ADSL. Surasak Sanguanpong Last updated: 9 Feb 2001

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1/6 Surasak Sanguanpong nguan@ku.ac.th http://www.cpe.ku.ac.th/~nguan Last updated: 9 Feb 2001 What is?

1 1/6 Surasak Sanguanpong Last updated: 9 Feb 2001 What is? 2/6 stands for Asymmetric Digital Subscriber Line is a new, super high-speed modem technology that provides data services, such as Internet access, over the existing telephone lines PC Upstream : 64 Kbps to 1 Mbps Internet Downstream : Mbps Example Speed offers : 384 Kbps downstream /128 Kbps upstream for general telecommuters 1.5 Mbps downstream / 384Kbps upstream for small offices

3/6 High speed communications over twisted pair. Originally standardized in ANSI T1 in 1993.

2 3/6 High speed communications over twisted pair. Originally standardized in ANSI T1 in Telephone and service can be used simultaneously Modem Concurrent with plain old telephone service (POTS) Is always terminated at the central office (CO). CO Modem and Line card filters determine bandwidth 4/6 PC modem modem Server 4 KHz Voice Channel Data limited to 33.6 Kbps Local loop determines bandwidth PC Server <1 MHz bandwidth data rate up to 52 Mbps depend on distance

3 Typical System Configuration 5/6??? User Telco Central Office Telco Backbone POTS Splitter POTS Splitter Class 5 Switch PSTN DLSAM ATU-R ATM Internet DSLAM Digital Subscriber Line Access Multiplexer. A concentrating platform for DSL modems transmission unit in CO. It refers to modems housed in DSLAMs. ATU-R transmission unit in remote (customer) locations. It refers to CPE. Typical Network 6/6??? Radius Server PC ATU-R DLSAM ATM Router Internet PPP Connection

4 xdsl Family HDSL 1.544/2.048 Mbps symmetric two twisted-pair wires to achieve full duplex High bit rate Digital Subscriber Line 7/6 DSL SDSL 1.544/2.048 Mbps symmetric single line version of HDSL, echo cancellation is employed Single Data line Digital Subscriber Line VDSL Mbps, asymmetric Single line over POTS Asymmetric Digital Subscriber Line Current View Mbps, asymmetric (A very fast version of for short length) Very High Bit Rate Digital Subscriber Line R based technology with different data rate depending on the type communications Rate Adaptive Asymmetric Digital Subscriber Line Speed shrinks with distance 8/ has a range of downstream speeds achievable depending on the distance and wire gauge. 30 VDSL Dominant impairment Attenuation Attenuation increases with distance and frequency Secondary impairments Cross Talk, Impulse noise, Bridged Taps Distance in kft of 24 (.5 mm) ga wire

5 Spectrum 9/6 bandwidth is split into three information channels: high-speed downstream channel, medium-speed duplex (upstream) channel conventional voice channel POTS Upstream Downstream Only 0-4 Khz is used for POTS 4 khz Upstream utilizes lower frequencies to take advantage of reduced near end cross talk (NEXT) at CO MHz Downstream uses as much of the remaining bandwidth as it can Echo-Cancelled 10/6 can be used in either an echo-cancellation (EC) or frequency division multiplexing (FDM) POTS Upstream Downstream Less useable downstream bandwidth but more simpler implementation POTS Upstream Downstream More of downstream bandwidth is in the higher quality part of the spectrum

6 Bands for 11/6 uses Discrete Multitone DMT signaling in upand downstream Consists of up to KHz channels, each containing a QAM modem (each QAM modem has a 4 KHz symbol rate) Upstream (25 channels) Downstream (224 channels) 256 POTS Compute Bit Rate 12/6 For each 4 KHz channel, max rate is equal to 4 Khz*15=60 Kbps POTS Upstream Downstream Upstream : 25 channels Bit rate = 25*60 Kbps=1.5 Mbps Practical use : 64Kbps to 1 Mbps Downstream : 224 channels Bit rate = 224*60 Kbps=13.44 Mbps Practical use : 500Kbps to 8 Mbps

14 15 14 13 11 Bits per Channel Allocation 13/6 SNR can be continuously monitored and have

response f Output f Bit rate = 4KHz*(14+15+14+13+11+8) =300 KHz DMT Tra DMT with N channels

7 Bits per Channel Allocation 13/6 SNR can be continuously monitored and have the bit loading table adjusted # of bits per Hertz # of bits per Hertz 8 Input f Frequency response f Output f Bit rate = 4KHz*( ) =300 KHz DMT Tra DMT with N channels 14/6 N bits Data Bit 1 Bit 2 QAM QAM Bit N QAM QAM modulation with 0-15 bits per baud per Hertz

8 Splitterless 15/6 Splitterless DSL, a subset of service. No splitter, hence low cost and easy to install G standard, also known as G.Lite standard No Splitter POTS Splitter Class 5 Switch PSTN DLSAM ATU-R ATM G.lite Spectrum 16/6 G.Lite technical aspects Utilizes only up to KHz (98 channels) Each bin limited to 8 bits per symbol Max data rate = 4KHz*8*98=3.136 Mbps Practical use : 1.5 Mbps/ 128 Kbps POTS Upstream Downstream G.DMT G.DMT G.lite G.lite

9 Problem of Splittlerless 17/6 Microfilter 18/6

10 ITU Study Group 15 Standards Activities 19/6 G.dmt A full-rate (6 to 8 Mbps) standard based on ANSI T1.413 Issue 2 G.lite A sub-rate (384 Kbps to 1.5 Mbps) standard which typically will require no splitter ITU Study Group 15 G.hdsl G.hs G.oam G.test An HDSL standard based on ANSI and ETSI standards A handshaking standard, describe the start-up protocol and signaling for identification of xdsl capabilities and negotiation of the operating modes A standard which will identify the requirements for a control channel for operations and maintenance for xdsl modems A standard which will define a network model and procedures for testing xdsl modems

Data and Computer Communications. Tenth Edition by William Stallings

Data and Computer Communications Tenth Edition by William Stallings Data and Computer Communications, Tenth Edition by William Stallings, (c) Pearson Education - Prentice Hall, 2013 CHAPTER 8 Multiplexing