AAccessccess Network, Access Technologies, Outline

Broadband Services and „ Introduction: Applications • Access network and service • Access technologies C.Courcoubetis • Broadband „ Broadband Services G.D. Stamoulis „ DSL „ Wireless Access Spring 2007 „ Other Access Media „ Concluding Remarks

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Access network - Access service

„ Access network: local loop infrastructure • It is the ‘last mile’ of the network • Connects the user with the first network POP • Can use different technologies • Usually is the bandwidth bottleneck Introduction „ Access service: more complex concept • connects to higher level services (Internet, VoD, etc.) • may be layered (physical layer, data link layer) • bundled with information service

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HDSL ADSL SDSL Powerline (emerging) ISDN „Twisted pair (copper): VDSL VBD • Digital Subscriber Line (DSL) MetroEthernet Home PNA twisted pair „Wireless (copper) Satellite HFC MMDS, LMDS • WiFi, WiMax, … Coax & wireless Cellular(GSM Æ 4G) fiber Free space optics „CATV Coaxial cable SDV transmission WiFi (802.11) „Optical fiber 100% WiMax (802.16) SDH PON „Power cable optical fiber MetroEthernet

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Rates vs Distance Access network architecture: the DSL case

Service provider networks Gateways (routers) BRAS interconnection networks

DSLAM twisted access pairs network

...... End users

Increasing loop length CPE - BRAS: Broadband Remote Access Server Central Office - DSLAM: Digital Serial Line Access Multiplexer DSLAM

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• A is a customer of Provider 1 Provider 1 Provider 2 using access service S1 ƒ Customer A: buys (P1, S1) Ν2 ƒ Provider P1: builds S1 by buying services from N1, N2

• B is a customer of Provider 2 Ν1 S1 S2 using access service S2 ƒ Customer B: buys (P2, S2) ...... ƒ Provider P2: builds S2 again by AB buying services from N1, N2

• Simple case of value chain

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Hierarchy in the access network architecture Feeding and distribution networks

Remote node or NIU

Remote node NIU . Hub .

. NIU Remote node

Feeding network Distribution network

„ Basic properties: • Feeding network: broadcast – switched • Distribution network: shared – dedicated

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Service Type Downstream Upstream Bandwidth Bandwidth Telephony Switched 4kHz 4kHz ISDN Switched 144kbps 144kbps Broadcast video Broadcast Analog or 6 Mbps 0 Broadband Services Interactive video Switched 6 Mbps Small Internet access Switched 1-… Mbps Small initally and Applications Videoconferencing Switched 6 Mbps 6 Mbps Business services Switched 1.5-622 Mbps 1.5-622 Mbps

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Access networks go broadband (I) Access networks go broadband (II) „ Local networks based on outdated principles became a bottleneck, limiting subscriber’s access to Key forces towards broadband (continued): modern services. „ New regulatory framework enabling competition Key forces: „ Emergence of alternative operators in local „ Data communications exceed telephony networks, who compete with incumbent operators • Need for High-Speed Internet in provisioning a wide set of additional services „ New business applications „ Wireless technologies have progressed and are „ New subscriber’s requirements to service provision being widely adopted „ Development of new services in voice, data and • Wireless/mobile subscribers exceed landline subscribers video information • Millions of WWW pages with powerful video information „ Development of high-speed core networks with a • New Multimedia applications, in modes: capacity of dozens and hundreds of Gbit/s ƒ Broadcasting, On-demand, Interactive

C. Courcoubetis, G.D. Stamoulis Broadband access - 15 C. Courcoubetis, G.D. Stamoulis Broadband access - 16 What is a broadband access service ? Comparison of download duration MP3 or high 1 h video Wireless E-mail resolution photo MPEG 4 in „ Always on wired TV-Quality • Easier and more convenient to use, instant gratification Byte 3 k 3 M 300 M • Heavier use bit/s GSM 9,6 k 2,5 sec 42 min 3 days

„ High speed, simultaneous provision of PSTN 56 k 0,4 sec 7 min 12 hours downstream and upstream GPRS 115 k 0,2 sec 3,5 min 6 hours • Bit-rate exceeds (often by far) ISDN 144kbps ISDN 128 k UMTS 2 M Å 0,01 sec 12 sec 20 min ADSL 8 M „ Low latency Cable 30 M 1 ms 130sec sec • Necessary for interactivity WLAN 80 M Fiber 800 G Broadband 30 ns 30 µsec 3 ms Live Video CodecsLive Video kbit/s 32 with starting

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Main areas of broadband applications Triple/Quad play „ High-speed Internet, both for residential and „ Everybody has fixed telephony, TV, internet business customers access for data „ Enterprise applications: „ Basic triple play is: • VPNs • Voice, video, data in a single bundle, with a single bill • Storage Area Networks, Data Centers, Server Farms „ Advanced triple play involves: „ Tele-working and remote collaboration • Equipment integration for customer and provider „ E-Government • Support of many devices (e.g. TV in PDAs) „ E-Health • User-friendly interfaces • Customization capabilities „ E-Learning • Advanced service features „ E-Home with infotainment and telematics • Advanced service software platform „ Online Gaming „ Quad play Æ Triple play + mobile telephony C. Courcoubetis, G.D. Stamoulis Broadband access - 19 C. Courcoubetis, G.D. Stamoulis Broadband access - 20 IPTV client Electronic program guide

„ Easy User interface Source: © NetCentrex „ Personalization; e.g. Language selection, font size „ Parental Control „ Extendable Catalog System • Video on Demand • radio/TV/music/games • Simple navigation • Quality & admittances rating „ Browse Based Activities • TV-friendly web browsing NetCentrex

• Bookmarks catalog © • Gaming • … Source: „ Messaging C. Courcoubetis, G.D. Stamoulis Broadband access - 21 C. Courcoubetis, G.D. Stamoulis Broadband access - 22

Some necessary (advanced) TV features The value chain for video content

„ Personal Video recorder functionality „ Trick Play: Play, Pause, IP Network Service Hosting Service Content Forward, Fast Forward, Operator Broker ProviderLogic Provider Provider Rewind, Fast Rewind, Instant Replay „ Pause Live TV •Content IP VXML storage FTP PHP •Production Prompts platform FTP Pictures Videos NetCentrex

© Source: © NetCentrex Source:

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„ Caller ID on TV „ Call history voice and video „ TV-based voice mail retrieval „ Message waiting indication on TV „ TV-based video calling and conferencing „ … Source: © NetCentrex DSL Forum © Source:

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Broadband Penetration in Greece An “exotic” application: home monitoring (99,2% is DSL) DSL Forum © Source:

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Definition

„ DSL enables broadband physical connectivity between a remote site (e.g. home) and the nearest telco CO over the telephone twisted pair copper wires. „ DSL is • an access line technology • a modem technology • an OSI physical layer Digital Subscriber Line (DSL) (layer1) protocol

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FDM Echo Cancellation PSTN upstream downstream PSTN upstream downstream HDSL

ISDN

Analog 4kHz26kHz 1.1MHz 4kHz26kHz 1.1MHz 0 4kHz 0.1MHz 0.5MHz 1.1MHz 10MHz

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Characteristics - Benefits DSL (xDSL) Classification „ DSL avoids the bandwidth bottleneck of the local „ Asymmetric vs. symmetric: loop in analog transmission, • asymmetric DSL Æ most bandwidth is devoted to „ DSL brings broadband to the home (BTTH) over the downstream direction ordinary telephone copper wires • symmetric DSL Æ equal bandwidth and data rates • can exploit ~750-800 million copper wires existing in the upstream and the downstream directions worldwide downstream upstream • postpones FTTH (Fiber to the Home) modem „ Always on network „ Concurrent transmission of voice and data over the User same copper wire „ PSTN can be provided in a splitter-based or a splitter- less mode, or it may not be provided at all. „ PSTN available even when DSL fails

C. Courcoubetis, G.D. Stamoulis Broadband access - 35 C. Courcoubetis, G.D. Stamoulis Broadband access - 36 xDSL data rates (I) xDSL data rates „ A wide variety of data rates is available. „ The data rate depends on the specific modem technology. Also affected as follows: • as the distance between CPE and CO increases, the achievable data rates decrease • thicker wires carry the same data rates further Mbps • more copper pairs Æ higher data rates 50 40 VDSL 30 RADSL 20 10 ADSL

1 2 6 Km

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Comparison of access technologies xDSL Architecture

Multiplexes many xDSL streams xDSL modem Pure fiber Hybrid fiber/copper Splitter DSLAM service network Copper cooper (Internet, VoD) FTTH FTTx + VDSL PSTN xDSL Customer (home) Switch ISDN (ADSL, SDSL, Local switch premises (PSTN) Voiceband/ HDSL) analog xDSL data stream modems interconnection service

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Impact of DSL penetration

„ Developing market, still dominated by incumbent despite competition

„ Symmetric DSL connections can serve as a substitute for leased lines with less than 2 Mbps in the retail market Wireless access technologies

„ VoIP over DSL offered by alternative providers competes with incumbent’s fixed telephony • Naked DSL

C. Courcoubetis, G.D. Stamoulis Broadband access - 43 C. Courcoubetis, G.D. Stamoulis Broadband access - 44 Wireless access to Internet (first steps) Broadband over Satellite satellite „ Three types of Internet service: • One-way broadcast (like TV) downstream • One-way plus terrestrial return over dial-up ƒ Down-channel rate may reach 24 Mbps direct Head receiver Internet end • Two-way, with very small aperture antenna upstream modem Telephone Twisted pair switch „ Available worldwide, yet more suitable for: • Remote and sparsely populated areas • Cellular: voiceband modems, 9.6kbps, CDPD = 19.2kbps • Broadcast applications, due to: • Terrestrial broadcast: MMDS and LMDS ƒ high propagation delay • Direct Satellite Broadcast (DBS): ƒ high cost of two-way capable customer’s antenna ƒ down link 400kbps - 1Mbps, possibly bidirectional

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MMDS (I) MMDS (II) „ Multichannel Multipoint Distribution Services (a.k.a. „ Spectrum in the 2-3 GHz range wireless cable network) „ High equipment cost • Multichannel: multiple spectral • both provider and end-user install an antenna bands, allocated in 6 MHz channels ƒ 10-27Mbps of shared capacity per channel „ Suitable for rural areas, due to low deployment • Multipoint: bandwidth is cost and large area coverage shared among end-users • Distribution Services: initially used as a cableTV substitute „ In general, limited commercial deployment „ Several multiplexing options „ In 2006, in USA, MMDS spectrum was auctioned • FDMA, TDMA, CDMA, OFDM for other applications „ Cell splitting increases capacity by reusing spectrum (scalability)

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„ Local Multipoint Distribution Service (a.k.a. wireless fiber- „ Many multiplexing options optic network) • FDMA, TDMA, CDMA „ Usually, TDMA for downstream and • Local: Cell range is 2.5-5 km FDMA for upstream • Multipoint:point-to-multipoint bidirectional connections „ Example ƒ point-to-point is also feasible • Total spectrum = 500 MHz, 250MHz upstream, downstream TDM ... „ Distribution Services: Internet/ • Upstream: Base • initially used as a substitute for FDMA 1 Data NW 1 link = 5MHz station cableTV/satellite PSTN = 7.5Mbps, Station 1 Station 2 Station n 50 FDMA links FDMA 2

„ Can also provide broadband . .

• Downstream: . point-to-point connectivity 375 Mbps FDMA k

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LMDS (III) WiFi (802.11)

„ Spectrum in the 28-GHz and 31-GHz range „ WiFi Æ Wireless Fidelity • Higher capacity than MMDS (up to 155Mbps) • Line-Of-Sight only operation „ An IEEE family of standards for Wireless LANs (WLANs). Usually used for: „ Was considered as a promising solution for fixed • Sharing access to Internet broadband wireless access • Allowing mobility to workers • In Greece, 6 licences for spectrum bands where auctioned in December 2000 „ Utilizes air frequencies for transmitting packets „ In general, limited commercial success, due to • Unlicensed band (2.4GHz) • 1999 bubble • Licensed band (5.4GHz) • Progress and penetration of DSL, WiMax • The band used affects transmission rates and range • Now, mostly used for point-to-point connections

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CSMA-CAÆCarrier Sense Multiple Access with Collision Avoidance „ 802.11b • Theoretical rate: 11 Mbps source destination others • Operates at 2.4 GHz “Air” is free • WiFi cards are low-priced Æ high adoption rate for DIFS time DIFS „ 802.11g period • Theoretical rate: 54 Mbps > All other devices • Operates at 2.4 GHz send frame data must defer while • Compatible with 802.11b “air” is busy „ 802.11a (using a binary • Theoretical rate: 54 Mbps > backoff • Operates at 5 GHz SIFS mechanism). Receive ACK back that Thus, latency • Low adoption rate frame was received intact! increases! „ 802.11i < ack (for all frames except from NAV: defer access • Improved security features (implemented on MAC layer) broadcast and multicast) < „ 802.11n SIFS - Short Inter-Frame Space (approx 28 µs) • Will provide higher rates: Theoretical 500 Mbps! DIFS - Distributed Inter-Frame Space (approx 128 µs) • Still under standardization, due to disputes

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WiFi topologies WiFi cells

„ Every access point creates a WiFi cell Meshed / Peer-to-peer WLAN Infrastructure-based WLANs • Channels range from 1 to 11 • Coverage range depends on WiFi standard (order of 100 m) „ Users can roam between cells • 802.11r will define the transition process of a mobile client as it moves between access points (promises 50ms delay during hand-off)

1 1 6 Access Point EtheEthe Ad Hoc WLAN rnetrnet 11 11 1

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WiMax (802.16) WiMax Transmission

„ WiMax Æ Worldwide Interoperability for Microwave „ Point-to-point with Line-Of-Sight Access • Mainly used for backbone connections „ An IEEE family of standards for: • Transmission rate decreases as range increases • creating Wide Area Networks (WANs) ƒ Highest data rate is 72 Mbps ƒ Maximum range is 50Km • providing wireless last-mile to: ƒ fixed users ƒ nomadic users „ Point-to-multipoint without Line-Of-Sight serving as a substitute of DSL • End-user services

„ Operates in a wide frequency spectrum: • 2 ~ 66 GHz

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„ ΙΕΕΕ 802.16c sub-standard A WiMax Base Station (BS) • Frequency range is 10-66 GHz with Line-Of-Sight restrictions „ • Cell radius is 1-5 km miles is placed on a high building „ IEEE 802.16a sub-standard • With wireless or wired • Frequency range is 2-11 GHz without Line-Of-Sight restrictions connectivity to other • Cell radius is 5-8 km BSs and the Internet • Max. range is 50 km with Line-of-Sight „ IEEE 802.16d sub-standard „ Many end-users are served • Quality-of-Service enabled • point-to-multipoint „ IEEE 802.16-2004 standard connection • ΙΕΕΕ 802.16a+ΙΕΕΕ 802.16c+ΙΕΕΕ 802.16d • without Line-Of-Sight „ IEEE 802.16e sub-standard • BS multiplexes the end- • With roaming support users’ traffic as the • Cell radius is 1-5 km DSLAM does in DSL

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WiMax coordination of transmissions WiMax in Greece

„ A Subscriber Station (SS) follows „ 4 licensed operators in Wi-Max slots in 3.5 GHz the Base Station (BS) instructions. Spectrum (EETT) Greece: • BS allocates space for the SS BS SS • OTE in the uplink subframe. Poll(UL-MAP) • SS Requests service Alloc(UL-MAP) Request • Q-Telecom • BS allocates the requested space Data • Europrom – Craig for the SS (if available). Wireless ƒ Different QoS levels are possible • COSMOLINE • SS uses allocated space to send data. for € 20.475M (July 06)

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„ More promising business cases for WiMax: „ May compete with DSL in both retail and wholesale • Backhaul solution, alternative to leased lines markets • Fixed broadband wireless access solution for sparsely populated areas, where it is not cost-effective to install: ƒ DSLAMs and backhaul for DSL „ May compete with broadband leased lines in the retail ƒ 3G market, particularly in urban areas • Complement to 3G, for more efficient utilization of spectrum: ƒ Push video or other demanding traffic to WiMax „ May compete with leased lines in the wholesale „ Achieving mobility support may be a key issue for its market: future success, but requires • Point-to-point WiMax vs connecting leased line segments • Support of roaming • Point-to-multipoint WiMax vs terminal leased line segments • Affordable customer’s equipment • Additional spectrum

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Mobile Wireless Access (I) Mobile Wireless Access (I) 2G 3G „ GSM (Global System for Mobile Communications) „ UMTS (Universal Mobile Telecom. System) or 3GSM • Rate 9.6kbps • Theoretically up to 384kbps for heavy mobility • May reach 2Mbps in more stable environments 2.5G • Æ 14 Mbps advertised „ GPRS (General Packet Radio Service) • Supports video-calls and videoconferencing • Data over mobile telephony network ƒ Very expensive Æ low demand • Based on packet rather than circuits (as GSM) • Recent evolution: 3.5G HSDPA (High-Speed Uplink Packet Access) • Theoretically up to 171.2kbps reaches 3.6 Mbps in the downlinkl • Much lower rates in practice (32-40 kbps) 4G • Large latency • Will provide: 100 Mbps to mobile phones, 1 Gbps WLANs „ EDGE (Enhanced Data rates for Global Evolution) or EGPRS • Full IP solution • Advanced version of GSM, supersedes GPRS • Yet to come! • Serves voice and data in 384kbps Æ 1Mbps (!!) recently advertised

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Cost Data QoS Security License Require- Rates Required ments LMDS Medium Very Low Low Yes LoS High Wi-Fi Low High ? Medium No - WiMax Low Very High Medium Yes/No LoS High Yes/No UMTS High High High Medium Yes - Siemens AG

Satellite Medium/ Very High High Yes LoS © Very High High Source:

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Cable TV networks

fibre optical-> electrical coax amplifier coax Head end Head end

Cable network HFC network Broadband access video+data over other media upstream downstream 6 MHz

54050 data 750 MHz d v 6 MHz video channel Æ 30Mbps data Head end optical->electrical electrical ->optical Upstream: <10Mbps shared Bi-directional HFC network

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downstream „ Fiber is the most appropriate medium for backbone network Cable coax fibre Head Fiber Internet modem node end upstream „ It can also be used in different parts of the access modem Telephone Bit-rates switch network Twisted pair • Business: 3 - 30 Mbps downstream • Residential: „ Supports: 0,384 - 6 Mbps Cable coax fibre Head • Symmetric or asymmetric rates Fiber Internet modem node end • From ~1 Mbps to ~1 Gbps upstream Telephone switch High penetration „ Several variations: FTTx Æ Fiber To The x, where only in U.S.A. x is the termination point

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Fiber networks (II) From the CO to the ONU

Point-to-point fiber One pair of optical fiber from Head end Local exchange Cabinet Curb Home SDH rings CO (Central Office) to each CO ONU NIU FTTEx ONU (Optical Network Unit) fiber Copper ONU ONU CO ONU NIU FTTCab ONU cable ONU CO CO CO ONU NIU FTTC/FTTB ONU ONU

FTTB/FTTH CO ONU/NIU ONU ONU No sharing of optical fiber, optical CO technologies No power splitting, no synchronization of nodes

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ƒ Allows for better exploitation of fiber capacity ƒ Time Division Multiplexing ƒ Reduces the cost of FTTH // // // // // T D H //

// Optical // Tom // // T D Dick // // Network Unit - // // ONU // // Passive Harry Optical Line Optical // H Terminal - Splitter OLT ƒ Multiplexing can alternatively be performed at the level of wavelength λ

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Remarks on fiber networks Impact of fiber networks to market „ FTTHome involves a dedicated fiber per customer, „ Fiber networks compete with broadband leased bringing ~1Gbps lines • Very expensive • in both retail and wholesale markets • mainly in urban areas „ FTTBuilding, FTTCurb and PON FTTH „ Combined with Internet access and VoIP, they • Are less expensive compete with fixed telephony • Fit present needs of customers

„ Can also compete with wholesale bitstream „ FTTB and FTTC are often combined with VDSL services of similar rate

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„ Transmits Ethernet frames on a Wide Area Network „ Allows flexible bandwidth profiles as a retail • As a retail service (i.e. for interconnecting LANs) service • As a wholesale service (interconnecting provider’s POPs) • Ranging from 1 Mbps to 1Gbps, with small step „ Ethernet Virtual Connections with ability for: • “point-to-point” E-line, which can also offer Internet access • Supports: • “multipoint-to-multipoint” E-LAN, for LAN services and VPNs Committed + Excess rates • Different service classes Multipoint-to-Multipoint Point-to-Point EVC „ Impact to market: EVC

UNI • Similar with fiber networks UNI CE UNI CE CE MEN MEN CE UNI

E-Line Service type CE UNI UNI CE E-LAN Service type

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Broadband over Powerline (BPL) Structure of the BPL network

„ Power distribution network can be used for High Voltage Network Medium Voltage Network Low Voltage Network delivering broadband services ~ MVolts ~ 1kVolts to 40 kVolts ~ 120/240 Volts Transformer „ Powerline is already there!: MV/LV Coupler Repeater

• “No more wires” Production • Very large base of potential customers Plant Substation „ “Point-to-multi point” • Total rates up to 200Mbps (upstream & downstream) Access network shared by all users

„ Symmetric and asymmetric rates TelephoneTelephone InternetInternet „ Still low commercial penetration NetworkNetwork „ Major issue: Interference Traffic C. Courcoubetis, G.D. Stamoulis Broadband access - 83 C. Courcoubetis, G.D. StamoulisConcentrator Broadband access - 84 Evolutionary Pathways for Broadband Access

References: The big picture “Evolutionary Pathways for the Broadband Access Network”, R. Heron and N. Van Parijs, Alcatel Telecommunications Review, June 2003 “High speed Internet in sparsely populated areas”, M. Cohen, D. Rouffet, L. Brignol and M. Coupechoux, Alcatel Telecommunications Review, August 2004 “Providing Always-on Broadband Access to Under-served Areas”, C. Boscher, N. Hill, Ph. Lainι and A. Candido, Alcatel Telecommunications Review , December 2003

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Solution: Extend Fiber Length+Add DSLAMs Densely populated areas

„ Goals: • Increase of coverage • Increase of bandwidth „ Green zone: bandwidth > 5.5 Mbit/s served by CO „ Red zone: distance > 5km from CO „ Gray zone: between red and green zones, low bandwidth served by CO

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„ Beyond ~5 km, offering broadband access to isolated communities requires an investment that operators will only consider for a minimum number of subscribers (100, on average)

„ With penetration 25% and on average 2.45 people per household, only the connection of villages with more than 1000 inhabitants is cost-effective

„ Thus, 10-30% of the population are going to be left without broadband access, unless regulation intervenes

„ Solution: Employ wireless technologies

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The big picture Cost Comparison of Different Solutions

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„ The operator must efficiently manage the bandwidth in the transport network: • Using as efficiently as possible the existing resources • Planning the introduction of traffic consolidation and concentration systems, but ƒ without sacrificing quality for a high over-subscription factor • Introducing transmission systems with increased capacity

Source: “Network solutions for Broadband-over-DSL services, Marco Rittore, July 2002

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Transport network dimensioning (III)

„ Multicast service imposes a heavy dimensioning of the network and intermediate traffic concentrators • approx. 9 times that required for phone traffic, Concluding Remarks when number of multicast channels = 16

C. Courcoubetis, G.D. Stamoulis Broadband access - 95 C. Courcoubetis, G.D. Stamoulis Broadband access - 96 And the winner is … The future picture „ DSL has significantly higher penetration so far, „ Wireless technologies progress very fast particularly for home customers in urban areas • Cellular moves towards broadband • Best combination of bit-rate, service quality, cost • Fixed wireless moves towards mobility • 3G (HSDPA) and WiFi/WiMax are expected to be the winning combination for mobile broadband „ Fiber To The Home delayed „ Higher bitrates are coming up for all technologies, „ Business customers’ demand for the various but this requires: solutions is more balanced • more fiber • Wireless is more successful there • upgrading of backhaul • more spectrum, for wireless technologies

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