1 xDSL Technologies Access Networks lectures 2008/09

2 Introduction Some notes and new terms: - PSTN and Internet - digital / analog - frequency bands, bandwidths - busy time of circuit - bandwidth, delay, latency - utilizing of twisted pairs (of metallic networks) - several forms of DSLs  xDSL - ‘bonded channels’ - statistical multiplexing - and others – see next pages

3 Fig.1 Shared transport of both voice and data

4 Fig.2 „Digital – only“ DSL transmission

5 Fig.3 History of DSL technology year data speed [Mbps]

6 Fig.4 Review of xDSL technologies xDSL HDSL group ADSL group VDSLPDSLFDSL standards HDSL HDSL2 variations: MVL SDSL MDSL IDSL standards ADSL RADSL G.lite ADSL2 ADSL2+ RE-ADSL2 variations 1-MPEG modem CDSL EZ-DSL eXtremeDSLMAX FasADSL standards: VDSL variations: VDSL2 VDSLPlus TotalVDSL

7 Tab.1 Review of xDSL technologies and their specifications [3] Name ITU-T standard Down stream [Mbps] Up stream [Mbps] Link codeReach [km]Application DSL (IDSL) -0,128 2B1Q6 Videoconf., Internet access HDSLG CAP 2B1Q pair pairs 5, pairs E1 transmission, LAN interconnection, Frame Relay SDSL-Up to 2,3 2B1Q2 to 5 SHDSLG.991.2Up to 2,3 16 PAM3 to 6 ADSL LiteG.992.1Up to 1,5Up to 0,5DMT4 to 7Internet access ADSL R-ADSL G ,5 to 8Up to 1DMT3 to 6 Internet access, Video on Demand VDSLG to 52 or 26 1,5 to 6,4 or 26 QAM DMT 0,3 to 1,5 Multimed.access to Internet, HDTV

8 Fig.5 DSL in local loop (splitter = LF filter – it devides off voice channel and reroutes it into PSTN)

9 - standard ITU – T I.430, european ETSI ETR 80 Fig. 6 IDSL system Digital Only 144 kbps Down 144 kbps Up  IDSL (ISDN DSL)

10 Specifications of IDSL: …

11 HDSL group

12  HDSL Fig.7 HDSL time frame for 2-pairs system data blocks synchro - group 1 st pair 2 nd pair H - HDSL service bits, S - stuffing symbols, Zn – identification bits of both pair and data block

13 Fig.8 HDSL transmission principle 2 x 3 x DLL = Dig.Local Line pairs service channel Tab. Comparision of 2- and 3-pair HDSL (for unique pair HDSL is v p = 2320 kbps) User side HDSL link portion terminal unit exchange unit I – application interface M – mapping circuits C – common circuits of link termination REG – regenerator H – HDSL transmitter and receiver

14 Fig. General reference configuration for xDSL systems [6]

15 Fig. HDSL reference model vs. xDSL general reference model [6] Note: - HDSL can consist of 1, 2 or 3 pc. of H, REG and DLL, in the dependence from data transmission intensity - REG is not obligatory

16  SHDSL Fig.9 Functional model of SHDSL transmission chain STU – SHDSL Termination Unit – Remote/Central PMD- Physical Media Dependent PMS-TC - Physical Media-Specific TC layer TPS-TC – Transmission Protocol-Specific... SRU – repeater = SHDSL Regenerator Unit γ R, γ C –reference points of transport protocol α, β – ref. point of application user interfaces application depence subbloc application indepence subbloc application depence subbloc application indepence subbloc not obligatory optional application interface

17 Fig.10 Layer reference model user data interface transmission medium link termination transport layer (e.g. SDH) not specificated

18 Fig. SHDSL reference model in the relation to general xDSL ref. model [6]

19 Fig.11 SHDSL frame structure 12 user subblocks Synchr. word head user data block head user data block stuffi ng bits

20  HDSL2  MSDSL -2 nd HDSL generation – not standardized - foregoer of SHDSL...self study …

21 Other xDSL systems are described in next presentations.

22 References [1] V.Kapoun: Přístupové a transportní síte (Access and Transport networks, czech language). VUT v Brně, [2] Vaculík: Prístupové siete (Access Networks, slovak l.). ŽU v Žiline, [3] J. Vodrážka: Přenosové systémy v přístupové síti (Transport Systems in Access Natworks, czech l.). ČVUT, [4] T. Anttalainen: Introduction to Telecom. Network Engineering, Norwood (USA - MA), [5] L. Harte: Introduction to Digital Subscriber Line (DSL): Technologies, Operation and Systems. ALTHOS, [6] Recommendation ITU_T G.995.1