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  • 앞 절에서 소개한 기술을 개략적으로 도시한 그림입니다 .
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    1. 1. Broadband Access Networks Chapter 1 INTRODUCTION Byeong Gi Lee Seoul National University EE 4541.759 Spring 2005
    2. 2. Core, Access & Home Networks CORE NETWORK -TCP/IP ACCESS NETWORK -xDSL -Cable -FTTx -Wireless Contents Provider Radio, Fiber, Coax, Internet HOME NETWORK -ATM -SDH/SONET -WDM/optics Access Node Network Termination
    3. 3. Broadband Access Networks & Services - The Scope of Service Processing Transport Processing Network Access -Streaming Video -Conversational -Interactive Video -Other services Service Processing Transport Processing Network Access CORE NETWORK (420.594) -TCP/IP -ATM -SDH/SONET -WDM/optics ACCESS NETWORK (4541,759) HOME NETWORK -xDSL -Cable -FTTx -Wireless Contents Provider BROADBAND SERVICES
    4. 4. TABLE OF CONTENTS <ul><li>Chap 1. Introduction </li></ul><ul><li>Chap 2. Twisted-pair based Access Network </li></ul><ul><li>Chap 3. Cable based Access Network </li></ul><ul><li>Chap 4. Fiber based Access Network </li></ul><ul><li>Chap 5. Broadband Wireless Access Network </li></ul><ul><li>Chap 6. Access Network Architecture </li></ul><ul><li>Chap 7. Broadband Services (TBD) </li></ul><ul><li>Chap 8. Home Networks (TBD) </li></ul>
    5. 5. I. INTRODUCTION <ul><li>Broadband Access Network (BAN) </li></ul><ul><li>Broadband Services for BAN </li></ul><ul><li>Conventional Subscriber Lines </li></ul><ul><li>Multiplicity of Access Networks </li></ul><ul><li>Structure of Broadband Access </li></ul><ul><li>Evolution of Subscriber Lines </li></ul><ul><li>Technical Foundation of BAN </li></ul><ul><li>Access Network Standards </li></ul><ul><li>Communication Environments </li></ul>
    6. 6. <ul><li>“ Subscriber loop” is the transmission and signaling facility that connects the subscriber terminal equipment (NT) to the central office (AN). </li></ul><ul><li>Access networks is a bridge that connects subscribers (i.e. users) to service providers </li></ul><ul><li>Information services’ demand </li></ul><ul><ul><li>Conversational telecommunication (telephones) </li></ul></ul><ul><ul><li>Broadband video distribution services (TV) </li></ul></ul><ul><ul><li>Interactive data services (computers) </li></ul></ul><ul><li>Requires large bandwidth and high interactivity </li></ul>Broadband Access Network (1)
    7. 7. Broadband Access Network (2) A9 A4 A3 A2 A1 A0 Access Network Reference model for BAN A0~A9: Interface S1~S3: Server NIU: Network Interface Unit STU: Set-Top Unit NT: Network Termination TE: Terminal Equipment RG: Residential Gateway Core Network Content Provider ----------------- Internet Transport Network Fiber Network Distribution Network Access Node Optical Network Unit (ONU) NT NIU RG STU TE STU Home Network TE TE TE S 1 S 2 S 3
    8. 8. <ul><li>Television (analog, digital, interactive TV) </li></ul><ul><li>Video on Demand (VoD) </li></ul><ul><li>Near Video on Demand ( nVoD) </li></ul><ul><li>World Wide Web </li></ul><ul><li>Datacasting </li></ul><ul><li>Video Streaming </li></ul><ul><li>Games </li></ul>Broadband Services for BAN
    9. 9. <ul><li>Metallic Transmission Media </li></ul><ul><ul><li>Twisted-pair, Coaxial Cable </li></ul></ul><ul><ul><li>Problems with High Frequency: Attenuation, crosstalk </li></ul></ul><ul><ul><li>External Impairments: Leakage, impulse noise, loading coils, thermal noise, bridged taps </li></ul></ul><ul><li>Fiber-Optic Transmission </li></ul><ul><ul><li>Modulation: on/off keying (OOK), FM, AM </li></ul></ul><ul><ul><li>Impairments: attenuation, dispersion, handling problems, cuts and other damages, bending, clipping </li></ul></ul><ul><ul><li>Improvements: DWDM </li></ul></ul>Communication Environment (1)
    10. 10. <ul><li>Wireless Transmission </li></ul><ul><ul><li>The higher frequency, the less distance </li></ul></ul><ul><ul><li>Modulation: QPSK, VSB, OFDM </li></ul></ul><ul><ul><li>Impairments: LOS, multipath, absorption, interference </li></ul></ul><ul><li>Noise Mitigation Techniques </li></ul><ul><ul><li>Forward Error Correction </li></ul></ul><ul><ul><li>Interleaving </li></ul></ul><ul><ul><li>Spread Spectrum/Code Division Multiple Access </li></ul></ul>Communication Environment (2)
    11. 11. <ul><li>Central office (CO):access node(AN)- remote node (RN)- network termination (NT):Home network </li></ul><ul><li>Feeder, distribution network </li></ul><ul><li>Digital loop carrier(DLC), fiber loop carrier (FLC) </li></ul><ul><li>Conventional subscriber lines </li></ul><ul><ul><li>enormous asset- 700 million subscriber lines worldwide </li></ul></ul><ul><ul><li>twisted-pair (TP) dominant – 90% of subscriber lines, 5 to 10-km of distance </li></ul></ul><ul><ul><li>so far, mainly for POTS(plain ordinary telephone service) </li></ul></ul><ul><ul><li>4 kHz bandwidth </li></ul></ul>Conventional Subscriber Lines
    12. 12. <ul><li>Embedded base – twisted pairs </li></ul><ul><li>Different characteristics – copper, coax, fiber, wireless </li></ul><ul><li>Different applications – point-to-pt, point-to-multipt </li></ul><ul><li>Different population densities – urban vs. rural </li></ul><ul><li>Different geography – ocean, hills, buildings, etc. </li></ul><ul><li>Different business conditions – infra, regulation </li></ul><ul><li>Entrepreneurship – investment, development </li></ul><ul><li>=> Matter of trade-in between investment and performance (bandwidth, loss, delay) </li></ul>Multiplicity of Access Networks
    13. 13. Structure of Broadband Access <ul><li>ADSL : Asymmetric Digital Subscriber Line </li></ul><ul><li>DBS : Direct Broadcast Satellite </li></ul><ul><li>FTTC : Fiber To The Curb </li></ul><ul><li>HFC : Hybrid Fiber Coaxial </li></ul><ul><li>LMDS : Local Multipoint Distribution System </li></ul><ul><li>MMDS : Multi-channel Multipoint Distribution System </li></ul><ul><li>MSO : Multiple Service Operator </li></ul>Digital DBS HFC FTTC/FTTO ISDN Line (DSL) VDSL Modem ADSL Modem Cable Modem Analog Modem ISDN Adaptor DBS STB/ MMDS/LMDS STB Coax MMDS/LMDS 56Kbps 6Mbps 640Kbps Fiber ONU Coax or Copper Fiber 52Mbps 3Mbps 30Mbps 3Mbps 64Kbps LMDS only Home Terminal MSO /CO Hub Station Fiber or Wireless Twisted-pair
    14. 14. <ul><li>Special treatments needed depending on </li></ul><ul><ul><li>the physical characteristics, </li></ul></ul><ul><ul><li>the distance from the serving core network, </li></ul></ul><ul><ul><li>the type of desired communication services. </li></ul></ul><ul><li>Three paths of evolution </li></ul><ul><ul><li>Apply advanced modulation techniques to TP- based transmission </li></ul></ul><ul><ul><li>Replace TP-based subscriber loops with optical fibers </li></ul></ul><ul><ul><li>Wireless-based supplement and renovation </li></ul></ul>Evolution of Subscriber Lines
    15. 15. <ul><li>TP-based evolution (1st stage of evolution) </li></ul><ul><ul><li>Mod Schemes: QAM, CAP, DMT, DWMT </li></ul></ul><ul><ul><li>HDSL, ADSL, SDSL, VDSL stages </li></ul></ul><ul><ul><li>No requirement of any new deployments or changes to the loop other than attachment of the converters </li></ul></ul><ul><li>Fiber-based evolution (2nd stage of evolution) </li></ul><ul><ul><li>FTTO, FTTC, FTTH stages </li></ul></ul><ul><ul><li>CATV network: HFC enhanced with bi-directional capability for interactivity </li></ul></ul><ul><li>Wireless-based evolution (3nd stage of evolution) </li></ul><ul><ul><li>Limitation of bandwidth and security </li></ul></ul><ul><ul><li>Economical alternative </li></ul></ul><ul><ul><li>Mobility and network tractability </li></ul></ul>Access Network Evolution Paths
    16. 16. <ul><li>Without modulation, 4kHz </li></ul><ul><li>Digital Subscriber Line (DSL), 144kbps </li></ul><ul><li>High-speed DSL (HDSL), 784kbps-1.5Mbps </li></ul><ul><li>Asymmetric DSL (ADSL), 1.5-8Mbps/16-820kbps (5.4-3.6km) </li></ul><ul><li>Very-high-speed DSL (VDSL), 13-52M/1.5-2.3M (300-1500m) </li></ul>*TP-based Bandwidth Expansion
    17. 17. <ul><li>Fiber-in-the-loop (FITL) </li></ul><ul><ul><li>investment vs. demand, chicken-and-egg </li></ul></ul><ul><li>Fiber-to-the-office (FTTO) first </li></ul><ul><li>Fiber-to-the-curb (FTTC) next </li></ul><ul><li>Fiber-to-the-home (FTTH) final </li></ul><ul><li>Hybrid-Fiber-Coaxial(HFC): contributes to evolution of CATV toward HTTH </li></ul>*Optical Fiber-based Evolution
    18. 18. <ul><li>Advantages </li></ul><ul><ul><li>Complements wireline access networks </li></ul></ul><ul><ul><li>Low initial investment, fast installation, </li></ul></ul><ul><ul><li>Mobility and flexibility </li></ul></ul><ul><li>Disadvantages </li></ul><ul><ul><li>Limited bandwidth, information security </li></ul></ul><ul><li>Narrow band services </li></ul><ul><ul><li>MPMP, cellular, cordless </li></ul></ul><ul><li>Broadband services </li></ul><ul><ul><li>MMDS, LMDS </li></ul></ul><ul><li>Fixed and mobile services </li></ul>*Wireless-based Evolution
    19. 19. Access Networks and Standards (1) Access Network Telephony Standards Data Standards Video Standards Broadcast DTV - ATSC/DASE ATVEF Analog TV (NTSC, PAL, SECA M), digital TV using ATSC or DVB Cable Packet Cable Data Over Cable Service Interface Specification (DOCSIS), DAVIC/DVB Open Cable SCTE DVS ADSL/G.Lite Analog IP/PPP/ATM (ADSL Forum) Switched Digital Video (TBD) Other DSLs Voice over ATM (VoATM) or Voice over IP (VoIP) Various packet mode protocols such as the Point-to-Point Protocol Over Ethernet (PPPoE) Switched Digital Video (TBD)
    20. 20. Access Networks and Standards (2) FTTx VoATM/VoIP FSAN and other initiatives Switched Digital Video (TBD) 3G Wireless IMT-2000 IMT-2000 - LMDS VoIP/VoATM TBD TBD MMDS - DOCSIS Analog TV, digital TV using 8-VSB Powerline, use of electric power lines for data transmission TBD TBD -
    21. 21. Modulation Techniques Service Modulation Techniques ISDN (US) 2B1Q US Direct Broadcast Satellite QPSK Vestigial Sideband (VSB) US Digital Over-the-Air Broadcast QAM-64, QAM-256 US Digital Cable Forward Channels QPSK US Digital Cable Return Channels OFDM European Digital Over-the-Air Broadcast 2B1Q HDSL DMT, CAP ADSL QAM, DMT VDSL
    22. 22. Transmission Media Summary Medium Modulation Techniques Bit Rate Bandwidth 750 MHz Distance Coaxial cable in downstream QAM-64/ 256 3.75 Gbps < 1.6 km 200kHz- 3.2MHz Coaxial cable in upstream QPSK 400Kbps- 5Mbps < 1.6 km 1 MHz TP pair (ADSL) DMT, CAP ~6 Mbps ~5 km 30 MHz TP pair (VDSL) QAM, DMT ~52 Mbps ~1.5 km 16 freq. of 2.4 Gbps each Single-mode fiber OOK, DWDM 40 Gbps 500 km 6 MHz Broadcast TV spectrum 8-VSB 19.39 Mbps >80 km 1.1 MHz LMDS spectrum QPSK, OFDM 2 Gbps < 5 km