Access Network Access Network Access network: local loop - - PowerPoint PPT Presentation

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Access Network Access Network Access network: local loop - - PowerPoint PPT Presentation

Oct 28, 2023 257 likes •372 views

Access network and access service Access Network Access Network 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

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SLIDE 1

Access Network Access Network

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 2

Access network and 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

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

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 3

Access network

... ...

Service provider networks Gateways interconnection networks DSLAM End users

BRAS

access network BRAS: Broadband Remote Access Server DSLAM: Digital Serial Line Access Multiplexer

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 4

Access network - Architecture

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SLIDE 2

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 5

Architecture

Hub

Remote node Remote node Remote node NIU NIU NIU Feeding network Distribution network

Basic properties: Feeding network: broadcast - switched Distribution network: shared - dedicated ...

  • r

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 6

Access service

... ...

A B

Provider 1 Provider 2

Α is a customer of Provider 1 using access service S1

S1 S2 Ν1 Ν2

Provider P1: builds S1 buying services from Ν1,Ν2 Customer Α: buys (P1, S1)

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 7

Local networks based on outdated principles are became a “bottleneck”, limiting subscriber’s access to modern services. Key forces: New subscriber’s requirements to providing new services New regulations Development of new services in voice, data and video information in interactive and broadcasting mode

# WWW pages with powerful video information

# Multimedia applications, Digital Video Broadcasting (DVB), Video-on-Demand (VoD), interactive TV

Emergence of alternative operators in local networks, who compete with incumbent operators in provisioning a wide set of additional services Construction of high-speed core networks with a capacity of dozens and hundreds of Gbit/s Wireless Technologies

Access networks go to broadband

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 8

Data communications exceed telephony

  • Wireless/mobile subscribers exceed landline subscribers
  • Broadband on Wireless
  • Emergence of the Next Generation Networks

Technology Trends

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SLIDE 3

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 9

Service requirements to the access network

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

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 10

E-mail

Cable WLAN 30 UMTS ADSL Fiber GSM PSTN GPRS ISDN bit/s Byte 1 0,01 30 3 2,5 0,4 0,2 1 30 sec min min 20 9,6 k 56 k 115 k 128 k 2 M 8 M 30 M 80 M 800 G

1 h video MPEG 4 in TV-Quality

MP3 or high resolution photo

Wireless wired

sec sec sec sec ms ns 7 3,5 12 sec µsec min sec ms

Live Video Codecs starting with 32 kbit/s

days hours 3 12 hours 6 min 42

3 k 3 M 300 M

Comparison of download duration

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 11

Rates vs Distance

5.5 Mb/s 3.5 Mb/s 1 Mb/s 7.5 Mb/s Central Office DSLAM

Increasing loop length

CPE

10 Mb/s

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 12

Basic technologies

twisted pair (copper) VBD ISDN HDSL SDSL ADSL VDSL wireless transmission Satellite Cellular WiFi (802.11) MMDS, LMDS 100%

  • ptical fiber

SDH PON Coax & fiber HFC SDV Free space opt Emerging: Powerline, HomePNA WiMax (802.16) MetroEthernet MetroEthernet

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SLIDE 4

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 13

Twisted pair: xDSL

DSLAM

xDSL modem Splitter cooper

PSTN Switch

service network (Internet, VoD) Customer (home) Local switch premises (PSTN) xDSL data stream interconnection service Multiplexes many xDSL streams DSLAM may belong to service provider, not to PSTN operator

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 14

xDSL

User network upstream downstream

modem ADSL: asymm. 8Mbps-2Mbps (<1.5km) ADSL lite: 1.5Mbps-0.5Mbps ADSL heavy: 8Mbps-1Mbps ADSL2: asymmetric, 12Mbps-1Mbps ADSL2+: asymm. 24Mbps-3.5Mbps HDSL: symmetric, 2Mbps (<4km) RADSL: rate-adaptive, 12-1 Mbps SHDSL: symmetric, 2.3Mbps (<3km) VDSL: 55Mbps-12Mbps (<0.3km) Mbps 50 40 30 20 10 Km 1 2 6 RADSL VDSL ADSL

4 30 138 1100 kHz

telephony

ADSL

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 15

Access service - Bitstream versions

The possibility to differentiate the service offered to the end user (and thus the extent to which value can be added by the new entrant) declines from Option 1 to 4.

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 16

Wireless access to Internet (first steps)

receiver modem

Head end Internet

Telephone switch Twisted pair

downstream

upstream

  • Cellular: voiceband modems, 9.6kbps, CDPD = 19.2kbps
  • Terrestrial broadcast:

– MMDS (wireless cable), 50km, 2GHz, 33 channels, 10(27)Mbps/ch – LMDS: 28GHz, 5km, 2-way

  • Satellite broadcast (DBS): down link 400kbps - 1Mbps, possibly bidirectional

satellite direct

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SLIDE 5

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 17

Comparison of wireless technologies Comparison of wireless technologies

  • Yes

Medium High High High UMTS LoS Yes High High Very High Very High Satellite Yes/No No Yes License Required

  • Medium

High Very High Low WiMax

  • Medium

? High Low Wi-Fi LoS Low Low Very High Medium LMDS Require- ments Security QoS Data Rates Cost

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 18

MMDS

  • Stands for Multichannel Multipoint

Distribution Services (a.k.a. wireless cable network)

  • Multichannel: multiple spectral bands,

allocated in 6 MHz channels (10-27Mbps

  • f shared capacity per channel)
  • Multipoint: available bandwidth is shared

among end-users

  • Distribution Services: initially used as a

cableTV substitute

  • Low deployment cost and large area

coverage are important factors for servicing rural areas

  • Cell splitting increases capacity by

reusing spectrum (scalability)

  • High equipment cost (both provider and

end-user install an antenna)

  • Several multiplexing options (FDMA,

TDMA, CDMA, OFDM) Basic concepts and directions in telecommunications C. Courcoubetis access networks- 19

LMDS

Stands for Local Multipoint Distribution Service (a.k.a. wireless fiber-optic network)

  • Local: Cell range is 1-3 miles
  • Multipoint:point-to-multipoint

bidirectional connections

point-to-point is also feasible

  • Distribution Services: initially used

as a cableTV/satelite substitute

Spectrum in the 28-GHz and 31- GHz range

  • Higher capacity than MMDS (Up to

155Mbps)

  • Line-Of-Sight only operation

Ability for cell splitting

Internet/ Data NW PSTN Basic concepts and directions in telecommunications C. Courcoubetis access networks- 20

Wi-Fi (802.11)

An IEEE family of standards for Wireless LANs (WLANs). Usually used for:

  • Sharing access to Internet
  • Allowing mobility to workers

Utilizes air frequencies for transmitting packets

  • Unlicensed band (2.4GHz)
  • Licensed band (5.4GHz)
  • The selected band affects transmission rates and

range

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SLIDE 6

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 21

WiFi standards

802.11b

  • Theoretical rate: 11 Mbps
  • Operates at 2.4 GHz
  • WiFi cards are low-priced high adoption rate

802.11g

  • Theoretical rate: 54 Mbps
  • Operates at 2.4 GHz
  • Compatible with 802.11b

802.11a

  • Theoretical rate: 54 Mbps
  • Operates at 5 GHz
  • Low adoption rate

802.11i

  • Improved security features (implemented on MAC layer)

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 22

WiFi topologies

Infrastructure-based WLANs Meshed / Peer-to-peer WLAN

Access Point

Ad Hoc WLAN

Ethe rnet Ethe rnet

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 23

WiFi cells

Every access point creates a WiFi cell

  • Channels range from 1 to 11
  • Coverage range depends on WiFi standard

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 6 11 1 1 11

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 24

WiFi transmission using CSMA-CA

Carrier Sense Multiple Access with Collision Avoidance

* SIFS - Short Inter-Frame Space (approx 28 µs) * DIFS - Distributed Inter-Frame Space (approx 128 µs)

“Air” is free for DIFS time period Receive ACK back that frame was received intact! (for all frames except from broadcast and multicast) send frame

source destination

  • thers

DIFS SIFS

All other devices must defer while “air” is busy (using a binary backoff mechanism). Thus, latency increases!

data ack

NAV: defer access

< <

> >

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SLIDE 7

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 25

WiFi Hotspots

Private hotspots (intra-enterprise) Public hotspots at popular places (airports, cafes,…) as a charged service Free hotspots

  • Open hotspots in neighbor
  • Municipal wireless networks are operating in several

places in Attica

Syntagmatos square (www.athenswifi.gr) Piraeus Port Wi-Fi (info.yen.gr/info/page_en.php?id=1200) …

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 26

Wi-Max (802.16)

An IEEE family of standards for creating Wide Area Networks (WANs) Operates in a wide frequency spectrum (2 ~ 66 GHz) Transmission can be:

  • Point-to-point with Line-Of-Sight

Highest data rate is 72 Mbps and maximum range is 50Km Transmission rate decreases as range increases Mainly used as backbone

  • Point-to-multipoint without Line-Of-Sight

End-user services

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 27

ΙΕΕΕ 802.16c sub-standard

  • Frequency range is 10-66 GHz with Line-Of-Sight restrictions
  • Cell radius is 1-3 miles

IEEE 802.16a sub-standard

  • Frequency range is 2-11 GHz without Line-Of-Sight restrictions
  • Cell radius is 3-5 miles

IEEE 802.16d sub-standard

  • Quality-of-Service enabled

IEEE 802.16-2004 standard

  • ΙΕΕΕ 802.16a+ΙΕΕΕ 802.16c+ΙΕΕΕ 802.16d

IEEE 802.16e sub-standard

  • With roaming support
  • Cell radius is 1-3 miles

Wi-Max (sub)standards

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 28

A Wi-Max Scenario

A Wi-Max Base Station is placed on a high building

  • With wireless or wired

connectivity to other BSs and the Internet

Many end-users are serviced

  • point-to-multipoint

connection

  • without Line-Of-Sight
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SLIDE 8

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 29

Wi-Max transmission

A Subscriber Station follows the Base Station instructions.

  • BS allocates space for the SS in the

uplink subframe.

  • SS Requests service
  • BS allocates the requested space for

the SS (if available).

Different QoS levels are possible

  • SS uses allocated space to send

data.

Poll(UL-MAP) Request Alloc(UL-MAP) Data BS SS

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 30

WiMax in Greece

4 licensed operators in Greece

  • OTE
  • Q-Telecom
  • Europrom - Craig

Wireless

  • COSMOLINE for €

20.475M (July 06)

WiMax slots in 3.5 GHz Spectrum (EETT)

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 31

Fiber networks

Fiber may be used in different parts of the access network

Head end Local exchange Cabinet Curb Home

CO ONU NIU FTTEx fiber Copper CO ONU NIU FTTCab CO ONU NIU FTTC/FTTB CO ONU/NIU FTTB/FTTH

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 32

Point-to-point fiber

CO ONU ONU ONU ONU CO ONU ONU ONU ONU cable Other solution: SDH rings No sharing of optical fiber, optical CO technologies No power splitting, no synchronization of nodes One pair of optical fiber/ONU

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SLIDE 9

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 33

FTTC

Not a shared infrastructure, TDM, fixed BW/NT 1400 channels available

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 34

//

// // // // // //

Optical Network Unit - ONU Optical Line Terminal - OLT Passive Optical Splitter

// //

//

Passive Optical Network (PON)

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 35

Passive Optical Network (2)

Passive star coupler . . . . . . Downstream: broadcast Upstream: TDM, multiple access ... 1 2 n 1 ... 1 2 n 1 1 laser receiver

Splitter/ combiner

laser receiver laser receiver

CO RN ONU

Receiver: N x data rate, sync

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 36

WDM PON

WDM laser receiver

Splitter/ combiner

laser receiver laser receiver

CO RN

N

λ λ λ ,..., , 2

1

1

λ

... ...

k

λ

N

λ λ λ ,..., , 2

1 Receiver: sync No CO sharing Problem: power splitting

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SLIDE 10

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 37

WDM Routing PON (WRPON)

WDM laser receiver

combiner

laser receiver laser receiver

CO RN

1

λ

... ...

λ

k

λ

Receiver: sync problem Expensive: 2 lasers/ONU

AWG

λ

ONU Basic concepts and directions in telecommunications C. Courcoubetis access networks- 38

WRPON (2)

WDM laser receiver

modulator

receiver

CO RN

1

λ

...

AWG

Cheaper solutions

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 39

Metro Ethernet

Transmitting Ethernet frames on a Wide Area Network

  • As a retail service (i.e. for interconnecting LANs)
  • As a wholesale service (interconnecting provider’s POPs)

Ability for “point-to-point” and “multipoint-to-multipoint”

  • Ethernet Virtual Connections (usually with MPLS/GMPLS)

CE CE CE

MEN

CE Multipoint-to-Multipoint EVC UNI UNI UNI UNI

E-LAN Service type

Allows flexible bandwidth profiles

  • As a retail service (i.e.

for interconnecting LANs)

  • Committed rate +

Excess rate

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 40

Broadband over Powerline

Power distribution network can be used for delivering broadband services “Point-to-multi point”

  • Total rates up to 200Mbps (upstream & downstream)

Symmetric and asymmetric rates

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SLIDE 11

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 41

Cable networks

Head end

coax amplifier Cable networks

Head end

coax

HFC network

  • ptical-> electrical

fibre

Head end

Bi-directional HFC network

  • ptical->electrical

electrical ->optical video+data data

v d 6 MHz video channel -> 30Mbps data

6 MHz

MHz 5 40 50 750 upstream downstream

Upstream: <10Mbps shared

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 42

Cable networks (2)

Cable modem modem

Fiber node coax Head end Internet

Telephone switch Twisted pair

fibre downstream

upstream

Cable modem

Fiber node coax Head end Internet

Telephone switch

fibre downstream

upstream

Basic concepts and directions in telecommunications C. Courcoubetis access networks- 43

LMDS (2)

Many multiplexing options (FDMA, TDMA, CDMA) Usually, TDMA for downstream and FDMA for upstream

Base station

TDM FDMA 1 FDMA 2 FDMA k Station 1 Station 2 Station n

... ...

Example

  • Total spectrum = 500

MHz, 250MHz upstream, downstream

  • Upstream: 1 link =

5MHz = 7.5Mbps, 50 FDMA links

  • Downstream: 375

Mbps