Download - 1 Access Networks Lecture 3 - 2008/09 – w.t. Part 3. : Classification of Access Networks Lectures
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Access Networks
Lecture 3 - 2008/09 – w.t.
Part 3. : Classification of Access Networks
Lectures
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AN:
- users networks
- hybrid n. (xDSL)
- optical…
- radio communications network
- TV cable distribution system (network)
- power lines communications network
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Exchange
MDF
ED
user distrib.frame
network distr.frame
track distr.frame
Main distribution frame = MDF)
connecting cable
user c. (station line)
network cable
track cable
Obr.3.1 Example of flexible users network [1]
3.1 Users networks (PSTN)
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3.2 Hybrid networks
-partially Cu and partially optical cables = optical feeder + transmission system for Cu-wires pair
Obr. 3.2 Hybrid network architecture
OLT
OLT
ONU
ONU
NT
NT
ODN ADSL
VDSL
Customer
Local exchange (the services node)
SNI UNI
Cu-pairs
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Fig.3.3
- several different xDSL systems – the new systems in original Cu net with different distances (reach, range)
Cable distribution box
End Cable distribution box
Distribution cableMain cableLE
Main Network
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xDSL:
IDSL = ISDN DSL (ISDN-BRA dig. user connection)
HDSL – High bit rate DSL
SDSL – Symmetric DSL (Single line DSL)
VDSL - Very high bit-rate DSL
ADSL – Asymmetric DSL
then: - ADSL 2
- ADSL 2+
- RE-ADSL 2
- RADSL
(DSL = Digital Subscriber Line)
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Fig. 3.4 Telephone access + ADSL system
ADSL
Teleph. network
High speed channel
Control channel
V -interface T - interfaces
Network side Connecting line User side
LP LP
LP – low pass filter
HP – high pass filter
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8Fig. 3.5 ADSL system in Cu-connecting lines principle
Telephone netw. /ISDN
User station
Splitter Splitter
e.g. ATM network
PA – Access point
T- interfaces
S- interface
Network interface
Connecting line: basic trunk, e.g. with 10 pairs of Cu wires
connecting line
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ADSL specifications:
- modems on each end of twisted pair....3 information channels, including basic teleph.service (POTS= Plain Old Telephone Service), filters
- modems are consistent with basic frames T1, E1 (see Switching technology)
- downstream speed – depends on : Cu-line length, wire diameters, bridged taps, crosstalks
- Attenuation of line increases with both its length and frequency, decreases with increasing wire diameter (or cross-section)
Data speed [Mbps] Diameter of wires [mm] Distance [km]
1,5 or 2 0,5 5,5
1,5 or 2 0,4 4,6
6,1 0,5 3,7
6,1 0,4 2,7
Tab.3.1 Requested phys. parameters of ADSL lines
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VDSL
Fig. 3.6 VDSL system in hybrid network - architecture
- statistical multiplex: . . .
(see also fig.3.2 and 3.3)
Telephone netw. /ISDN Cable branching
Splitter Splitter
T- interfaces
S- interface
e.g. ATM net
Network interfaces
Cu-connecting line
optical connecting line
User station
300m-500m!
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Name Meaning Data speed Type of connection
Reach Applications
DSL Digital subscriber Line
160kb/s Symmetrical
~5 km ISDN group, voice and data
HDSL High Data Rate Digital Subscriber Line
2Mb/s Symmetrical
4-5km no POTS, E1 LAN/WAN, Service access feeder plant.
SDSL Single Line Digital Subscriber Line
2Mb/s Symmetrical
3-4km Same as HDSL + POTS
ADSL Asymmetric Digital Subscriber Line
1.5 to 8Mb/s Down 128kb-768kb Up
Asymmetrical
3-6km Interest access, video on demand, simplex video, remote LAN access, interactive multimedia.
VDSL Very High Data Rate Digital Subscriber Line
13-52Mbp/s Down 1.5-2.3Mbp/s Up
Asymmetrical
0.3-1.5km Same as ADSL+ HDTV
Tab. 3.2 Comparison of xDSL technologies
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Service lines of ISDN - BRA
- PRA
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ISDN – line – for rarely connecting to the Internet
[2] Fig. llustration of ISDN lines
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Interfaces V5.x for user systems connecting
Fig. 3.7 Architecture of the network with interfaces V5.x
Users ANLocal Exchange
Transit network
V5.x
- interfaces between AN and exchange
- are defined by ETSI and ITU (G.964/965)
- they do not depend on outputs of differents AN types including radiowave AN
- possibility of interconnecting networks of different operators
- differences between V5.1 a V5.2: ... - see next tab.and figure
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Fig. 3.8 Example of architecture of AN with both interfaces V5.x
V 5.1 V 5.2
1 x PCM 30/32 each with 2048 kbps 16 x PCM 30/32 with 2048kbps
It does not have concentration (only 1 line between exchange and AN)
It can concentrate traffic and dynamically allocate time slots for users connecting thousands users
Static allocating of channels Dynamic allocating of channels – protocol BCC
It does not allow connecting ISDN-PRA, only –BRA (15xPOTS+15xISDN,or 30xPOTS)
ISDN-BRA aj -PRA
Signalling without back-up …saving data in the case of failed channel
Access device of AN
Access device of AN
Exchange
channels
channels
Network of ren circuits
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16Obr. 3.9 V5.2 interface communications protocol
they support also analogue user lines
- interfaces protocols - see fig.3.9 and 3.10
switching system
control of access network control of access network
Physical layer of access network Physical layer of access network
Analogue user terminals
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Fig.3.10 An example of process of creating and aborting connecting, which was initiated from dig. user line.(by protocol BCC-part od protocol V5.2
from end point of AN – request for dispose communications channel...
-request for disconnect
- data transmission (by onother protocol)
KBPS-TE
Communicatio
ns
process
Access netw. Switching syst.
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Referencie:[1] V.Kapoun: Přístupové a transportní síte. VUT v Brně, 1999.[2] Vaculík: Prístupové siete. ŽU v Žiline, 2000.[3] J. Vodrážka: Přenosové systémy v přístupové síti. ČVUT, 2003.[4] Wikipedia, http://en.wikipedia.org/wiki/Image:Tdma-frame-structure.png#file[5] G.Fairhurst: MAC. http://www.erg.abdn.ac.uk/users/gorry/course/lan-pages/mac.html[6] K.Blunár, Z. Diviš: Telekomunikačné siete, časť IV..- skriptum ŽU v Žiline, 2000.