1、 TIA STANDARD ANSI/TIA-876-2002 Approved: August 8, 2002 North American Network Access Transmission Model for Evaluating xDSL Modem Performance TIA-876 SEPTEMBER 2002 TELECOMMUNICATIONS INDUSTRY ASSOCIATION Representing the telecommunications industry in association with the Electronic Industries Al
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17、, INCIDENTAL OR CONSEQUENTIAL DAMAGES (INCLUDING DAMAGES FOR LOSS OF BUSINESS, LOSS OF PROFITS, LITIGATION, OR THE LIKE), WHETHER BASED UPON BREACH OF CONTRACT, BREACH OF WARRANTY, TORT (INCLUDING NEGLIGENCE), PRODUCT LIABILITY OR OTHERWISE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. THE FO
18、REGOING NEGATION OF DAMAGES IS A FUNDAMENTAL ELEMENT OF THE USE OF THE CONTENTS HEREOF, AND THESE CONTENTS WOULD NOT BE PUBLISHED BY TIA WITHOUT SUCH LIMITATIONS. TIA-876 i Contents TABLES AND FIGURES iii FOREWORD .vii INTRODUCTION viii 1. SCOPE1 2. NORMATIVE REFERENCES 2 3. DEFINITIONS AND ACRONYMS
19、.3 3.1 DEFINITIONS.3 3.2 ACRONYMS.5 4. DESCRIPTION OF MODEL.9 4.1 INTRODUCTION.9 4.2 MODEL DESCRIPTION .10 4.3 PHYSICAL ARCHITECTURE OF THE NETWORK MODEL11 5. IMPAIRMENT LEVEL SETUP13 5.1 DEFINITION OF IMPAIRMENTS13 5.1.1 Crosstalk13 5.1.1.1 Near-end crosstalk (NEXT) . 13 5.1.1.2 Far-end crosstalk (
20、FEXT) 13 5.1.2 Loop Impairments13 5.1.2.1 Bridged Taps 13 5.1.2.2 Amplitude Distortion. 13 5.1.2.3 Moisture. 14 5.1.2.4 Temperature. 14 5.1.3 Steady State Impairments.14 5.1.3.1 Splitter/Distributed Filter. 14 5.1.3.2 Background Noise . 14 5.1.3.3 AC Induced Interference 14 5.1.3.4 Longitudinal Bala
21、nce. 14 5.1.3.5 PC Monitor Interference 15 5.1.3.6 AM Radio Interference 15 5.1.3.7 Premises End Crosstalk (PEXT) 15 5.1.4 Transient Impairments.15 5.1.4.1 CO Ringing Transients 15 5.1.4.2 Ring Trip Transients 15 5.1.4.3 On-Hook/Off-Hook Transients 15 5.1.4.4 Impulse Noise 15 5.2 DETAILED NETWORK EL
22、EMENT MODELS .17 5.2.1 Central Office (CO) Model 17 5.2.2 Loop Models 18 5.2.3 Drop Models 18 5.2.3.1 Drop Model for Single Digital Service . 18 5.2.3.2 Drop Model for Second Service Environments 18 5.2.4 Drop Model for Business Entrance Cable 18 5.2.5 Models for Premises Wiring 18 5.3 TEST SETUP 18
23、 5.4 IMPAIRMENT COMBINATION TABLES23 5.4.1 Crosstalk Impairment Combination Tables 23 5.4.2 Specified Steady-State Impairments50 5.4.3 Specified Transient Impairments .51 TIA-876 ii 5.4.4 Network Model Coverage 52 A.1 TEST LOOP LIKELIHOODS OF OCCURENCE (LOOS) .54 A.2 TEST LOOPS.55 A.3 LOOP SIMULATOR
24、 IMPLEMENTATION 57 B.1 SINGLE FAMILY AND SMALL OFFICE PREMISES MODELS .59 B.1.1 Daisy Chain Wiring (P1) .59 B.1.2 Star Wiring (P2) 59 B.1.3 Star Wiring (P3) with Central ADSL Splitter and Direct Line 60 B.1.4 Crosstalk Insertion.60 B.2 MULTI-UNIT/BUSINESS WIRING .60 B.2.1 Multi-Tenant Residence / Bu
25、siness - Daisy Chain Wiring (P3)60 B.2.2 Multi-Tenant Residence / Business - Star Wiring (P4).61 B.2.3 Small Office Wiring (P1 and P2).62 B.2.4 Large Office Wiring.62 B.2.5 Crosstalk Insertion for Multi-Tenant and Business Loops 62 B.3 PREMISES CROSSTALK (PEXT) 62 B.3.1 PEXT Transfer Function Non-pa
26、ired Station Wire 62 B.3.2 PEXT Transfer Function Twisted (Cat 3) Station Wire 62 B.3.3 PEXT Transfer Function Single Phone Cord .62 C.1 LOOP MODEL63 C.2 CONNECTION TYPES.66 C.2.1 Connection Type CT1.66 C.2.2 Connection Type CT2.67 C.3 IMPAIRMENT RANGES.69 C.3.1 Background Noise69 C.3.2 Ringing Impu
27、lse Noise.69 C.3.3 Hook Switch Coupling .69 C.3.4 Dial Pulse Coupling.69 C.3.5 Longitudinal Power Line Induction69 C.3.6 Power Related Metallic Noise .69 C.3.7 Crosstalk (for coupling equations, see Section F.1 of Annex F)70 C.3.7.1 NEXT Coupling Configurations . 70 C.3.7.2 FEXT Coupling Configurati
28、ons 70 C.3.7.3 PEXT Coupling. 70 C.3.8 Radio Frequency Interference (RFI)70 C.4 CONNECTION TYPE AND IMPAIRMENT COMBINATION SCORES .70 C.4.1 Connection Type Scores.70 C.4.2 Crosstalk IC Scores .71 C.5 CROSSTALK DISTURBER DEPLOYMENT 71 C.5.1 Residential Crosstalk Model72 C.5.2 Business Crosstalk Model
29、72 C.6 COMPOSITE CEXT.74 D.1 INTRODUCTION.75 D.2 CONSIDERATIONS .75 D.2.1 Protocol level issues 75 D.2.2 Measurement types 75 D.3 DISCUSSION75 D.4 TEST SUMMARY .75 D.5 TEST STATION 76 D.5.1 Equipment this standard models the DSL access network over the frequency range of 0 to 1.104 MHz. It is intend
30、ed that this standard may be used with PN-3-4255, “Test Procedures for evaluating xDSL Modem Performance.” (PN-3-4255 was under development at the time of publication of this standard.) The document is organized as follows: Sections 1 through 3 define the Scope of the test model and provide Referenc
31、es and Definitions. Sections 4 and 5 describe the model, test setup and impairments under which testing is to be conducted. Annex A (Normative) defines the test loops and specifies the likelihood of occurrence of each. Annex B (Normative) defines the premises models. Annex C (Informative) provides t
32、he rationale for the various elements of the model. Annex D (Informative) gives examples illustrating the use of the model. Annex E (Normative) defines how the model is used for evaluating dual communications through both broadband and voiceband channels over a common subscriber loop. Annex F (Norma
33、tive) defines how impairments are to be characterized for testing purposes. There are a total of six annexes in this standard. Annexes A, B, E and F are normative and are considered part of this standard while Annexes C and D are informative and only those portions referenced by normative text are c
34、onsidered part of this standard. TIA-876 viii INTRODUCTION This standard defines the North American network access transmission model to be used in evaluating performance of DSL modems. The standard can be applied to both splittered and splitterless xDSL systems. The model is described in terms simi
35、lar to prior ANSI and ITU modem test standards (e.g., V.56bis) and allows comparison of DSL modem performance in terms of percent network coverage. This model is intended for use by network service providers, magazine product reviewers, users and designers to evaluate and compare modem performance.
36、The purpose of this standard is distinct from that of ITU standard G.996.1 and DSL Forum Technical Report TR-029. G.996.1, Test Procedures for Digital Subscriber Line Transceivers, contains network models and test procedures for verifying DSL transceiver conformance to the performance requirements c
37、ontained in each of the G.99x DSL transceiver Recommendations. TR-029, ADSL Dynamic Interoperability Testing, contains test suites and test procedures to determine the level of interoperability between different vendor brands of ATU-Cs and ATU-Rs. The network model consists of many impairment combin
38、ations to provide a statistically significant sample of impairment conditions. The tests are intended to allow completion of a full set of testing within one day or less depending on the type of test that is being run. The test methodology easily lends itself to automation. The DSL System under test
39、 is run over each impairment combination to provide a statistically significant result. This approach can be viewed as running many individual SNR points over a wide range of line conditions. The method of testing offers significantly more information about the real world performance than margin tes
40、ting (stress testing to determine the point of maximum performance at an acceptable error rate) with particular impairments. This network model provides a statistically accurate indication of performance over good, medium and worst-case line conditions, not just stress conditions, which allows for a
41、ccurate evaluation of such things as AFE performance. For example, AFE noise problems cannot be found using margining because the high noise impairment overshadows the poor performance of the AFE. The objective of this standard is to define a realistic North American network access transmission mode
42、l for comparing DSL modem performance in terms of network model coverage (NMC). The goal of the model is to provide a portrait of the real network as it exists in the year 2002. The model is technology independent. Because some important elements of the model (crosstalk disturber model, for example)
43、 are based on projections, it is recognized that the model will need to be revised based on actual rollout of DSL services. ANSI-accredited committee TR-30.3 has developed this standard. TR-30.3 has developed modem performance testing standards currently used throughout the industry for evaluation o
44、f dial and leased line modems (e.g., V.34, V.90). TIA-876 1 North American Network Access Transmission Model for Evaluating xDSL Modem Performance 1. SCOPE This standard defines a model of the characteristics of the North American access network that determine xDSL modem transmission performance. It
45、 is intended to be the basis for performance testing of systems consisting of central site modems that interface with the broadband telecommunications network and remote modems at the customer premises. The model includes specifications for the configuration and setup of suitable simulator equipment
46、 used in evaluations and comparisons of such modem systems. Warning The network models represented in this specification do not model all possible connections that can be encountered between a central site modem and a remote modem in the North American loop plant. Limitations on this model: 1. This
47、model does not include very low-probability connection scenarios. 2. Steady-state loop current and loop battery parameters are not specified. Refer to ANSI/EIA/TIA 496-A for information on those parameters. 3. This model does not reflect the characteristics of network equipment operating outside of
48、its normal operational specifications, referred to as “trouble” conditions. 4. The network transmission impairments used in this model are those that exist in the access network and affect the performance of present-day DSL modems. New network equipment or new modem designs may result in additional
49、parameters, not currently characterized, becoming important. Results derived from tests using this model are suitable for comparative purposes, and should be viewed as no more than a rough estimate of expected performance over the real network. 5. This standard models the DSL access network over the frequency range of 0 to 1.104 MHz. It is not intended for use in testing VDSL modems. While the percentages of network model coverage (NMC) derived from the tests contained herein may provide a suitable basis for comparing modems, they should only be considered indicative of p
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