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Contents
1 EWSD in ISDN 3
1.1 Applications of EWSD in the ISDN 4
1.2 EWSD Feature Overview 6
2
EWSD Hardware Overview 9
2.1 Mechanical Design 10
2.2 Overview: System Architecture 12
3 Functional Structure of the Digital Line Unit (DLU) 19
3.1 Function Overview DLU B/D 20
3.2 Overview of DLU G Functions 32
3.3 xDSL Interfaces at EWSD DLU 44
4 Functional Structure of the Line Trunk Group (LTG) 47
4.1 External 2 Mbps Interfaces to LTG 48
4.2
Function Overview LTG 504.3 LTG Functional Types 52
4.4 Functional Units of the LTG 54
5 Functional Structure of the Remote Switching Unit RSU 57
5.1 Function Overview 58
5.2 RSU Functional Units 60
5.3 RSU Capacity Stage 62
5.4 RSU Emergency Operation 64
6 Functional Structure of the Switching Network (SN) 67
6.1
Internal EWSD Interfaces on the SN 68
6.2 Function Overview SN 70
System Overview EWSD
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6.3 SN B (EWSD-CLASSIC) 72
6.4 SN D (EWSD-POWERNODE) 76
7 Functional Structure of the Coordination Processor (CP) 81
7.1
Function Overview CP 82
7.2 System Features of the CP113 84
7.3 Functional Units of the CP 86
7.4 Input-Output Processors of the CP113 88
8 Functional Structure of the SS7 Network Control 91
8.1 Function Overview of the SS7 Network Control 92
8.2 Structure of the CCNC 96
8.3 Structure of the Signaling System Network Control SSNC 100
9 Application Program System (APS) 107
9.1
Components of the APS 108
9.2 APS Facts 110
10 Overview: EWSD Internal Call Setup 113
11 Exercise 119
12 Solution 123
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1 EWSD in ISDN
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1.1 Applications of EWSD in the ISDN
The fully digital switching system EWSD was released on the world market in 1981and has since then been constantly further developed.
In addition to the standard EWSD exchange which is offered in different hardwareconfigurations, the following special solutions are also available:
For lightly populated areas, it is however possible to use very small exchangesfrom the EWSCountry range (e.g. the Small Digital Exchange SDE for up to 3000subscribers).
If there is no infrastructure for telecommunications equipment, EWSD can then bedelivered in containers which in addition to the EWSD switching equipment, alsocontain the required equipment for power supply, air conditioning, transmission
technology and a main distributor.
Application options in ISDN/PSTN:
Local network node:
Up to 250,000 analog/digital subscribers (1 million in the EWSD powernode) canbe connected either directly or via V5 interfaces using access networks.With direct connection, the EWSD units for subscriber interfaces can be installedboth remotely and in exchange buildings. Remote installation (Remote DLU /Remote Switching Unit RSU) supports the direct connection of subscribers ofdifferent local networks to one EWSD.
It is also possible to offer with EWSD a so called high bit rate access to theInternet (i.e., the hardware required for xDSL solutions can be integrated intoEWSD).Furthermore EWSD can be equipped with an integrated Point of Presence PoP(Remote Access Server for 64kb/s Internet access of dial-in users).These two options enable internet traffic off loading in the local EWSD networknode.
Transit network nodes:
Up to 60,000 digital trunks (240,000 in the EWSD powernode) from/to other
exchanges can be connected to EWSD via 2Mbps PCM routes. The 2Mb/sinterfaces for the trunks can be installed both in the exchange building or remotely(Remote Switching Unit RSU solution).
Gateway network nodes:
EWSD offers networks of other operators/countries all gateway functions such asinternational signaling procedures, echo compensation for inter-continentalconnections or satellite routes and inter-administrative billing and statistics.
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Service Switching Point SSP of the IN:
EWSD can serve as SSP for IN connections. EWSD can also support the dialogbetween subscriber and Service Center Point SCP (User Interactive Dialog) using
voice recognition and individual announcement systems. It also provides access toexternal intelligent peripherals such as voice or faxmail systems.
All applications can be combined in an exchange.
direct connection of
subscribers via local
DLU or remote RDLU/RSU V5 interfaces to theaccess networks
Local Node
(optional with
internet trafficoff-loading)
Transit Node
EWSD
Gateway Node Service Switching Point SSP
EWSD in the ISDN/PSTN
S IE ME NS S IE ME NS SIEMENS
S IE ME NS S IE ME NS SIEMENS
SIEMENS SIEMENS S IE MENS SIEMENS SIEMENS SIEMENS
Local or remote (via RSU)connection of 2 Mb/s
systems (E1)
Fig. 1
TIP
It is also possible to configure EWSD in such a way that it can be used as a verypowerful stand alone Signaling Transfer Point STP (called hiS700).
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1.2 EWSD Feature Overview
EWSD features should offer subscribers the possibility to use the telecommunications services with
operating comfort in a versatile manner
yield optimal business management results for the operating company
adapt to current needs easily.
So far as feature recommendations or standardizations of ETSI or ITU-T exist, theseare taken into consideration upon the realization of the feature in EWSD.
The offer of features has grown a great deal since the introduction of EWSD. Thistrend continues, following the demands of the market. Here a difference must be
made between the offer of features and the scope of features of an EWSD versiondelivered to a network operator. The actual feature scope of an EWSD versiondelivered to a network operator is the contractually regulated subset of the featureoffer. It is established in a project-specific feature list.
The abundance of EWSD features is subdivided into feature groups:
Interface tosubscriberequipmentfeatures
Analogsubscriberfeatures
Systemfeatures
e.g.
Automatic
Calldiversion
callback
Malicious
Call tracing
as with
analogsubscribers,but in additione.g.
Closed usergroup
Multiplesubscribernumbers
e.g.
analog a/binterface
digital Uinterface
V5interfaces
e.g.
Controlof the systemtime witha radio clock
File transferto the post-processingcenter
Numbering and routingfeatures
Interexchangesignalingfeatures
e.g.Digit translation withconsideration to callingparty attributes(e.g. local area codeof the calling party)
Selection of the routeof a call by meansof fixed alternativerouting or optimizeddynamic routing
e.g. Channel
associatedsignaling suchas MFCR2, E&M...
Commonchannel signalingCCS7 withuser/applicationparts such asITUP, ISUP,SCCP, TCAP,INAP...
Chargingfeatures
e.g. Metering
procedure
Automaticmessageaccounting
Billingbetweennetworkoperators
ISDNsubscriberfeatures
Fig. 2
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GEOcentrex features ADMOSS features
Implementation of exchangefeatures for one group of
subscribers directly connected to
EWSD (CENTREX group) such
as
Common abbreviated
directory number list
Call Pick Up
The possibility to administrate
the database of the CENTREXgroup from one subscriber-
equivalent connected control
terminal
ADMOSS (Advancedmultifunctional operator service
system), with its multifunctional
operator's position (MSB) facilitates
the provisioning of operator
services in the network such as
Directory number information
with immediate forwarding
Language assistance for
international calls
Booking of calls
Setup of large conference
circuits
O&M features
Service handling point tasks for
handling IN features such as
Freephone
Televoting Universal personal
telecommunication
e.g.
Decentralized O&M terminals:
operation and maintenace
terminal (NetM-boot orBCT/BOOT)
Centralized operation via a
network management center
with net manager NetM
Intelligent network features
Fig. 3
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2 EWSD Hardware Overview
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2.1 Mechanical Design
RackrowOne or several network elements of the same or different types can be installed inan installation room. The individual installation units are installed in rows. Such arow is called a rackrow. These rackrows are numbered consecutively (rackrownumber) inside a room to make it possible to find them for maintenance.
Rack
A rack is subdivision within a rackrow. A rack has two doors on both the front andrear side for reaching the HW modules or the cabling of the rack. A rack isidentified by the rack number.
FrameThe frames are located inside the rack. A frame comprises a metal frame as amechanical carrier, plastic shelves on the front side for holding the hardwaremodules, and a multilayer backplane on the back side for the electric connections
within a frame and for plugging the cable to other frames or external equipment. Aframe can hold one or two horizontal rows of modules, depending on the size ofthe backplane. A frame is identified by the so-called mounting unit or MUT. TheMUT serially numbers the individual horizontal sections of a rack from top tobottom.Two types of frames are used in the moment: SIPAC and SIVAPAC. Both typesmainly differ in the structure of the backplane and the plugs.
Module
The HW modules are located within the frame. The module rows within a MUTare identified with the letter A or C in order to facilitate finding the modules even
with frames of several rows. The position of the modules within a module row areidentified by the module location or MOLOC (with SSNC called PITCH), whichis stamped on the metal carriers of the frame.
The entire rear wall cabling is pluggable. The cables are delivered with connectedcable connectors and in the required length.
EWSD installations get their supply voltage (48 V or 60 V DC) from central powersupply systems with battery.
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SIEMENS SIEMENS SIEMENS
SIEMENS SIEMENS SIEMENS
SIEMENS SIEMENS SIEMENS
SIEMENSSIEMENS SIEMENS D 900
4
EWSD Mechanical Setup
01
02
03
04
05
06
MUT
1
2
3Rack rows
Racks1 2 3
Module location
001 007 013 019 025 031 037 043 049 055 061 067 073 079 085 091 097 103 109 115 121
Module frame
Module
Fig. 4
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2.2 Overview: System Architecture
2.2.1 Overview of Hardware Configurations and SoftwareReleases
Currently EWSD is used in over 100 countries where the hardware configurationsand software releases in the table below are mainly used.
The different HW units are described on the following pages.
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HardwareConfiguration
SoftwareVersion
max. switchedtraffic volume
in ERLANG
Busy Hour
Call Attempts
EWSD CLASSIC
with Common
Channel NetworkController CCNC
with Switching
Network SN A/B
with Remote
Switching Unit RSU
(only V14A / V15)
V11 / V12 /V13A / V14A /V15
up to 25000 more than1000000
EWSD POWERNODE
with Signaling
System NetworkControl SSNC
with Switching
Network SN D
with Remote
Switching Unit RSU(only V15)
V13T / V15 up to 100000 up to 4000000
Fig. 5
TIP
Following additional features can be also used with EWSD SW versions V12I, V13I,V14A and V15:
high bit rate Internet access via xDSL lines
integrated PoP for dial-in users
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2.2.2 Overview: HW Units of EWSD CLASSIC Configuration
EWSD-CLASSIC includes the following HW units which are all equipped with theirown control processors.
Digital Line Unit (DLU)
Digital Line Unit version A/B/D are connected to 2 LTG's via a maximum of four2Mbps. Digital Line Unit version G is connected to 4 LTG's via a maximum of16x2Mbps. Compared with the DLU A/B/D, more subscribers can be connectedhere and a larger traffic volume can be relayed towards the LTGs.By default, ISDN BA and analog subscribers are connected to the DLU. Here theDLU serves as a digital concentrator. Furthermore the DLU can contain a packethub which is used as an interface to the Internet for the High Bit Rate Data of the
xDSL subscribers of this DLU (ATTANE hiA functionality). Line Trunk Group (LTG)
The LTG serves to connect up to four PCM30 systems (2Mbps) which are used toconnect other exchanges, DLU's and PBX's. The individual LTG's are connectedto the duplicated switching network via 8Mbps highways.Furthermore a PoP can be connected to the LTG. Such a PoP takes over theRemote Access Server RAS functions for dial-in users. In case of using aSURPASS hiG1000 as a RAS, we speak about a so called "integrated PoP" with aPA interface to "his" EWSD exchange.
Switching Network (SN A/B)
The SN serves to through connect the individual user channels of the 8Mbpshighways from the incoming LTG's to the corresponding outgoing LTG'S, tothrough connect the SS7 signaling channels to the Common Channel SignalingController and of the messages channels from the LTG's to the CP. The SN isduplicated and can be equipped with a maximum of 504 LTG's. It receives setupcommands from the CP for parallel through connecting in both SN's.
Remote Switching Network (RSU)
The RSU enables the operation of DLU`s and LTG's at a site remote from the hostexchange. The LTG's of the RSU are connected to the Remote Timeslot
Interchange (RTI) which is an RSU internal switching network. The RTI isconnected via PCM30 links to the Host Timeslot Interchange (HTI) in the hostEWSD. The HTI itself is linked by 8Mbps highways to the SN. Calls between twoports of an RSU are normally directly switched in the RTI and not routed via thehost exchange. It is possible to connect the RSU to other exchanges or to anotherRSU of the same host exchange.
Common Channel Signaling Controller (CCNC)
The CCNC ensures the security, message distribution and message routing of theCCS7 messages. It is connected to the SN via a maximum of two 8Mbps highwaysand via this has access to the individual SS7 signaling channels of the PCM30
systems connected to the LTG's. Within EWSD the CCNC communicates with theuser parts in the LTG via the messages channel system.
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Central Clock Generator (CCG)
The CCG synchronizes the clock generators in MB, CCNC, SN, LTG and DLU.This guarantees synchronism between transmitter and receiver on the EWSD
internal 8Mbps highways. In synchronous networks the CCG's of the individualnetwork nodes work with the same clock.
Coordination Processor (CP)
The CP controls the setup of connections (call-processing) and carries outsafeguarding tasks for the entire exchange. Therefore it is connected via theMessage Buffer (MB B) to the control of the SN as well as to the control of theLTG's (via the SN). The MB itself is connected to the SN using 8Mbps highways.Furthermore the CP has a connection to the CCNC control to relay the CCS7messages to the corresponding users in the LTG's and vice versa.The duplicated Magnetic Disk Memory (MDD) and the Magneto-optical Disk(MOD) / Magnetic Tape Device (MTD) are used as back-up memories for thecomplete EWSD software.The CP additionally performs operation and maintenance O&M tasks and offerstherefore interfaces to the local O&M terminals (Basic Craft Terminal). The systempanel SYP is connected to the CP for visual and audible alarming.
Via x.25 links the CP can be connected to a billing Post-Processing Center as wellas to a Network Management Center (with Net Manager NetM).
CCNC
MBCCG
SN
0 & 1
LTG
Partner
exchange
(2Mbps with
trunks & SS7 links)
LTG
LTGDLU
PBX
Main station
subscribers
SIEMENS
NIXDORF
CP
X.25 connections
to NetM and
postprocessing
centers
BCTMDD
MOD
HTIRTILTGDLU
RSU
EWSD CLASSIC
max. 6 CAP
Fig. 6
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2.2.3 Overview: Hardware Units of EWSD POWERNODEConfiguration
Compared with the CLASSIC configuration, the following new HW units are used inthe EWSD POWERNODE:
SN Version D (instead of SN A/B)The SND connects up to 2016 LTG's.
MB Version D (instead of MB B)Serves to distribute the message flow CP-LTG, CP-SND, SSNC-LTG and LTG-LTG.
Netmanager (NetM)The Netmanager is used for local and central operation and monitoring of theEWSD Powernode.
Signaling System Network Control (SSNC) (instead of CCNC)
The SSNC ensures the security, message distribution and message routing of theSS7 messages. This occurs with high capacity and flexibility which meet thecurrent and future demands with respect to message throughput and new features.It primarily provides the protocol functions of the Messages Transfer Part (MTP)and the Signaling Connection Control Part (SCCP, user part for non-user channelrelated signaling applications).
In opposite to the CCNC it is possible to directly connect 2Mbps systems to the
SSNC. These contain either 31 x 64Kbps SS7 channels or one 2Mbps SS7channel (high speed link with ATM protocol)
The SSNC has its own OAM platform. To operate it, it is equipped with V24/LANinterfaces to connect the Net Manager NetM.
Coordination Processor
The CP is connected via an so called ATM bridge processor (AMP) to the SSNC.
The switching efficiency of the CP (BHCA) is considerably better with thePOWERNODE then when used in the CLASSIC configuration. This is becausemessages between LTG - LTG and LTG - SSNC directly passed by the MB D and
are not routed through the CP (CP is not loaded by the EWSD internal messageexchange.
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EWSDPowernode
LTG
LTG
SSNC
MBD
2Mbps with
Trunks and
64kbps SS7 Links
64 kbps orHigh Speed
SS7 Links
207Mb/s
CP
NetM
207Mb/s
LTG
LTG
DLU
SND
Fig. 7
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3 Functional Structure of the Digital Line Unit
(DLU)
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3.1 Function Overview DLU B/D
The DLU is used as a digital concentrator for the connection of subscriberstothe EWSD.
In this paragraph only the connection of analog and ISDN-BA subscribers to the DLUis described. The so called High Bit rate access to the internet via xDSL will bedescribed at the end of the DLU chapter.
3.1.1 Connectivity
Analog connectivity is for:
Main station lines with pulse dialing, pushbutton dialing, call charge display
Coinbox telephones
Small analog private branch exchanges with/without direct-inward-dialing
Digital connectivity is for:
ISDN Basic Accesses
Small digital private branch exchanges
Connection of an access network (AN) via V5.1 interface
3.1.2 Connection Capacity and Expansion Possibility of a DLU
Depending on used module types and required traffic volume:
up to approx. 900 analog subscriber lines or
up to approx. 800 digital subscriber lines (ISDN BA)
up to 32 V5.1 interfaces
Mixture of analog subscribers, digital subscribers and V5.1 interfaces in view of thefact that max. 120 calls can be held simultaneously
Expansion in small modular steps:
Each with an analog subscriber line module (SLMA for 16 subscribers) Each with an digital subscriber line module (SLMD for 16 subscribers)
Each with a subscriber line module (SLMX) for two V5.1 interfaces with 30subscribers each (access network AN)
Note:
The DLU type DLUV can be used as an alternative to SLMX in the standard DLU.Only V5.1 access networks can be connected to a DLUV (max. 10 x V5.1 per DLUV).
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digital
maximum120 user
channels
with 64 kbps
DLU B/D
Concentrationof the subscriber accesses
Analog/digital conversionfor analog subscribers
Modules
SLM for the connection of
a/b interfaces
(SLMAwith 16 subscriberline circuits SLCA)
U interfaces(SLMDwith 16 subscriber
line circuits SLCD)
V5.1 interfaces(SLMXwithtwo V5.1 interfaces)
External interfaces to DLU
Analog 2 wire interface for a/b
connection
Digital 2 wire interface for basic
access (U interface of BA)
2 Mbps PDC
Analog subscribers
Small PSTN PBX
Digital subscribers
Small ISDN PBX
V5.1 interface to the AN
Fig. 8
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3.1.3 Connecting Possibilities of the DLU B/D to EWSD
The DLU is connected to the LTG by a maximum of four primary digital carriers(PDC), whereas a DLU is linked with two LTG as a rule for reasons of availability. Asan exception the HW type DLUV provides up to two PDC which may be regarded asPDC0 and PDC2 in the following text.
The DLU can be used locallyin the exchange or remotelyin the vicinity of thesubscriber.
It is possible to connect the local DLUB to the LTG by two 4096 kbps routesinsteadof four 2Mbps routes.
All features are regardless of whether the DLUB is operated locally or remotely.
Common channel signaling (CCS)
Channel 16 in the first and third PDC is used for the transmission of controlinformation messages between the DLUB and the line/trunk groups (LTG).
Here channel 16 on the first PDC transmits the control information messages for the60 user channels to PDC 0 and 1, and channel 16 on the third PDC the controlinformation messages for the user channels to PDC 2 and 3.
For the local DLU interface, channel 32 on both 4096-kbps connections is used forCCS.
High reliabilityHigh reliability is yielded by:
the connection of the DLUB to two LTG
The duplicating of DLU units with central functions
constant self testing
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PDC3
DLU LTG
LTGDLU
Local applicationPDC0
PDC1
PDC2
CCS
CCS
CCS
CCS
PDC3
PDC0
PDC1
PDC2
Remote application
DLULTG
CCSPDC0
PDC1
60 user channels
one CCS time slot between DLU control DLUC
and LTG control GP
alternative: 1 x 4 Mbit/s for local DLU interface
Fig. 9
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3.1.4 Central Functional Units of the DLU B/D
Control unit for DLU (DLUC)
The control unit for DLU (DLUC) controls the DLU internal functional sequenceand distributes or concentrates the signaling from and to the subscriber linecircuits. For reasons of reliability and to increase the throughput rate, there are twoDLUCs in the DLU. They work independently of each other in load sharing so thatthe one DLUC takes on all tasks should other DLUC fail. Every DLUC isresponsible for two PDC (60 user channels, one CCS).
Each DLUC has access to the processors of all subscriber modules and other DLUfunctional units via the DLU internal control bus. Present messages are cyclicallyrequested of the modules; the modules are selected directly for transfer of
commands and data. Digital interface units of the DLU (DIUD or DIU:LDID)
The DIUD has two interfaces for connecting two PCM30 primary digital carriers(PDC). The PDC link the DLU with the LTG. Symmetrical or coaxial lines can beconnected.
The DIU:LDID has a 4096 kbps interface for connecting a DLU in local use to theLTG. The connection ensues via a symmetrical copper line. With the DIU:LDID,the contents of 60 user channels and of one CCS signaling channel aretransmitted via a single 4096 kbps primary digital carrier (instead of two PCM30primary digital carriers).
The DIUD gathers the control information message from channel 16 of a PDC andrelays it to the DLUC. In the reverse direction, the control information messagescoming from the DLUC are inserted into channel 16 of the same PDC and thentransmitted to the LTG.
With the DIU:LDID, the signaling in channel 32 is transmitted.
Furthermore the DIUD or the DIU:LDID forms the interface between the channelsof the DLU internal 4096 kbps user information network and the channels of the 2or 4 Mbps routes to the LTG. The user information is distributed to the subscriberline modules (SLMs) or relayed from them to the LTG via the 4096 kbps bus.
Test unit (TU)
The TU carries out manual or routine testing of the subscriber lines and subscriberline circuits. No TU is necessary if exclusive use is made of ILTF (integrated linetest function).
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SLM DIUD
DLUC
DLUC
SLM
TU
Controlnetwork 0
0
1
PDC
DLU-System
0
DLU-System
1
2
3
Subscriber
accesses
DLU
DIUD
Control
network 1
User information
network 0
User information
network 1
Testbus
to all SLM
Fig. 10
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3.1.5 Subscriber Line Modules
Subscriber Line Module SLMA
The standard modules for connecting analog subscribers (SLMA:FPE or ILTF-SLMArespectively) have 16 analog subscriber line circuits (SLCA), an SLMCP control unit,and a duplicated interface to the two control and user information bus systems. Theygenerate the ringing current and the charge pulses for the analog telephones.
The SLMA with integrated test function for subscriber lines (ILTF = integrated line testfunction) replaces the SLMA:FPE and the Test Unit (TU). The functions otherwiseperformed by the TU are implemented in the subscriber line circuits (ILTF-SLCA).Therefore no Test Unit (TU) is needed in cases where exclusive use is made of ILTF-SLM.
The ILTF-SLMA is implemented in two variants:
SLMA:ITF (without Metallic Test Access)
SLMA:ITM (with Metallic Test Access)
Special SLMA modules are available for special cases (e.g. connection ofsubscribers via pair gain, connection of non-ISDN exchanges with direct-inward-dialing). If use is made of those special SLMA modules or of SLMA:FPE with externalringing generator, the TU is still needed.
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Analog
subscriber
line Standard SLMA
SLCA
Control part SLMCP
0
15
Control bus 0
(DLUC0)
Control bus 1
(DLUC1)
4096-kbps-bus 0
(DIUD0 or
DIU:LDID0)
4096-kbps-bus 1
(DIUD1 or
DIU:LDID1)
Test bus
(not in case of
ILTF-SLMA)
Battery Supply
Overvoltage Protection
Ringing
Signaling
Coding
Hybrid 2/4-Wire
Testing
Fig. 11
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Subscriber Module SLMD
The standard module for connecting digital subscribers (SLMD:QFB) has 16 digital
subscriber line circuits (SLCD), a control section, and a duplicated interface to thetwo control and user information networks.
Depending on the project specific encoding on the digital 2 wire subscriber line, themodule SLMD:TFB can also be used.
TIPILTF-SLMA can provide for SLMDs the necessary test functions which otherwise areperformed by the TU. This works for the so called ILTF-SLMD (ILTF = integrated linetest function). Therefore no SLMD-modules with integrated ILTF is existing.
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ISDN
subscriber
lines SLMD
SLCD
Control part
0
15
Test bus
Control bus 0 (DLUC0)
Control bus 1 (DLUC1)
4096-kbps-bus 0
(DIUD0 or DIU:LDID0)
4096-kbps-bus 1
(DIUD1 or DIU:LDID1)
Overvoltage protection
Provisioning of the time multiplex interfacewith the 2B and D channel with a total
of 144kbps and the 16kbps for the clock synchronization (layer 1 of the DSS1)
Echo compensation for the bidirectional digital transmission on the 2-wire
subscriber line (layer 1 of the DSS1)
2-wire/4-wire conversion and adaption of the line code used on the subscriber
line (layer 1 of the DSS1)
Separation of the DSS1 signaling messages from the X.25 data packets of the
subscriber (layer 2 of the DSS1)
Protection of the transferof the DSS1 signaling messages in the D channel
(layer 2 of the DSS1)
Test access to the subscriber line/circuit
Fig. 12
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3.1.6 Stand-alone Service of a DLU
If both control units of a DLU lose their signaling channel to the LTG owing totransmission faults (failure of the PDC) or LTG failures, a DLU can continue to workin stand alone service. This feature is as a rule available to all remote DLU. For thisthe DLU must be equipped with a stand alone service control module (SASC-E).
This module assumes the control of the call setup between subscribers of the sameDLU when in stand alone service. The through-connection of the voicecommunication follows internally in the DLU. Metering does not take place.
TIPIf several remote DLU are next to one another, they can be aggregated to a remote
control unit(RCU). Up to 6 remotes DLU are linked to one another for this (inter-DLU connections).
If the individual DLU of an RCU go into stand alone service, calls betweensubscribers on different DLU of the RCU are still possible.
The inter-DLU connections are used in stand alone service only.
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Remote control unit (RCU)
Analog and
ISDN sub-
scriber lines
Links
between
the DLUsof an RCU
DLU1
DLU6
DLU2
DLU4
DLU3
DLU5
LTG
LTG
PDC0
PDC1
PDC2
PDC3
PDC0
PDC1
PDC2
PDC3
with CCS
without CCS
Fig. 13
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3.2 Overview of DLU G Functions
From software release V15 the DLUG can be used as a digital concentrator toconnect subscribers to EWSD. This section only deals with connecting analog andISDN-BA subscribers, the xDSL solutions for high bit rate Internet access are dealt
with in a later section.
3.2.1 Options to Connect to DLU G
There are analog connection options for:
individual connections with pulse dial, key dial, charge display
coin telephones
small analog PBX's with/without extension
There are digital connection options for:
ISDN -
small digital PBX's
the connection of Access Network to PSTN or ISDN subscribers via a V5.1interface (DLUV)
3.2.2 Allocation Capacity and Upgrade Options of a DLU G:
Maximum load: 390 ERL
Depending on module equipping:
up to approx. 2000 analog subscriber lines or
up to approx. 1500 digital subscriber lines (ISDN basic connections)
up to 40 x V5.1 interfaces
Upgrade in small modular steps: each with one analog subscriber line module (SLMA for 32 subscribers)
each with one digital subscriber line module (SLMD for 16 subscribers)
each with one V5.1 line module DLU-V for 10 V5.1 interfaces with 30 subscribersper interface (Access Network AN)
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DLU G
Concentration
of the subscriber accesses
Analog/digital conversion
for analog subscribers
Modules
SLM for the connection of
a/b interfaces
(SLMAwith 32 subscriber
line circuits SLCA)
U interfaces
(SLMDwith 16 subscriber
line circuits SLCD)
V5.1 interfaces
(DLUVwith
ten V5.1 interfaces)
External interfaces to DLU
Analog 2 wire interface for a/b
connection
Digital 2 wire interface for basic
access (U interface of BA)
2 Mbps PDC
Analog subscribers
Small PSTN PBX
Digital subscribers
Small ISDN PBX
V5.1 interface to the AN
Fig. 14
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3.2.3 Options to Connect DLUG to EWSD
The DLU is connected to LTG's via a maximum of 16 primary multiplex lines (PDC),although for reasons of availability, a DLUG is usually connected to four LTG's.
The DLU can be used locally in the exchange or remotely close to the subscribers.
For the local DLU interface it is possible to connect the DLU to the LTG via 4096kbps routes (local digital interface LDI) instead of two 2Mbps routes.
All features are independent of whether the DLU is operated locally or remotely.
Each DLUV module (10 V5.1 interfaces) is connected independently of the other DLUparts via 2 PDC's.
Common Channel Signaling (CCS)For the transmission of control information between the DLU and the line modules(LTG), a 64kbps channel is used by default per LTG which is located in PDC0 timeslot 16.
This channel transmits the control information for all user channels on all PDC's tothis LTG. Here a modified CCS7 protocol is used.
High service reliability
High service reliability results from:
the connection of the DLU to at least two LTG's the duplicating of DLU units with central functions
constant self-testing
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DLUC 1,DLUC:LDI
for local DLUG
or
DLUC30
for remote
DLUG
LTGN
LTGN
LTGN
LTGN
ALEXoption.
SASC-Goption.
MTAoption.
Special 2)
module types
SLMD16DLUG
TS16
TS16
TS16
TS16
(2Mbps) or (4Mbps) per LTG4 x
signaling channel between DLU and LTG for controlling all speech channels
between DLU and LTG
2 x
TS16
Fig. 15
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3.2.4 Central DLUG Functional Units
The DLU controller (DLUC30/DLUC:LDI) controls the DLU-internal functional processand distributes and concentrates the signaling and the user channels from and tosubscriber line circuits. For reasons of service reliability and to increase thethroughput rate, there are two DLUC's in the DLU. They work independently of oneanother in load sharing so that if one DLUC fails the other DLUC take over all tasks.
Connection of the DLU control to the LTG's
DLUC30 to control max. 8 PDC (2Mbps) to 2 LTG'sEach DLUC is responsible for a maximum of 8 PDC's which connect this DLU to 2LTG's. All user channels of maximum 4 PDC's to an LTG are usually controlled byone signaling channel (TS16 of the first PDC).
DLUC:LDI to control max. 4 x 4Mbps to 2 LTG'sEach DLUC:LDI (only local DLU's) is responsible for a maximum of four 4096-kbpsinterfaces which connect this DLU to 2 LTG's. All user channels of maximum two4096 kbps multiplex lines (instead of 4 PCM30 multiplex lines) to an LTG areusually controlled by one signaling channel (transmission in the first 4096 kbpsmultiplex line).
Connection of the DLU control with the DLU subscriber modules
Each DLUC has access to all peripheral DLU modules via the DLU-internal bussystem.The DLU-internal bus systems are routed separately for both DLUC's via the so-
called bus distributors (BD) to the individual SLM's.Each DLUC takes care of one bus system per connected LTG so that eachsubscriber module is connected to both DLUC's via a total of 4 bus systems.However, generally the SLMD modules only have interfaces to two bus systems,therefore subscribers are only served by 2 of the maximum 4 LTG's (normally thefirst LTG at each DLUC).
Control bus:The control bus enables the DLUC to access the processors of all subscribermodules and other DLU functional units. The modules are queried cyclically onexisting messages (e.g. subscriber state change). These messages are relayed to
the relevant LTG via the signaling channel. In the other direction the control busserves to hand over commands and data to the relevant subscriber module. TheDLUC receives these commands via the signaling channel from one of themaximum two connected LTG's.
Payload network:The DLUC continues to form the interface between the channels of the DLU-internal payload network and the user channels of the 2 or 4 Mbps routes to theLTG. The useful information is distributed to the subscriber line module (SLM) andfrom there forwarded to the LTG via this network.The payload network can work with 4 or with 8 Mbps.
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1) up to 4 PCM30 or 2 LDI with 1 CCS /
2) e.g. LTOD, LTCD, COTU etc.
DLUG
DLUC 1,DLUC:LDI
for local DLUG
orDLUC30
for remote
DLUG
DLUC 0,DLUC:LDI
for local DLUG
or
DLUC30
for remote
DLUG
LTGN
LTGN
LTGN
LTGN
1)
ALEXoption.
SLMA32
SASC-Goption.
MTAoption.
1)
Special 2)
module types
1)
1)
SLMD16
Fig. 16
DLUC 0
LTG x 1
LTG x 0
DLUC 1
LTG y 1
LTG y 0
I
O
P
I
O
P
DLU Bussystem
(control & user info)
BDs 0
BDs 1
max.
4 PDC
per LTG
SLMA
(SLMD only
connected toone bus per
DLUC)
Fig. 17
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3.2.5 DLUG Subscriber Line Modules
SLMA subscriber line modules
The standard modules used to connect analog subscribers (SLMA) have 32 analogsubscriber line circuits SLCA, a control SLMCP and four interfaces to the internalcontrol and payload (PCM) networks. Ringing current and call-charge impulses forthe analog telephones are produced on the module. Simultaneously they contain therequired hardware for internal/external testing of the connected subscribers.
There are three variants of the SLMA:
SLMA:ITFG (subscriber check via EWSD)
SLMA:ITMG(with Metallic Test Access for external subscriber check)
SLMA:ITHG (with Metallic Test Access and increased power supply for cointelephones)
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Port 0
Port 31
.
.
.
.
SLICsubscriber line
interface circuitSLMCP
FEprom
feeding-
interfacePowersupply
DC- DCconverter
overvoltage protection
2/4 wire
line feeding
ringing and metering
analog/digital conversion
testing
SLMA:ITFG
2x PCM-busto DLUC0
2x PCM-bus
to DLUC1
2x Control-bus
to DLUC0
2x Control-bus
to DLUC1
Fig. 18
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Subscriber Module SLMD
The standard module for connecting digital subscribers (SLMD:QFB) has 16 digital
subscriber line circuits (SLCD), a control section, and interfaces to two control andpayload (PCM) networks (one per DLUC only).
Depending on the project specific encoding on the digital 2 wire subscriber line, themodule SLMD:TFB can also be used.
TIP
ILTF-SLMA can provide for SLMDs the necessary test functions which otherwise areperformed by the TU. This works for the so called ILTF-SLMD (ILTF = integrated line
test function). Therefore no SLMD-modules with integrated ILTF is existing.
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ISDN
subscriber
lines SLMD
SLCD
Control part
0
15
Test bus
(not in case of
ILTF-SLMD)
Control bus 0 (DLUC0)
Control bus 1 (DLUC1)
4096-kbps-PCM bus 0
(DLUC0)
4096-kbps-PCM bus 1
(DLUC1)
Overvoltage protection
Provisioning of the time multiplex interfacewith the 2B and D channel with a total
of 144kbps and the 16kbps for the clock synchronization (layer 1 of the DSS1)
Echo compensation for the bidirectional digital transmission on the 2-wire
subscriber line (layer 1 of the DSS1)
2-wire/4-wire conversion and adaption of the line code used on the subscriber
line (layer 1 of the DSS1)
Separation of the DSS1 signaling messages from the X.25 data packets of the
subscriber (layer 2 of the DSS1)
Protection of the transferof the DSS1 signaling messages in the D channel
(layer 2 of the DSS1)
Test access to the subscriber line/circuit
Fig. 19
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3.2.6 Emergency Operation of a DLU G (Stand-alone Service)
If both DLUC lose all their signaling channels to the LTG because of transmissionerrors (PDC failure) or LTG failure, a DLU can continue to work in emergencyoperation (stand alone service). This feature is usually available to all remote DLU's.The DLU must be equipped with an emergency operation control module SASC-G.
In emergency operation, this module takes over the control of setting up a connectionbetween subscribers of the same DLUG. Voice connections are through connectedinternally in the DLU. Calls are not metered. There is no connection to subscribers atother DLU's.
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LTGSLM
SLM
D
L
U
C
SASC Gcontrol
LTG
LTG
LTG
A
Btraffic
Fig. 20
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3.3 xDSL Interfaces at EWSD DLU
Subscriber modules which provide xDSL subscriber line interfaces can also beintegrated into a DLU. The administration of these modules require the NetM.
Such a DLU is then called a hiA7100 which belongs to the ATTANE product family.
The xDSL technology provides the subscriber simultaneously with
high bit rate Internet access
normal POTS or ISDN connections to other analog or digital subscribers
The POTS / ISDN connections of the xDSL subscriber are routed to an LTG as withother analog / digital EWSD subscribers via the DLU-internal control and payloadnetwork and the DLUC.
With high bit rate Internet access the useful information must by contrast be handedover directly from the DLU into the IP network of the Internet Service Providers ISP.This means, here is no circuit-switched connection setup by EWSD towards a Pointof Presence PoP of the ISP as is the case with conventional remote dial-in users.Therefore neither the DLUC of the DLU nor any other EWSD system unit is loaded bythe data transfer of these high bit rate accesses.
The DLU must be upgraded by three components to become a hiA7100:
Packet Hub SLMI:PHx with interface to the ISP's packet network
The Packet Hub offers access to the ISP's data network for maximum 14 xDSLsubscriber modules. Here the Packet Hub supports the following interfaces towardISP: Ethernet, Frame Relay or ATM.
DLU-internal ATM connection between the individual xDSL subscriber modulesand the Packet Hub
These connections are implemented individually for each xDSL subscriber moduleeither using plug-in cable (front side of the subscriber module for the front side of thePacket Hub) or via the backplane of the DLU.
Subscriber modules with xDSL interfaces SLMI:FMxfor 8 subscriber lines with ADSL.Lite Protocol:
For each subscriber, a POTS connection (analog telephone) and a high bit ratedata connection (PC with ADSL.Lite network interface card NIC) cansimultaneously exist through EWSD to the ISP. The following maximum bit ratesapply to the data connection: downstream 1.5 Mbit/s, upstream 512 kbit/s
SLMI:AMxfor 8 subscriber lines with ADSL protocol:For each subscriber, one POTS or 2 ISDN connections through EWSD and a highbit rate data connection to the ISP can exist simultaneously. For the POTS / ISDNconnections, another SLMA / SLMD is currently required in the DLU in addition to
the SLMI:AMx module.
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The following equipment is required at the subscriber side:
a) ISDN terminal equipment connected to the NT BA or analog telephone for thecircuit-switched connections through EWSD
b) PC with Ethernet interface connected to an ADSL NT or PC withintegrated ADSL network interface card NIC for high bit ratedata connection to the ISP
c) NT splitter as termination of the ADSL line at the subscriber. NT BA or ananalog telephone as well as ADSL NT or ADSL NIC are connected to thissplitter
The following maximum bit rates apply to the data connection:downstream 6 Mbit/s, upstream 640 kbit/s
High Bit Rate Data Services
in DLU used as hiA7100DLU
ADSL
ADSL.Lite
Micro
filter
Voice
Splitter
ADSL.Lite
(HBR data
plus
POTS)
NT BA
SLMI:FMx
SLMI:AMx
+ SLMA/D
SIEMENSNIXDORF
SIEMENSNIXDORF
SIEMENSNIXDORF
DLU System
Packet
Hub
HBR data
via ATM
Voice via
DLU Bus
to
LTG
to ISP via
ATM/FR/
Ethernet
ADSL
(HBR data
plus
POTS/BA)
ADSL NT
Ethernet
Fig. 21
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4 Functional Structure of the Line Trunk
Group (LTG)
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4.1 External 2 Mbps Interfaces to LTG
for the connection of digital trunks with CAS signaling from/to nodes of the PSTN for the connection of digital trunks from/to nodes of the ISDN, for the connection of
CCS7 signaling channels from/to nodes of the ISDN or central databanks such asthe service control point (SCP) of the IN
For the connection of large PSTN private branch exchanges with CAS signaling
for the connection of large ISDN private branch exchanges, intelligent peripherals(IP) of the IN, or packet handlers of a X.25 packet network (PSPDN) by theprimary access (PA) with DSS1 signaling
Connection of access networks with PSTN or ISDN subscribers by V5.2 interface
Connection of local or remote DLU
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LTG
4x
2 Mbps
PDC
Digital trunks with CAS
Digital trunks and CCS7
signaling channels
PABX lines with CAS
PABX lines with DSS1 (PA)
V5.2 interface to the AN
DLU
External 2 Mbps interfaces
Fig. 22
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4.2 Function Overview LTG
The line trunk group (LTG) forms the interface between the digital environment of thenode and the digital switching network (SN).
Connection to the duplicated switching network:
8Mbps SDC with 128 time slots
(If the LTG is part of an RSU the SDC are connected to the RTI of the RSU. The RTIitself is connected to the SN via the so called HTI.)
Function of the LTG:
The LTG take on decentralized control tasks for reducing the load on the coordinationprocessor (CP).
The LTG communicate with the CP / SSNC or CCNC / other LTG via messagechannels (MCH) for this.
The LTG always sends and receives the speech information via both switchingnetworks (SN0 and SN1).
However the LTG only relays the speech information from the active switchingnetwork outward. The other SN is designated as inactive. The LTG can immediatelysend and receive the current user information with it in case of a fault.
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Call processing:decentralized controltasks for call setup toreduce the load of the CP
Interface conversionbetween duplicated SNand the digitalenvironment of the node(through-connectionof the user information)
LTG
SN0
SN1
8Mbps SDC
8Mbps SDC
PDC 3
PDC 2
PDC 1
PDC 0
Signaling to other nodes, DLU/subscribers and PBX:
- Generation of signaling messages to be sent
upon initiative of the CP
- Pre-evaluation of received signaling messages and
relay to the CP
Communication via the message channelswith:
- the CP
- the SSNC / CCNC
- other LTG
Generation of audible signaling tones for the subscriber (tone
generator) and evaluation of the DTMF dialed digits (code receiver)
Call processing tasks of the LTG
Fig. 23
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4.3 LTG Functional Types
In order to optimally realize various line types and signaling systems, several LTGfunctional typeseach with specific application programsare available.
These various functional types of the LTG SW determine the connecting capabilitiesto an LTG.
Different types of LTG frames exist simultaneously.
The table opposite shows which LTG software functional type is compatible withwhich hardware implementation.
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LTG
Software Functional Type
Compatible
LTGHW - Type
Funktional type B
can be applied to connect:
DLU
PBX
Intelligent peripheral
Packet handler of a X.25 packet network
V5.2 Access Network (only to LTG M/N )
LTG G/M/N
Funktional type C
can be applied to connect:
Trunks with CAS signaling
Trunks with CCS7 signaling
CCS7 signaling channels
LTG G/M/N
Funktional type D
can be applied to connect:
International trunks with echo suppression /
No5 signaling
LTG D
Funktional type H
Frame handler for (de)concentration of X.25
data packets from ISDN subscribers
LTG H
Fig. 24
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4.4 Functional Units of the LTG
Group processor (GP)The GP converts signaling messages of the connected nodes/DLU/PBX into theEWSD intra-system message format and controls the functional units of the LTGvia the signal highways (SIH).
The GP communicates with the CP, the SSNC/CCNC, and other LTG via theduplicated message channel (MCH).
Group switch GS
The group switch realizes the following at the instigation of the GP:
The through-switching of individual speech channels between the PDC and the
SDC with and without attenuation.
The interconnection of tones of the TOG and of code receivers to the userchannels of the PDC.
The formation of three-way conferences
The link to the LTU is realized by speech highways(SPH), the link to the SN bythe LIU.
Link interface unit (LIU)
The LIU serves to connect the LTG to the duplicated SN (SN0 and SN1) via an 8
Mbps SDC each. Code receiver (CR)
The code receiver (CR) of the signal unit makes DTMF/MFC signaling for the callprocessing SW of the LTG available.
The essential tasks are
a) Reception and detection of multi-frequency signals (DTMF, MFC-R2, MFC-R1,CTC)
b) Report of detected signal to the GP
Tone generator (TOG)
The tone generator (TOG) of the signal unit centrally generates the necessaryaudible signaling tones for subscribers and the frequencies necessary for the MFCsignaling.
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Line trunk unit (LTU)
The line trunk unit (LTU) adapts the connected lines to the internal interfaces ofthe LTG and equalizes delays (synchronization of nodes and line bit rate).
The digital interface units (DIU)serve to this purpose (connection of PDC or 4Mbps routes of local DLU).
In addition, the LTU can also include modules with special functions such as testequipment for trunks or an individual announcement system.
DIU
Specialmodule
DIU
GP
SPH
SPH
SPH
8Mbps
SPH
Signal Unit
CR / TOG
SIH
PDC
PDC
SIH
SIH
LTU GS LIU
Speechroute
EWSDinte
rnalmessageexchange
S
N
0
S
N1
Fig. 25
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5 Functional Structure of the Remote
Switching Unit RSU
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5.1 Function Overview
The RSU enables the operation of up to 50,000 subscribers with DLU`s and LTG's atone of the sites remote from the host exchange. The connection from the hostexchange to the LTG's of the RSU is realized from the switching network (host) viathe Host Timeslot Interchange HTI via PCM30 with Interface Trunks to the RemoteTimeslot Interchange RTI.
The heart of the RTI is a switching network which should be considered an extensionof the host switching network. Connections between Subscriber-, trunk- or PBXLine-ports connected at the same RSU are directly switched in the RSU switching network
without having to route the connection via the host exchange.
It is possible to connect the RSU via Backdoor trunks to other exchanges or via
Sidedoor trunks to another RSU (the same host exchange).In the event of a fault (e.g. failure of the host exchange or failure of the transmissionroutes from the host exchange to the RSU), RSU enables stand-alone operation.This means that calls between subscribers of an RSU are possible.
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Interface
trunks
Interface
trunks
Sidedoor trunks
Backdoor
trunks
HTI Host timeslot interchangeRSU Remote switching unitRTI Remote timeslot interchange
Other exchange Other exchange
SNSN
CP
DLU
LTG
HTI
LTG
EWSD RSU
LTG
DLU
EWSD RSU
LTG
DLU
Backdoor
trunks
RTI
RTI
CCNC/SSNC
EWSD host exchange
Fig. 26
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5.2 RSU Functional Units
Each HTI and RTI is internally duplicated with the exception of the interface moduleDIU240 (Plane 0 and 1 of HTI / RTI). The essential functional units of HTI and RTIare:
TSI (AMUX and TSIM)
The core of the HTI/RTI is the TSI (Time Slot Interchange) unit which consists of theAMUX modules (0 to 7) and the TSIM module. The TSI forms the switching networkin the RSU with a matrix 128 x 8 Mbit/s.
MH module
The message channels (MCH) between the LTG's and the host message buffer areadministered in the HTI/RTI by the MH modules. The message channels have theirown transmission protocol (High Speed Link HSL) for transmission on the interfacetrunks. Each MH module administers 16 MCH the individual MH modules togetherform an MH pool.
RSUC module
The RSUC module is responsible for controlling the HTI/RTI. It communicates withthe host CP in a similar manner to the CP with the GP (Group Processor) of the LTG.The RSUC module communicates internally with the TSI and MH modules for
connection setup, connection release and OA&M.
DIU240 module
The interfaces module for the interface trunks/sidedoor trunks is the DIU240. EachDIU240 has 8 x 2 Mbit/s interfaces. Each DIU240 is connected to both redundantsystem halves (plane 0 & 1) of their RTI and HTI.
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plane0
plane1
SN 0
SN1
HTI
L
T
G
TSI
TSI
M
H
M
H
R
S
U
C
R
S
UC
MH MH
RTI
TSI
TSI
M
H
M
H
R
S
U
C
R
S
UC
MH MH
DIU
240
DIU
240
DIU
240
DIU
240
Fig. 27
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5.3 RSU Capacity Stage
Maximum number of HTI on a host EWSD
Up to 32 HTI can be connected to a host exchange. The maximum value of the HTI isdifferent according to switching network type:
SNA/B = 8 HTI
SND = 32 HTI.
Maximum number of RTI / remote LTG per HTI / host EWSD
Per HTI it is possible to connect maximum 14 RTI.In total however a maximum of 254 RTI and therefore 254 RSU can be connectedto a host EWSD.
Up to 71 remote LTG's can be connected to a HTI via the maximum 14 differentRTI's (RSU).
All remote LTG's in the host exchange must have their own 8Mbps interfacebetween switching network and the supporting HTI. In addition the RSUC of theHTI requires its own 8Mbps highway to the SN.Therefore it is not possible using RSU to exceed the maximum number of LTG'spre-specified by the switching network size of the host EWSD.
RSU module frames
The module frames are housed in a rack together with LTG's. Depending on thenumber of the connected LTG's and according to the expected traffic load, in additionto this basic frame, up to three extension frames with additional MH, DIU240 and
AMUX are required. A frame always contains the identical modules for both planes ofRTI / HTI.
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Interface
Trunks
CP
DLU
LTG
LTG
TSIM +
AMUX
RTI
RSU
Host Exchange
RSUC
MH
DIU 240
DIU 240
LTG
DIU 240
SN
RSUC
MH
DIU 240
DIU 240
DIU 240
HTI
Interface
Trunks
to other
RSUs
Sidedoor
Trunks
to other
RSUs
up to
71 LTGs
up to
24 DIUs
up to
192 PCM30
(E1 links)
up to
24 DIUs
1 ... 14 RSU per HTI
(max. 71 LTG per HTI)
up to 8 HTIs with SN A/B
32 HTIs with SN D
up to 254 RSU
per EWSD Host
TSIM +
AMUX
Backdoor
Trunks
Fig. 28
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5.4 RSU Emergency Operation
If an RTI looses all signaling channels to the host owing to transmission errors (PCMfailure) or HTI/host total failure, the RSU can continue working in emergencyoperation (stand alone service).
In emergency operation, this RTI tasks over controlling the connection setup betweenall subscribers connected to this RTI. The voice connection is through connectedinternally in the RTI (TSI).
During stand alone operation no charge registration is performed.
Call set ups via sidedoor trunks or via SS7ISUP backdoor trunks are not possible.Only connections between 2 subscribers of the same RSU and connections viaspecially administered "default backdoor trunks with CAS signaling" are set up.
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RSU
DLU
LTG
Host
DLU
LTG
possible trafficpaths
Signaling
LTG
predefined CAS-
backdoor trunks
or PAslave
CSS7
backdoor
tunks
LTG
sub-
scriber
sub-
scriber
sidedoor
trunks
Fig. 29
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6 Functional Structure of the Switching
Network (SN)
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6.1 Internal EWSD Interfaces on the SN
The internal interfaces from LTG, HTI, CCNC and MB to the SN are implementedusing Secondary Digital Carrier SDC with 8Mbps (the SSNC has no direct interfaceto the SN).
Here the SN serves to establish the transient bi-directional through connecting ofdata of a 64kbps connection between two LTG's (payload) and also to the semi-permanent through connecting of the 64kbps message channels MCH to exchangeinternal messages between the LTG, SSNC/CCNC and CP.
The CP and SSNC have access to this internal message channel system via the MB.(The CCNC of EWSD Classic has access via the CP.)
The processor of each LTG (Group Processor GP) uses the time slot 0 on the SDC
to the SN as its message channel.
In the case of the RSU the interfaces on the SN and the LTG are as described. Onlybetween HTI and RTI are the SDC implemented in several 2Mbps PCM.
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Collection of the MCH
from the various LTGCP
Time slot 0:
Message channel (MCH) between
LTG and MB (semipermanent through-connection)
for communication between LTG/CP/SSNCorCCNC
Time slot 1-127:
Used for the transient
through-connection of the calls
between two subscribers/trunks
LTG
LTG
MB
SN
2 Mbps PDC
8 Mbps SDC
SSNC
CCNC
or
Fig. 30
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6.2 Function Overview SN
The switching network SN is the link within a node for: User channel connections between the LTG (temporary through-connections)
the EWSD internal message exchange between the controls of the LTG,SSNC/CCNC, and CP via the fixed message channels (MCH)
the CCS7 signaling messages between the CCS7 signaling channels on the PCMroutes connected to the LTG and the SSNC/CCNC (by MML commandestablished nailed-up connections NUC, in case of SSNC the NUC is establishedvia a so called "inward LTG").
The switching network is completely duplicated (SN0 and SN1). All calls are always
simultaneously through-connected through both SN, whereas the LTG only though-connects the user channel information coming from the active SN to the PCM routes.If the active SN fails, the other SN (stand-by SN) is switched to without any loss.
The through-connection in the SN B takes place according to the time - space - timeprinciple (change of the time slot, change of the highway, change of the time slot), inthe SN D a so called switching matrixis used. Every through-connectionguarantees in both cases a transparent bi-directional 64kbps path through the SN.
Sequence for the temporary through-connection of the circuit connections:
The CP call-processing programs look for a free call path in the software switching
network image of the CP database from the LTG of the calling party to the LTGof the called party, for instance.
CP issues setting instructions to the control units of the SN for through-connectingthe calculated call path.
The SN - control units execute the setting instructions in the responsible modules.The call path from the LTG of the calling party through the SN to the LTG of thecalled party is thus through-connected.
Afterward the call-processing programs start a call path through-connection testoutgoing from the A-LTG (cross office check COC) in order to check whether theperformance of the call path through the SN is free of fault.
Along with the temporary through-connections (transient connections), there are alsothe semi-permanent connections:
The nailed up connections (NUC) set per MML command
The through-connection (set by the CP software) of the message channelsbetween the control unit of the LTG and the message buffer (MB)
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LTG
LTG
CCNC
MB
User channels between 2LTG
EWSD internal messages
between LTG, SSNC/CCNC,
and CP (message channels)
Control
CP
Setting
instructions
Message
channels
of all LTG
8 Mbps
Switching moduleshandling
SN 0 & SN 1EWSD-CLASSIC
SN A or SN B
SSNC
Fig. 31
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6.3 SN B (EWSD-CLASSIC)
6.3.1 Functional Units of the SN
The SN is offered in various increments. Except for the small switching networks formax. 31 or 63 LTG (combined space-time stages), the SN comprise the subdivisionstime stage group (TSG) and space stage group (SSG).
Time stage group (TSG):
Every time stage group serves to connect the SDC to/from the LTG, the CCNC,and the MB (together with max. 64 of this SDC). An SN can consist of a maximumof 8 duplicated TSGs.
There is a switch group control (SGC) in every TSG which is connected to the CPby means of an own SDC via the message buffer (MB). The SGC receives thesetting instructions for the temporary or permanent bi-directional 64 kbps through-connection from the CP. The SGC realizes the through-connection by setting theindividual time stage modules (TSM) of a TSG. Every TSM can change theposition in time and space of any time slot in any manner for a group of 8connected SDC in a TSG.
The following types of SDC differentiate:
SDC:LTG, secondary digital carrier between SN and every LTG for the circuitconnections (time slots 1-127) and for the message exchange between the LTG
control unit GP and the CP (message channel to time slot 0).
SDC:CCNC, one or two secondary digital carrier for through-connecting the CCS7messages between CCNC and the signaling channels on the PCM routes to theLTG.
SDC:TSG, a secondary digital carrier between SN and MB for relaying themessage channel of all LTG of this TSG to the CP.
SDC:SGC, a secondary digital carrier between the control unit SGC of this TSGand the MB for relaying the setting instructions of the CP to the TSG.
Space stage group (SSG):
The SSGs serve to through-connect the calls between TSMs in the same or indifferent TSGs. An SN can consist of a maximum of 4 duplicated SSGs.
There is a switch group control (SGC) in the SSG which is connected to the CP viathe message buffer (MB). The SGC receives the setting instructions for thetemporary or permanent bi-directional 64 kbps through-connection from the CP.The SGC realizes the through-connection by setting the individual space stagemodules (SSM) of an SSG. Every SSM can change the highway of the time slot forall connected SDC in any manner.
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The individual TSGs and SSGs are connected to one another by SDC:SSG. Here theTSGs and the SSGs of the same switching network (SN0 or SN1) normally worktogether. In the case of an error, a TSG of SN0 can work together with an SSG of
SN1, for instance. This possibility of protection switching grants the duplicated SN avery high failure security.
SDC
time slot y
TSM
SDC
Time Stage module TSM
time slot x
time slot x
SSM
time slot x
Space Stage module SSM
TSG0-0LTG0-x
CCNC
MB
CP
SGC
TSM
TSM
SSG0-0
SGC
SSM
SSM
TSG0-7
SGC
TSM
TSM
SSG0-3
SGC
SSM
SSM
Setup of an SN (example: SN0)
Fig. 32
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6.3.2 Capacity Stages of the SN
Since the SN is offered in many capacity stages, the actual size of the SN can beadapted to the expected amount of traffic of an exchange. Here the traffic to bethrough-connected measured in Erlang as dimensioning sizes is to be observed.
Remark:
Except the beside shown capacity stages there are also offered a SN for 31LTGanda SN for 63 LTG.
Notes on capacity/ space requirements of the SN capacity stages
For the given values, the highest technically possible values are concerned.
If a CCNC is connected, 1 to 2 SDC:CCNC is added depending on the number ofthe CCS7 signaling channels and the number of SDC:LTG reduces accordingly.
Space requirements in the rack:
Every TSG needs only one frame in the rack.
Every SSG needs only a half of a frame in the rack.
The remaining space in the rack can be used for LTG.
a) A maximum of 4 LTG frames can be additionally mounted in a rack for TSG.
b) A maximum of 3 LTG frames can be additionally mounted in a rack for SSG.
c) A maximum of 4 LTG frames can be additionally mounted in the rack of theSN:63LTG.
d) The SN:31LTG is put in the rack of the CP.
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TSG
0.0
TSG
1.0
TSG
0.1
TSG
1.1
SSG
0.0
SSG
1.0
SN:126LTG
SN0
SN1
SN:252LTG
TSG
0.0
TSG
1.0
TSG
0.1
TSG
1.1
TSG
0.2
TSG
1.2
TSG
0.3
TSG
1.3
SSG0.0
SSG0.1
SSG1.0
&
SSG1.1
SN0
SN1
SN:504LTG
SSG0.2
&
SSG0.3
SSG1.2
&
SSG1.3
SSG0.0
&
SSG0.1
SSG1.0
&
SSG1.1
TSG
0.7
TSG
1.7
TSG
0.6
TSG
1.6
TSG
0.5
TSG
1.5
TSG
0.4
TSG
1.4
TSG
0.3
TSG
1.3
TSG
0.2
TSG
1.2
TSG
0.1
TSG
1.1
TSG
0.0
TSG
1.0
SN0
SN1
SN for
max.126 LTG
SN for
max.252 LTG
SN for
max.504 LTG
Traffic (ERL.) 6300 12600 25200
Number of subscribers with
pure local exchange60000 120000 240000
15000 30000 60000
Ratings
Number of trunks with
pure transit exchange
Fig. 33
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6.4 SN D (EWSD-POWERNODE)
6.4.1 Functional Units of the SN D
The SND is a completely new switching principle based on a single-stage switchingmatrix (grate-like matrix) compared to SNB. Here the "time-space-time" structure isno longer used. To ensure a particularly high level of reliability, SND is completelyduplicated.
SND is based on two types of frames
Frame SwitchingNetworkMUltipleXer (F:SNMUX) and
Frame SwitchingNetworkMatrix (F:SNMAT).
A multiplexer and a demultiplexar are provided for the existing environment withF:SNMUXA which bundle 2 x 64 x 8 Mbit/s LTG lines to two optical lines connectedto F:SNMAT. Switching is implemented by F:SNMAT.
In smaller exchanges (up to 252 LTG's) F:SNMUXA can execute switching by itself(without SNMAT). Here the two required SNMUX's (per SN side) are connecteddirectly to one another using the optical lines.
To connect the SND with the co-ordination processor CP, an MBD messagedistributor is required.
The following interfaces can be differentiated:
SDC:LTGSecondary multiplex line between SN (SNMUX) and each LTG for the userchannel connections (time slots 1-127) as well as for the message exchangebetween the LTG control GP and the CP (Message Channel on time slot 0). TheSDC:LTG are identical to the SDC:LTG at the SN B.
SDC to the MBDH in the MB DSecondary multiplex line between SNMUX and MBDH to relay the messagechannel of half of all LTG's of this SNMUX to the CP. This corresponds to theSDC:TSG in the SN B.
MBD-SxSecondary multiplex line between the control module in SNMUX / SNMAT and theMB-D to relay the setting instructions of the CP to the switching network.
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LTG 0-1
LTG 0-63
LTG 1-1
LTG 1-63
SNMUX
0
LTG 30-1
LTG 30-63
LTG 31-1
LTG 31-63
SNMUX
15
SNMAT
CP
MBD
.
.
.
. . .
.
.
.
.
.
.
0
1
0
127
30
31
0
127
8 Mbit/s
SDC-interface
920 Mbit/soptical interface
920 Mbit/s
optical interface
2 x MBD-S1 1 x MBD-S3
(1 x MBD-S3
only with SN252 LTG)
920 Mbit/s
optical interface
920 Mbit/s
optical interface. . .
. . .
. . .
MBDH
2 x MBD-S1
Fig. 34
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6.4.2 SN D Capacity Stages
max.number ofLTG
DE-TYPE max.numberofSNMUXper SNside
SNMAT-per SNside
TrafficErl
252 DE6.0 2 0 12600
252 DE6.1 *) 2 1 12600
504 DE6.2 4 1 25200
756 DE6.3 6 1 37800
1.008 DE6.4 8 1 50400
1.260 DE6.5 10 1 63000
1.512 DE6.6 12 1 75600
1.764 DE6.7 14 1 88200
2.016 DE6.8 16 1 100800*)use DE6.0 instead of DE6.1 if not more thane 252 LTG areplanned (because DE6.0 does not require an SNMAT).
Fig. 35 Capacity stages of SN D
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F:SNMUXA 0
F:SNMUXA 1
F:SNMUXA 0
F:SNMUXA 1
F:SNMUXA 0
F:SNMUXA 1
F:SNMUXA 0
F:SNMUXA 1 F:SNMAT 0
F:SNMAT 1
0 1 2 15
F:SNMUXA 0
F:SNMUXA 1
F:SNMUXA 0
F:SNMUXA 1
F:SNMUXA 0
F:SNMUXA 1
0 1
SN D - DE6.0
for 126 LTG
SN D - DE6.0
for 252 LTG
SN D - DE6.8
for 2016 LTG
Fig. 36
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7 Functional Structure of the Coordination
Processor (CP)
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7.1 Function Overview CP
The CP coordinates the work of the individual EWSD system units. For call processing, the CP assumes the central tasks for a call setup. In the
course of this, LTG and the SSNC/CCNC reduce the load on it.
For operation and maintenance, the CP makes the interfaces available for theman-machine dialogue (input of commands, output of messages and alarms) andto the mass storage devices (magnetic tape/magnetic disk).
For safeguarding, the CP assumes the master-function for monitoring the EWSDhardware and software.
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Call processing: Digit translation Routing Zoning Path selection through the
SN
Charging
Traffic data administration Network management
Operation & maintenance: Input and output from/to
external memories (EM)
Communication with thelocal and central O&Mterminals for the purposeof administration of the
database Alarm indication
CP113C / CP113CR
Safeguarding:
Self-supervision
Supervision of all EWSD functional units
Fault detection
Fault analysis
Fig. 37
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7.2 System Features of the CP113
CP types:
the coordination processor 113C (CP113C) or
the coordination processor 11CR (CP113CR) as a special version for use inrural/container exchanges
The primary features of a CP113C/CR are:
Application of a modular multiprocessor system with combination of task and loadsharing
adaptability to different exchange sizes:
The performance is dependent on the capacity stage, with CP113C more than1,500,000 busy hour call attempts (BHCA).
(The effective, dynamic call setup performance depends on the available featuresand the actual call-mix. They must be individually specified for every time in use.)
Redundancy by duplication of major functional units and pool formation with thecall processors
Use of high performance microprocessor types (processing width of 32 bit/addressing capacity up to 4 Gbytes)
Common memory with a capacity of (at present) 64 Mbyte to 1024 Mbyte (1Gbyte)(used chip at present: 16 Mbit DRAM)
Local memory per processor with a capacity of max. 64 Mbyte (used chip atpresent: 16 Mbit DRAM)
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Input/output processors to:
EWSD functional units
Mass storage devices
Local O&M terminals for manual Boot
NetM
Post processing center
Interfaces of the CP
High-performance multiprocessor system with
32 bit processing width
More than 4,000,000 call setups per hour
Security redundancy of the central units
Modular expandable hardware
(number of processors and memory size)
System features of the CP
Fig. 38
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7.3 Functional Units of the CP
By adding functional unit of the same type, it is possible to expand the basic capacityof the CP113C, depending on necessity. This applies both for the arithmetic andstorage capacity and for the connection of call processing and administrativeperipherals.
Base processors (BAP)
One of the two base processors is operated as master (BAPM) and the other asspare (BAPS). The BAPM handles the administrative tasks and in addition callprocessing tasks proportionally. The BAPS handles only call processing tasks. If theBAPM fails, the BAPS becomes master and assumes the administrative tasks(active/stand-by redundancy for the administrative tasks).
Call processors (CAP)
The call processors (CAP) of the CP113C exclusively handle call processing tasks.They work in according to the load sharing principle. The CAP generate a poolredundancy for call processing tasks together with the BAPS and BAPM in that onemore processor is available than required for the fulfillment of the nominal callprocessing handling capacity (n + 1 redundancy). The CP113C can thereforecontinue to produce the full nominal load even if one processor (BAP or CAP) fails.
With EWSD CLASSIC the maximum number of CAPs is 6 while with EWSDPOWERNODE you can have up to 10 CAPs in the CP.
Input-output controls (IOC)The IOC each generate a common interface to bus B:CMY for max. 12 in-outputprocessors (IOP) via bus B:IOC. The input-output controls (IOC) and the connectedinput-output processor (IOP)for the connection of administrative/datacommunication devices (e.g. input device, mass storage device) and the peripheralEWSD system units (e.g. LTG/SN