LTG

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INTRODUCTION

The name is the abbreviated form of German equivalent of Electronic Switching System Digital (Electronische Wheler Systenic 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. It can carry 25,200 Erlang traffic and can withstand 1.4 million BHCA. .

It can work as local cum transit exchange and has CCS No.7, ISDN and IN capabilities.

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OMT PRINTER

SN

DLU LTG(B)

LTG(C)

CCNC

CPMB

CCG

SYP

LINES

TRUNKS

MTD MDD

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1    

Digital Line Unit (DLU) – functional unit on which subscriber

lines are terminated.

Line/Trunk Group (LTG) – Digital Trunks and DLUs are

connected to LTGs.

Switching Network (SN) – All the LTGs are connected to the SN

which interconnects 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.

SYSTEM ARCHITECTURE

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Coordination Processor (CP) – It is used for system-wide

coordination functions, such as, routing, zoning, etc. However, each

subsystem in EWSD carry out practically all the tasks arising in

their area independently.

Common Channel Signalling 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.

SYSTEM ARCHITECTURE

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DLUDigital Line Unit

LTG

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DLU

The DLU is used as a digital concentrator for the connection of subscribers to the EWSD.up to approx. 900 analog subscriber lines orup to approx. 800 digital subscriber lines (ISDN BA)up to 32 V5.1 interfacesMisture of analog subscibers, digital subscribers and V5.1 interfaces in view of the fact that max. 120 calls can be held simultaneously

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LTG

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Analog 2 wire interface for a/b connection

Analog subscribers

Small PSTN P (A) BX

Digital 2 wire interface for basic access (BA)

Digital subscribersSmall ISDN (A) BX

2 Mbit/s PDC

V5.1 interface to the AN

DLU

Concentration of the subscriber accesses

Analog/digital conversion for analog subscribers

Modules

SLM for the connection of

- a/b interfaces

(SLMA with 16 subscriber line circuits – SLCA)

- U interfaces

(SLMD with 16 subscriber line circuits – SLCD)

- v5.1 interfaces

(SLMA with two V5.1 interfaces)

a/b, U

or

V5.1 interfaces

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LTG

One DLU contains 8 SLCAs (Subscribers Line Circuit Analog) + SLMCP (Subscribers Line Module Circuit Processor).

One DLU can handle 100 Erlangs traffic.

LTG

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LTGLine Trunk Group

LTG

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INTRODUCTION

THE LTG FORMS THE INTERFACE BETWEEN THE DIGITAL ENVIRONMENT OF AN EWSD EXCHANGE AND THE SWITCHING NETWORK (SN).

THE LTG PERFORM NON-CENTRAL CONTROL FUNCTIONS AND THUS RELIEVE THE COORDINATION PROCESSOR (CP) OF ROUTINE WORK.

SEVERAL LTG TYPES ARE AVAILABLE FOR OPTIMAL IMPLEMENTATION OF THE VARIOUS LINE TYPES AND SIGNALING METHODS. THEY HAVE THE SAME BASIC STRUCTURE AND OPERATE ACCORDING TO THE SAME PRINCIPLES. THEY DIFFER IN FEW HW UNITS AND SPECIFIC APPLICATION PROGRAMS

IN ITS MAXIMUM CONFIGURATION, THE EWSD SWITCHING SYSTEM CAN CONNECT UP TO 504 LTGS.

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OMT PRINTER

SN

DLU LTG(B)

LTG(C)

CCNC

CPMB

CCG

SYP

LINES

TRUNKS

MTD MDD

LTG

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1   

     WITH DIGITAL TRANSMISSION LINK (PRIMARY DIGITAL CARRIER, PDC)• 

- DLUs OPERATING AT TRANSFER RATE OF 2048 KBIT/S.  • - V5.2 ACCESS NETWORK

-     FOR DIGITAL TRUNKS WITH TRANSFER RATE OF 2048 KBIT/S.

     WITH DIGITAL TRANSMISSION LINK FOR LOCAL OPERATION OF DLUs) AT TRANSFER RATES OF 4096 KBIT/S•      WITH PRIMARY RATE ACCESS (PA) :• • FOR MEDIUM-SIZE AND LARGE ISDN PBXS (ISDN SUBSCRIBERS WITH

PA) OPERATING AT TRANSFER RATE OF 2048

CONFIGURATION OPTIONS

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OTHER DETAILS:

-TRANSFER RATE ON THE SDC:LTG FROM THE LTG TO THE SN AND VICE VERSA IS 8192 KBIT/S ( 8 MBPS).

-EACH OF THESE SDCS HAS 128 TIME SLOTS ,OUT OF WHICH 127 TIME-SLOTS ARE USED FOR USER INFORMATION AND ONE TIME SLOT FOR MESSAGES.

-USER INFORMATION IS THE INFORMATION RELEVANT TO THE COMMUNICATION PARTNERS (VOICE, TEXT, DATA, IMAGES).

-MESSAGES ARE USED FOR INTERPROCESSOR COMMUNICATION IN THE EWSD SYSTEM.

OTHER DETAILS

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LTG TYPES

FUNCTIONAL LTG TYPE LTG HW TYPE

TYPE B:-DLU-PBX (ISDN-PA)-V5.2 ACCESS NETWORK(ONLY TO LTG M/N/P)CAN BE EQUIPPED WITH OCANEQ,COU, MDTOG

LTG G/M/N/P

TYPE C:-TRUNKS WITH CAS SIGNALING-TRUNKS WITH CCS7 SIGNALING- CCS7 SIGNALING CHANNEL

LTG G/M/N/P

TYPE D: INTERNATIONAL TRUNKS LTG D

TYPE H: X25 DATA PACKETS FROM ISDN SUBS.

LTG H

LTG

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LTG FUNCTIONS

(a) CALL PROCESSING FUNCTIONS :

-RECEIVING AND EVALUATING SIGNALS FROM TRUNK AND THE SUBS

- -SENDING SIGNALS & AUDIBLE TONES

- -SENDING MESSAGES TO THE CP AND RECEIVING COMMANDS FROM CP

- -SENDING/RECEIVING REPORTS TO/FROM THE GROUP PROCESSORS (GP)

- -SENDING/ RECEIVING ORDERS TO/FROM CCNC

- -CONTROLLING THE SIGNALS TO DLU, PA

- -ADAPTING THE LINE CONDITIONS TO THE 8 MBPS INTERFACE TO THE

SN

- -THROUGH-CONNECTION OF MESSAGES AND USER INFORMATION

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LTG FUNCTIONS

(b) SAFEGUARDING FUNCTIONS :

- -DETECTING ERRORS IN THE LTG

- -DETECTING ERRORS ON THE CONNECTION PATHS WITHIN THE

EXCHANGE VIA CROSS-OFFICE CHECKS AND BIT ERROR RATIO COUNTING

(BERC)

- -TRANSFERRING ERROR MESSAGES TO THE CP

- -EVALUATING ERRORS TO DETERMINE PENETRATION RANGE

- -INITIATING MEASURES CORRESPONDING TO THE PENETRATION

RANGE

- -EXCHANGING ROUTINE TEST MESSAGES WITH THE CP SO THAT CP

CAN DETECT A FAULTY LTG

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LTG FUNCTIONS

( c ) ADMINISTRATIVE FUNCTIONS :

- -SENDING MESSAGES TO THE CP FOR TRAFFIC MEASUREMENTS AND

TRAFFIC OBSERVATION

- -SWITCHING OF TEST CONNECTIONS

--TESTING OF TRUNKS AND PORT-SPECIFIC AREAS OF THE LTG USING THE

-ATE:T INTEGRATED IN EWSD AND THE ATE:TM

--INDICATING IMPORTANT INFORMATION

(E.G. CHANNEL ASSIGNMENTS) TO THE FUNCTIONAL UNITS

--CREATING, BLOCKING, RELEASING DEVICES VIA MML COMMANDS

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SUBSCRIBER CONNECTION (SN0 ACTIVE)

  

CP

nSDCSDC

SDC 1SDC

SN1

ZZ

n

1

SN0

ZZ

n

1SDC 1

SDC

LTG1LIU x

x

Time slot

xx

GP

A-side

MB0

IOP

MB1

IOP

SDC n

SDC

LTGnLIU y

y

Time slot

yy

GP

B-side

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EXCHANGE OF MESSAGES BETWEEN LTG AND CP, LTG AND LTG (SN WITH 63 LTGS)

  

CP

63

1

SN1

63

1

SN0

63

1 1

00

Time slot

00

MB0

IOP

MB1

IOP

63

00

Time slot

00

xx

xx

126 2*

2* 126

126*

2

2

126*LTG63LIU

GP

LTG1LIU

GP

-- Message channel LTG-SN/SN-LTG through connected, but not active *) Message channel SN-MB/MB-SN through connected, but not active

yy

yy

LTG

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STRUCTURE OF THE LTGG

FUNCTIONAL UNITS IN THE LINE/TRUNK UNIT (LTU) FUNCTIONAL UNITS IN THE SIGNALING UNIT (SU) GROUP SWITCH AND LINK INTERFACE UNIT (GSL) GROUP PROCESSOR (GP)

FUNCTIONAL UNITS OF LTGG

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Add. signals

SIHOSIHI

SPHO

SPHI

LTU

DIU30

LTU

COUB

LTU

CR

LTUATE:T

LTU

OCANEQ

TO/FROM SU

to/from SN

GSL

GP

FUNCTIONAL UNITS OF THE LINE/TRUNK UNIT (LTU)

DIU:LDIB

ATE:TM

ETEAE

LTG

08/04/23 24 FUNCTIONAL UNITS IN THE SIGNALING UNIT (SU)

SU

TOGRM:CTC

LTU

ADDR. SIGNAL

SIHO

SIHI

SPHO (2 Mb/s)

SPHO (2 Mb/s)

to/from SN

GSL

GP

SPHO (2 Mb/s)

CRPCRM

LTU

LTG

08/04/23 25 Functional Unit ‘Group switch and interface unit (GSL)’ for LTGG

SPHO/I2 Mb/s

0,10/1*

2

DATI0

DATO0

SU

GSL

GP

GS part LIU part

LTU0

LTU4/SU*

To/fromSILCB(GP)

SYNI MCHO/I

*) SPHO/I1 for LTGG with C-function (SU instead of LTU4)

SN0SN1

SN0SN1

6/1*

DATI1

DATO1

CDIM/CDAM SPHO/I 11

LTG

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  Note: SILCB(_ _ _) ONLY FOR LTG WITH DLU/PA

Functional unit “Group processor (GP)

DATO/I

DATO/I

 

CGSM     

MCH 0/1 

      

GP

GSL

GS

partLIU

part

LTU

 

SM PARTADDRESS SIGNALS

 

 

CG PART

MCH PART

PMU

SILCB

RESET SYNI

SIB O/I

SIHO to LTU/SU 

SIHI from LTU/SU to/

fromSN

LTU

CLOCK TO PMUetc

TO/

FROM

SN

LTG

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DETAILS OF MODULES OF LTGM

       DIU 120A OR DIU: LDIM: - DIU120A:THE 4 PCMS ARE COMBINED TOGETHER WITH THE CURRENT CONVERTER ON THIS MODULE. LOGICALLY, THIS MODULE IS TREATED AS LTU0 TO LTU3 WITH ORDINARY DIU30 MODULES. - DIU:LDIM:OPTIONALLY, THIS MODULE CAN BE USED TO CONNECT A DLU VIA A 4MBPS LOCAL DLU INTERFACE

THE GPL MODULE (GROUP PROCESSOR FOR LTGM): IT HOLDS THE PMU AND, IF REQUIRED, THE SILC FUNCTIONALITY. TWO DIFFERENT MODULES ARE USED:

-GPL: GROUP PROCESSOR FOR LTGM WITHOUT SILC FUNCTION-GPLS: GROUP PROCESSOR FOR LTGM WITH SILC FUNCTION

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DETAILS OF MODULES OF LTGM

        The GSM (group switch for LTGM) : - It is a combination of GSL, TOG, RM : CTC, CR and

GCG. Depending on the available on board components, different GSM modules are used.

- The last three digits of the GSMabc modules define the module type. The 4th character (called a) designated by Y the PCM30, by Z PCM24 . For the 5th and 6th character the following table applies:

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DETAIL OF MODULES OF LTGM4th module in LTGM (LTU:S)

A PHMA can be installed to connect an Access Network AN via V5.2 interface.

An MDTOG can be installed to support the feature CLIP for analog subscribers. This module is used to deliver the A-party number to analog wired subscribers of the exchange. The used method is called Frequency Shift Key FSK. A MDTOG can be connected via SN to any analog DLU port of the EWSD exchange (pool solution).

A COUC can be installed to support large conferences. The new COUC module has 32 ports, which can be used in any combination (e.g. one conference with 14 subscribers and two with 9 subscribers. compensation.

An MCT can be installed to support the mid call trigger function.

An ATE : N can be installed as automatic test equipment.

LTG

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LTU

with DIU 120 A or DIU : LDIM*

LTU : S with

COUC or PHMA or MDTOG or MCT or ATE : N

GS, LIU, TOG , RM: CTC, CR, GCG

GSM

GPLPMU, SILC*

STRUCTURE OF THE LTGM

8 Mbps SDC to SN 0/1

*2 x 4 Mbps link forLocal DLU interface

LTG

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STRUCTURE OF LTGN

THE LTGN IS THE NEWEST RELEASE OF THE LTG. ONLY ONE MODULE MAKES UP A COMPLETE

LTGN FOR THE BASIC TASKS THE LTGN HARDWARE COMBINES EVERY

POSSIBLE FUNCTIONAL UNIT ON THIS SINGLE MODULE, E.G. DIFFERENT CODE RECEIVERS IN LOGICAL LTU AND SU POSITIONS.

FOR SPECIAL FUNCTIONS A SECOND MODULE E.G. PHMA,MDTOG,COUC,MCT AND ATE:N BEING USED.FUNCTIONS ALREADY COVERED IN LTGM.

ANOTHER MODULE NAMELY OCEN IS USED FOR OCANEQ FUNCTIONS.

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STRUCTURE OF LTGN

DEPENDING ON THE APPLICATION, DIFFERENT MODULE TYPES ARE USED AND GIVEN IN FOLLOWING TABLE:

NAME TYPE MEMORY SILC

GPNLE LOCAL DLU INTERFACE

64 Mbyte YES

GPNLD LOCAL DLU INTERFACE

32 Mbyte YES

GPNYE PCM30 64 Mbyte YES

GPNYD PCM30 32 Mbyte YES

GPNYC PCM30 16 Mbyte NO

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DIU part GCG part CR part

SILC part

GS, LIU, TOG part

GP part

LTU:S(optional)

GPN

IOP Part

4 x PCM30 or2xLDI (4Mbps)

STRUCTURE OF THE LTGN 

COUCMDTOGPHMAMCTATE:N

8Mbps

SDC to

SN 0/1

LTG

SNSwitching Network

LTG

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SN

Switching network (SN) performs the switching function for speech as well as for messages in an EWSD exchange.

It is connected to LTGs and CCNC for speech/data and to CP (through MB) for exchange of control information.

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DLU LTG(B)

LTG(C)

CCNC

MB

CCG

SYP

OMT PRINTER

CP

MTUMDD

SN

Figure 1. Position of Switching Network in EWSD

LTG

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SN

* SDC:LTG interface between SN and LTG: time slot 0 for message exchange between the LTG and coordination processor (CP) as well as between two LTGs, time slot 1 to 127 for subscriber connections.

 * SDC:CCNC interface between the SN and the

common channel signaling network (CCNC): for common channel signaling.

 

LTG

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SN

* SDC:TSG interface between SN and a message buffer unit assigned to CP (MBU:LTG) for message exchange between the CP and the LTGs as well as between the LTGs.

 * SDC:SGC between the SN and an

MBU:SGC of the CP for setting up and clearing connections .

LTG

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SN

Switching network in EWSD exchanges uses time and space switching and therefore it is functionally divided into Time Stage Group (TSG) and Space Stage Group (SSG).

TSGs and SSGs are interconnected through internal 8 Mb/s interfaces called SDC:SSG. TSGs of both planes are connected to SSGs of both planes, and thus these provide further security.

LTG

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LTG 1

LTG n

CCNC

CP

MBU

MBU

MBU

SPACE STAGE GROUP

OF

SN:DE5

TIME STAGE GROUP

OF

SN:DE 5

OR

SN:DE4

SGC

SGC

Figure 2: SN Internal and External Interfaces

SDC:LTG

SDC:LTG

SDC:CCNC

SDC:TSG

SDC:SGC

SDC:SGC

SN

MB

SDC:SSG

SDC:SSG

LTG

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Capacity stages of

switching network

SN:63LTG

(DE 4)

SN:126LTG

(DE 5.1)

SN:252LTG

(DE 5.2)

SN:504LTG

(DE 5.4)

Switchable traffic(E) 3150 6300 12600 25200

Local Exchanges

No. of lines 30000 60000 125000 250000

Transit Exchanges

No. of trunks7500 15000 30000 60000

Structure TST TSSST TSSST TSSST

Connectable no. of

LTGs or

LTG+CCNC

63

or

62+1

126

or

125+1

252

or

251+1

504

or

503+1

LTG

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SSG1.0

LTG

MBU:SGC

TSG1.0

TSG0.0

LIL TSM LIS

SGC LIM

TS0

TSI

MBU:SGC

SSG0.0

LIS SSM 8|15 SSM16|16

SGC LIM

SSM

15|8

SSM

8|15

Figure 3: The seven module types in SN:DE5

LTG

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CP Coordinating Processor

LTG

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CP

The Coordination Processor is the heart of a Siemens exchange.

It controls all other functional units, does the main call processing tasks and processes MML.

LTG

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CP Functions

Call processing digit translation routing zoning path selection through the switching

network call charge registration traffic data administration network administration

LTG

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CP Functions

Operation and maintenance  input and output from/to external

memories (EM) communication with the local operation

and maintenance terminals (NetM boot or BCT Boot/ OMT) via V.24

communication with the Net M either via X.25 (EWSD Classic) or Via SSNC/Ethernet (EWSD Powernode)

LTG

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CP Functions

Safeguarding

self -supervision error detection error handling

LTG

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CP Hardware

The CP113 consists of a modular multiprocessor system with a processing width of 32 bits and an addressing capacity of 4 Gbytes.

LTG

08/04/23 49

CP Hardware

base processors (BAP) call processors (CAP); not included in the basic

capacity stage ATM bridge processors (AMP) ; in case of EWSD

powernode input/output controls (IOC) bus for common memory (BCMY) common memory (CMY) input/output processors (IOP):

LTG

08/04/23 50

CP Hardware

a) IOP:MB (input/output processor for message buffer)

  b) IOP:TA (input / output processor for time and

alarms)   c) IOP:LAU (input/output processor for X.25 line

adaption unit)   d) IOP:UNI (input/output processor unified for O &

M devices)

LTG

08/04/23 51

Maximum configuration of CP113C

BCMY0

CAP0 IOC1IOC0BAPSBAPMCAP5

IOP

IOP IOP

IOP

CMY1

CMY0

IOC3 IOC2

IOP IOP

IOP IOP

BCMY1

Basic configuration of CP 113C,

11

.

.

0

11

.

.

0

B:IOC B:IOC

AMP0 AMP1

LTG

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CP Hardware

Unit Minimum Maximum

BAP 2 2

CAP 0 6 (Classic)10 (Powernode)

IOC 2 4 (Classic)2 (Powernode)

AMP 0 2 (only is Powernode)

CMY(Mbytes) 64 1024

B:CMY 2 2

IOP:MB 8 (Classic)4 (Powenode)

14

IOP:TA 2 2

IOP:UNI 2 8

IOP:SCDP(IOP:LAU) 0 12