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LTG
08/04/23 1
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.
LTG
08/04/23 2
OMT PRINTER
SN
DLU LTG(B)
LTG(C)
CCNC
CPMB
CCG
SYP
LINES
TRUNKS
MTD MDD
LTG
08/04/23 3
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
LTG
08/04/23 4
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
LTG
08/04/23 5
DLUDigital Line Unit
LTG
08/04/23 6
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
LTG
08/04/23 7
LTG
08/04/23 8
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
LTG
08/04/23 9
LTG
One DLU contains 8 SLCAs (Subscribers Line Circuit Analog) + SLMCP (Subscribers Line Module Circuit Processor).
One DLU can handle 100 Erlangs traffic.
LTG
08/04/23 11
LTGLine Trunk Group
LTG
08/04/23 12
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.
LTG
08/04/23 13
OMT PRINTER
SN
DLU LTG(B)
LTG(C)
CCNC
CPMB
CCG
SYP
LINES
TRUNKS
MTD MDD
LTG
08/04/23 14
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
LTG
08/04/23 15
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
LTG
08/04/23 16
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
08/04/23 17
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
LTG
08/04/23 18
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
LTG
08/04/23 19
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
LTG
08/04/23 20
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
LTG
08/04/23 21
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
08/04/23 22
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
LTG
08/04/23 23
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
08/04/23 26
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
08/04/23 27
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
LTG
08/04/23 28
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:
LTG
08/04/23 29
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
08/04/23 30
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
08/04/23 31
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.
LTG
08/04/23 32
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
LTG
08/04/23 33
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
08/04/23 35
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.
LTG
08/04/23 36
DLU LTG(B)
LTG(C)
CCNC
MB
CCG
SYP
OMT PRINTER
CP
MTUMDD
SN
Figure 1. Position of Switching Network in EWSD
LTG
08/04/23 37
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
08/04/23 38
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
08/04/23 39
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
08/04/23 40
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
08/04/23 41
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
08/04/23 42
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
08/04/23 43
CP Coordinating Processor
LTG
08/04/23 44
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
08/04/23 45
CP Functions
Call processing digit translation routing zoning path selection through the switching
network call charge registration traffic data administration network administration
LTG
08/04/23 46
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
08/04/23 47
CP Functions
Safeguarding
self -supervision error detection error handling
LTG
08/04/23 48
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
08/04/23 52
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
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