access networks
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Access Networks
lectures 2008/09part: 1
Telecommunications network
foto: http://www.ctuf.za.org/26telcodirections.htm
Ing. Ľudmila Maceková, PhD.ludmila.macekova@tuke.sk Vysokoškolská 4, 119A
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Access Network (AN)
= the part of communications network, which connects (joins?) users – subscribers, customers to their immediate provider (in PSTN: to the first/ local telecomm. exchange)
- so called the “first mile”
AN - The Plan of Lectures Telecommunications Networks = TN Access Networks = AN xDSL Technologies (ISDN Networks)
- Introduction- abbreviations and some basic terms (their list will be updated step by step)- the term and evolution of TN- structure (architecture) of TN- types (sorts) of TN
Telecommnications Networks:
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telecommunications = interchange (relaying) of information (remote)
the main tasks of telecommunications from the point of view of customers (end-users)
evolution = enhancing of Quality of Services (QoS / p.17) – ... sequential transformation from partially analogous to completely digital networks
the requirements to system from the side of operator ... history ...(fire-light signaling, ..., cipher signalling,
electric signals - telephone and telegraph = telecommunications, ...)
Telecommunications - Introduction
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Some basic terms in area of AN:
•4-Wire Transport(switching)
•duplex
•…etc. - see ‘TN_basic_terms.doc’
• a good terminology source - see [4]
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Term and evolution of TN
•Network vs. system
•TN = ... (nowadays also PC networks)
•Voice TNs =
• Evolution ... , digitizing
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The sorts of TNs (TN classification)and their differentiation aspects
Tab.1
Point of view Network types
a)Level (order, location) of telecommunications chain
. . .
b) Transport media
c) User access to network
. . .
j)
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a)...Structure (architecture) of TN – Layer model of TN
T
M
N Access network
End devices network
6.
5.
4.
3.
2.
1.
7.
Switching network
Transmission (transport) network
Signalling network
Intelligent network
Fig. 1
1.= end devices (=terminals)+ transmission network connecting them to interface (end point of AN)- in the PSTN, it deals with subscribers
2. . . ........ - subscriber (connecting) net3.... - exchanges and interconnection between them, different types of exchanges [1]/p.38-fig.2.12 , terms: switched network, switching, PSTN = Public Switched Telephone Network4.(tr.n.)(transport network) ... – transmission systems utilizing (SDH!) a transport media (optical! and others)- several levels (national transmission n., regional tr.n. ....)-Backbone n., Core Network = tr.n. + switch.n.(connections of any-to-any devices on the network)
TN Architecture - continue
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TN Architecture – continue 2:
TMN
t.n.
t.n.t.n.
e.n e.n.
SDH, PDH, ATM
WAN
C MDLAN
TD
AN
Tr.n.
TD TD TD TD TD TD
TU-terminal device (end d.), K-concentrator, MD–muldex,LAN-local area network, e.n.- end node (terminal n.), t.n.-transit node, TMN-telecom.management network, SDH-synchr.dig.hierarchy, PDH-plesiochron.dig.hierarchy, ATM-asynchr.transport mode, WAN- wide area network
Fig.1 The basic parts of both access and transport networks
5. Signalling network – logical independent, packet oriented net-sig.system CCITT/ITU No.7
6. Intelligent network – IN -(virtual)– the all-network services; they are appended to existing technology; distributed intelligence
7. TMN = Telecomm. Management Network - monitoring and control systems – controling of whole network; under condition of the following the interface and protocols standards
TN Architecture – continue 3:
Continue: segmentation (classification) of TNs:b) The transport media- wire vs. wireless (radio waves)Classification of wire media:-according to material: metallic (copper)
optical (light conducting)-according to construction.:symetrical vs. assymetrical (…)
-further survey:- wire -metallic outdoor (conductiong)media – telephone copper line above earth
surface - telephone lines with broadening band
-very high voltage power lines - cables - symetrical pairs – LF copper lines (with load coils –
Pupin Coils; pupinization) (additional inductance was required to balance the cable capacitance and to voice signal spectrum flatten; but – disadvantage: HP suppressing → loid coils must be removed /or switched befor DSL - technology installing)
-without load coils (unloaded lines)
-HF cables - Coaxial cables (asymmetrical lines) – microcoax.
- small coax
- Waveguides
Optical fibres: single-mode fibre (for long distances)
- multimode fibres – with stepped index
- with graded index s
Wireless (radiofrequency) telecomm. media:- microwave lines- tropospheric- stratospheric (HAPS – High Altitude Platform
systems) – in developing – comunications airships and small unmanned airplains flowing in the about 17-25 km above earth
- satellite
Transmission lines – continue:
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c)user access to network: public or private (closed) networks, branch netw.d) transport an switch equipment (time-, freq.-,apce-, code-division; analogous- digital or hybrid networks
e) Classification accordig to type of terminal equipments:Specialty networks – telephone, telegraph, teleprint, PC – networks, radio broadcasting or TV networksIntegrated – based only on digital principles (IDN, ISDN), NISDN, BISDN – the aim: services , economical aim - profit (!)...
f) according to creation of connection: fixed network, commuted, unidirect or bidirect network
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g) according to transmission type: 2-Wire or 4-Wire
h) according to process of switching: circuit switching or message switching, packet switching, …, virtual channels and virtual network
i) topology: (see next –Fig.3: spider net, star net, lattice (trellis, grid?) net., combined (mixed) net, tree net, ring -, and line (tandem) net
j) according to evolution (progress) of digitization: digital islands and overlaping nets
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Fig.3 Some net topology examples
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Applications and requirements: access to information sources ...
TB parameters: data speed, etc.
(Requirements from the side of user: ...)
- Quality of Services (QoS)- ... ITU-T G.1000 and - 1010
aplikácia Symetria Typ.rýchlosť [kbps]
Oneskorenie [s]
Kolísanie onesk.[ms]
PLR (Packet loss rate)
Prenos zvuk. informácie
Telef. Symetricky 4 - 64 <0,4 (0,15) < 1 < 3%
Hlas.správy Jednosm. 4 – 32 < 1 < 1 < 3%
Audio on dem.
Jednosm. 16 – 128 < 10 <<1 < 1%
Prenos obrazovej informácie
Videotelef. Symetr. 16 - 384 <0,4 (0,15) < 1%
VoD Jednosm. 16- Mbps < 10 < 1%
Tab.2 Basic quality criteria for transport of voice and video information
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Aplikácia Symetria Typický objem dát[kB]
Onesk.
[s]
Chybovosť BER
Hľadanie inf.
(browsing)
Asym. ~10 < 2
Prípustné <4
~ 0
Sťahovanie súb. a stat.obrázkov
Asym. 10 – 10 000 < 15
Prípustné <60
~ 0
Obch.transakcie
Symetricky < 10 < 2
Prípustné <4
~ 0
Ďiaľk.riadenie a interakt.hry
Asym. < 1 < 0,2 ~ 0
E-mail (prístup k servru)
Jednosmerne < 10 < 2
Prípustné <4
~ 0
E-mail (medzi servermi)
Jednosmerne < 10 Niekoľko min. ~ 0
Telefax Jednosmerne ~ 10 Niekoľko min. < 10-6
Tab.3 Zákl.kvalitatívne ukazovateľe pre prenos dát [3]
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Ešte niektoré ďalšie druhy sietí v súlade s PC technológiami: TS [3] /13 :
WAN – rozsiahla..
MAN- metropolitná – súčasť PrS
LAN- miestna – v objekte účastníka TS
PAN- Personal Area Network- v rámci miestnosti –BlueTooth a IR prenos
Požiadavky na TS zo strany zriaďovateľov a poskytovateľov služieb: ...
* Pozn: Iný pohľad na štruktúru TS:
-Zariadenia sieťových uzlov
-Chrbtová sieť
-Prístupová sieť
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References
[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] L. Harte: Introduction to Digital Subscriber Line (DSL). Technologies, Operation and systems, Althos, 2005.
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