ECS5365 Invited Lecture Overview of Digital Subscriber Line

1. ECS5365 Invited LectureOverview of Digital Subscriber Line James Kershaw Transmission Systems Division NEC Australia Pty Ltd http://www.nec.com.au

2. Agenda • What is Digital Subscriber Line? • Standardization • DSL Architecture • Technical Issues • Typical Applications

3. Digital Subscriber Line • Modem based Access Technology • Existing Subscriber Infrastructure • Higher Speed Connections • Pair Gain Capability

4. Advantages of DSL • Point to Point Connection • Dedicated bandwidth • Inherent Security • Existing Infrastructure • Reduced roll-out costs • Cheaper Operating Costs

5. ISDN IDSL - ISDN DSL MDSL - Multi-rate DSL SDSL - Single-loop DSL HDSL - High-speed DSL SHDSL - Single Pair HDSL RADSL - Rate Adaptive ADSL ADSL - Asymmetric DSL VDSL -Very-high-speed DSL Performance Types of DSL

6. Standardization • What needs to be standardized? • Who is involved with Standardization? • What standards exist?

7. What needs to be standardized? • Physical Interfaces • Electrical Interfaces • Link Layer Behaviour • Network Layer Behaviour • Signaling and Negotiation • Test Procedures • Electrical Compatibility

8. Who is Involved • National Bodies eg. ANSI • Regional Bodies eg. ETSI • International Bodies eg, ITU-T, IETF • Special Interest Groups eg. ADSLF, ATMF

9. International DSL Standards • ITU-T Standards • G.991 (G.hdsl) - T1/E1 symmetric • G.991.2 (G.shdsl) - under study • G.992.1(G.dmt) - 16 Mbit/s down, 1.1 Kbit/s up • Annex A - ADSL over POTS • Annex B - ADSL over ISDN • Annex C - ADSL over POTS, suitable for Japan • G.992.2 (G.lite) - 1500/640Kbit/s • G.993 (G.vdsl) - under study • G.994.1 (G.handshake) - DSL Negotiation

10. National/Regional Standards • American National Standards Institute • eg T1.413  G.992.1, TR 28 = HDSL • European Telecommunications Standardization Institute • eg ETR 328  ADSL, TS101 135  TR 28

11. Special Interest Groups • ADSL Forum • System Architecture and Interoperability • Creates Technical Reports • ATM Forum • ADSL is yet another physical layer for ATM • Creates Industry Specifications • Others

12. DSL Architecture • Reference Architecture • Medium • Modulation • Spectrum • Typical Configurations

13. V U T S Regional Broadband Network Customer Premises Network Customer Premises Equipment Service Provider Access Node Network Termination (B-NT) Core Network A11 A10 Reference Architecture (ADSLF) A11, A10 are from DAVIC V,U,T, S are from ITU-T

14. DSL Medium • Twisted Pair • Two Wire • ADSL, IDSL, SDSL, HDSL2, VDSL • Four Wire • HDSL • Six Wire • HDSL

15. Modulation • Carrierless Amplitude-Phase Modulation (CAP) • Discrete Multi-Tone (DMT) • 4B3T - 16 codes mapped onto 27 • 2B1Q - 4 codes mapped onto 4 • Others 4B3T 2B1Q

16. 25 Channels Upstream <255 Channels Downstream POTS 4.3125 kHz 4 26 Upstream Rates: 16 - 1600 kbit/s Downstream Rates: 32 - 16320 kbit/s Frequency Spectrum G.992.1 DMT • 16 bits/symbol • 4 Kbaud/tone • 64 Kbit/s/tone 1104 f(kHz)

17. Technical Problems • Cross Talk • Interference • Impulse Noise • Radio Noise • Line Impairments

18. Near End & Far End Increase with Frequency Decrease with Separation NEXT is the biggest problem Increasing Power doesn’t help!! Solutions Reduce Coupled Power Reduced Rates Reduced Reach Frequency Separation Spectral Masking Spatial Separation Asymmetric Rates NEXT FEXT Cross Talk

19. Noise Sources Local in Time Spread in Frequency e.g. from POTS signaling Solution (for G.992.1) Add Redundancy Forward Error Correction Read-Solomon Coding Trellis Coding Spread the Signal Various Interleave Depths 1  256 (x 250ms frames) 250ms  64ms Delay Increase Received Power Reduce Reach Impulse Noise

20. Noise Sources Local in Frequency Spread in Time eg Radio Stations eg Other Transmitters Solutions Spectrum Negotiation ie During Start-up Dynamic Rate Adaptation Increase Received Power Reduced Reach Radio Noise

21. Bridge Taps Cause Attenuation Loading Coils Block higher frequencies Split Pairs Electrical Imbalances Impedance Imbalance Increases Noise Solutions Select good Lines Reduce Reach Spectrum Negotiation Line Impairments

22. Digital Loop Carrier Scarcity of good pairs Pair Gain with virtual lines High Speed Modems Business Data Applications Residential Data Applications WAN Access Branch offices Small Campuses ATM, Frame Relay FDDI, SMDS PABX access Branch Offices Small Campuses T1/DS1, E1 Typical Applications

23. Emerging Technologies • Voice over DSL (VoDSL) • Broadband Loop Emulation Service (BLES) • PABX Extension • Voice over Multi Service Data Services (VMSDS) • Symmetrical DSL • SHDSL, HDSL2, VDSL • Network Management • Integrated ILEC, CLEC, ISP • Out of Box Plug and Play

24. VoDSL Issues • Which Service Types? • POTS, CCS, CLASS, CENTREX, IN, AIN • Delay Limits? • Interleaving, ISDN time-out risk • Lifeline Service? • Remote Power Feed • Signaling? • Network Interface? • PSTN (V5.1, V5.2, GR.303, TR.008) • B-ISDN (Circuit Emulation)

25. Market Status • Systems • 53 Announced Trials • 80 Service Deployments • Market Information • 35 million homes passed • 100K installed modems • 800M installed copper pairs • 170 ISPs offering DSL in USA • 70% of World does NOT have Cu-pair • ?? Mobile Technology ??

26. Supercom’99 • ADSL Interoperability Stand • 14 DSLAM Vendors • 25 CPE Vendors • ~35 Market Announcements • ~25-30 CPE Vendors displaying • ~15-20 DSLAM Vendors displaying • ~10 ISP’s displaying“Everyone was showing Video”

27. More Information • ADSL Forum • Moving to a generic focus (DSL Forum) • http://www.adsl.com • Technology overview pages • http://www.aspergantis.com/adsl/index.htm