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Published on November 28, 2007

Author: Octavio

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A DSL Path to 100 Mbps everywhere: Dynamic Spectrum Management:  A DSL Path to 100 Mbps everywhere: Dynamic Spectrum Management John M. Cioffi Prof. EE, Stanford U. And all the work by students: Taek Chung, Jungwon Lee, Dimitris Toumbakaris, M. Mohseni, Bin Lee, & V. Pouramod April 1, 2003 Copper DSL vs Fiber PON?:  Copper DSL vs Fiber PON? 50 cu-line binder (100 Mbps/line) = 5 Gbps (DSM) .5 km EPON shares 1 Gbps , more users APON shares 622 Mbps , more users Costs? What wins (happens)?:  What wins (happens)? High-speed DSLS on shorter lines Incrementally deployed on basis of cogent, profitable ILEC business plans 10G fiber to access points (pt to pt on fiber?) Ethernet or ATM or both Matches Recent FCC ruling (and Tech Net) Reliable All lines connected on only installation – no further visits Evolution of DSL & Regulation:  Evolution of DSL & Regulation time ADAPTIVE (“dynamic”) DSL:  ADAPTIVE (“dynamic”) DSL Migration up: Reliability, Range and Rates mixes of service ADSL (.3 to 7), ….. ADSL+’s (25), 10MDSL, 100MDSL FEXT NEXT NEXT impulses radio VDSL What is needed (Others)?:  What is needed (Others)? Universal, reliable DSL Line Engine A, A+, V, 10/100M (allows bonding) Access Net connect DSL engine A, A+, V, 10/100M (allows bonding) Level 2/3 functionality Connection to PC/apps Consistent interoperable standards sequence A to A+ to 10/100M and/or V Reliable high-speed connection/device Interfaces to access network & to client network Outline:  Outline Autonomous (de-regulated) DSL Vectored DSLAM (one sided) DSM Multi-user Rate REGIONS:  DSM Multi-user Rate REGIONS Plot of all possible rates of users ADSL & some VDSL use DSM – any point is possible More than 2 users (vector of possible rate-tuples) Region’s size (volume) can vary with: each binder transmission methods (i.e., DMT has much larger regions with continously adapting spectra) ADSL: Verizon Expt. (CO/RT Mix):  ADSL: Verizon Expt. (CO/RT Mix) Short line autonomously migrates to higher frequencies when power is minimized Data rate on long line improves from 100 kbps to 2 Mbps (short is also 2 Mbps) Two lines here, but idea carries to any number (although 20 kft would reduce) Can be implemented with existing DSLAMS (parameter change in software) and no change to installed client modems Can make yet better with G.dmt-compliant software patches Telcordia DSM-ADSL Rate Regions [T1E1.4/2002-063]:  Telcordia DSM-ADSL Rate Regions [T1E1.4/2002-063] Nominal 15 kft data rate without DSM 300 kbps DSM Algorithm (Iterative-Water-filling):  DSM Algorithm (Iterative-Water-filling) NSR(f) S(f) Water-filling is known optimum on single-user channel Use DMT, and MINIMIZE POWER for given rate/margin Best autonomous solution to “interference problem” in binder The more lines that do DSM, the better they all work NEVER any worse than existing fixed/static Spectrum Management Passes T1.417 (Static SM) method-B tests with no mask (power minimized less than 20 dBm) Each line autonomously minimizes red area Method B Analysis:  Method B Analysis Even old ADSLs get better Pull off psd altogether on DSLAM modem, let RT adapt according to min-power criterion at fixed rate Satisfies T1.417 Method B (annex A) A=4.8 Mbps , B=3.1 Mbps, C= 425 kbps 24 new, 1 old ADSL 12 new, 1 old ADSL, 12 other What about A migration up?:  What about A migration up? 10MDSL and ADSL+ example VDSL example 25 10MDSLs in same binder (same length):  25 10MDSLs in same binder (same length) No coordination (current unbundling state) Example PSD for 4000’:  Example PSD for 4000’ Overlap (EC) to 800 kHz Each has 3 basic bands MDSL with ADSL (+?) present:  MDSL with ADSL (+?) present Range of ADSL and of MDSL unaffected if DSM is used Not true for Static SM (or SHDSL) ADSL at CO, MDSL at RT :  ADSL at CO, MDSL at RT Cabinet is 10 kft from CO – last 2 to 6 kft in same binder ADSL at CO “swamped” by 64 PAM ADSL at CO largely unaffected by IW 10M/A Mixture – (all DMT) Footprint:  10M/A Mixture – (all DMT) Footprint C S A 998 Plan with Iter-water (VDSL):  998 Plan with Iter-water (VDSL) All Curves are DMT 998 plan hurts symmetric IW is compatible with it in any case No Coordination so far:  No Coordination so far Modems measure their own SNR(s) React autonomously Coordination can replace autonomous if operator uses spectrum masking instead of letting modems adapt Some ILECs are doing this Modems can initialize in any order Adaption is continuous Do not need re-starts or bring down other services Outline:  Outline Autonomous (de-regulated) DSL Vectored DSLAMS (one sided) Network Central Office Content 1 Content 2 ILEC LT Switch router Fiber Or multi-channel DSL twisted pair D S L A M time 20-100 Mbps (symmetric) SMC Evolving DSL 2002+: Bonding Vectoring Common DSLAM (LT or RT) b i n d e r Fundamental Vectoring Problem::  Shared channel Fundamental Vectoring Problem: “broadcast” and “multiple-access” probs in IT One-sided vectoring, FDM of up/down Broadband Access problem in combination What is (one-sided) VECTORING ?:  What is (one-sided) VECTORING ? Co-generation of many Downstream DSL signals Central processor Save on statistical mux (power, space, level 2/3, etc) Potential analog matrix source connection/hybrid Up to 2n+1 (49 on 25-pair cable) Co-reception of many Upstream DSL signals Central processor Save on statistical mux (power, space, level 2/3, etc) Potential analog matrix termination connection/hybrid Up to 2n+1 (49 on 25-pair cable) NEXT cancellation (narrower band needed than down because of this effect – excellent match to current asymmetric plans, but rates are symmetric) Matches Recent FCC Ruling Single service provider at the LT point 998 with/out Vectoring (BAD noise):  998 with/out Vectoring (BAD noise) Gains at short length only with bad (non DSM) noise from uncoordinated users All results one-sided One-sided Plots – All use vectored DMT:  One-sided Plots – All use vectored DMT Increases data rates at all lengths when all do vectoring from DSLAM Power can be lowered – possible to do 10 dBm or less No phantoms included yet Not optimum up/down partioning of band yet Broadband DSL:  Broadband DSL Symmetric shown (double for asym) Still not optimum (bands and phantoms) So 5 Gbps possible on 50 pair, at least at 500m! Single-Line Card:  Single-Line Card Maintenance Same system – regression tests, etc – common technology Reduce problems with operation as new DSLs added Provisioning No line-card swap Easier qualification / smaller number of choices Recommendations:  Recommendations DSL evolution Early autonomous, adaptive spectra Later Vectored DSLAM Consistent standards progression Multiple standards causes greater spectrum management difficulty QAM VDSL, SDSL are fixed spectra and limit themselves and all others Helps industry investment focus in low-capital times Architecture – Client:  Architecture – Client BUS DSM High-speed DAC and ADC Fast FFT and En/Decoding Can do any number of tones Architecture – DSLAM:  Architecture – DSLAM BUS DSM High-speed ADC and DAC, but low xmit power Matrix Fast FFT and En/Decoding Shares processing (very low power/cost) Network maintenance Shared by many l ines Specific Recommendation:  Specific Recommendation A/A+/M/V DSL interoperable single platform DSLAM architecture allows any More ports at lower speeds Client architecture capable of supporting all Support and Promote in standards Migrate to advanced DSM techniques higher speeds . . . Binder 100 Mbps/user Fiber(s) 10Gbps Universal, reliable DSL Line Engine A, A+, V, 10/100M (allows bonding) Access Net connect DSL engine A, A+, V, 10/100M (allows bonding) Level 2/3 functionality Connection to PC/apps 100 Mbps Everywhere! both directions:  100 Mbps Everywhere! both directions

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