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.