Network Access Transmission Model for Evaluating xDSL Modem Performance

1. Network Access Transmission Model for Evaluating xDSL Modem Performance Jack Douglass, Paradyne International Chair TIA TR30.3 Sept 5, 2002, FS-VDSL TR30.3 302090064 FS0261 jackdouglass@hotmail.com

2. Presentation Overview • Purpose of Presentation to FS-VDSL • Access Network Models Projects for Evaluating xDSL Modem Performance • Value of xDSL Network Model • Network Model Overview • Access Network Simulator • Advantages of NMC Methodology • Obstacles to Creating a European Network Model that implements NMC methodology • Proposal for Creating European Network Model • Discussion

3. Purpose of Presentation • Establish a formal liaison between FS-VDSL and TR30.3 • Request that FS-VDSL open a project to assist in the develop of a European xDSL Network Model that uses Network Model Coverage (NMC) methodology • TIA/EIA-876, North American Network Model, has been released for publication • ETSI has opened a project in the form of a Permanent Document (ETSI TM6 PD (02) 07) to create an European Network Model • Initial model would be for frequency range of 0 to 1.104 MHz • Principles can be applied to VDSL

4. Purpose of Presentation (continued) • Work with FS-VDSL to acquire European Network Statistics (e.g., loop, crosstalk, ingress, etc.) that are needed to build the Network Model(s) • In the past FS-VDSL has be able to reduce obstacles such as: lack of publicly available information regarding loop and crosstalk statistics, unbundling competition issues, regulation issues • Provide a template that can be used to develop European Network Model(s) • Determine the best way to forward FS-VDSL/TR30.3 work to ETSI TM6 • Contribution to ETSI TM6 concerning Network statistics for development of Network Model(s) in TM6 — may be anonymous • Contribution to ETSI TM6 that has completed Model(s) for inclusion into appropriate ETSI document (e.g., Technical Report) — may be anonymous

5. Access Network Model Projects for Evaluating xDSL Modem Performance

6. TIA/EIA-876 — North American Network Model • Uses Network Model Coverage (NMC) methodology and principles to evaluate and compare the performance of xDSL modems • Statistically based portrait of the access network and impairments • Loop Model based on a combination of loop surveys, including an anonymous 14 million line survey • Central Office wiring models • Central Office impairments (e.g., CEXT, Composite CEXT) • Intermediate xDSL interferers • Customer Premises drop and wiring models • Customer Premises impairments (e.g., RFI, POTS signalling, splitters/filters, AC induced interference) • Definitive set of loop and noise conditions for consistent and repeatable test results

7. TIA/EIA-876 — North American Network Model • Models DSL access network over the frequency range of 0 to 1.104 MHz • Technology independent • Can be applied to both splittered and non-splittered xDSL systems • Principle of TIA/EIA-876 readily apply to higher frequencies such as used by VDSL • Crosstalk, Ingress, Loop Models may require some modification • Test equipment must be able to support the desired operating range • Model to be used by Network Service Providers, PTTs, test houses, magazines, product reviewers, users and designers • TIA/EIA-876 is intend to compliment the existing xDSL testing standards • It is a performance test not interoperability or conformance test

8. TIA/EIA 876 Network Model xDSL Network Block Diagram with Impairment Injection Points

9. ETSI TM6— European Network Model • Project opened in the form of a Permanent Document to create a European xDSL Network transmission Model based on the NMC principles and methodology

10. Value of xDSL Network Model

11. Value to Operating Companies and Service Providers • Predict candidate product performance on their networks as Percentage of the network where satisfactory operation will be obtained • Determine the potential market coverage as a function of different parameters/factors such as: Quality of Service, line rate, data throughput, connect time, stability, technology, modulation technique and modem enhancements • Select optimum technology for a proposed service based its Network Model Coverage Performance • Develop Business Cases and establish Tariff objectives • Minimize costs associated with loop qualification, loop modifications and truck rolls

12. Value to Manufactures and Design Engineers • Helps find design weaknesses • Facilitates isolating and resolving field problems • Assists in evaluating different technologies • Predicts real access network performance

13. Comparison Testing • Model can be used by test houses, magazines and product reviewers to compare the performance of different brands of xDSL modems or systems • Test results are intended to reflect the customer experience

14. Network Model Overview

15. Telephone Exchange Street Cabinet MDF Local Distribution Point DSLAM Exchange 0.5 mm 150 m Drop Wire 0.5 mm PE 50 m Branch Cable 25-pair binder 0.5 mm PE 0.25, 0.5, 0.63, 1.0 km Distribution Cable 25(?)-pair binder 0.4, 0.5, 0.63 mm 2 to 7 km Exchange Noise Injection Intermediate Noise Injection CPE Noise Injection Example General European Access Network Model • Cable lengths and types are intended as a basis for discussion. • Intermediate noise injection (Remote DSLAM) point may not be necessary.

16. Cumulative Distribution for Crosstalk Models • Cumulative Distribution Values • Basis for the crosstalk mix used in Crosstalk Impairment Combination Tables • Residential/Multiunit Model • asymmetrical weighting • Business Model • symmetrical weighting • Projected for the year 200x • Current xDSL deployment statistics • Projected xDSL deployment • Assumes 25 (?) -pair binders with yy% vacant pairs • Churn/disconnect — cross-connected at street cabinet to reserve loop assignment for the next tenant • Defective pairs • Reserved for future growth

17. Residential/Multiunit Cumulative Distribution (CD) Number of Disturbers of Each Type

18. Business Cumulative Distribution (CD) Number of Disturbers of Each Type

19. Crosstalk Impairment Combinations • Crosstalk Impairment Combinations (IC) are specified for each Loop • Residential/Multiunit model • Business model • A, B, C and D Crosstalk severity levels • A — Most severe • D — Least severe • LOOs — A = 5%, B =15%, C = 30% and D = 50% (Total = 100%) • FEXT may be handled differently in mathematical analysis and hardware simulation • Hardware simulator • NEXT is inserted at both ends so that tests can be run in both directions simultaneously • Insertion of NEXT at one end of the loop produces an approximation of FEXT at the other end • Mathematical analysis • FEXT should be included at both ends • Assumes Worst-case crosstalk coupling • Disturber Model may vary between Exchange and CPE end • CPE Crosstalk is xx% co-located and yy% distributed • Distributed crosstalk may be do to operating range of some system is less than the loop can accommodate • Crosstalk may be distributed as a result of distributing services to other customer along the way.

20. Crosstalk Impairment Combinations (IC) Loop XX (LOO/Length) – Residential/Multiunit

21. Crosstalk Impairment Combinations (IC)Loop XX (LOO/Length) – Business

22. Specified Steady-State Impairments • Specified Steady-State Impairment Combinations Severity levels 0 - 3 • Primarily ingress noise • Severity 0 is a baseline null case • Severities 1 through 3 have increasing levels of ingress noise • Do not have an associated LOO

23. AM Radio Interference • Severity level 1, 2, and 3

24. Specified Transient Impairments • Not part of the NMC calculation • Important part of the Access Network Transmission Model • Must be accounted for in testing

25. Distribution Cable xx-pair binder 0.4, 0.5, 0.6 mm 2 to 7 km Branch Cable 25-pair binder 0.5 mm PE 0.25, 0.5, 1.0 km MDF Wiring 0.5 mm 100 m Drop Wire 0.5 mm PE 50 m CPE DSLAM Example General Loop Diagram

26. Example Test Loop Make-up and LOOs *Loop Loss values @ 100 kHz and @ 300 kHz are approximate and assume same cable type is used for entire length

27. Premises Wiring Models • Based on G.996.1, section 6.2.2 • Single Family and Small Office Premises Models • Daisy Chain Wiring • Star Wiring • Star Wiring with Central ADSL Splitter and Direct Line • Multi-Unit/Business Wiring • Multi-Tenant Residence / Business -- Daisy Chain Wiring • Multi-Tenant Residence / Business -- Star Wiring • Small Office Wiring • Large Office Wiring

28. Example Customer Premises Models Based on G.996.1, section 6.2.2 Daisy Chain Wiring Model

29. Network Model Coverage Tables • Tables for Network Model Coverages (NMC) of 100%, 95%, 90% and 65% are typically provided • Used for both Residential/Multiunit and Business Models • Test Channel Score • intersection of the IC and test loop • Score is Product of Loop LOO and IC LOO • < 100% NMC Tables • Remove Loop/IC combinations with lower percentage Scores • Run on Test Channels that have Scores • Reduces the test time with slightly reduced resolution

30. Network Model Coverage Tables

31. Example Network Model Coverage Tables • Examples NMC=100% and NMC=90% Tables are provided to illustrate how to construct and use NMC Tables • Arbitrary values have been assigned to the loop LOO, so that the example test channel scores can be calculated • A Test Channel Score is calculated by taking the product of the loop LOO and the IC LOO • All Test Channels are included in an 100% NMC Table • Lower percentage scores have been removed from 90% NMC Table (actual total score is 90.05) • Actual NMC Table can be constructed once the Loop LOOs have been assigned based on loop network statistics

32. Example Network Model Coverage = 100%

33. Example Network Model Coverage = 90%

34. Test Procedure and Network Model Coverage (NMC) Curves • Run each test channel (that has an associated score), in the NMC Table along with Specified Steady-State Impairment Severity 0 (null case) and one of the Premises Wiring Models. Note: The number of tests can be reduced by using a lower percentage NMC Table. • Measure desired parameter(s) (e.g., connect rate, throughput, connect time, etc.). • Repeat each test channel with Specified Steady-State Impairment Severities 1 through 3. Tests may also be repeated with different Premises Wiring Models and/or Specified Transient Impairments. • Sort measured parameter(s) along with associated NMC Scores in a descending order using a spreadsheet or similar mechanism. • Plot the measured parameter(s) on the Y axis and the associated NMC Score on the X axis. • The resulting curve shows the performance (in terms of the measured parameter) as a percentage of the Network Model.

35. Family of 65% NMC Curves for Steady-State Impairments Severity 0 to 3

36. Access Network Simulator

37. Network Model Simulator Implementation • Network Model Simulators • Mathematical Simulator • Hardware Simulator • Ideal Network Model Simulator • Separate Loop sections • Separate Noise sources • Practical and Cost-Effective Simulator • Single loop simulator • Exchange wiring • Distributed Cable • Branch Cable • Drop wire • Composite Exchange Interferers and the Composite CPE Interferers • FSAN mixed crosstalk combination method • Account for associated loop sections • Account for noise injection points. • Typically use Arbitrary Waveform Generator (AWG). • Premises wiring simulator • Device(s) Under Test (DUT).

38. Exchange xx mm yy m Drop Wire Zz mm PE ww m Network Interface Local Distribution Point DSLAM DUT MDF Street Cabinet *CPE Injection Point *MDF Injection Point *Intermediate Injection Point *Exchange injection Point *Inject noise at designated point as specified in Tables 5, 6, 7 and 10 Ideal Network Model Simulator

39. PSDX Exchange (f) Exchange Composite Interferer* AWG PSDX CPE (f) CPE Composite Interferer* AWG DSLAM DUT CPE DUT Loop Simulator Premises Wiring *Crosstalk simulation is a composite of different interferers from different injection points and includes the effects of loops Practical and Cost-Effective Network Model Simulator

40. Typical Test SetupxDSL Simulator and Modems xDSL CPE Modems (ATU-R) Telephone Network Simulator (Line Current/Dial Tone) – ADSL only xDSL DSLAM s (ATU-C) Loop Simulator Premises Wiring Simulator AWG AWG

41. Screen of Arbitrary Waveform Generator (AWG) showing Crosstalk Impairment on CO Side Uses Loop and Crosstalk transfer functions to accurately simulate impairment combinations

42. Screen of Arbitrary Waveform Generator(AWG) showing Crosstalk and RFI Impairment on CPE Side Uses Loop and Crosstalk transfer functions to accurately simulate impairment combinations

43. Advantages of NMC Methodology

44. Advantages of NMC Methodology • Predicts the performance of the system/modem over the real access network • Statistically accurate indication of overall performance based on operation over good, medium and worst case loop and noise conditions • Evaluates more than just stress conditions • Test results are displayed as a family of NMC Curves • Performance differences between products or technologies can be easily seen • NMC testing can be viewed as running many individual SNR points over a wide range of loop and noise conditions • NMC methodology which was implemented in both TIA Standards and ITU Recommendations was a key factor in improving the quality and performance of voiceband modems, over the years • NMC principles can do the same for xDSL Technology

45. Advantages of NMC Methodology • Operating Companies and Service Providers • Predict candidate product performance on their networks as Percentage of the network where satisfactory operation will be obtained • Determine the potential market coverage as a function of different parameters/factors such as: Quality of Service, line rate, data throughput, connect time, stability, technology, modulation technique and modem enhancements • Select optimum technology for a proposed service based its Network Model Coverage Performance • Develop Business Cases and establish Tariff objectives • Minimize costs associated with loop qualification, loop modifications and truck rolls

46. Advantages of NMC Methodology • Manufacturers and Design Engineers • Predict real access network performance • Find design weaknesses • Isolate/resolve field problems • Evaluate different technologies

47. Advantages of NMC Methodology • Model to be used by test houses, magazines and product reviewers to compare the performance of different brands of xDSL modems or systems • Test results are intended to reflect the customer experience

48. Proposal for Creating European xDSL Network Model

49. Proposal • Establish a formal liaison between TR30.3 and FS-VDSL to develop a European xDSL Network Model that uses Network Model Coverage (NMC) methodology • FS-VDSL Committee opens a Network Model Project • Study NMC Methodology • Acquire European Network Statistics (e.g., loop, crosstalk, ingress, etc.) that are needed to build the model(s) • Assist in developing a European xDSL Network Transmission Model(s) based on NMC principles and sample templates • Initial model would not include VDSL • Jointly determine the best method to forward FS-VDSL / TR30.3 work to ETSI TM6 • Contribution to ETSI TM6 concerning Network statistics, so a Network Model(s) can be developed in ETSI — may be submitted anonymously • Contribution to ETSI TM6 that have Model(s) for inclusion into appropriate ETSI document (e.g., Technical Report) — may be submitted anonymously

50. Key Committees and Role • FS-VDSL • Vehicle for acquiring network statistics and creating network model • Ad hoc meetings to analyze network statistics and draft document • TIA TR30.3 • Experience in creating network model • Liaison/Work with FS-VDSL and ETSI TM6 to create network model • Work on drafting the model during TR30.3 meetings • Possible vehicle to anonymously submit final network model • ETSI TM6 • European Access Network Model