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Network Survey ISDN Siemens

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1

Contents

1 Basic Structure of a Telecommunication Network 3

1.1 Basic Requirements of every Telecommunication Network 4

1.2 Basic Structure of a Telecommunication Network 6

1.3

Basic Functioning Modes of the Switching Equipment 8

2 Comparison of the Characteristics of ISDN and PSTN 11

2.1 General Characteristics 12

2.2 Characteristics of the Main Station Subscriber Interface 14

2.3 Characteristics of the Interface to other Exchanges/PBX 16

3 Hierarchical Structure of the ISDN Core Network 19

3.1 Basic Features of the Network Architecture 20

3.2 Tasks of an Exchange in the ISDN Core Network 22

4 Call Setup in the ISDN 25

4.1

Internal Call Setup in Local Exchange 26 4.2 Setup of a Trunk Call 28

5 Billing in the ISDN 31

5.1 Billing by Means of Metering 34

5.2 Billing by Means of AMA 36

6 Call Setup in the ISDN with the Support of the Intelligent Networks (IN) 39

6.1 Components of the IN 40

6.2 Call Setup 42

7 Access Implementations in the ISDN 45

7.1

Interfaces for the Direct Connection of Main Station Subscribers 46

7.2 Interfaces for the Connection of Private Branch Exchanges 48

Network Survey ISDN



Siemens Network Survey ISDN

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7.3 Implementations for Remote Connection of Main Station Subscribers 50

8 Exercise 53

9 Solution 57





3

1 Basic Structure of a Telecommunication

Network




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1.1 Basic Requirements of every TelecommunicationNetwork

Requests of telecommunication networks

Sufficient transfer capacity (ERLang value of the network call

handling facilities) for simultaneous fulfillment of all call attemptsduring the busy hour (busy hour call attempts – BHCA)

Provisioning of transitions (gateways) to other networks

Billing

Traffic measurement and grade-of-service monitoring

Overload control(preventing the collapse of a network when overloaded)

Failure protection (possibilities for protection switching)

Management network for the central control and monitoringof all network elements

Fig. 1





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The network must have a sufficient capacity in order to make an adequate number ofsimultaneous routes between any given subscribers available at any time.

The technical expenditure (number of switching and moving mechanisms) must be

optimized by utilizing statistic conditions (e.g. average holding time of a subscriberduring the busy hour) as well.

The traffic theory supplies models and procedures for the correct provisioning ofnetworks.

Major terms:

Busy Hour Four consecutive 15 min. intervals of a day with thehighest traffic load

Busy Hour Call AttemptsBHCA The number of call attempts a network element must beable to handle (important for the provisioning of theprocessor capacity of the network elements)

ERLANG Measurement variable for the traffic quantity to becarried by a network element; it is therefore important forthe provisioning of transfer performance of networkelements (0.1 ERLANG: e.g. traffic volume of anaverage subscriber which is occupied 6 minutes duringone hour)




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1.2 Basic Structure of a Telecommunication Network

Telecommunication networks are subdivided into the following areas:Transport Transmission facilities

Switching Switch or Exchange

Access Equipment for the access of subscribers (Accessnetworks AN)

Customer PremisesEquipment

Subscriber terminal equipment

Switching equipment and transmission facilities together form the corenetwork

The customer premises equipment is connected to the core network via theaccess network

The transmission facilities make transparent channels available between theswitching elements.

The user information is carried between the subscribers in these channels.

The routes (channels/trunk) for the user information are through-connected in the

switching equipments according to the call attempts of a subscriber .

Control information messages must be exchanged between subscribers andswitching equipment as well as between the switching elements.

Transport and switching are the two basic functions for the transfer of userinformation.





7

Transport

AN AN

N

T

N

T

AN

N

T

AN

N

T

Exchange

Access Network (AN)

with subscriber

terminals (CPE)

Transport channels (inter exchange connections):

• Trunks for transmitting user information

• Signaling links for transmitting the control information

SIEMENS

NIXDORF

SIEMENS

NIXDORF

SIEMENS

NIXDORF

SIEMENS

NIXDORF

Fig. 2




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1.3 Basic Functioning Modes of the SwitchingEquipment

Circuit switching (circuit switched networks)

The continuous message flow of every call is transparently through-connected to anexclusively reserved communication channel in the switching equipment for theduration of the call.

Memory switching (store and forward, e.g. packet switched networks orasynchronous transfer mode networks)

The user information of a call is divided into blocks (packets or cells). These blocks

are individually through-connected with buffering in the switching elements; thephysical channels are not reserved for the packets of individual calls.

Rather a statistic multiplex takes place on the communication channels. Thus thesame physical channel is used for packets of different calls.





9

Example of circuit switching:

3 calls, each with its own line (e.g. 64 kb/s channel on a link

between both switches)

switch switch

subs.

subs.

subs.

subs.

subs.

subs.

Each line sysmbolizes

an own channel

for the continuous

information transfer

Example of memory switching:

The data packets of all three calls share the same line(e.g. 64 kb/s channel on a link between both switches)

switch switch

subs.

subs.

subs.

subs.

subs.

subs.

Statistic multiplex

of the individual data

packets onto one channel

Fig. 3




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2 Comparison of the Characteristics of ISDN

and PSTN




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2.1 General Characteristics

The conventional telephone network (public switched telephone network PSTN) andthe integrated services digital network ISDN are compared below.

The ISDN is a further development of the PSTN as seen from a historicalperspective.

The transition from the PSTN to the ISDN takes place through the (gradual)digitalization of the switching, access, and transport elements of the PSTN.

Note:

Note that the term PSTN does not have a standard definition in language usage.

Thus PSTN can as a generic term stand for both conventional analog telephonenetworks and the ISDN. In this document however, PSTN is always used as a term incontrast with ISDN.





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ISDN

PSTN

digitalization of theswitching, transport

and access facilities

• circuit switched• transferred user information:

tones with 300 to 3400 Hz

bandwidth

• service: AUDIO 3.1 kHz

(also called plain old telephone service – POTS)

• circuit switched

• transferred user information:

64 kb/s bit stream

• service: TEL3K, FAX3/4, VIDEOTEL,

AUDIO 3.1 kHz......

(service is also signalled)

Fig. 4




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2.2 Characteristics of the Main Station SubscriberInterface

Analog PSTN ISDN

Subscriber interface

for a single party line

(a/b interface):

2 wire copper linebetween exchange and

analog terminal device

with analog transmissionof the user information

(3.1 kHz) and the signaling

Subscriber interface

single party line

(basic access – BA – with

U and So interface):

2 wire copper line

between exchange and

network terminator (NT)

with digital transmission

in the time switch(U interface):

• User information on 2Bchannels with 64Kb/s each

• DSS1 signaling messageson one D channel with

16 kb/s each

4 wire copper line between

NT and ISDN terminaldevices (So interface)

in the residence of the

subscriber

Fig. 5





15

N

T

B B DB

2 wire copper line

digitally operated in the time switch (160 kb/s)

(U interface)

1. ISDN subscriber access

(basic access – BA)

2 wire copper line

analog operated (3.1 kHzbandwidth)

(a/b interface)

PSTN subscriber

access

Alternative:

•FAX2/3 via modem

•PC via modem

4 wire S bus with So

interfaces for digital

terminal devices

SIEMENS

NIXDORF

Fig. 6




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2.3 Characteristics of the Interface to otherExchanges/PBX

Analog PSTN ISDN

? Interface between twoexchanges:

Analog or digital trunksfor transmission of userinformation

Analog or digitalsignaling channels:each trunk has its ownsignaling channel

?

?

Interface between two

exchanges:Digital trunks with 64 kb/sfor transmission of userinformation

Digital signaling links with64 kb/s for transmissionof CCS7 ISUP messagesbetween two exchanges(common signaling channelinstead of trunk individualsignaling channels)

Interface between

exchange and PBX:

PBX are connected eithervia many a/b interfaces orvia PCM30 lines(similar to interfacebetween exchanges)

Interface betweenexchange and PBX:

ISDN PBX are connectedeither via BA or primaryaccess (PA)PA: 2 Mb/s PCM system

with 30 x 64 kb/s PBX linesfor user information anda D channel as 64 kb/scommon signaling channelfor DSS1 signalingmessages between PBXand exchange

Fig. 7





17

Setup of a PCM30 route in the PSTN

Time slot 0:synchronization of

the bit stream

Time slots 1-15 and17-31:30 trunks for trans-mission of the userinformation of a call

Time slot 16:30 trunk individual 2 kb/ssignaling channels fortransmission of the channelassociated signaling (CAS)

30 Trunks

30 Trunks

31 Trunks

31 Trunks

Signaling link:Transmits the CCS7 signaling messages as commonsignaling channel for all trunks between both exchanges.The number of signaling links is based on the amountof signaling messages to be transmitted betweenboth exchanges.

Setup of the PCM routes in the ISDN

Exchange BExchange A

Fig. 8




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3 Hierarchical Structure of the ISDN Core

Network




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3.1 Basic Features of the Network Architecture

Core networks are as a rule composed of several network layers.In this way, for instance, a difference is made between the local level (local network)and the long-distance level (transit network for the connection of local networks).

The number of network layers and to what degree the network has a star-shaped,intermeshed, or a mixed structure differs from network operator to networkoperator.





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local network A local network C

local network B local network D

local network A local network C

local network B local network D

transit

network

transit

network

Connection of the local networks by a mesh-shaped transit network

Connection of the local networks by a star-shaped transit network

Fig. 9




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3.2 Tasks of an Exchange in the ISDN Core Network

Transit exchange: Function: Through-connecting an incoming call on one trunkto an outgoing trunk

Local exchange: Function: Interface for ISDN subscribers and PBX as wellas for analog subscribers and PBX (network interworking toPSTN at the subscriber interface)

Gateway exchange: Function: Placing one call from one exchange of its ownnetwork through to the exchange of a foreign network

Combined exchange: An exchange which unifies several functions within





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Gateway Ex.

Transit

Ex.

Transit

Ex.Transit

Ex.

Transit

Ex.

Local network

Local Ex.

Local Ex.

Localnetwork

Local Ex.

Local Ex.

Localnetwork

Local Ex.

Local Ex.

Localnetwork

Local Ex.

Local Ex.

Transit network

layer for trunk callsbetween various

local networks

Note:

Transport mechanisms are not shown.

Exchanges in the ISDN core network

Fig. 10




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4 Call Setup in the ISDN




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4.1 Internal Call Setup in Local Exchange

Digit translation

All dialing information is evaluated.

The local area code (LAC) 089 of the calling party is taken into consideration duringthe evaluation in case the dialing information only includes a directory number (DN)

without a local area code.

The port of subscriber 3333 in local network 089 is designated as the destination ofthe attempt (the called party).

Test whether the called party is free

Through-connection

A bi-directional 64kb/s call is connected between the ports of subscribers A and B.

Signaling to the terminal devices of the called party

The call is offered to the terminal devices.

(calling the called party)

For ISDN subscribers, the information about the service (FAX/TEL/DATA...) of thecalling party is additionally signaled to the terminal devices of the called party.





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Setup of a local call:Signaling of the calling party:Go off-hook, dialing information 3333

(service included with ISDN)

LocalExchange

Localnetwork

089

DN:2222

DN:3333

Localnetwork088

AN

N

T

DN:3333

Callingparty

SIEMENS

NIXDORF

Fig. 11




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4.2 Setup of a Trunk Call

Procedure in local A

Digit translation: 06 leads to the symbolic destination transit1.

Routing:

Trunk group A1 is selected as the route and a free trunk is seized.

Through-connection of the switching network

Signaling message to transit1:

Identifier of the seized trunk A-DN

All dialing information

Service

Procedure in transit 1

Digit translation: 069 leads to the symbolic destination local B.

Routing:

Selection of the route to local B (either trunk group 1B or 12)

Example: Free trunk on primary route (1B) is found and seized

Through-connection and signaling as in local A

Procedure in local B

Digit translation: Evaluation of all the dialing information (0693333) leads to the port of the calledparty.

Through-connection and signaling to the called party as in the example of aninternal call.





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Local exchange A

Setup of a trunk call:Signaling of the calling party: Go off-hook,

dialing information 0693333 (service included with ISDN)

Local network069

Local network06027

Transitexchange 1

Localexchange B

Transitexchange 2

DN:3333

Localnetwork

089

DN:

2222

Trunk group 12

Trunk group 2B

Trunk group 1B

Signaling link forCCS7 signaling

Trunk group with

trunks for userinformation

Trunk group A1

Calling party

Fig. 12




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5 Billing in the ISDN




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As a rule, the charges for a call are:

charged to the calling party

recorded in the local exchange of the calling party

Exceptions:

Non-chargeable calls

Collect call (reverse charge call)

Billing between network operators (inter-administrative charging):The servingnetwork operator charges the calling party for the costs of the entire call, transitand destination network operators settle the costs for the part of the call throughtheir network with the serving operator.

Procedure for the recording of the charges:

Billing by means of metering

Billing by means of Automatic Message Accounting AMA





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SIEMENS

Pulsemetering or Detailled Billing

local exchange

SIEMENS SIEMENS

Gateway exchange Gateway exchange

Operator BOperator A IACHASTA

Fig. 13




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5.1 Billing by Means of Metering

For determining the tariff of a call, zoning is carried out in the exchange with thedialing information. Every dialing information leads to a so-called zone. A tariff(call time per call-charge pulse) is established for every zone.

The call-charge pulses are added up on the meter at the end of the call.Furthermore, the pulses can be carried to the terminal device of the calling party(advice of charge).

The meter counts are transmitted monthly to a computer center for drawing up bills(post processing).

SI EMEN S S IEMENS SIEMENS SI EMENS SI EMENS SIEMENS

SI EMENS S IEMENS SIEMENS

SIE ME NS SI EMENS SIEMENS

1.) Zoning and generating the meter pulse

in the local exchange of the local network 089

Local network

088

Local network

087

Local network

06

Local network

07

Zone 1 for local calls

(dialing information

without LAC)

Zone 2 for calls

to local networks

087 & 088

Zone 3 for calls

to local networks

06 & 07

Called party

in local

network

089

Day rate Night rate3 min.

per chargeunit

4 min.per charge

unit


per chargeunit

3 min.per charge

unit


per chargeunit

2 min.per charge

unit

Fig. 14





35

2.) Storage of the meter pulses on the charge meter of the calling party in the local exchange at the end of the call

Directory number Current sum of meter pulses

x x x x x x . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

One chargemeter per

directory number

3.) Monthly transmission of the charge meters of all

subscribers to the post-processing center for billing

per subscriber

Number of pulses for this month

*

Price per pulse

Filetransfer

total

bill

HOST

in the post-

processing

center

SIEMENS S IEMENS SIEMENS

Fig. 15




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5.2 Billing by Means of AMA

The automatic message accounting (AMA) is also called detailed billing DEB. A data record (AMA record) is recorded with A-DN, dialing information, begin

time/date and duration, and service of the call.

The data records are submitted to the post processing center for drawing up bills.

For this procedure, the database for determining the tariff of a call is exclusively inthe computer center and not in the exchange.





37

Localexchange089

1.) Local exchange generates one AMA record per call (calling party in own

exchange) and stores this in an AMA file

DN:

3333

AMA-record

Calling party : 089 3333Service : AUDIO 3.1 kHz

Dialed digits : 0692222Begin date : 1.1.99

Begin time : 12:00:05Duration : 365 sec

Calling party

0692222(dialing

information)

Local

exchange089

HOSTin the

postprocessingcenter

1. call

n. call

2.) Periodical transmission of the AMA file with all records of all subscribers

to the post-processing center for billing

File

Zoning

and billing

every call

Detailed bill

for everysubscriber

SIEMENS SIEMENS SIEMENS


Fig. 16




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6 Call Setup in the ISDN with the Support of

the Intelligent Networks (IN)




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6.1 Components of the IN

Central facilities for the control of telecommunication network services are madeavailable with the intelligent network (IN) outside the ISDN.

Thus a disconnection is carried out by:

Connection control in the exchanges of the ISDN

Service control in the network nodes of the IN

In comparison to previous decentralized service administrations in the exchanges ofthe ISDN, this allows a more effective and economic administration of the services inthe centralized IN control facility.

Components of the IN Service Switching Point (SSP) (selected exchanges of the ISDN):

All ISDN calls which use IN services are routed by the local exchange to the nextSSP in the ISDN.

The SSP is responsible for the connection control of the ISDN calls.

Special software programs facilitate the communication with the centralizedservice control in the IN for it. This communication serves to conclude the INservices for calls in ISDN.

Service Control Point (SCP) (network node of the IN):

This computer has a database for the central control of the IN services. Thecommunication with the SSP takes place by means of CCS7 INAP signaling (SSPrequests service control, SCP supplies the necessary data). The circuitconnections do not run via the SCP.

Service Management Point (SMP):

System for administration of the database in the SCP

Intelligent Peripheral node (IP)

From the SSP accessible hardware to the support of the dialog with the subscriber

who wants to use IN services (user interactive dialog). An IP makes announcements, code receivers, and speech recognition functionsavailable. The dialogue between subscriber and IP is controlled by the SCP,

whereas the SSP realizes the physical interconnection.





41

SMP

Service

Management

SCP

ServiceControl

IP

SIEMENS SI EMENS SIEMENS

SSP

Exchange

Intelligent

Network

CCS7 INAP

Signaling

ISDNTrunks with CCS7ISUPsignaling to other

exchanges of the ISDN

SIEMENSNIXDORF

Fig. 17




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6.2 Call Setup

1. Local exchange A

• evaluates the 0130 in the dialing information

• sets up a normal trunk call to the next exchange with SSP function by

means of CCS7ISUP signaling. (Here further transit exchanges may

be between local A and SSP)

2. SSP

• converts the received dialing information 0130 into an IN trigger point

• starts the INAP dialogue with the SCP responsible for this service

(here service 0130) and transfers the dialing information and the

directory number of the service user

3. SCP

• translation of the received dailing information 3333 into one of the ISDN/PSTN

directory numbers (here 0897777 or 0305555) assigned in the SCP database to the

service subscriber 01303333 (dispatch house)

(During the translation, the locality of the service user and time/weekday of the

call may be taken into consideration)

• Return signal to the SSP: destination ISDN/PSTN directory number

4. SSP

• sets up of a normal trunk call to the local exchange of B1 or B2 (by CCS7 ISUP)

Fig. 18





43

SIEMENS SIEMENS SIEMENSSIEMENS SIEMENS SIEMENSSIEMENS SIEMENS SIEMENS


Local

exchange B1

Local

exchange B2

Local

exchange A

or

DN = 08027 222 DN = 089 7777 DN = 030 5555

INAP sign.

SCP

Exchange with

SSP functionTrunk with

ISUP sign.

3.)

1.) 4.)

2.)

or

Service user

dials IN number of a mail

order firm: 0130 3333

Service subscriber 1 Service subscriber 2

of the mail order firm

Call setup with IN support for "Service 130"

Subscriber dials the no charge number 01303333 of a mail order firm

Fig. 19




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45

7 Access Implementations in the ISDN




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7.1 Interfaces for the Direct Connection of MainStation Subscribers

Two basic types of main station subscribers can be directly connected to the corenetwork of the ISDN:

Digital subscribers with multiple subscriber number

(Basic Access (BA) in POINT TO MULTIPOINT configuration via 2 wire copperline)

Analog subscribers (classic subscribers of the analog PSTN)

(analog a/b interface via 2 wire copper line)

If a network operator has a pure ISDN core network but also wants to connectanalog subscribers, the local exchanges perform a network transition to analogPSTN subscribers by offering a/b subscriber interfaces.

In this case the PSTN is a telecommunications network which has only an accessarea but no core area.





47

N

T

N

T

N

T

PSTN

per a/b

connected

analog

subscribers

per BA connected

digital subscribers

Interface for network transition

between ISDN and PSTN

Connection of individual subscribers

ISDN

S IE ME NS S IEME NS S IE ME NS

ISDN

Exchange

SI EME NS S IE ME NS S IE ME NS

ISDN

Exchange

S IE ME NS S IE ME NS S IE ME NS

ISDN

Exchange

SIEMENS

NIXDORF

SIEMENS

NIXDORF

SIEMENSNIXDORF

Fig. 20




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7.2 Interfaces for the Connection of Private BranchExchanges

A difference must also be made between ISDN capable and ISDN incapable systemsfor private branch exchanges.

ISDN PBX offers the possibility to connect both digital and analog terminaldevices.

ISDN PBX are connected to the ISDN core network via either one or several2 Mbit/s primary accesses (PA) or several basic accesses (each in POINT TOPOINT configuration)

PSTN PBX only offers the possibility to connect analog terminal devices.

PSTN PBX are connected to the ISDN core network via either one/several 2 Mbit/sPCM routes with CAS signaling or several a/b interfaces. With this the signaling tothe a/b interfaces can be expanded to include the possibility of sending out dialeddigits from the local exchange to the PBX (direct dialing in).





49

4 wire primary access

(with 30 PBX lines each)

2 wire basic access(with 2 PBX lines each)

B B DB

30 x B D

30 x B D

Connection of ISDN Private Branch Exchanges


ISDN Local

Exchange

I

S

D

N

P

B

X

Connectionof ISDN

andanalog

terminaldevices

Fig. 21




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7.3 Implementations for Remote Connection of MainStation Subscribers

Aside from a direct line via a 2 wire copper line with a ca. 8 km range, the followingvariants for the remote line are possible:

Connection via proprietary remote facilities of the local exchange.

Example EWSD:

Remote DLU (RDLU) for the connection of ca. 900 subscribers, the RDLU isconnected to EWSD with a maximum of 4x2 Mbit/s via a proprietary interface andit carries out concentration.

Connection to remote units of an access network (AN):

Since the V5 interfaces between local exchange and AN are standardized by theETSI, AN and local exchange can be taken up by various manufacturers.

At the moment, two interfaces and AN types are specified:

V5.1

2Mbit/s PCM line between local exchange and AN for connecting max. 30subscribers to the non-concentrating AN facility.

The subscribers can be connected as “fixed“ or “cordless“ (via a radio interface) tothe AN

V5.2

Several (currently max. 8 in EWSD) 2 Mbit/s PCM lines between local exchangeand AN for the connection of (currently) max. 2048 subscribers to theconcentrating AN facility.

The subscribers can be connected as “fixed“ or “cordless“ (via a radio interface) tothe AN





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Local

exchangeConcentrating

access network

via standardized V5.2

interface connected

to the local exchange

Non-concentrating

access network viastandardized V5.1

interface connected to the

local exchange

Connection of up to 30 subscribers

AN

Connection of up toca. 2000 subscribers

AN

1x2 Mbit/s

max. 8 x 2 Mbit/s

Fig. 22




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8 Exercise




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Exercise

Title: Features of the ISDN/PSTN/IN

Objectives: The course participant will be able to:

Explain the fundamental characteristics of ISDN/PSTN

Sketch a call setup supported by IN

Delimitate various access implementations from each other

Pre-requisite: None

Task

Answer the following questions

Questions: Answers:

What kind of user information can twoPSTN subscribers exchange with oneanother?

How many simultaneous calls with64kbit/s user information transfer can

an ISDN main station subscriber setup?

Which signaling highway is usedbetween the exchanges of the ISDN?

Which billing procedures are principallyavailable for local exchanges?

Which network entities of the INexchange messages with one anotherper INAP signaling?

Which internationally standardizedinterface serves to connectconcentrating access networks to alocal ISDN exchange?




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9 Solution




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Solution

Title:Features of the ISDN/PSTN/IN

Objectives: The course participant will be able to:

Explain the fundamental characteristics of ISDN/PSTN

Sketch a call setup supported by IN

Delimitate various access implementations from each other

Pre-requisite: None

Task

Answer the following questions

Questions: Answers:

What kind of user information can twoPSTN subscribers exchange with oneanother?

Audio information with 3.1 kHz bandwidth

How many simultaneous calls with64kbit/s user information transfer can

an ISDN main station subscriber setup?

2 simultaneous calls not dependent onone another

Which signaling highway is usedbetween the exchanges of the ISDN?

CCS7 ISUP

Which billing procedures are principallyavailable for local exchanges?

Pulse metering

AMA

Which network entities of the INexchange messages with one anotherper INAP signaling?

Service control point (SCP) and serviceswitching point (SSP)

Which internationally standardizedinterface serves to connectconcentrating access networks to alocal ISDN exchange?

V 5.2 interface




Documents

01_sn2010eu13sn_0001_network_survey_isdn.pdf