EWSD Overview

04/17/23 SW-II/EWSD_Overview/HSJ 1

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ALTTCBSNL

EWSD Overview

H.S.JakharD.G.M. (SW-II)ALTTC Ghaziabad


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ALTTCBSNL System Features

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

• The name is the abbreviated form of German equivalent of Electronic Switching System Digital (Electronische Wheler Systeme Digitale).

• EWSD switch can support maximum 2,50,000 subscribers or 60,000 incoming, outgoing or both way trunks, when working as a pure tandem exchange.


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ALTTCBSNL System Features

• It can carry 25,200 Erlang traffic and can withstand 1.4 million BHCA.

• It can work as local cum transit exchange

• Can support

– CCS No.7– ISDN – IN – V5.X features.


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System Architecture

The main HW units of an EWSD switch are as under:

• (1) Digital line unit (DLU) - functional unit on which subscriber lines are terminated.• (2) Line/Trunk Group (LTG) - Digital Trunks and DLUs are connected to LTGs.• (3) Switching Network (SN) - All the LTGs are connected to the SN which inter connects the line and

trunks connected to the exchange in accordance with the call requirement of the subscribers. CCNC and CP are also connected to SN.


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ALTTCBSNL System Architecture

• (4) Coordination Processor (CP) - It is used for system-wide coordination functions, such as, routing, zoning, etc. However each subsystem in EWSD carryout practically all the tasks arising in their area independently.

• (5) Common Channel Signaling Network Control (CCNC) Unit - This unit functions as the Message Transfer Part (MTP) of CCS#7. The User Part (UP) is incorporated in the respective LTGs.


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DLU

DLUC

LTG

GP

LTG

GP

COMMON CHANNEL SIGNALING

CCNC

CCNP

ACCESS

COORDINATION

CPSYPSYPC

MBMBC

CCG

EM

OMTSGC

SWITCHING NETWORK

DISTRIBUTED CONTROLS IN EWSD


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Digital Line Unit (DLU)

• Analog or Digital (ISDN) subscribers, PBX lines or V5.1 interface are terminated on DLU

• DLUs can be used locally within the exchange or remotely as remote switch unit , in the vicinity of the groups of subscribers.

• DLUs are connected to EWSD sub-systems via a uniform interface standardized by CCITT, i.e., Primary Digital Carrier (PDC) to facilitate Local or Remote installation. A subset of CCS# 7 is used for CCS on the PDCs.

• One DLU is connected to two different LTGs for the reasons of security.


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PDC3 W/o CCS

PDC2 WITH CCS

PDC1 W/O CCS

PDC0 WITH CCS

SUBSCRIBER LINES AND PBX LINES

REMOTE APPLICATION

LOCAL APPLICATION

4Mbps

SNLTG

LTG

CP

4 MbpsDLU

DLU

SUBSCRIBER LINES AND PBX LINES

APPLICATIONS AND CONNECTION OF DIGITAL LINE UNIT


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Digital Line Unit (DLU)• A local DLU is connected to two LTGs via two 4 Mbps (64

TSs) links, each towards a different LTG.

• In case of remote DLUs, maximum 4 PDCs of 2 Mbps (32 TSs) are used per DLU, two towards each LTG.

• 120 channels are used for user information (speech or data) and signaling information is carried in TS16 of PDC0 and PDC2. In case of a local DLU interface, TS32 carries CCS.


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ALTTCBSNL Digital Line Unit (DLU)

• Within the DLU, the analog subscribers are terminated on SLMA (Sub scriber Line Module Analog) cards (module).

• Digital (ISDN) subscribers are terminated on the SLMD modules. • Each module can support 16 subscribers.• One DLU can carry traffic of 100 Erlangs. • A standard rack of DLU (local ) can accommodate two DLUs of

992 subscribers each. • In case the link between a remote DLU and the main exchange is

broken, the subscribers connected to the remote DLU can still dial each other.


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Digital Line Unit (DLU)

• For emergency service DLU-controller (DLUC) always contain up-to-date subscribers data.

• Stand Alone Service Cr. card (SASCE) is provided in each R-DLU for switching calls in such cases.

• This card is also used for interconnecting a number of remotely situated DLUs (maximum 6), in a cluster, called a Remote Control Unit (RCU)

• All DLUs are provided with a Test Unit (TU) for performing tests and measurements on SLCAs, subscribers lines and telephones.

• An ALEX (ALarm Externals) module is used for forwarding external alarms.

• Numbers of SLMAs are accordingly reduced to accommodate these modules.


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DLU

Test line

DIUD0

DLUC1

DIUD1

DLUC0

PDC1

PDC0

PDC2

PDC3

TO TWO LTGS

SLMA

SLMD

4096 KBPS NETWORK 04096 KBPS NETWORK 1CONTROL NETWORK 0CONTROL NETWORK 1

TU

ANALOG AND ISDN SUBSCRIBER LINES, PBX LINES

MAIN COMPONENTS OF A DLU


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Line/Trunk Groups(LTG)

LTG forms the interface between the digital environment of an EWSD exchange and the SN. They are connected in any of the following ways :

-(i) Via 2/4 Mb/s PDCs with remote/local DLUs to which analogue or ISDN subscribers are connected.

-(ii) Via 2 Mbps digital access lines to other digital exchanges in the network ( MF R2 Trunks, CCS#7 Trunks).( MF R2 Trunks, CCS#7 Trunks).

--(iii)(iii) Via Primary rate Access lines to ISDN PBXs (ISDN Via Primary rate Access lines to ISDN PBXs (ISDN sub scribers with PA).sub scribers with PA).

-(iv)-(iv) V5.2 Trunks, Announcements Trunks, OCANEQ, V5.2 Trunks, Announcements Trunks, OCANEQ, IP (SSP). IP (SSP).


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• FunctionsFunctions• Call processing functions, i.e., receiving and analyzing

line and register signals, injecting audible tones, switching user channels from and to the switching network, etc.

• Safeguarding functions, i.e., detecting errors in the LTG and on transmission paths within the LTG, analyzing the extent of errors and initiating counter-measures such as disabling channels or lines, etc.

• Operation and maintenance functions, i.e., acquiring traffic data, carrying out quality-of-service measurements, etc.



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ALTTCBSNL DIFFERENT Functional DIFFERENT Functional

TYPES IN LTGTYPES IN LTG

FRAME TYPE FRAME TYPE of LTGNof LTGNFUNCTIONAL FUNCTIONAL

TYPETYPE

LTGLTGLTGLTG

B FUNCTION (FOR DLUS[L&R], PRI,V5.2,OCANEQ,COU)

C FUNCTION (FOR TRUNKS ON CAS & CCS AND CCS#7 SIGN.CHLS)

F: LTGN(B) (FOR SPL. FUNCTIONS LIKE COUC, PHMA ( V5.2), ATE:N, OCE:N)

F:LTGN(A) (FOR DLUS[L&R], PRI, TRUNKS)

ONE LTG SUPPORTS 128 TS (I/P & O/P) ONE LTG SUPPORTS 128 TS (I/P & O/P) MAX. ERLANG CAPACITY PER LTG IS 100 ERL.MAX. ERLANG CAPACITY PER LTG IS 100 ERL.


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• Although the subscriber lines and trunks employ different signaling systems, the LTGs present signaling independent inter face to the switching network.

• The bit rate on all highways linking the line/trunk groups and the switching network is 8192 kbps ( 8 Mbps ).

• Each 8 Mbps highway contains 128 channels at 64 kbps each.

• Each LTG is connected to both planes of the duplicated switching network.


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The functional units of the line/trunk group are:

• Line / Trunk Unit (LTU) is a logical unit that comprises a number of different functional units, i.e.

- Digital Interface unit ( DIU30 ) for connection of 2 Mbps digital trunks and either DLU or PA. One LTG can comprise four DIU30.

- 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.

- Automatic Test Equipment for Trunks (ATE:N) checks trunks and Tone Generators (TOG) during routine tests.


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Signaling Unit (SU) comprises Tone Generator (TOG) for audible tones, Code Receivers (CR) for MFC signaling and push-button dialing and Receiver Module for Continuity Check (RM:CTC)

Group Switch (GS) which 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 & LIU are processed with help of GP SW.


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8Mb/s

Addr. signals

SIHOSIHISPHOSPHI

LTU

DIU30

LTU

COUB

LTU

CR

LTU

ATE:T

CR TOG CTC

SU

SN0

SN1

to/from SN(8Mbps)

GSLIU

or

or

or

GP (PU, MU, SMX and GCG) SILC

INTERNAL STRUCTURE OF LTG

DIU:LDIB

COUC

PHMA

OCANEQ


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ALTTCBSNL Line/Trunk

Groups(LTG)• In LTGG, GS and LIU have been combined into GSL

module. One LTG rack can accommodate 40 PCMs in five LTGG frames, each containing two LTGGs.

• LTGM was the next standard type of LTG. Only three modules are necessary for a complete LTGM namely DIU120A or DIU:LDIM, GPL and GSM. Upto 30 LTGM can be installed in one rack with each frame containing 5 LTGM.

• LTGN is the latest release of LTG. Only one module makes up a complete LTGN for the basic tasks. Upto 16 LTGN can be installed in one frame and a rack can contain 64 LTGN.


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Switching Network

• Different peripheral units of EWSD, i.e., LTGs, CCNC, MB are connected to the Switching Network (SN) via 8192 kbps highways called SDCs (Secondary Digital Carriers), which have 128 channels each.

• The SN 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 Switch Group Controls (SGC) provided in each TSG and SSG, in accordance with the switching information from the coordination processor (CP).

• The SGCs also independently generate the setting data and set the message channels for exchange of data between the distributed controls.


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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


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Switching Network

• The switching network is always duplicated (planes 0 &1). • Each connection is switched simultaneously through

both planes, so that a standby connection is always immediately available in the event of a failure.

• Each TSG can accommodate 63 SDCs from LTGs and one SDC to MB. One SDC is extended from SGC of each TSG and SSG towards MB.

• The switching network can be expanded in small stages by adding plug-in modules and cables and if necessary by assigning extra racks.


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Switching Network

• The smallest duplicated SN:63 LTG configuration which can handle 30,000 subscriber lines or 7,500 trunks when fully equipped is installed in a single rack and can handle 3150 erlangs traffic.

• In its maximum configuration, the EWSD switching network has 8 TSGs and 4 SSGs ks) to connect 504 LTGs and has a traffic handling capacity of 25,200 erlangs.

• SNs for 126 LTGs and 252 LTGs are also available which can handle 6300 and 12600 erlangs traffic respectively.

• SN has 7 type of modules.


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Switching Network• SN(B) has only 5 types of modules.Each TSG & SSG is accommodated in only

two shelves of the respective racks. Remaining shelves accommodate LTGs.

• Main Functions:

- Speech Path Switching - Message Path Switching - CCS#7 signalling channels connection (NUC)

•


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ALTTCBSNL Coordination Area•Coordination Processor (CP) handles the data base as well as configuration and coordination functions, e.g.:• Storage and administration of all programs, exchange and subscriber data,• Processing of received information for routing, path selection, zoning, charges.• Supervision of all subsystems, receipt of error messages, alarm treatment, error detection, error location and error neutralization and configuration functions.• Handling of the man-machine interface.


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ALTTCBSNL Coordination Processor (CP)

•The CP113C is multiprocessor and can be expanded in stages. •It has a maximum call handling capacity of over 1,400,000 BHCA. •The rated load of n processors is distributed among n+1 processors. •This means that if one processor fails, operation can continue without restriction (redundancy mode with n+1 processors).


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BCMY1

CAP0 IOC1IOC0BAPSBAPM CAP5

IOP

IOP IOP

IOP

IOP IOP

IOP IOP

BCMY0

BASIC CONFIG. OF CP 113C

11 . .

0

11 . .

0 B:IOC B:IOC

HARDWARE STRUCTURE OF THE CP113C

. . .

CMY0

CMY1

IOC3 IOC2


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Coordination Processor (CP)The Basic functional units of CP 113C are as follows:

• Base Processor (BAP) for operation & maintenance and call processing. • Common Memory (CMY)- 256 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.• Input/output processors (IOP) -Various types of IOPs to connect the CP113C to other subsystems & to the external mass storage devices (EM i.e., MDD, MTD, MOD), the two O&M terminals (OMT/ BCT). Maximum 12 IOPs can be connected to one IOC. • The other functional units of CP 113C are call processors (CAPs) which are similar to BAPs


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BIOC0

Alarm function : monitors fans of CP racks

CCG

MBG

CCNP IOP:MB

IOP:MB

IOP:MB

IOP:MB

IOP:MB

IOP:TA

IOP:TA

IOP:UN1

Number depends on SN size. IOP:MB

MDDMODMTDOMT/BCTData line,

MDDMODMTDOMT/BCTData line, V.24/V.28 X.21/V35

BIOC1

IOP:UN1

IOP: SCDP

LCUB LAUB

LCUB LCUB

(IOP:LAU) (LAU)

X.25 links to e.g. OMC,CT or billing centre

IOP:MB

IOP:MB SYPC

IOC1IOC0

BCMY0

BCMY1

Structure of the CP113C input/output system with 2 IOCs


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ALTTCBSNL Coordination Area

Other units assigned to CP are:

• Message Buffer (MB) for coordinating internal message traffic between the CP, the SN & the LTGs.• Central Clock Generator (CCG) for the synchronization of the exchange and, where necessary, the network. The CCG is extremely accurate (10-9). It can, however, be synchronized even more accurately by an external master clock (10-11).• System Panel Display (SYPD) to display system internal alarms and the CP load. The SYP also displays external alarms such as fire and air-conditioning system failure . It is installed in the Equipment Room or in the Exploitation Room.


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Coordination AreaSome more units assigned to CP are:• Operation and Maintenance Terminals/ Basic Craft Terminal for Input/output. Two OMTs/ BCTs are provided for O&M functions.• External memory (EM), for

- Programs & data that dont always have to be resident in CP

- An image of all resident programs and data for automatic recovery,

- Call charge and traffic measurement data.• To ensure that these programs and data are safeguarded under all circumstances, the EM is duplicated (two MDDs). The EM also has a magneto optical disk ( MOD) and/or magnetic tape device (MTD), for input and output.


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Common Channel Signaling Network Control (CCNC)• The CCITT- CCS#7 is one of the systems that is used for inter-exchange signalling in EWSD. • For flexibility, a distinction is made between a message transfer part (MTP) and the user parts (UP). • The user parts vary according to the specific application (e.g. TUP: telephone user part, ISUP: ISDN user part. • The common MTP functions in an EWSD exchange are handled by the common channel signalling network control (CCNC). • The UP is incorporated in the software of the relevant LTG.


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Common Channel Signaling Network Control:• A maximum of 254 common signaling channels can be connected to the CCNC . • The digital links are extended from the LTGs over both planes of the duplicated SN and multiplexers to the CCNC. • The CCNC is connected to SN via two 8 Mbps highways.• Analog signaling links are linked to the CCNC via modems.• CCNC consists of upto 32 signaling link terminal (SILT) groups, each with 8 signaling links & one duplicated CCNP. The CCNC, equipped in one rack can handle upto 48 signaling links. Equipments handling upto 96 signaling links can be equipped in additional racks.


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CCS via digital data links

CCS via analog data links

0 31 0 31

0 7 0 7

SILT group 31

SILT group 0

CCNP 0 CCNP 1

CP bus system

COMMON CHANNEL SIGNALLING NETWORK CONTROL

MultiplexerModem


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System Data

• Call-handling capacity

No. of Subscriber lines max. 250 000

No. of Trunks max. 60 000

Switchable traffic max. 25 200 E.• Supply voltage: -48 V nominal D.C. • Clock accuracy:

Maximum relative frequency deviation :

Plesiochronous 10-9;

Synchronous 10-11

• Signaling systems All conventional signaling systems:MF R2, No.7 etc.


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ALTTCBSNL System Data• Traffic routing Per destination one primary route &

max. 15 alternate routes. Sequential or random selection of idle trunks of a trunk group

• Number of trunk groups per exchange:

Max. 1000 incoming and

Max. 1000 outgoing and

Max. 1000 bothway

• Call charge reg. Periodic pulse metering,

AMA Billing (CAMA, LAMA)

IACHASTA


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System Data• Call Charge reg. Max. 511 zones

Max. 6 tariffs per zone

Tariff switchover possible in 15m intervals

• Space requirements:

Example: Exchange for 24000 lines units approx. 100m2

• Environmental conditions

Ambient temperature: 5°C to 40°C

Relative humidity: 10% to 80%


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ALTTCBSNL EWSD Overview

THANK YOU

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