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Network Access Transmission Model for Evaluating xDSL Modem Performance

Network Access Transmission Model for Evaluating xDSL Modem Performance. Jack Douglass, Paradyne International Chair TIA TR30.3 Sept 9 - 13, 2002, ETSI TM6 TD23 TR30.3 302090067 023t23 jdouglass@paradyue.com. Presentation Overview. Purpose of Presentation to Value of xDSL Network Model

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Network Access Transmission Model for Evaluating xDSL Modem Performance

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  1. Network Access Transmission Model for Evaluating xDSL Modem Performance Jack Douglass, Paradyne International Chair TIA TR30.3 Sept 9 - 13, 2002, ETSI TM6 TD23 TR30.3 302090067 023t23 jdouglass@paradyue.com

  2. Presentation Overview • Purpose of Presentation to • Value of xDSL Network Model • Network Model Template • Access Network Simulator • Proposal for Creating European Network Model

  3. Purpose of Presentation • Skeleton Network Model to form the basis of Permanent Document TM6(02)07 (m02p07) • European Network Access Model(s) for xDSL Performance testing.

  4. Value of xDSL Network Model

  5. 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

  6. 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

  7. 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

  8. Network Model Template

  9. 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.

  10. 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

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

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

  13. 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.

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

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

  16. 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

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

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

  19. 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

  20. 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

  21. 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

  22. 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

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

  24. 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

  25. Network Model Coverage Tables

  26. 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

  27. Example Network Model Coverage = 100%

  28. Example Network Model Coverage = 90%

  29. 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.

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

  31. Access Network Simulator

  32. 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).

  33. 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 CPE DUT

  34. 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

  35. 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

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

  37. 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

  38. Proposal for Creating European xDSL Network Model

  39. Obstacles • Country to country variations of loop/crosstalk/noise statistics and characteristics • Lack of publicly available information regarding loop/crosstalk statistics • Unbundling Competition • Regulations

  40. Proposed Procedure • Create straw-man Network Model(s) using sample template and experience • Gather anonymous statistical information on European Access Network where ever possible • Loop (configuration, binder size, type of cable, gauge, etc.) • Crosstalk data (numbers and types of interferers currently installed and marketing deployment information) • Steady-State Impairments (e.g., Ingress impairments, AM Radio, etc.) • Transient Impairments • Revise straw-man Network Model(s) based on statistical information • Validate model using real xDSL equipment of different technologies • Compare validation results with known real world performance

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