![Power Cut Back
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Measured Power Cut
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26 AWG cable
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Distance 26 awg [feet]
• Reduces dynamic range required by Modem
• Reduces overall cable plant crosstalk level but reduces data rate
• DSLAM measures US power on bins 7 – 18
• DSLAM applies a 0 – 12 dB reduction to Downstream power
DSL2-27
Fast Path versus Interleaved Path
• Dual paths exist within the ADSL standard
DSL2-28](https://image.slidesharecdn.com/dslphysicallayer-120805080219-phpapp02/85/Dsl-physical-layer-14-320.jpg)
Dsl physical layer
- 1. DSL Physical Layer Prepared by: peter.macaulay@ZDSL.com © 2005 by ZDSL.com ADSL, HDSL, IDSL, SDSL, VDSL = xDSL DSL2-1 ITU-T Updates G.992.3 = ADSL2 ADSL G.992.5 = ADSL2+ • Asymmetric Digital Subscriber Line • ANSI T1.413-1998 • G.992.1 = G.dmt = 8.1/0.8 Mbps (256 bins) • G.992.2 = G.lite = 1.5/0.5 Mbps (128 bins) • G.992.1 with S=1/2 line coding yielding 12 Mbps • G.992.3 = G.dmt.bis (July2002) aka ADSL2 (256 bins) • G.992.3 Annex L = Reach Extended RE-ADSL2 • G.992.4 = G.lite.bis • G.992.5 = ADSL2+ = 24 Mbps at 5,000 feet (512 bins) • G.993.2 = VDSL2 = 100 Mbps (May 2005) DSL2-2
- 2. DMT ADSL • 4kHz low pass filter (LPF) for voice • sub-carrier spacing for discrete multitones (DMT) Pilot Tone #64 = 276kHz DSL2-3 p ow er spe ctrum upstrea m dow nstream DMT Operation PO T S 4 kHz 1.1 MHz 2.2 MHz . frequency Energy / tone DMT - Discrete Multi-Tone Modulation Orthogonal Sub-channels Spaced @ 4.3125 kHz frequency SNR (Signal to Noise Ratio) Margin signal above the background noise floor (i.e. +8dB) QAM Modulated With 2 - 14 Bits Note: 64-QAM 4-QAM 22 = 4 Constellation Points 214 = 16,384 Constellation Points DSL2-4
- 3. Three Down Stream (DS) Speeds 1. Theory – Possible 256 bins, 12 Mbps max 2. Actual – Actual for the copper local access loop – Perhaps 188 bins, 9.6 Mbps max – Some bins disabled by the copper loop – Will depend upon “bits-per-bin” loading 3. Tariff – The service you requested, purchased – Perhaps 140 bins, 1.5 Mbps max or less bits-per-bin – Some bins disabled by the service provider DSL2-5 Quad Spectrum Proposal • Extend the DS (Downstream) bins to 3.75 MHz • Widen the US (Upstream) from 138kHz to 276 kHz • Enhance the bit loading beyond 15 bits per bin VDSL2 ADSL2+ ADSL1 US DS Bins Bins Bins Bins 6-31 … 256 … 512 … 870 26kHz 138kHz 1.1MHz 2.2MHz 3.75MHz DSL2-6
- 4. Bits Per Tone (Annex A: Upstream) • Bits per tone Upstream Bits Per Tone • Bits per bin 16 14 • POTS=1-5 12 Bits Per Tone • Annex A 10 8 • US=6-31 6 4 • Note: 2 0 • Tone 10 = 1 6 11 16 21 26 31 36 41 46 51 56 61 – 11 bits Tone Number – 10*4.3125 (43.125kHz) DSL2-7 Bits per Tone (Downstream 32-256) Tone kHz Bits … ADSL2 … … 35 150.937 0 36 155.250 0 37 159.562 3 38 163.875 5 Tone # 46 1 1 1 1 1 1 1 1 1 1 1 39 168.187 5 @ 198.375 1kHz 0 0 0 3 5 5 7 7 9 9 0 1 3 3 3 3 4 5 5 5 40 172.500 7 = 11 bits 41 176.812 7 42 181.125 9 43 185.437 9 44 189.750 10 ... 45 194.062 11 46 198.375 11 Tone … … DSL2-8 kHz = tone number x 4.3125
- 5. Bits per Tone (Downstream 32-256) Tone kHz Bits Tone 242 • … ADSL2 … … Ouch! 241 1039.312 15 242 1043.625 2 243 1047.937 15 244 1052.250 15 … … … 249 1073.812 15 250 1078.125 15 ADSL2 251 1082.437 15 Tone 256 252 1086.750 15 @ 1.1MHz 253 1091.062 14 = 15 bits • 254 1095.375 14 ... 255 1099.687 14 DSL2-9 256 1104.00 15 Bit Swap • If the SNR changes for one tone, the bit swap protocol re-deploys the allocation of bits among the sub-carrier tones with no retrain of the modems or change in the net data rates. • Bit swap only works for an equal number of bit (+/-) • For testing a tone in the range 70-100 is selected • Tone power is increased to –75dBm power • Tone power in then increased by 5dBm until a bit swap occurs while recording the bits per tone map • Reference: DSL Forum TR-067 “ADSL Interoperability Test Plan” DSL2-10
- 6. Seamless Rate Adaptation (SRA) • SRA was introduced with ADSL2 and is included in ADSL2+ • SRA dynamically re-assign bits per tone with no modem retrain • DSL Forum WT-100 “ADSL2/ADSL2plus Interoperability Test Plan” may add this test DSL2-11 G.992.5 Upstream PSD (ADSL2+) Power Spectral Density (PSD) PSDin dBm/Hz –34.5 dBm/Hz peak PSD -72 dB/octave 21.5 dB/octave –100 dBm/Hz peak PSD in 10 kHz window –97.5 peak -15 dB/dec peak PSD +15 dBrn in 1 MHz window 0-4 kHz above 3750 kHz -93.2 dBm/Hz –92.5 dBm/Hz –100 dBm/Hz –110 dBm/Hz –112 dBm/Hz Frequency 0 4 25.875 138 243 686 1411 1630 5275 12000 in kHz Passband 26 – 138 kHz DSL2-12 POTS
- 7. G.992.5 Downstream PSD (ADSL2+) • G.992.5 PSD in –18 dB/octave dBm/Hz –36.5 dBm/Hz peak PSD –3 dB/octave 36 dB/octave –65 dB/octave –100 dBm/Hz peak PSD 4.63 dB/octave –78 dB/octave in 10 kHz window –46.5 dBm/Hz –97.5 peak peak PSD –47.8 dBm/Hz in 1 MHz window +15 dBrn –44.2 dBm/Hz above 3750 kHz 0-4 kHz –72.5 dBm/Hz –59.4 dBm/Hz –92.5 dBm/Hz –80 dBm/Hz –100 dBm/Hz –110 dBm/Hz –112 dBm/Hz Frequency 0 4 80 138 1104 1622 2208 3001.5 3750 4545 7225 12000 in kHz 2500 3175 Passband 138 – 2208 kHz DSL2-13 ANSI and ITU (G.dmt) • ANSI T1.413 - 1998 • ITU-T G.992.1-1999 = ADSL (ADSL1) • ITU-T G.992.3-2002 = ADSL2 (July 2002) • ITU-T ADSL includes localization for different countries; – Annex A with POTS – Annex B with ISDN – Annex C with TCM-ISDN for Japan – Annex H for Japan • G.992.1 has an enhanced activation compared to ANSI called G.994.1 (G.hs – handshake). Instead of a single tone being used to indicate optional features supported by a DSL modem, several tones digitally transmit the same information for a more robust startup. • G.997.1 (G.ploam) -- management DSL2-14
- 8. G.992.3 (G.dmt.bis) = ADSL2 • ITU-T Study Group 15, Question 4 (SG15-Q4) • May 2002 consent, July 2002 approved • Technical freeze on ADSL • “.bis” means “other” or second version • Major changes in ADSL2 … – Improved bit rate in the downstream – Mandatory Trellis Code – Line Diagnostics – Reduced Power – All Digital Mode DSL2-15 G.992.3 (ADSL2) - Bonding • ADSL2 provides support for inverse multiplexing • Bonding of multiple copper pairs for transport of a • Single ATM stream (ATM Forum Standard af.phy- 0086.001 Inverse Multiplexing for ATM (IMA), Version 1.1) 32 Mbps on 4 bonded pairs 24 Mbps on 3 bonded pairs 16 Mbps on 2 bonded pairs DSL2-16
- 9. G.992.3 (ADSL2) – Bonding Rates Diagram source: www.aware.com DSL2-17 G.992.3 (ADSL2) – Speed Change • Improved bit rate – Was 2-15 bits, now also 1-bit signal constellations – four-dimensional, 16-state trellis-coded and 1-bit quadrature amplitude modulation (QAM) constellations – Results in a 96-192 kbps greater downstream • Reduced framing overhead for faster transfers • Adaptable pilot tone location (carrier #64 = 276kHz) – Will result in better clocking • Mandatory Trellis coding and Reed Solomon RS=15 • Explicit rate negotiation – Will be good for multi-vendor configurations – Better tone reordering for RFI robustness DSL2-18
- 10. G.992.3 (ADSL2) – Rate & Reach 21.5 kft = 6.5 km Diagram source: www.aware.com DSL2-19 G.992.3 (ADSL2) – SRA • ADSL2 can dynamically adapt to changes in line conditions: – Crosstalk from other DSL in the same cable – Narrow band AM (radio) disturbers – Temperature changes – Water in the cable bundle • Uses online reconfiguration (OLR) when SNR changes • SRA is important for video to avoid tiling (pixelization) • Seamless rate adaptation (SRA) enables the transceiver to monitor line conditions and dynamically adapt the data rate “seamlessly”, i.e. without bit errors or requiring a service interruption for retraining DSL2-20
- 11. G.992.3 (ADSL2) - Digital Mode • All digital mode (no POTS, could have derived voice) • About 256 kbps additional up stream data rate • 0-26 kHz used for digital transmission not voice • This option is not suitable for line sharing DSL2-21 G.992.3 (ADSL2) Line Diagnostics Changes: • Line diagnostics and background noise measurement • Provides information when line quality is too poor to link • Measure of line noise, loss, SNR • Built-in to the DSLAM and CPE • Includes standard messages to the operator Benefit: • Will result in less technicians to the field (less truck rolls) • Will be helpful in troubleshooting RFI and bridged taps DSL2-22
- 12. ADSL2 DELT • DELT (Dual-Ended Line Test) • Defined by the ADSL2 (G.992.3) • Enables the measurement of line conditions at both ends without dispatching maintenance technicians to attach test equipment to the end of the line. • The information helps to isolate the location and the sources of impairments caused by crosstalk, radio- frequency interference and bridge taps. • Data Collection is "DELT physical-layer technology” • Data Processing is "Loop Identification” • SELT (Single-Ended Line Test) future option DSL2-23 SELT/DELT Comparison DSL2-24
- 13. G.992.3 (ADSL2) – Low Power • L0 is ADSL2 full power mode • L2 is low power mode at the ATU-C (DSLAM) while idle will result in better power especially for remote DLC (Digital Loop Carrier) configurations • L3 is low power mode at the ATU-R (user) and ATU-C enables the modem to sleep when information is not being transmitted (e.g. overnight) – it takes 3 seconds to come out of L3 (sleep mode) • Ability to disable tones to aid spectral compatibility • Extended training intervals • Power back off during startup DSL2-25 SNR Margin Capacity per tone depends On SNR – About 3 dB SNR difference per modulation bit – Coding Gain, Noise Margin, Timing Accuracy – BER 10-7 – There is a direct correlation of the SNR Margin and the modulation bits per tone in each sub-channel Total Rate = Sum of Bits-per-Bins x 4,000 DSL2-26
- 14. Power Cut Back 14 Power Cut Back 12 10 Power Cut Back [dB] 8 Measured Power Cut Back 6 Predicted Cutback for 26 AWG cable 4 2 0 0 00 50 00 50 00 50 0 0 0 25 50 75 10 12 15 17 20 22 Distance 26 awg [feet] • Reduces dynamic range required by Modem • Reduces overall cable plant crosstalk level but reduces data rate • DSLAM measures US power on bins 7 – 18 • DSLAM applies a 0 – 12 dB reduction to Downstream power DSL2-27 Fast Path versus Interleaved Path • Dual paths exist within the ADSL standard DSL2-28
- 15. Interleave Depth • The interleave depth is defined by the S and D parameters or the Impulse Noise Protection (INP) • INP = 0 (none), ½, 1, 2, 4, 8, 16 • S = 1,2,4,8,16 D = 1,2,4,8,16,32,64 • Interleave delay can be from 4.25 to 263.75 msec DSL2-29 Interleave • S: Interleave DMT symbols per FEC (forward error correction) Reed Solomon (RS) code word – S = 1, 2, 4, 8, 16 • D: Interleave depth – D = 1, 2, 4, 8 DSL2-30
- 16. Superframe DSL2-31 G.992.3 (ADSL2) – Ethernet • ADSL2 includes a packet mode transmission convergence layer (PTM-TC) that enables connection of ADSL2 modems to packet services (Ethernet) • Extensive configuration capability for PTM-TC with configuration of … – latency – bit error rate – minimum/maximum data rate to meet packet protocol requirements DSL2-32
- 17. Reach-Extended ADSL • G.992.3 Annex L • Approved November 2003 • RE-ADSL2 performance improvements result from new power spectral density (PSD) masks designed to improve data rates on extra-long phone lines • For downstream data rate of 384 kbps, results in 20% • RE-ADSL2 is expected to operate as an alternative mode of an ADSL2 or ADSL2+ chipset that a carrier can choose to activate for particular customers DSL2-33 RE-ADSL2 (Down Stream Rate) • ADSL 2 Annex L • 256 bins • 500 kbps at 18,500’ • 18,500’ = 5.6 km • 384 kbps at 28,000’ • 28,000’ = 8.5 km • RE is adding ½ km • 1,500’ = 0.460 km • 26 AWG • 12 other ADSL DSL2-34
- 18. G.992.5 (ADSL2+) • January 2003 approved (512 bins up to 2.2 MHz) • 24 Mbps @ 3kft (0.9km), 16 Mbps @ 6kft (1.8km) • >8kft (2.4km) ADSL1, ADSL2, ADSL2+ similar DSL2-35 G.992.5 (ADSL2+) • Possible to reduce cross talk by using different bins for different users • Possible to mix ADSL2 (1.1 MHz) with ADSL2+ (2.2 MHz) DSL2-36
- 19. Annex Summary #1 - 5 Bins #6 - 31 #32 - 64 #65 - 255 #256 - 512 ANNEX TYPE =0 =25.875 =138.0 =280.3 =1.104 to Hz kHz kHz kHz 2.208 MHz A (NA, EU, Asia) POTS POTS UP DOWN DOWN DOWN B (Germany) ISDN ISDN ISDN UP DOWN DOWN C (Japan) TCM- POTS UP DOWN DOWN N/A ISDN I (Japan ADSL) TCM- POTS UP DOWN DOWN DOWN ISDN I (Japan ADSL2) - UP UP DOWN DOWN N/A I (Japan - UP UP DOWN DOWN DOWN ADSL2+) J (All Digital) - UP UP UP DOWN DOWN L (RE-ADSL2) POTS POTS UP DOWN DOWN N/A M (ADSL2+) POTS POTS UP UP DOWN DOWN More Upstream DSL2-37 Automode Loop CO DSLAM CPE 1. ADSL2 would connect at 690 kbps for CPE at 18,000 feet (4.5 km). Instead … 2. ADSL2/ADSL2+ CO collects loop data during initialization and training 3. Automode determines RE-ADSL2 is the best configuration based on line conditions 4. DSLAM configures customers port for RE-ADSL2 mode 5. CPE line at 1.1 Mbps (a 160% improvement over ADSL1) DSL2-38
- 20. Summary of Rate/Reach VDSL2 100Mbps 2.4 km 8 kft 3.0 km 10 kft 4.3 km 14 kft DSL2-39 DSM (Dynamic Spectrum Mgmt) • DSM level 0 – No coordination • DSM level 1 – Distributed multi-user power allocation – Implementation of Iterative Water Filling (IWF) • DSM Level 2 – Centralized multi-user power allocation – Optimal Spectrum Management (OSM) • DSL Level 3 – Multi-user detection – Also called vectoring DSL2-40
- 21. ADSL Line Repeaters • Telrad DataRacer – ARU (ADSL Repeater Unit) 2-wire with data + voice • Symmetricom GoLong – Mid-span ADSL repeater (data only, no voice ) – 1.5Mbps/128kbps down/up to 30,000 feet (9100 m) DSL2-41 SHDSL • Single-Pair High-bit-rate DSL (SHDSL) • 16 level TC-PAM line coding • Trellis Coded Pulse Amplitude Modulation (TC-PAM) • ITU G.991.2 approved April 2001 (was G.shdsl) – 2-wire (2.36/2.36) … 192 kbps steps – 4-wire (4.7/4.7) … 384 kbps steps • STU-R connects to STU-C • Very good spectral compatibility with other services • Some vendors are providing SHDSL over POTS DSL2-42
- 22. GoDigital (Pole Mounted RT x8) • Pole mounted • Single pair serves x8 CPE • 24,000’ @ 24 AWG – 7.3km • 32,000’ @ 22 AWG – 9.8km • Optional midspan pole RT – 38,000’ @ 24 AWG – 11.6km DSL2-43 VDSL2 • Very-High-Data-Rate Digital Subscriber Line • ITU-T G.993.2 • Downstream rates: – 12.96 Mbps (4,500 ft.– 1500m) – 25.82 Mbps (3,000 ft.– 1000m) = FTTN (Fiber-to-the-Node) – 51.84 Mbps (1,000 ft. – 300m) = FTTC (Fiber-to-the-Curb) – 100 Mbps (300 ft. – 100m) • Upstream rates from 1.6 to 2.3 Mbps • Symmetric rate (13 Mbps) possible • Simpler than ADSL – Shorter lines, fewer transmission constraints – Ten times faster • Enables multiple video streams • HDTV compatible (19 Mbps or 10 Mbps compressed) DSL2-44
- 23. VDSL2 Frequency Plan (NA) • North American Band Plan • 0-US0: Upstream start f0L = 4 kHz or 26 kHz • 0-US0: Upstream end f0H = 138 kHz or 276 kHz • 1-DS1: Downstream 138 kHz –3.75 MHz • 1-US1: Upstream 3.75 MHz – 5.8 MHz • 2-DS2: Downstream 5.8 MHz – 8.5 MHz • 2-US2: Upstream 8.5MHz –12.0 MHz DSL2-45 VTU-R Transmit (Upstream) North America (NA) 25 kHz <PSD1> 138-276 kHz DSL2-46
- 24. VTU-O Transmit PSD (Downstream) NA 30000 DSL2-47 VDSL2 Frequency Plan (Europe) DSL2-48
- 25. VDSL Spectrum • Frequency Plan 998 138kHz 3.75MHz 5.2MHz 8.5MHz 12MHz DSL2-49 VDSL2 Proposed Rate/Reach • rate 2200 ft = 670m DSL2-50
- 26. DSL Configuration Design note; 1) DSLAMs can support multiple DSL line cards (xTU-C) – For example; – DSLAM with G.dmt, G.shdsl, G.vdsl – CPE can then choose speed/service required – Future cross connects at the DSLAM could provide for customer speed/service increases 2) DSLAMs could be integrated with the POTS line card to provide POTS -or- DSL options to all telephone subscribers – this will benefit facilities based exchange carriers DSL2-51 DSL Deployment Model 1. ILEC/CLEC sends CPE to customer for self install 2. ILEC/CLEC drives to customer site for the install 3. Retail: Customer buys the DSL CPE in a store (Radio Shack, Fry’s,…), customer does self install,ILEC/CLEC activates the DSL line (connects the DSLAM) DSL2-52
- 27. DSL Flavors • ADSL = ITU-T G.dmt = G.992.1 (world standard) • SHDSL = ITU-T G.shdsl = G.991.2 (world standard, business focus) • VDSL = Standards track with ETSI/ANSI • IDSL = longest reach (part of DSL Anywhere) • SDSL = multirate DSL (business focus) • HDSL = T1 4-wire (most popular DSL to date) • HDSL2 = T1 2-wire • MVL = Paradyne proprietary, long reach • RADSL = Globespan proprietary (voice, data, video) • 1-Meg = Nortel proprietary • xDSL = any of the above • YDSL = CATV solution (“why” DSL?) DSL2-53 EFM • Ethernet in the First Mile (EFM) • IEEE P802.3ah, copper track • 10 Mbps for 750m – Ethernet over VDSL – Dual mode, EoVDSL + 100Base-Cu • http://www.efmalliance.org/ • www.t1.org for T1E1.4 Working Group DSL2-54
- 28. PON (Passive Optical Network) • APON – Asynchronous Transfer Mode (ATM) PON • EPON – Ethernet PON • BPON – Broadband PON – Combination of Passive Optical Networking (PON) and Wavelength Division Multiplexing (WDM) • GPON – Gigabit Capable PON – ITU-T G.gpon.gsr DSL2-55 • blank DSL2-56
- 29. DSL2-57