1.512-1994(R1999) and historical information regard
6、ing switched treated lines.This document is written in the context of a carrier purchasing connectivity to the end-user, i.e., subscriber access. The document focuses only on analog voiceband services.Document T1A1.7/99-005r3Prepared byT1A1.7Working Group on Signal Processing andNetwork Performance
7、for Voiceband ServicesiForewordChanges in telecommunications law and markets have caused the industry to reviewand modify the way services are, and will be, provided in North America. The “local loop”represents one area in which the practices of the past are undergoing substantialchange. Although it
8、 is not the only network element that the Telecommunications Act of1996 has mandated for unbundling, the local loop represents a major area wheretransmission performance clarification and definition is needed. Other network elementsthat may effect end-to-end transmission or related performance inclu
9、de (trunk) transportand switching.With the publication of this technical report, the industry has taken an important step inrecognizing and addressing changes in the voicegrade telecommunicationsenvironment. However, while this technical report is forward looking in its scope, itmaintains clear sigh
10、t on the traditional aspects of service provisioning that have led tothe quality of service associated with the Public Switched Telephone Network.This document is written in the context of a carrier purchasing connectivity to the end-user, i.e., subscriber access. The document focuses only on analog
11、 voiceband services.Suggestions for improvement of the Technical Report are welcome and should be sentto the Alliance for Telecommunications Industry Solutions - Committee T1 Secretariat,1200 G Street N.W., Suite 500, Washington, D.C. 20005.At the time this report was completed, T1A1.7 had the follo
12、wing members:D.J. Atkinson Ricky B. Grams Max J. Roesch, Jr.Chuck Balogh Eric Hauch John RoquetDick Bobilin Ralph E. Jensen Glenn J. ScheydLorence F. Brown Michael Kalb Ernest SchmidtCarl Bushue Gary Knippelmier Dan ThomasE. Mel C. Celi Mustafa Kocaturk Pat TweedyGregory Cermak Gary Koerner Sangames
13、h VinayagamurtyAntony Crossman Barry Lerich Stephen VoranMahmoud Daneshmand Tom Oshidari Arthur WebsterChuck Dvorak Mark E. Perkins Bernard WorneGeorge Fawcett, Jr. A. C. Morton J. A. ZebarthMichael Floyd An Nguyen William R. WycoffSuhas S. Gandhi Matt Noah Kevin ZhangTom Geary Jess ReyesiiThis page
14、 intentionally blank.iiiContents1 Purpose, Scope, and Application.11.1 Purpose. 11.2 Scope 11.3 Application 12 References12.1 Standards 12.2 Texts. 23 Generic Terminology .23.1 Definitions . 23.2 Abbreviations and Acronyms. 44 Unbundled Subscriber Access.44.1 Physical Service Elements 54.2 Expected
15、Performance Limits - Unbundled Subscriber Access. 65 Local Access Lines75.1 Summary of IEEE Standard Telephone Loop Performance Characteristics(ANSI IEEE 820-1992) 85.2 Loop Design Methodologies 95.3 Signal Levels125.4 Bridged Tap .126 Treated Lines 126.1 Summary of Point-to-Point Voice-grade Specia
16、l Access Network VoicebandData Transmission Objectives (ANSI T1.512-1994 (R1999) .126.2 Switched Treated Lines13ivThis page intentionally blank.1Unbundled Voicegrade Analog Loops1 Purpose, Scope, and Application1.1 PurposeIn order to stimulate competition, the Telecommunications Act of 1996 (TA96) a
17、llows forCompetitive Local Exchange Carriers (CLECs) to offer switched local network services totheir (retail) telecommunications customers. CLECs may obtain part or all of the physicalmeans for providing these services from the Incumbent Local Exchange Carriers (ILECs).The purpose of this technical
18、 report is to help the telecommunications industry planquality, voiceband transmission performance on unbundled voicegrade analog loops.Therefore, the technical report describes transmission performance parameters ofunbundled loops used to provide connectivity to a subscribers premises for analogvoi
19、ceband services. The technical report is as quantitative as available sources permit.The information in this document will help the industry to cooperatively meet objectivesfor providing end-user analog voiceband services. This document fosters the provisionof quality end-to-end service, as perceive
20、d by the end-user of analog voicebandservices.This document is written in the context of a carrier purchasing connectivity to the end-user, i.e., subscriber access. The document focuses only on analog voiceband services.1.2 ScopeThis technical report describes voiceband transmission performance para
21、meter levels ofvoicegrade analog unbundled subscriber access (section 4), local access linesterminated at the NI at one end and the end office switching system at the other (section5), and treated lines (section 6). In addition the technical report describes traditional andexisting methods of ILEC l
22、oop facility design integral to local access service.The technical report contains information which should be useful in CLEC design oflocal access lines regardless of the loop transport technology employed.1.3 ApplicationThis technical report is intended to help the telecommunications industry plan
23、 qualityvoicegrade local networks. The report accomplishes this by providing performanceinformation for: unbundled subscriber access to the CLEC/ILEC INI collocated with the ILEC DFwhich terminates the loop, local access lines, and treated lines.2 References2.1 StandardsANSI/IEEE Standard 820-1992,
24、Telephone Loop Performance Characteristics.ANSI T1.512-1994 (R 1999), Point-to-Point Voice-Grade Special Access NetworkVoiceband Data Transmission Objectives.Technical Report No. 6022.2 TextsEngineering and Operations in the Bell System, Members of the Technical Staff and theTechnical Publication De
25、partment, Bell Laboratories, Bell Telephone Laboratories, Inc,Murray Hill, NJ, 1977 (Seventh Printing, 1982).Engineering and Operations in the Bell System (Second Edition), R.F. Rey, TechnicalEditor, AT&T Bell Laboratories, Murray Hill, NJ, 1983.Transmission Systems for Communications (Fourth Editio
26、n), Members of the TechnicalStaff Bell Telephone Laboratories, Murray Hill, NJ, 1970.Telecommunications Transmission Engineering, Volume 3 -Networks and Services(Third Edition) (ST-TEC-000053), BELLCORE, August 1989.3 Generic Terminology3.1 Definitions3.1.1 Competitive Local Exchange Carrier (CLEC)F
27、or the purposes of this document, an alternative provider of local access service (otherthan the ILEC).3.1.2 Competitive Local Exchange Carrier (CLEC) NetworkThe network composed of network elements that are owned by the CLEC or leased bythe CLEC from some other carrier to provide service to its tel
28、ecommunicationscustomers.3.1.3 ChannelFor the purposes of this document, a bi-directional voiceband transmission pathbetween two points (one point may be a NI).3.1.4 ConnectionA temporary concatenation of transmission channels or telecommunication circuits,switching, and other functional units set u
29、p to enable a transfer of information betweentwo or more points in a telecommunication network.3.1.5 End-User (EU)The calling party, or the called party, or both involved with a connection. End-users aretypically on the customer side of the NI.3.1.6 Incumbent Local Exchange Carrier (ILEC)The Local E
30、xchange Carrier that on the date of enactment of the TelecommunicationsAct of 1996, provided telephone exchange service in a specific geographical area.3.1.7 Incumbent Local Exchange Carrier (ILEC) NetworkThe network composed of network elements that are used to provide service to anILECs telecommun
31、ications customers.3.1.8 Internal Network Interface (INI)A point in the local network transmission path that may be used as a point forinterconnection, unbundling, and testing of network elements.Technical Report No. 6033.1.9 Local Access LineExchange network switching and transmission equipment and
32、 facilities that provide theservice offering, commonly referred to as Plain Old Telephone Service (POTS) thatenables an end-user to obtain access to the Public Switched Telephone Network.3.1.10 LoopFor the purpose of this document, the channel between the NI and a distributing frame(DF).3.1.11 Netwo
33、rk Interface (NI)The point of demarcation between the exchange carriers facilities and the end-userinstallation that establishes the technical interface and may establish division ofoperational responsibility.3.1.12 Terminal EquipmentEquipment, such as telephone sets, PBXs, and voiceband data modems
34、, at the end of acommunication circuit.3.1.13 UnbundleThe process whereby an ILEC makes available to a CLEC specified ILEC networkelements (e.g., facilities, or switching system technology), under a tariff, contract, orspecial assembly service offering.3.1.14 Unbundled Voicegrade Analog LoopThe voic
35、egrade analog channel leased by a CLEC from an ILEC that extends from thedistributing frame (DF) to the network interface (NI).3.1.15 Unbundled LoopFor this report, this term is used as a shorthand equivalent of an unbundled voicegradeanalog loop.3.1.16 Unbundled Network Element (UNE)A network eleme
36、nt owned and maintained by an ILEC that has been leased to CLEC.An unbundled network element is self-contained.3.1.17 Unbundled Subscriber AccessThe bi-directional channel, that contains an unbundled voicegrade analog loop, betweenthe end-user NI and the first CLEC/ILEC INI.3.1.18 VoicebandThe set o
37、f frequencies between approximately 300 Hz and approximately 3300 Hz (notnecessarily a passband).13.1.19 VoicegradeSuitable for transmitting a voice signal.1The frequencies, approximately 300 Hz and approximately 3300 Hz, are based on cables with H88 loadingscheme described in Section 5.2. If anothe
38、r loading scheme is used, e.g. D66, or if the plant is not loaded,the upper frequency of the voiceband is constrained by the anti-aliasing filter of the analog-to-digitalconversion process to approximately 3,400 Hz.Technical Report No. 6043.2 Abbreviations and AcronymsCLEC Competitive Local Exchange
39、 CarrierCREG Concentrated Range Extension with GainDF Distribution FrameILEC Incumbent Local Exchange CarrierINI Internal Network InterfaceLF Linking FunctionMDF Main Distribution FrameNI Network InterfacePOT Point of TerminationSCS Subscriber Carrier SystemTA96 Telecommunications Act of 1996UNE Unb
40、undled Network Element4 Unbundled Subscriber AccessThis section provides diagrams, technical parameters, and transmission objectivesdescribing unbundled subscriber access. As shown in figures 1 and 2, an unbundledvoicegrade analog loop is intended to refer to the portion of unbundled subscriberacces
41、s between the NI and the DF. The ILEC loop, normally used to provide voicebandtelephone service has 2-wire analog voice frequency interfaces at both ends and maybe unbundled for use by a CLEC. In both of the unbundled loop applications shown inthese figures, a linking function (LF) couples the unbun
42、dled loop to the CLEC facility.From here, as shown in figure 1, switching may be done by CLEC equipment to whichthe signal is transported (CLEC switching systems are generally not in collocatedspace.) Alternatively, as shown in figure 2, switching may be done by an ILEC switchingsystem that couples
43、to the CLEC facility with another LF. It is the responsibility of theCLEC to determine if impairment compensation such as gain is required to provide itsservice and to implement such impairment compensation or to arrange to have itimplemented.Figure 1 CLEC Local Access Line Architecture Using Unbund
44、ledVoicegrade Analog Loop and CLEC Switching SystemTechnical Report No. 605Figure 2 CLEC Local Access Line Architecture Using Unbundled VoicegradeAnalog Loop and ILEC Switching SystemThe technologies used in unbundled voicegrade analog loops are illustrated in figure 3.They include purely metallic f
45、acilities, loaded (e.g., H-88) metallic facilities and thoseprovisioned with subscriber carrier systems (SCS).2However, an unbundled voicegradeanalog loop is understood to be a bandwidth-limited facility whose bandwidth would beconsistent with a (e.g., H-88) loaded metallic facility or one provision
46、ed with SCStechnology. When SCS is used, it may be implemented in terms of analog carrier,universal digital loop carrier, or other pair-gain systems.Figure 3 Unbundled Voicegrade Analog Loop TechnologiesThis document does not attempt to delineate the possible unbundling methods.4.1 Unbundled Subscri
47、ber Access ElementsUnbundled subscriber access to an end-user is provided via an unbundled voicegradeanalog loop and a linking function. Figure 4 is an example of this architecture. Centraloffice intra-office3transmission facilities link a terminal block or frame at the CLEC/ILECINI to a terminal bl
48、ock on the main distribution frame (MDF). (In this example the INI-to-MDF transport is provided by the ILEC, but there are also arrangements in which theCLEC or other agents may provide this transport.) A jumper wire (which is part of the LF2Unbundled voicegrade analog loops provisioned with SCS wil
49、l also generally include metallic or loadedmetallic facilities between the SCS remote terminal and the NI.3This assumes the CLEC/ILEC INI is collocated with the ILEC DF that terminates the unbundled loop. Thisreport recognizes that the CLEC/ILEC INI may be remotely located from the traditional ILEC serving centraloffice. However, in this technical report expected performance limits have not been provided for non-collocated CLEC/ILEC INI-DF configurations.Technical Report No. 606in this example) is inserted between the aforementioned MDF terminal block andanother MDF terminal block that
