Introduction to wired broadband communication topics like broadband services (core network technologies X.25, Frame Relay, ATM) and access network technologies (xDSL, Cable Modem, FTTx)

1. Wired Broadband
Communication
CS4422 Wireless and Broadband Networking
Dilum Bandara
Dilum.Bandara@uom.lk
Some slides extracted from ZigBee by J. Dohl, F. Diehm, & P. Grosa and
ZigBee by E. Ünal CSE 401 Special Topics In Computer Networks

2. Outline
 Broadband services
 Core network technologies
 X.25, Frame Relay, ATM
 Access network technologies
 xDSL, Cable Modem, FTTx
 Primary focus
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3. Triple Play
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Source: www.datavoiz.com/solution_network_triple_play.aspx

4. Broadband
 A transmission medium’s ability to transport
multiple signals & traffic types simultaneously
 Source – Wikipedia
 A transmission facility having a bandwidth
sufficient to carry multiple voice, video, or data
channels simultaneously
 Broadband often refers to Internet access service with
transmission speed from 100s of Kbps to several Mbps
 Source – Prof. Stephen McLaughlin
 Medium can be coax, twisted pair, optical fiber,
wireless, etc.
 We already discussed about wireless 4

5. Broadband Adoption at Home
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6. Broadband Access Network
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Source: www.iptvmagazine.com/2005_08/iptvmagazine_2005_08_dsl_series.htm

7. WAN Devices
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Source: http://sclabs.blogspot.com/2010/07/ex4-chapter-1-introduction-to-wans.html

8. Broadband Basic Architecture
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Source: www.overturenetworks.com/solutions/ethernet-infrastructure/boost-broadband-bonded-
copper-dslam-backhaul
DSLAM – Digital Subscriber
Line Access Multiplexer

9. Core Network Technologies
 X.25
 Frame Relay
 Asynchronous Transfer Mode (ATM)
 These technologies are disappearing with
advent of Ethernet over fiber optics, MPLS,
VPN, & dedicated broadband services (cable
modem & DSL)
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10. X.25
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DCE – Data Circuit-terminating Equipment
DTE – Data Terminal Equipment
PSE – Packet Switching Exchange
Source: Wikipedia
Leased lines,
POTS, or ISDN

11. Frame Relay
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Source: Wikipedia

12. X.25 vs. Frame Relay
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X.25 Frame Relay
Layer 1 Specification Yes None
Layer 2 Protocol Family HDLC HDLC
Multiplexing of virtual circuits Yes Yes
Layer 3 Support PLP None
Variable length packets Yes Yes
Error Correction Node to Node None
Propagation Delay High Low
Ease of Implementation Difficult Easy
Good for Interactive Applications Too Slow Yes
Good for Voice No Yes
Good for LAN File Transfer Slow Yes
HDLC – High-level data link control

13. Asynchronous Transfer Mode (ATM)
 Fixed size (6 + 48 byte) packets
 Connection-orientated technique  Virtual circuit setup
 Packet label-based forwarding
 Fast
 No error control
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Source: http://docwiki.cisco.com/wiki/Asynchronous_Transfer_Mode_Switching

14. Digital Subscriber Line (DSL)
 Limited distance to local exchange / Central Office (CO)
 Dedicated line from CO to home
 Asymmetric flow
 Speeds up to 9 Mbits/s downstream 14

15. DSL (Cont.)
 Generic name for technologies which transport
high-bit-rate digital services over ordinary phone
lines
 Data is only transmitted as far as local exchange
 Hence, distinct from conventional modems that go all
the way up to CO
 xDSL
 Few Kbps to 100 Mbps
 Data rate reduces with distance
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16. xDSL – Speed vs. Distance
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Source: http://wapiti.telecom-lille1.eu/commun/ens/peda/options/ST/RIO/pub/exposes/exposesrio2007/
Mirgot-Sagnimorte/limites-du-cuivre.html
ADSL – Asymmetric DSL
SHDSL – Single High-speed DSL
VDSL – Very high data rate DSL

17. xDSL Comparison
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Source: http://cocxel.blogspot.com/p/wan-network-2.html
HDSL – High-bit-rate digital subscriber line
IDSL – ISDN Digital Subscriber Line
RADSL – Rate-adaptive digital subscriber line, proprietary technology by AT&T
CDSL – Consumer Digital Subscriber Line, trademarked by Rockwell Corp.

18. Asymmetric DSL (ADSL)
 Asymmetric
 Different up & down link rates
 Typically high downstream bandwidth
 Purely digital
 Subscriber Line
 Data is carried over a single twisted pair copper loop
to subscriber premises

19. ADSL Standards
Standard name Common name Downstrea
m rate
Upstream
rate
ITU G.992.1 ADSL (G.DMT) 8 Mbit/s 1.0 Mbit/s
ITU G.992.2 ADSL Lite (G.Lite) 1.5 Mbit/s 0.5 Mbit/s
ITU G.992.3/4 ADSL2 12 Mbit/s 1.0 Mbit/s
ITU G.992.3/4 Annex J ADSL2 12 Mbit/s 3.5 Mbit/s
ITU G.992.3/4 Annex L RE-ADSL2 5 Mbit/s 0.8 Mbit/s
ITU G.992.5 ADSL2+ 24 Mbit/s 1.0 Mbit/s
ITU G.992.5 Annex L RE-ADSL2+ 24 Mbit/s 1.0 Mbit/s
ITU G.992.5 Annex M ADSL2+M 28 Mbit/s 3.5 Mbit/s
ADSL4 (ADSL2++) 52 Mbit/s 5.0 Mbit/s
Source: Wikipedia

20. unused tones
due to line conditions
tone spacing
(4.3 kHz)
frequency
= QAM-modulated
subchannel (tone)
individually optimized
as a function of impairments
20 kHz
4 kHz 1.1 MHz
power
spectrum
spectrum used
for dow nstream data
spectrum used
for up stream data
POTS
unused tones
due to line conditions
tone spacing
(4.3 kHz)
frequency
= QAM-modulated
subchannel (tone)
individually optimized
as a function of impairments
20 kHz
4 kHz 1.1 MHz
power
spectrum
spectrum used
for dow nstream data
spectrum used
for up stream data
POTS
Bandwidth Division in ADSL
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Source: www.froydwess.com

21. Discrete Multi-Tone (DMT)
 DMT separates DSL signals s.t. usable
frequency range is separated into 256 channels
of 4.3125 kHz each
 224 downstream frequency bins (or carriers)
 32 upstream frequency bins
 Constantly shifts signals between different channels
to ensure that the best channels are used for
transmission & reception
 Uses OFDM

22. DMT Technique
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23. ADSL Modem
 G.Lite & UADSL do not use splitters
 Typically low bandwidth
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24. ADSL Speed Factors
 Distance from local exchange
 Type & thickness of wires used
 No & type of joins in the wire
 Proximity of wire to other wires carrying ADSL,
ISDN, & other non-voice signals
 Proximity of wires to radio transmitters

25. Crosstalk in Network
 DSM = Dynamic Spectrum Management
 Adapt transmit spectrum dynamically
 Reduce crosstalk (i.e., noise) for other users in
network
 DMT is very suited to apply DSM (flexible spectrum
allocation)
Central
Office
User
Modem
User
Modem
Central
Office

26. Traditional Cable Network
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Challenge – designed to support one-way traffic

27. Hybrid Fibre-Coaxial (HFC) Network
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28. Cable Technology
 Shared lines to the nearest splitter
 Generally higher speeds
 Coaxial cables  high bandwidth
 Reaches more households since distance limitation is
removed
 Typical offering 4 Mbits/s
 Last mile advantage 28

29. Cable Modem (CM)
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30. Cable Modem Transmission System
(CMTS)
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31. DSL vs. Cable Modem
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DSL Cable Modem
Always-on Yes Yes
Speed 8 Mbps down
1.5 Mbps Up
Depends on location
27 – 36 Mbps down
0.5 – 10 Mbps Up
Shared bandwidth
Security Dedicate line, better security Shared line, easier to snoop
Wire Twisted-pair Coax cable
Price High Lower, if bundled
Coverage Growing Widely used

32. Passive Optical Networks
 Fibre to the home/business is a long-term goal
 FTTx (Fibre To The x)
 Passive optical networks
 No active electronics in network
 Some implementations are emerging
 SLT offer FTTH/FTTO
 http://slt.lk/en/personal/broadband/ftth/new-connection-
charges
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33. Passive Optical Networks
 FDH – Fiber Distribution Hub
 OLT – Optical Line Terminal
 ONT – Optical Network Terminal 33
Source: www.3-edge.de/en/solutions/measure-applications/fttx-pon-networks/FTTx-PON-Network-Overview/

34. Multiple Services on Passive Optical
Networks
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Source: www.infocellar.com/networks/new-tech/EPON/EPON.htm

35. FTTx Topologies
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Source: www.foss.ae/products-services/gigabit-ethernet-passive-optical-network-solutions-gepon/

36. Hybrid Networks
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Source: www.3-edge.de/export/sites/default/.content/3Edge_Artikelbilder/Apps_FTTx_Fig3.png
Still there are many places that none of these
technologies cover

37. Satellite Broadband Services
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Source: www.isatafrica.com/satellite-broadband.html

38. Satellite Broadband Services (Cont.)
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Source: http://measuretek.com/pages/
products/data-communications.aspx
Source: www.broadbandanywhere.eu/about-
broadband-anywhere/how-it-works
Sometimes uplink may not be through satellite

39. Summary
 Bandwidth is increasing
 Triple-play is becoming preferred choice
 Core network technologies
 X.25, Frame Relay, ATM
 Access network technologies
 xDSL, Cable Modem, FTTx
 Satellite data services
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