1. ADSL technology Access Networks lectures 2008/09

2. ... once more... Broadband Network (Internet) Wiring Distribution Frame) Customer Premises Wiring

3. = Assymmetric Digital Subscriber Line - inmodulation band (not baseband) - ANSI standards (T1.413 of T1E1.4 group), ETSI (european requirement added to T1.413), ITU (groups of standards ITU-T G.991, 992, 995 etc. – they are downloadable from : ITU - publications – ITU-T) ADSL Specifications: high bit rate transmission + telephone (and also analog) connection, or ISDN max. downstream from 1,5 to 8 Mbps / max. upstream from 16 to 832 kbps (basic ADSL system) – various data speeds in dependence from user distance freq.band up to 1,1 MHz, DMT modulation scheme (Discrete Multitone Transmission), max. 256 DMT channels, each is 4 kHz wide for analog teleph.- lower 4 kHz, for ISDN up to 80 kHz (if there is ISDN transmission, the band for digital data is reduced) reach - 5,5 km frame transmission by means Cu- lines Full / Lite versions

4. Analog teleph.signal Frequency Fig. 1 ADSL spectrum with various variants [2] ADSL variant number of subchannels fromto speed number of subchannels speedfromto only data Tab.1 Comparison of ADSL variants ISDN-BRA

5. POTSUpstream Downstream Fig. ADSL spectrum in frequency multiplex Frequency POTS Upstream Downstream Frequency Fig. ADSL spectrum with echo compensation

6. ADSL and ISDN UpstreamDownstream Frequency Basic Access (4B3T link code) Basic Access (2B1Q link code)

7. ADSL

8. btw., relation between bandwidth and data speed: Shannon-Hartley theorema for information capacity of channel with both digital signal with mean power S and additive Gauss noise with mean power N. Bandwidth of channel is B [Hz]. [bps]... channel information capacity B... bandwidth [Hz] S...power of signal in the given band B [V 2 or W] N...power of noise in the given band B [V 2 or W] S/N... signal–to-noise ratio [-] (we know already SNR [dB] =10 log (S/N) )

9. symmetrical pair LF HF Fig.2 Typical termination of ADSL line on the user side Fig.3 ADSL line configuration with splitters user Provider Data network user line ATU-C = ADSL transceiver unit at the central office, ATU-R.....at the Remote home or business

10. Splitter

11. Fig.4 Reference model of ADSL in comparison to general xDSL model [6] ATU-C (ATU-R) =ADSL Transceiver Unit (on the user side) koncentrator and/or switch (switching array)multiplexor/demultiplex. filtre DP a HP PHY = physical interface

12. Fig.5 Functional scheme of ADSL modem (and steps of data treatment …) data interface transmitt ed data scramblerRS coder bit sequence securing trellis coder carrier mapping dig.QAM power spreading CP adding D/A conversion analog transmit.part hybrid lineanalog section analog receiver part A/D conversion Echo cancelling secured bit sequence decoding received data

13. Fig.6 ADSL 2+ system 2,2 MHz 1,1 MHz Up to 18,000 feet (5.5 km) Up to 25 Mbps down Up to 1 Mbps Upstream ADSL2+

14. ADSL2 - ITU-T G. 992.3,.4 - 2 nd generation of ADSL standard - downstream - up to 12 Mbps - DMT modulation - bandwidth - up to 2,2 MHz - but: shorter reach (only from 1,5 to 2 km) ! - CVoDSL ADSL2 + (fig.6) - ITU-T G. 992.5 - downstream - up 24 Mbps - bandwidth - up to 2,2 MHz (512 subchannels DMT, each 4kHz wide, up to 2,2 MHz) - full data speed only in reach of max. 1,5 km from DSLAM (!)

15. RE-ADSL = Reach Extended ADSL -ITU-T G.992.3 – Annex L (it is annex to ADSL2 standard) - optimalized DMT channels with the goal of larger length (manipulation with PSD of some channels  their higher throughput - dedicated to long lines (not for short ) – up to 5,5 km with the same date speed as in ADSL2 RADSL = Rate Adaptive DSL - it is in development - both symetrical and assym.transmission transmission speed is adaptive (it depends on transmission conditions and distance) down 1-12 Mbps / up 128kbps-1Mbps DMT or CAP (and QAM) are supposed - for applications without synchronization requirements (IP services, ATM, Frame Relay) Bonded ADSL - combines (bonds) 2 or more (up to 32) Cu-pairs for higher or extreme data speeds (for big and reach companies)

16. Literatúra [1] Vaculík: Prístupové siete. ŽU v Žiline, 2000. [2] J. Vodrážka: Přenosové systémy v přístupové síti. ČVUT, 2003. [3] T. Anttalainen: Introduction to Telecom. Network Engineering, Norwood (USA - MA), 2003. [4] L. Harte: Introduction to Digital Subscriber Line (DSL): Technologies, Operation and Systems. ALTHOS, 2005. [5] ITU_T G.995.1 Recommendation, Geneva, 2001.