EWSD “ELECTRONISCHE WHELER SYSTEME

DIGITALE”

Introduction: EWSD is the abbreviated form of German equivalent of

Electronic Switching System Digital (Electronische Wheler Systeme Digitale).

EWSD Digital switching system has been designed and manufactured by M/s Siemens, Germany.

SYSTEM FEATURES: EWSD system can withstand a BHCA of 4 million with CP-

113C in case of EWSD Power mode (two million in case of EWSD Classic).

It can work as local cum transit exchange and supports CCS No.7, ISDN and IN and V5.X features

SYSTEM ARCHITECTURE: Digital line unit (DLU) Line/Trunk Group (LTG) Switching Network (SN) Coordination Processor (CP) Common Channel Signalling Network Control (CCNC)

Unit or Signalling System Network Control (SSNC)

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EWSD ARCHITECTURE:

Distributed controls in EWSD:

DLU (DIGITAL LINE UNIT):

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EWSD

CCNC

OMT PRINTER

MDD MTD

MB

CCGCCGSYP CP

DLU LTG(B)

LTG(C)

SNSN

SUBSCRIBERSSUBSCRIBERS

TRUNKS

DLUDLUCC

LTGGP

LTGGP

Common channel signalling/ Signalling System Network Control

CCNC/SSNC

Access

Coordination

CPSYPSYP

C MBMBC CCG

EMOM

T

SGC

Switching Network

It is a functional unit on which subscriber lines are terminated.

DLUs are connected to EWSD sub-systems via a uniform interface standardized by CCITT i.e. PDC.

One DLU is connected to two different LTGs for the reasons of security via two 4 Mbps links.

Total 124 channels are available between a DLU out of which the two LTGs signalling information is carried in TS16 of PDC0 and PDC2.

Applications and connection of Digital Line Unit:

One DLU can carry traffic of 100 Erlangs.

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PDC3 without ccs

PDC2 with ccs

PDC1 without ccsPDC0 with ccs

Subscriber lines and PBX lines for small and medium-sized PBXs

Remote application

Local application

4Mbps

SNLTG

LTG

CP

4 MbpsDLU

DLU

Subscriber lines and PBX lines for small and medium-sized PBXs

CCITT standard interface

G.703

Remote application :

in same directory number area,

in another directory number area,

as extension to conventional exchange.

For emergency service DLU-controller (DLUC) always contain up-to-date subscriber’s data.

Stand Alone Service Controller card (SASCE) is provided in each R-DLU for switching calls in emergency cases.

All DLUs are provided with a Test Unit (TU) for performing tests and measurements on SLCAs/ (subscriber line ckt. Analog), subscriber’s lines and telephones.

MAIN COMPONENTS OF DLU: SLMAs and / or SLMDs  Two Digital Interface Units for DLU (DIUD) for connections

of the PDCs.  Two DLU Controls (DLUC). Two 4 Mbps networks for the transmission of user

information between SLMs and the DIUDs. Two control network for the transmission of control

information between SLMs and DLUCs.  Test Unit (TU), External Alarm module (ALEX).

LTG (LINE/TRUNK GROUPS):

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DLU

Test line

DIUD0

DLUC1

DIUD1

DLUC0

PDC1

PDC0

PDC2PDC3

to

two

LTGs

SLMA

SLMD Te

st 4096 kbps network 0

4096 kbps network 1

Control network 0

Control network 1

TU

Analog

and ISDN

Subscriber

lines, PBX

lines Main

Components of a DLU

The line/trunk groups (LTG) forms the interface between the digital environment of a EWSD exchange and the switching network (SN).

Maximum traffic handling capacity per LTG is 100 Erlang.

PRIMARY FUNCTIONS OF LTG: Call processing functions – receiving and analyzing line and

register signals. Safeguarding functions – detecting errors in the LTG and

on transmission paths within LTG. Operation and maintenance functions –acquiring traffic

data, carrying out quality-to-service measurements.

FUNCTIONAL UNITS OF THE LINE/TRUNK GROUPS:

Line / Trunk Unit (LTU). Digital Interface unit (DIU30) for connection of 2 Mbps

digital trunks and either DLU or PA. Code Receivers (CR) are Multi-frequency code receivers for

trunks or DTMF subscribers. Conference Unit, module B or module C (COUB or COUC)

for conference calls. This is installed in special function LTGMs or LTGNs.

Automatic Test Equipment for Trunks (ATE: N) checks trunks and Tone Generators (TOG) during routine tests. This is installed in special function LTGMs or LTGNs.

Internal Structure of LTG:

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Signalling Unit (SU): Tone Generator (TOG) for audible tones. Code Receivers (CR) for MFC signalling and push-button

dialling. Receiver Module for Continuity Check (RM: CTC), etc.

Group Switch (GS): This functions as non-blocking time stage switch (512 TS)

controlled by the GP.Link Interface Unit (LIU):

Connects LTG to SN via two parallel 8 Mbps SDCs.Group Processor (GP):

Controls the functional units of the LTG. The received signals from LTU, SU, GS and LIU are processed with the help of GP software.

SWITCHING NETWORKS:

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(8Mbps)

Address signals

SIHO

SIHISPHO

SPHI

LTU

DIU30

LTU

COUB

LTU

CR

LTU

ATE:T

CR TOG CTC

SU

SN0

SN1

to/from SN (8Mbps)

GS

LIU

or

or

or

GP (PU, MU, SMX and GCG) SILC

DIU:LDIB

COUC

PHMAOCANEQ

Different peripheral units of EWSD, i.e., LTGs, CCNC, MB are connected to the Switching Network (SN) .

Through 8192 kbps highways called SDCs (Secondary Digital Carriers), which have 128 channels each.

It consists of several duplicated Time Stage Groups (TSG) and Space Stage Groups (SSG) housed in separate racks.

Connection paths through the TSGs and SSGs are switched by the SGC.

Each TSG can accommodate 63 SDCs from LTGs and one SDC to MB.

COORDINATION PROCESSOR:

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LTG 1

LTG n

CCNC

CP

SPACE STAGE GROUP

TIME STAGE GROUP

SGC

SGC

Switching Network

SDC:LTG

SDC:LTG

SDC:CCNC

SDC:TSG

SDC:SGC

SDC:SGC

SN

MB

SDC:SSG

SDC:SSG

Storage and administration of all programs, exchange and subscriber data.

Processing of received information for routing, path selection, zoning, charges.

Communication with operation and maintenance centres. Supervision of all subsystems, receipt of error messages,

alarm treatment, error messages. Handling of the man-machine interface.

BASIC FUNCTIONAL UNITS OF CP 113C: Base Processor (BAP) – For operation & maintenance and

call processing.Common M emory (CMY) –64 to 1024 MB in 4 memory

banks consisting of 4 Mb DRAM chips. Input / Output Controller (IOC) –2 to 4 IOCs coordinate

and supervise accessing of CMY by IOPs. ATM Bridge Processor (AMP) – If a SSNC (EWSD

powermode) is connected, the AMP is used. It represents the interface between the ATM equipment in the SSNC and the CP.

Input/output processors (IOP) – Various types of IOPs are used to connect the CP113C to the other subsystems and functional units of the exchange as well as to the external mass storage devices.

Hardware Structure of CP:

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COMMON CHANNEL SIGNALLING NETWORK CONTROL (CCNC):It consists of:-

Up to 32 signalling link terminal (SILT) groups, each with 8 signalling links and

One duplicated common channel signalling network processor (CCNP).

FUNCTIONS OF CCNC: In the originating or destination exchange in associated

signalling, it operates as signalling end point (SEP). In transit exchange in quasi-associated signalling, it

operates as a signalling transfer point (STP).

Common Channel Signalling Network Control:

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Maximum configuration of CP113C

CAP0

IOC1

IOC0

BAPS

BAPM

CAP5

IOP

IOP IOP

IOP

CMY1

CMY0

IOC3

IOC2

IOP

IOP

IOP

IOP

Basic configuration of CP 113C,

11

.

.

0

11

.

.

0

B:IOC

B:IOC

AMP0

AMP1

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CCS via digital data links

CCS via analog data links

0 310 31

0 70 7

SILT group 31

SILT group 0

CCNP 0 CCNP 1

CP bus system

MultiplexerModem

Trunks and SS7 Links

LTGLTG

SNB

CCNC

MB B

IOP:MB

IOP:MB

CP EWSD Classic

Configuration

PCM30

8 Mb/s4

Mb/s

OMT/

OMT/CT

LTGLTG

SNB

SSNC

MB DA

MPC

IOP:MB

CP EWSD

Powermode Configuration

Trunks and SS7 Links

PCM30/24

270 Mb/s

207 Mb/s

High Speed

SS7 Links

NetM

SIGNALING SYSTEM NETWORK CONTROL (SSNC):

a) ATM Switching Network ASN (2 module frames for ASN 0 and 1):

Switches the communication- streams of the individual SSNC functional units with MB-D and CP.

Switches the communication-streams between the individual SSNC functional units.

b)SSNC basic frames SCB: Line Interface Card (LIC) -The duplicated Line Interface

Card LIC forms the physical interface between the SSNC units and the SS7 network.

Main Processor MP:MP: OAM: MP for Operation, Administration and Maintenance.MP: SLT: MP for Signalling Link Termination.MP: SM: MP for Signalling Manager. MP: STATS: MP for statistics.

ATM Multiplexer Type-E (AMXE):Provides 32 x 207 Mbps ATM interfaces to connect the internal SSNC units LIC and MP and the optical cables to the AMP of the CP and MBDA of the MB.

c) Extension frame SCE (maximum 7 for 1500 signalling channels)

The SCE contains a duplicated AMXE and serves to include other MPs and LICs.

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SSNC Interfaces:

System Panel Layout:The system panel SYP is used for the visual and audible signaling of critical alarms, major alarms, minor alarms, advisories and system data both within the exchange and externally.

The system panel consists of the system panel control (SYPC), which is housed in rack R:MB/CCG or in rack R:SE, and a maximum of 8 system panel displays (SYPD).The SYPDs may be located in the exchange, in a maintenance center or at any other location from which the exchange is to be supervised.

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Output LTG

ISUP LTG

Inward LTG

AMP MB- D (MBDA)

CP

SNSignaling link

Affecting speech channel

SSNC

OAMLevel 2 & 3(MTP)

Net M

31 SS7- Links

with 64 Kbit/s

or

1 HS- Link

with 2 Mb/SDirect connected E1 exclusively used for

SS7 links

Overall view SYPD:

S=

***************THANKS***************

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- : MONTH DAY TIME EXTERNAL ALARMS

ENTRY SUPERVISION

FIRE

DC POWER MAIN POWER SUPPLY SUPPLY

AIR CONDITIONING

LINE/TRUNK GROUPSLTG

MAITAIN SERVICE EXTERN.ALARM ALARM EQUIPM.

SWITCHING NETWORK SN

COORDINATION PROCESSOR CENTRAL MESSAGECP UNITS BUFFER

ERL CLOCK COM. CHAN. PROCESSOR SIGNALING LOAD

SYSTEM PANELSYP

UPDATE TEST ACCEPT

TRUNK GROUP TRUNG GROUP EXT. DLU HW-UNITS MBLALARM BLOCKED ALARM

LINE LOCKOUT CAT 1 ADMIN. SIGNALING ALARM LINK NO.7SIGNALING BLOCKEDLINK NO.7 CAT 2 RECOVERY ALARMCALL IDENTI- SYSTEM TIME DISPLAYFICATION OPERATOR INSECURE SUPPRESSION