project
TRANSCRIPT
ABOUT C-DOT
BRIEF HISTORY: -
The Center for Development of Telemetric (C-DOT) is the telecom technology
development center of the government. It was established in August 1984 as an autonomous
body. It was vested with full authority and total flexibility to develop state-of-the-art
telecommunication technology to meet the needs of the Indian telecommunication network.
The key objective was to build a center for excellence in the area of telecom technology.
ORGANIZATION: -
The management of C-DOT has a three-tier structure: -
The governing Council: provides policy guidelines and approves the annual budget of the center.
The Steering Committee: has the role offs reviewing and monitoring the performance of the center.
The Project Board: is responsible for the implementation of C-DOT’s project and the day-to-day function of the center.
OBJECTIVES: -
Work on telecom technology products and services.
Provide solutions for current and future requirements of telecommunication and converged networks including those required for rural application.
Provide market orientation to R & D activities and sustain C-DOT as center of excellence.
Build partnerships and joint alliances with industry , solution provides, telcos and other development organizations to offer cost effective solution .
MANPOWER: -
Electronic Design automation (EDA) Tools for hardware and ASIC Design
Case Tools for Development and testing of software
Captives labs
Computing center
Pilot production plant
Existing manpower –907
Planned Manpower - 963
The Center has state-of-the-art development environment comprising client/ server
network of RISC workstation, latest software development tools and very mature and effective
development and support methodologies, Extensive use is made of case tools, object-oriented
methodologies, software metric etc.
The jobs have the latest test and measurement instrument, microprocessor development
system and prototyping facilities.
ACHIEVEMENTS: -
C-DOT Technology based system from 200 lines to 40,000 lines capacity in operation
More than 30,000 C-DOT Exchange totaling approximately 25 million telephone lines installed and operational in field
Deployed telecom equipment value of Rs.7500 core
significant technology transfer and royalty earnings
Technology development with low capital investment
Wide portfolio technologies, products and solution
Created large reservoir of technical manpower in telecom
established a technology transfer process for production by multiple manufacturers
The C-DOT DSS FAMILY
GENERAL
C-DOT DSS MAX is a universal digital switch can be configured for different application as
local, transit or integrated local and transit switch. High traffic or capacity of 40000 lines as local
exchange or 15000 trunks as Trunk automatic exchange.
The design of C-DOT DSS MAX has seen by a family concept because of it’s advantages
like standardized components, commonality in hardware, field hardware that used minimum
number of cards, standard cards, racks, frames, cabinets and distribution frames are used
which facilitated flexible system growth that make C-DOR DSS MAX easy to maintain and highly
reliable.
FLEXIBLE ARCHITECTURE
C-DOT DSS is a modular and flexible digital switching system which provides economical
means of serving metropolitan, urban and rural environments. It includes all important feature
and compulsory services, required by the user with option of up gradation to add new
feature and services in future. The architecture for the C-DOT DSS is such that it is possible to
upgrade a working C-DOT Single Base Module.(SBM) or Multi Base Module (MBM)exchange to
provide Integrated Services Digital Network (ISDN) service by adding minimum addition
hardware modules while continue to having existing hardware units. Another factor of
architecture Remote Switching Unit (RSU). Is support ISDN. This RSU provides switching facility
locally even in case of failure of the communication path to the parent exchange.
The resources, which depend upon the number of terminal, are provided within the
basic growth unit the Base Module. Base Processors are provided for handling call processing
locally. In a small system application, these processors independently support call processing,
exchange operation and maintenance function.
ARCHITECTURE OF C-DOT DSS MAX
C-DOT DSS MAX exchanges can be configured using four basic modules.
1. Base Module
2. Central Module
3. Administrative Module
4. Input Output Module
HARDWARE ARCHITECTURE
Structure of C –DOT DSS MAX
C-DOT MAX exchange can be configured using four basic modules:-
CENTRAL MODULE
AM
BM1
BMn
PBAX LINES
ANALOG
TRUNKS
DIGITAL
TRUNKS
DIGITAL TRUNKS FROM
RSU
ISDN INTER-FACES
(BRI/PRI)
ADP
IOM
DISKVD
U
PRIN
TERR
TAPE
1. BASE MODULE (BM)
2. CENTRAL MODULE (CM)
3. ADMINISTRATION STRATIVE MODULE (AM)
4. INPUT OUTPUT MODULE (IOM&IOP)
(a) BASE MODULE (BM) : -
The Base Module is the basic growth unit of the system. It interfaces the external world
to the switch. The interfaces may be subscriber lines, Along and digital trunks. Each Base
Module can interface up to 2024 terminations. The number of Base Modules directly
corresponds to the exchange size. It carries out majority of call processing function and in a
small exchange application; it also carries out operation and maintenance function with the
help of Input-Output Module.
The Basic functions of base modules are:-
1. Analog to digital conversion of all signals on analog lines and trunks.
2. Interface to digital trunks and digital subscriber.
3. Switching the calls between terminals connected to the same Base Module.
4. Communication with the AM via the CM for administrative (i.e. Call processing)
functions.
5. Provision of special circuits for call processing support e.g. Digital
6. Tones, announcement, MF/DTMF Senders/receivers.
7. Provision for local switching Unit (RSU) as well as in case of Single Base Module
Exchange (SBM_RAX).
There are two types of Base Modules:-
1. Single Base Modules(SBM)
2. Multi Base Module(MBM)
In SBM exchange configuration, the Base Module acts as an independent switching BM directly
interface with the Input Output Module for bulk data storage, operations and maintenance
function. Clock and synchronization is provided by a source within the BM. It is a very useful
application for small urban and rural environments. Communication with the AM via the CM for
administrative (i.e. Call processing) functions. Provision of special circuits for call processing
support .
The Base cabinet houses total 6 frames:-
Terminal Unit (TU, Top 4 Frames) system and provides connection to 1500 lines and 128 trunks.
Base Processor Unit (BPU, 5th frame)
Time switch unit (TSU)
TERMINAL UNIT 1
TERMINAL UNIT 2
(TU 1)
(TU 2)
(TU-4)
BASE PROCESSOR UNIT (BPU )
TIME SWITCH UNIT (TSU)
FRAME 1
FRAME 2
FRAME 3
FRAME 4
FRAME 5
FRAME 6
There are following four terminals units:-
1. ANALOG TERMINAL UNIT (ATU):-
The Analog Terminals Unit (ATU) is used for interfacing 128 analog terminations which
may be lines or trunks and providing special circuits as conference announcements and
terminal tester. It consists of terminal cards, which may be a combination of Analog Subscriber
Line Cards, Analog Trunk card & some Special Service Cards.
(a) Analog Subscriber Ling Cards: -
Two variants of subscriber line cards as LCC (Line Circuit Card) or CCM (Coin Collection
Monitoring) with interfaces up to 8 subscribers. Analog to digital conversion is done by per
channel CODEC according to A-Law of Pulse Code Modulation so we can say that it for the
subscriber connected for subscriber to exchange.
A unit has 16 line cards so 16*8=128 subscribers.
There are 4 unit so 4*128= 512 subscribers.
4 cards make 1 Terminal Group (TG) so TG = 4.
(b) Analog Trunks Cards:-
Analog trunk cards interface analog inter exchange trunks which may be of three types
as TWT, EMT & EMF. These interfaces are similar to subscriber Line Cards, with only difference
that the interfaces are designed to scan/drive events on the trunks as predefined signaling
requirement.
(c) Signaling Processor Cards: -
SP Processes the signaling information received from the terminals cards. SP processes
the signaling information consists of scan/drive function like original detection, answer
detection, digit reception, reversal detection etc. The validated events are reported to Terminal
interface controller for further processing.
(d) Terminal interface controller (TIC) Cards: -
TIC controls the four terminals group (TG) of 32 channels and multiplex them to form a
duplicated 128 channels, 8 mbps link towards the Time Switch. For Signaling information of 128
channels it communicates with signaling processor to receive/send the signaling event on
analog terminations. It also uses to communicate with BPU.
(e) Special Service Cards: -
A Terminal unit has some special service cards such as Conference (CNF) cards to
provide six party conferences. Speech Samples from five parties are Terminal Test Controller
(TTC) card is used to test analog terminal interfaces via the test access relays on the terminal
cards.
Announcement controller card provides 15 announcements on board cast basis.
(2) DIGITAL TERMINAL UNIT ( DTU ) : -
Digital terminal unit is used to interface digital trunks, i.e. used between the exchanges.
One set of Digital Trunks Synchronization (DTS) Card along with the Digital Trunk Controller
(DTC) card is used to provide one E-1 interface of 2mbps.
Each interface occupies one TG of 32 channels and four such interfaces share 4 TGs in a
DTU. Here Terminal Unit Controller (TUC) is used of TIC and DSP cards. Out of 32 channels, 30
for voice communication and remaining two for Signaling and Synchronization.
In DTU 4 TGs are there so total number of unit are 4*30 = 120 units in DTU.
(3) # 7 or Signaling Unit Module (SUM): -
It is used to support SS7 protocol handlers and some call processing function for CCS7
calls.SS7 capability in C_DOT DSS MAX exchanges is implemented in the form of a SS& Signaling
Unit Module (SUM) the sum hardware is packaged into a standard equipment frame, similar to
that of terminal unit.
ISDN (INTEGRATED SERVICE DIGITAL NETWORK )
To support termination of BRI/PRI interfaces and implementation of lower layers of DSSI
Signaling protocol. They are used as carriers to transport bulk volume of data. With the
increasing use of internet access, the use of ISDN interface is likely to go up as it provides the
reliable access to the user at the rate of 64/128kbps. It is of two types i.e. circuit switched
voice and data and packet switched data. In circuit switch the traffic is routed through ISDN
and is packet switched data the traffic is routed through PSPDN.
REMOTE SWITCH UNIT : -
In this time switch card BMs are replaced by Enhanced Switch Cards (ETS). It is used
when the e exchange is at a far distance from the central module. It can modified BM via 2
mbps digital links. Analog and Digital trunk interfaces are also implemented in RSU to support
direct parenting of small exchanges from RSU. Instead of parenting it to the main exchange.
RSU is an autonomous exchange capable of local call completion. Only the even numbered BMs
can be configured as RSU i.e. a maximum 16 RSUs are possible in C-DOT DSS MAX-XL and 8
RSUs in MAX-L Maintenance and operation function are handled by the host exchange.
Remoter Switch Unit Normal BMs
1. Type of connectivity used is 1.Type of connectivity is through E-1 data cables cards of 2mbps and E-3 cards of 32Mbs.
2. Contains Time Switch Cards. 2. Contains Enhanced Switch Card.
3. Situated at a Distance. 3. Should be in side of CM.
TIME SWITCH UNIT (TSU):-
Time Switch Unit (TSU) implements three basic functions as time switching within the
Base Module, routing of control message within the Base Module and across Base Module and
support services like DTMF circuit, answering circuit, tones etc. These functions are performed
by three different functional units, integrated as Time Switch Unit in a single frame. i.e.
SERVICE UNIT : -
It is integrated around three different cards as Tone Generator with Answering Circuit (TGA),
Service circuit interface Controller (SCIC) and DTMF Controller, (MFC) Card. These three forms
TGs towards Service Circuit interface (SCI). SCI multiplexes these TGs together with another
terminal group from the Base Message. Switch (BMS) to form a 128 channel, 8 Mbps link &
send it to the Time Switch.
BASE MESSAGE SWITCH (BMS) : -
Base Message Switch (BMS) route the control message with in the
Base Module, across different Base Module and also Administrative Module via the Central
Module. It is implemented around two cards as Message Switch Controller (MSC) with the
Message Switch Device (MSD) with 16 HDCL links. So total 22 HDLC channels are
implemented for communication with the Base Processor, Time Switch Controller, and Service
Circuit interface Controller within the BM. It transfers the message between the Base processor
and these controllers.
To supports 8, 00,000 BHCA,MSC AND MSD cards are replaced by a high Performance
Switch(HMS) with high speed up to 750 Kbps, 32 bit microprocessor.
TIME SWITCH (TS): -
The Time Switch complex is implemented using three different functional cards as
multiplexer/demultiplexer (TSM), Time Switch (TSS) and Time Switch Controller (TSC).
The Time Switch complex performs time switching within the Base Module: -
Four 128 channel multiplexed link from four different terminal units which may be any
combination of ATU, DTU, #7SU AND ISTU.
One 128 channel multiplexes BUS from the Service Circuit interface Controller (SCIC) in
the Time Switch Unit.
Three 128 channel link to support on board three party conference circuits (3*128).
BASE PROCESSOR UNIT:-
Base Processor Unit (BPU) is the master controller in the Base Module. It is implanted as
a duplicated controller with memory units. These duplicated sub-units are realized in the form
of the following cards :-
1. Base Processor Controller (BPC) Cards.
2. Base Memory Extender (BME) Card.
1. Base Processor Controller (BPC) Cards : -
BPC control time switching within the Base Module via the Base Message Switch and
the Time Switch Controller. It communicates with the Administrative processor via Base
Message Switch for operations and maintenance functions. In a SBM configuration, BPC directly
interface with the Alarm Display Panel and the input Output Module.
To support 8,00,000 BHCA, the BC card is replaced by High performance processor card.
(HPC) i.e. Protocol Handler Card (PHC) which contain 26 slot,8slot for the power supply, 2 for
memory and remaining 10 for message switching.
2. Base Memory Extender (BME) Card: -
It is for the storage purpose i.e. saving memory purpose. It can store up to 16 bits
CENTRAL MODULE
Central module is responsible for space switching of inter-Base Module calls, communication
between Base Module and Administrative Modules, clock distribution and network
synchronization. For these function central module has a Space Switch, Space Switch Controller,
a Administrative Processor and a Central Message Switches CMS (A, B, C, D). In a 32 Base
Module configuration, there are 64 bit parallel buses carrying the voice information from Base
Module to the Central Module, and also the Switched information in the reverse direction
The complete control conceptually is shown in following figure: -
Concept Control Scheme for Space Switch
The administrative processor communicates with the IOPs which act like a central storage.
Administrative processor is also connected to Central Message Switches CMSA and CMSB
Space switch controller
Administrative processor
CMS
C
CMS
D
CMS
B
CMS
A
Space switch
through which AP communicates to SSC. The SSC is connected to all the CMSs (A,B,C,D) so as to
communicate with all the BMs through these Central Message Switches (CMS_A,B,C,D). ). In a
32 Base Module configuration, there are 64 bit parallel buses carrying the voice
information from Base Module to the Central Module, and also the Switched information in the
reverse direction.
There are two types of Central Module: -
1.CM-XL (Extra Large)
2. CM-L(large)
Central Module Large (CM-L) Central Module Extra Large (CM-XL)
1.There are one BTU (Base Terminal Unit) and one SSU (Space Switch Unit)
2. The 8 MHz clock may be locally generated at the Space Switch Clock (SSK) card in CM-L. or may be derived by using Network Synchronization Equipment(NSE) in this.
3. In CM-L, CM provides connectivity to 16 BMs.
4. Each message switch is a high performance message routing block, implemented by using high speed 16 bit microprocessor Motorola Company (MC).
1. There are two BTU and two SSU.
2. The 8 MHz clock may be locally generated at the Central Clock (CCK) Card in CM-XL. Or may be derived by using Network Synchronization Controller Card.
3. In CM-XL, CM provides connectivity to 32 BMs.
4. Each message switch is a high performance message routing block, implemented by using high speed 16 bit microprocessor Motorola Company (MC).
Each BM interfaces with CM via two 512 channel parallel buses as BUS-0 and BUS-1,
each operating at 4 Mbps. These buses carry voice information of 512 termination of the Base
Module towards CM. In the reverse direction, after space switching has been done in the Space
Switch under the control of Space Controller (SSC), the same buses carry the switched voice
information for 512 terminations towards BM. Thus, in a 32 Base Module configuration, there
are 64 parallel buses carrying the voice information from Base Modules to the Central Module,
and also the switched information in the reverse direction. Each message switch is a high
performance message routing block, implemented by using high speed 16 bi microprocessor
Motorola Company (MC).
These buses carry voice information of 512 termination of the Base Module towards
CM. In the reverse direction, after space switching has been done in the Space Switch under the
control of Space Controller (SSC), the same buses carry the switched voice information for 512
terminations towards BM.
CM FRAME ORGANIZATION
Space Switch Administrative Central
Switch Processor Message
1. Space Switch Mux 1.Bus Interface 1.CMS A
Demur Card (SSM) Controller (BIC) Card (For TS0,Bus 0)
2. Space Switch 2.Bus interface 2.CMS B
Switch Card (SS) CPU (BIC) Card (for TS0,Bus1)
3. Space Switch 3.Memory (MEM) 3.CMS C
Clock Card (SCK) (For TS1,Bus 0)
CM HARDWARE DISTRIBUTION:-
CM Hardware is distributed in following frames: -
Bus Terminal Unit (BTU) Frame
Space Switch Unit (SSU) Frame
Space Switch Controller Unit (SCU)
Administrative Processor Unit (APU)
BUS TERM INAL UN IT
SPAC E SWITC H UN IT
(BTU)
(SSU)
(SC U)
(APU)
FREE
FREE
FRAM E 1
FRAM E 2
FRAM E 3
FRAM E 4
BUS TERM INAL UN IT
SPAC E SWITC H UN IT
(BTU)
(SSU)
(SC U)
(APU)
BTUBUS 1
SSU
FRAM E 1
FRAM E 2
FRAM E 3
FRAM E 4
BUS 0
BUS TERMINATION UNIT: -
It contains Multiplexer and Demultiplexer. It is basically an Interface Unit Between the
BM and Space Switch. There are two buses-Buses 0 and Bus 1.Bus 0 contains all even time slots
and Bus 1 carries all odd time slots.
FUNCTION: -
(a) Caters to maximum 16 BMD in release one.
(b) Multiplexes the data for Space Switching.
(c) De multiplexes the Switched Bus.
(d) Distributed 8 MHz clock and 8 KHz sync. To BMs.
(e) Acts as a Gateway for CMS by message extraction/insertion scheme
Types of cards used: -
1. Space Switch Mux Card (SSM): - It multiplexes two BMs data.
2. Space Switch Mux Termination Card (SMT) :- It is used in an unequipped. SSM slot in the BTU
frame to avoid any noise generated due to termination of a bus from BM in BTU frame. It offer
2A load at 5V.
3. Power Supply Card: - It supplies power to the cards and unit it work as a load sharing mode in
each bus.
4. Space switch unit: Space Switch provides connectivity between two subscribers of two
different BMs on time slot basis. It is responsible for switching of cards between various base
modules
FUNCTION: -
(a) Establishes Inter Base Module Switching.
(b) Caters for 16*16 Base Module switching.
(c) Implements two 16*16 switching; one for bus 0 and other for bus 1.
(d) Provides redundancy as copy 0,copy1(switch duplicated)
Types of cards used: -
1. Space Switch Switch Cards (SSS): -
The switch card forms the part of the space switch which is situated in the Central
Module. Each SSS Card caters for four base modules (16*4 switches in CM).
2. Space Switch Termination Card (SST): -
It provides proper termination to the MUX data bus received from 16 space Switch MUX
Cards. The card is used if corresponding SSS slot is unequipped.
3. Space Switch CU Bus Termination Cards (SCT) : -
It is used in Space Switch Unit and Space Switch Control Unit frames of CM. It
terminates CPU, address, data and control signals.
4. Power Supply Cards : -
SSU employs 4 cards for supplying power and it is used in BPU,TSU ,IOP.
3. Space Switching Controller Unit(SCU) : -
It is a CPU complex and interfaces with space switch and clock for controlling the space switch. SSC communicates with the CMSs which in turn enable the SSC to communicate with the BMs. It contain Power Unit
FUNCTION: -
(a) Controller for the Switch
Time slot management and allocation
Switch monitoring for sanity
Switch diagnosis
(b) Communication b/w the central message switch and Asp, BMs
(c) System clock generation
(d) Management of power alarms in BTU,SSU and SCU
Space Switch (SS) and Space Switch Controller (SSC) : -
1. In order to take care of the large number of interface signals, the switch portion of CM is
divided into three stages viz. MUX stage, Switch stage and DEMUX stage. The MUX and DEMUX
stage are implemented on single card to provide the Base Module to Central Module interface
in each direction. Interfacing and switching are controlled by SSC which provides control signals
for the MUX/DEMUX cards and the space Switch cards.
2. MUX/DEMUX Cards extract the information from time slots 0 and 1 of Bus 0 and Bus 1 from
the Base Modules. These time-slot carry control message from each base Module and these
messages are sent to the Central Message Switch (CMS). The CMS sends these messages to the
Space Switching controller (SSC) on a 128 kbps link to control space switching based upon the
information.
3. Four 512-channel buses from four BMs are multiplexed to form a 2048-channel,16Mbps
multiplexed BUS which is sent to both copies of the Space Switch Switch Card. Space switching
of these 2048 channels is done based upon the switching information received by Space Switch
Controller (SSC) from CMS . The CMS sends these messages to the Space Switching controller
(SSC) on a 128 kbps link to control space switching based upon the information.
Central Message Switch (CMS) : -
It consists of four different message switches and each one of them is implemented by
using high speed 32 bit microprocessor. All Central Message Switches (CMS 1, 2, 3 & 4) are used
for routing of messages across the Base Modules. Only CMS1 and CMS2 interface with the
Administrative Module for routing control message between Base Processors and
Administrative Processor.
Type of Cards used: -
1. CPU Complex
Space Switch Controller Card (SSC) (CPU) : - This is to serve as central processing
engine for the C-DOT DSS both in the BM & the CM mode. It coordinates system activities
and performs call processing functions. It is used as Base Processor (BP) in the BM& as
administrative processor (AP) and Space Switch Controller (SSC) in CM.
Bus interface-CPU(BIC) Card : - It is used to access memory and space switch in plane
copy-0 & copy –1.
Bus interface Device (BID) Card : - It along with bus interface CPU (BIC) card provides
the cross connection b/w duplicate CPU’s (controller) an duplicate device (memory) in such
a way that any one failure either at CPU or at device does not bring down the whole
processor complex.
Memory Card (2MB) : -It provides storage space and interfaces to a standard 6800 CPU
bus. Both word & byte accessory are possible on the memory space.
2. Switch Interface
BIC Card
Bid Card
Space Switch Controller Termination (SCT)
3. System Clock and PSU errors
Space Switch Clock Card (SCK) : - It is the source of clock signal to the space switch switch
cards & the space switch mux cards which constitute the space switch. It is used for the
control of timing and for synchronizing of the space switches.
4. Administrative Processor Unit (APU) : -
Status of all module of the exchange is maintained by the AP and whenever a problem is
reported required action is initiated to clear the problem. All the global resource like trunks.
Time slots etc are managed by the A.P. Directory to equipment number translation for the
establishment of a call is performed by AP.
Function of APU: -
1. All administrative function in the system
2. Interaction with SSC through central message switches CMS (A,B) (SSC/BM to IOP via
AP).
3. Communication to ADP.
4. Administrative Processor (AP) somewhat similar to BP.
5. Maintain status of all modules of the exchange.
6. Initiate whenever a problem is reported required action to clear the problem.
7. Switch over of copies, diagnostic of faulty units and put in service units which are out of
service etc, are initiated and supervised by the AP.
8. Manage all the global resource (like trunks, ts etc.)
9. Perform directory to equipment no. translation for the established of a call.
10. Connects of exchange to the operator through IOP.
11. Handle the man-machine communication.
12. During initialization of the multimode exchange AP gather initialization request from
BMS.
Types of Card used: -
1. CPU Complex (APU)
CPU Card
BIC Card
BID Card
Memory Card (2MB)
2. Central Message Switch-CMS (A, B,C ,D)
Message Switch Controller Card (MSC)
Message Switch Device Card (MSD)
CALL PROCESSING
GENERAL CONCEPT
There are five function steps of call processing including the location of the originating
and terminating equipment. These steps are : -
Origination: - Origination begins when the subscriber line goes off hooker incoming trunks seized. It receives the incoming digits, selects the digit analysis tables, and determines the screening information for this call.
Digit Analysis: - It interprets the digits it receives from origination, select a destination for each call, and passes the dialed digits to routing.
Routing/Screening:- Routing uses the destination information from digit analysis and screening information origination to select the terminating trunk group or line.
Charging: - It uses the charging information from routing to expand the charging data into a format usable by call accounting process.
Termination: - The last step in call processing is termination. Termination Processor is different for calls destined for lines and call destined for trunks.
1 .Trunk termination: - A trunk member of the trunks group is selected based on a
predetermined pattern. After selection the digits are out pulsed to the distant office.
2. Line termination: - The line identified in routing is checked to determine the line has any
special features. Ringing is applied to the line if applicable or the special feature is activated.
SIGNALING
What is Signaling?
Signaling refers to the exchange of information between call components required to
provide and maintain service.
As users of the public Switched telephone network, we exchange signaling with network
element all the time. Examples of signaling between a telephone user and the telephone
network include. Dialing digits, providing dial tone, accessing a voice mailbox, sending a call
waiting tone, dialing *66(to retry a busy number), etc.
Signaling system 7 is means by which element of the telephone network exchange
information. Information is conveyed in the form of messages. Signaling System 7 messages can
convey information such as :
SS7 is characterized by high-speed packet data, and out-of-band signaling.
OUT OF BAND SIGNALING
Out-of-band signaling is signaling that does not take place over the same path as the
conversation.
We are used to thinking of signaling as being in-band. We hear dial tone, dial digits, and
hear ringing over the same channel on the same pair of wires. When the call completes, we talk
over the same path that was used for the signaling. Tradition telephony used to work in this way
as well. The signals to set up a call between one switch and another always took place over the
same trunk that would eventually carry the call. Signaling took the form of a series of multi
frequency (MF) tones, much like touch tone dialing between switches.
Out-of-band signaling information. This channel is called a signaling links are used to
carry all the necessary signaling messages between nodes. Thus, when a call is placed, the
dialed digits, trunk selected, and other pertinent information are sent between switches using
their signaling links, rather than the trunks which will ultimately carry the conversation. Today,
signaling links carry information at a rate of 56 or 64 kilobyte per second (kbps).
It is interesting to note that while SS7 is only used for signaling between network
elements, the ISDN D channel extends the concept of out-of-band signaling to the interface
between the subscriber and the switch. Win ISDN service, signaling that must be conveyed
between the user station and the local switch is carried on a separate digit channel called the D
channel. The voice or data which comprise the call is carried on one or more B channels.
Why Out-of-Band Signaling?
Out of-band signaling has several advantages that make it more desirable than tradition in-band signaling:
It allow for the transport of more data at higher speeds (56 kbps can carry data much faster than MF out pulsing)
It allow for signaling at any time in the entire duration of the call, not only at the beginning.
It enables signaling to network element to which there is no direct trunk connection.
BASIC OF SIGNALING SYSTEM # 7
Common channel Signaling System no.7 (i.e.,SS7 or C7) is a global standard for
telecommunication defined by the international Telecommunication Union(ITU),
Telecommunication Standardization Sector(ITU-T).The standard defines the procedures and
protocol by which network element in the public switched telephone network (PSTN)
exchange information over a digital signaling network to effect wireless(Cellular) and wire
line call setup, routing control. The ITU definition of SS7 allow for national variants such as
the American Nation Standards Institute (ANSI) and Bell Communication Research (bell
core) standards used in North America and the European Telecommunication Standards
Institute(ETSI) standard used in Europe. , signaling that must be conveyed between the user
station and the local switch is carried on a separate digit channel called the D channel. The
voice or data which comprise the call is carried on one or more channels.
The SS7 network and protocol are used for :
Basic call setup, management and tear down
Wireless service such s personal communications services (PCS), wireless
roaming, and mobile subscriber authentication.
Local number portability (LNP)
Toll-free(800/888) and toll(900) wire line services
Enhanced call features such as call forwarding, calling party name/number
display, and three-way calling
Efficient and secure worldwide telecommunication.
Signaling Links
SS7 messages are exchanged between element over 56 or 64 kilobit per second
(KBPS) bi-directional channels called signaling links. Signaling occurs out-of-band on
dedicated channels rather than in-band on voice channels. Compared to in band signaling
out-of-band signaling provides.
Faster call setup times(compared to in-band signaling using multifrequency (MF)
signaling tones)
More efficient use of voice circuits
Support for intelligent Network (IN) services which require signaling to network
element without voice trunks (e.g., database system)
Improved control over fraudulent network usage
Signaling Points
Each signaling point in the SS7 network is uniquely identified by a numeric point
code. Point codes are carried in signaling messages exchanged between signaling point to
identify the source and destination of each message
There are three kinds of signaling points in the SS7 network.
SSP(Service Switch Point)
STP (Signal Transfer Point)
SCP (Service Control Point)
SS7 Signaling Points
SSPs are switches that originate terminate, or tandem calls. An SSP sends signaling
message to other SSPs to setup, manage, and release voice circuit required to complete a
call. An SSP may also send a query message to a centralized database (an SCP) to determine
how to route a call (e.g., a toll-free 1-800/888 call in
North America). An SCP sends a response to the originating SSP containing the
routing number(s) associated with the dialed number. An alternate routing number may be
used by the SSP if the primary number is busy or the call is unanswered within a specified
time. Actual call features vary from network and form service to service.
Network traffic between signaling points may be routed via a packet switch called an
STP. An STP routes each incoming message to an outgoing signaling link based on routing
information contained in the SS& message. Because it act as a network hub, an STP provides
improved utilization of the SS7 Network by eliminating the need for direct links between
signaling points. An STP may perform global title translation, a procedure by which the
destination signaling point is determined from digits present in the signaling message (e..,
the dialed 800 number, calling card number, or mobile subscriber identification number).
An STP can also act as a “firewall” to screen SS7 messages exchanged with other networks.
Because the SS7 network is critical to call processing, SCPs and STPs are usually
deployed in mated pair configuration in separate physical location to ensure network-wide
service in the event of an isolated failure. Links between signaling points are also
provisioned in pairs. Traffic is shared across all links in the link set. If one of the links fails,
the signaling traffic is rerouted over another link in the link set. The SS7 protocol provides
both error correction and retransmission capabilities to allow continued service in the event
of signaling point or link failures. Network traffic between signaling points may be routed
via a packet switch called an STP. An STP routes each incoming message to an outgoing
signaling link based on routing information contained in the SS& message. An STP may
perform global title translation, a procedure by which the destination signaling point is
determined from digits present in the signaling message. .
SS7 Signaling Link Types
Signaling links are logically organized by link type ('A' through 'F') according to their uses in the
SS7 signaling network.
SS7 Signaling Links Types
A link: An “A”(access) link connects a signaling end point (e.g., an SCP or SSP) to an STP.
Only messages originating from or destined to the signaling end point are transmitted on a
“A” link.
B link: A “B” (bridge) link connects an STP to another STP.
Typically, a quad of “B” links interconnection peer(or primary) STPs (e.g., the STPs
from network to the STPs of another network). The distinction between a “b” link and a “D”
link is rather arbitrary. For this reason, such links may be referred to as “B/D” links.
C links : A “C”(cross) link connects STPs performing identical function into a mated pair. A 'C' link is used only when an STP has no other route available to a destination signaling point due to link failure(s). Note that SCPs may also be deployed in pair to improve reliability; unlike STP’s however mated SCPs are not interconnected by signaling links
D link: A “D” (diagonal) link connects a secondary (e.g., local or regional) STP pair to a primary
(e.g.; inter-network gateway) STP pair in a quad-link configuration. Secondary STPs within the
same network are connected via a quad of “d” links. The distinction between a “B” link and a
“D” link is rather arbitrary. For this reason, such links may be referred to as “B/D” links.
E links : An “E” (extended) links connects an SSP to an alternated STP.”E” links provide an
alternate signaling path if an SSP’s “home” STP cannot be reached via an “A” link. “E” links are
not usually provisioned unless the benefit of a marginally higher degree of reliability justifies
the added expense.
F link : An “F” (fully associated) link connects two signaling end points (i.e.,SSPs and SCPS). ”F”
links are not usually used in network with STPs. In network without STPs, “F” links directly
connect signaling points.
ISDN (INTEGRATED DIGITAL SERVICE NETWORK TERMINAL UNIT)
One of the four ATUs/DTUs in a Base module be replaced by ISTU to provide Basic Rate
Interface (BRI)/Primary Rate Interface in C-DOT DSS. It is directly connected to TSU on 8 Mbps PCM
Link.
INTRODUCTION
ISDN is comprised of digital telegraphy and data transport services offered by region
telephone carries ISDN involves the digitization of the telephone network which permits voice, data,
text, graphics ,music ,video and other source material to be transmitted over exiting telephone
wires. One of the four ATUs/DTUs in a Base module be replaced by ISTU to provide Basic Rate
Interface (BRI)/Primary Rate Interface in C-DOT DSS. It is directly connected to TSU on 8 Mbps PCM
Link The emergence of ISDN represent an efforts to standardize subscriber service user/network
interface and network and inter network capabilities.
ISDN application includes high speed image application , addition telephone lines in home to
serve the telecommuting industry, high speed file transfer and video conferencing. Voice service is
also an application for ISDN.
Architecture of ISDN Terminal Unit
In C-DOT DSS architecture the ISDN interface are terminated on a new add on terminal unit as
ISTU. A maximum of 256 bearer channels are provided by integrating one ISTU which can be
configured to support any combination of BRI or PRI interfaces. If the requirement of PRI/BRI
interfaces more than 256 bearer channels ,one or more. ISTU, can be integrated in C-DOT DSS with
the option of equipment them in the same BM of distributed across different BMs in the exchange.
The architecture also support in signaling providing time slots for switching channels, carrying
data & voice.
SERVICE
There are two types of services associated with ISDN:-
1. BRI
2. PRI
1. ISDN BRI Service
The ISDN Basic rate interface (BRI) Service offers Two B channels and one
D channels (2b+D). BRI B channels service operated at 64 Kbps and is carry user data. . ISTU, can be
integrated in C-DOT DSS with the option of equipment them in the same BM of distributed across
different BMs in the exchange.
BRI d channels service operates at 16 Kbps and is meant to carry control and signaling
information, although it support user data transmission under certain circumstances. The BRP also
provides for framing control and other overhead, bringing its total bit rate to 192 Kbps.
The BRI physical layer specification is International Telecommunication Standard Section
(ITU-T). (Formerly the consultative committee for international telegraph and telephone (CCITT)
2. ISDN PRI SERVICE
The ISDN traffic is of two distinct types:-
Circuit switched voice & data
Primary Rate Line (PRL)
Basic Rate Line (BRL) Card
The BRL is an interface to the switching system supporting 8 U-interface towards the user. It
interfaces with the ISDN Terminal Controller(ITC)/Switching Network for signaling and switching of
voice and packet information.
The function of the BRL card include HYBRID for 2 to 4 conversion and echo cancellation
monitoring of lines status, it’s activation and deactivation, over voltage protection (for protect the
exchange and the BRL card from high voltages),test access.
Primary Rate Interface Line Card(PRL)
The PRL Card is an interface to terminate a 2.048 Mbps link ,using symmetric twisted pair
cables with characteristic impedance of 120 ohms.
Each PRL card form a terminal group (TG) and a maximum of 8 PRL, cards can be
accommodation in each ISTU.
ISDN USER PART ( ISUP )
The ISDN User Part(ISUP) defines the protocol and Procedures used to set-up. Manage, and
release trunk circuit that carry voice and data calls over the public switched telephone
network(PSTN). ISUP is used for both ISDN and non-ISDN calls. Calls that originate and terminate at
the same switch do not use ISUP signaling.
Basic ISUP Call Control
1. When a call is placed to an out-of-switch number, the originating SSP transmits an ISUP initial
address message (IAM) to reserve an idle trunk circuit from the originating switch to the destination
switch:-
The IAM includes the originating point code, destination point code, circuit identification
code dialed digits and, optionally, the calling party number and name. In the example below,
the IAM is routed via the home STP of the originating switch to the destination switch
Note that the same signaling links are used for the duration of the call unless a link failure
condition forces a switch to use an alternate signaling link.
2. The destination switch examine the dialed number, determines that it serves the called party, and
that the line is available for ringing. The destination switch transmits an ISUP address complete
message (ACM) to the originating switch
(via its home STP) to indicate that the remote end of the trunk circuit has been reserved. The
destination switch rings the called party line and sends a ringing tone over the trunk of the
originating switch. The STP routes the ACM to the Originating switch.
which connects the calling party’s line trunk to complete the voice circuit from the calling
party to the called party. The calling party hears the ringing tone on the voice trunk.
In the example shown above, the originating and destination switches are directly
connected with trunks. If the originating and
Destination switches are not directly connected with trunks , the originating switch
transmits an IAM to reserve a trunk circuit to an intermediate switch. The intermediate switch sends
an ACM to acknowledge the circuit reservation request and then transmits an IAM to reserve a trunk
circuit to another switch.
This processes continues until all trunks required to complete the voice circuit from the
originating switch to the destination switch are reserved. The IAM includes the originating
point code, destination point code, circuit identification code dialed digits and, optionally,
the calling party number and name. In the example below, the IAM is routed via the home
STP of the originating switch to the destination switch
3. When the called party picks up the phone, the destination switch terminates the ringing tone and
transmits an ISUP answer message (ANM) to the originating switch via its home STP
The STP routes the ANM to the originating switch
Which verifies that the calling party’s line is connected to the reserved trunk and, if so,
initiates billing.
4. If the calling party hangs-up first, the originating switch sends and ISUP release message (REL) to
release the trunk circuit between the switch
The STP routes the REL to the destination switch
If the called party hangs up first, or if the line is busy, the destination switch sends an REL to
the originating switch indicating the release cause(e.g.; normal release or busy).
5. Upon receiving the REL, the destination switch disconnects the trunk from the called party’s line, sets
the trunk state to idle, and transmits an ISUP release comlete message (RLC) to the originating switch
To acknowledge the release of the remote end of the trunk circuit. When the originating switch
receives(or generated) the RLC
It terminates the billing cycle and sets the trunk state to idle in preparation for the next call.
ISUP message may also be transmitted during the connection phase of the call (i.e.; between the ISUP Answer (ANM) and Release (REL) messages.
ALARM DISPLAY PANEL (ADP)
The ADP is used in the C-DOT to display the status of the system in single base module
configuration. It can also be used with a two base module system.
The status is displayed on light emitting diodes (LEDs) and seven segment LED display.
Fresh faults are reported on the panel by blinking the LEDs accompanied by an audio alarm to
draw the attention of the operator in turn is expected to acknowledge the faults.
ADP is a microprocessor based hardware unit which is attached to the BP (in SBM) or
AP(IN MBM) by HDLC(HIGH DATA LINK CONTROLLER) link for providing audio visual indication
of system faults . a seven segment display shows the count of lines and trunks currently faulty.
ALARM PHILOSOPHY:-
In a C-DOT DSS, there are three categories :-
-non urgent => green LEDs.
-urgent => orange LEDs.
-critical => red LEDs.
FUNCTIONAL DESCRIPTION:-
The ADP is housed on three cards:-
1. Controller card.
2. Display card.
3. Power supply card.
1. Controller card:-
It is a subdivided into following blocks:-
(a) CPU LOGIC:-
It generates clock required by microprocessor, buffers for buffering for CPU address
and data bus power on reset logic to generate the signal.
(b) MEMORY:-
Occupies address space RAM.
(C) DISPLAY CARD INTERFACE:-
Consist of logic which generates the various strobes for the registers on the display
card
(D) INTERRUPT AND WATCHDOG DOG :-
The sources of interrupt for the CPU are :-
(i) Real time timer
(ii) Acknowledge switch
(iii) LED test switch
(iv) The two HDLCs.
The sources for generate one interrupt line for the microprocessor.
(E) INPUT /OUTPUT PORTS AND AUDIO ALARM :-
Input port is used to determine the configuration of the system and the source of the
interrupt. Output port is used for cleaning the various interrupts & for enabling the audio
alarm. The audio alarm is implemented using a piazza-electric buzzer
(f) COMMUNICATION INTERFACE:-
Consists of clock generator for the HDLs.
INTERCONNECTION
Various interconnection required in the ADP are as follows :-
1. Link connection: The two links from the two copies of BPs are terminated on the back panel.
2. Controller card to display card connection: This connection is made with a 34 pin flat cable
also carries the power for the display card .
SYSTEM CAPACITY
INTRODUCTION
The capacity of C-DOT DSS is defined in terms of the following parameters:
The termination capacity express as the number of lines and trunks
The amount of traffic (in elands) that can be switched
The number of Busy Hour Call Attempts (BHCA) that can be processed with a given call-mix while meeting the overall service quality requirements.
This section indicates the maximum capacity of different system element as well as that
of complete exchange, equipped to its ultimate termination capacity. It has been ensured that
the specified parameters are valid to meet overall reliability objectives for the C-DOT DSS as
specified in ITU-T recommendation.
TERMINATION CAPACITY
A terminal Card is the basic system element. It interfaces/terminates the lines and
trunks. The next higher element is a Terminal Unit. The types of terminal card and terminal unit
used in C-DOT DSS along with its function are already explained in chapter ‘3’ &’4’. Termination
capacity of BM is 488 analog lines and that of LM in 768 analog lines. A BM can be concentrated
with 2 LM’s to provide maximum termination capacity of 2024
Analog lines. In case of BM, a maximum of 256 B channels are provided at the cost of
512 analog lines. One to one replacement of Base channel is planned in immediate future. Base
Module and Line Module are the highest level of system elements. Each Base Module has four
Terminal Units whereas a Line Module has six Terminal Units. Because the SS7 network is
critical to call processing, SCPs and STPs are usually deployed in mated pair configuration in
separate physical location to ensure network-wide service in the event of an isolated failure.
Links between signaling points are also provisioned in pairs. Traffic is shared across all links in
the link set. If one of the links fails, the signaling traffic is rerouted over another link in the link
set. The SS7 protocol provides both error correction and retransmission capabilities to allow
continued service in the event of signaling point or link failures. Network traffic between
signaling points may be routed via a packet switch called an STP. An STP routes each incoming
message to an outgoing signaling link based on routing information contained in the SS&
message. One to one replacement of Base channel is planned in immediate future. Base
Module and Line Module are the highest level of system elements. Each Base Module has four
Terminal Units whereas a Line Module has six Terminal Units. Because the SS7 network is
critical to call processing, SCPs and STPs are usually deployed in mated pair configuration in
separate physical location to ensure network-wide service in the event of an isolated failure.
Links between signaling points are also provisioned in pairs. Traffic is shared across all links in
the link set.
Table summaries the termination capacities of the various system element of C-DOT DSS MAX.
S.NO. SYSTEM ELEMENT TERMINATIONCAPACITY
DESCRIPTION
1 TERMINATION CARD
1.1 Analog Line Card LCC-8 analog subscribers
CCM-8 CCB subscriber with
last two
ports supporting16 KHz
metering pulse
1.2 Analog Trunk Card TWT or EMF -8 Trunks
1.3 A set of DTS/DTC Cards One,2 Mbps E-1 link as
CAS/CSS7 trunks
1.4 #7 PHC Card (SHM) 8 Nos. protocol
handlers/signaling links
1.5 ISDN-BRI Cards 8BRI (2B+1D) interface I.e. 16
Bearer Channels
1.6 ISDN-PRI Cards One PRI (308+D) interface
I.e. 30 Bearer Channels
2 TERMINATION UNIT/FRAM
2.1 Analog TU (ATU) 16 analog terminal
cards(LCC,CCM,EMF,TWT)
to
support any combination of
lines and Trunks in
multiple of eight termination
2.2 Digital TU (DTU) 4 Nos. 2 MbpsE1 links
asCAS/CSS7
2.3 #7Signalling Unit Module
(SUM)
64 Nos; 37 protocol
handlers/signaling links
2.4 ISDN-Terminal Unit (ISTU) 256 Bearer channels to be
configured as BRI, PRI
or any combination of them.
3 BASE MODULE/RACK
3.1 Link Module(line) 480 analog subscribers. A
maximum 256 Bearer
Channels for ISDN interface
can be provided at the
EXCHANGE CONFIGURATION
C-DOT DSS MAX can be configured to support any combination of lines and trunks, for
different application in the network as local Exchange, Local cum Tandem Exchange. Trunks
Automatic Exchange(TAX) or Integrated Local cum Transit (ILT) Exchange.
In this maximum configuration, upto 40,000 lines and 5,500 trunks are supported when
configured as Local/Local cum Tandem. When configured as TAX. 14,500 trunks are supported.
Termination Capacity of Exchange Configuration
S. No. Exchange Configuration Termination Capacity Description1.
Single Base Module(SBM) 1500 lines and128 trunks. The trunks may be analog and/or digital. The no. of trunks can be increased at the cost of reducing subscribers.
2.
Multi Base Module (DSS-MAX)
(i) MAX-XL
Ideal configuration to support 40,000 lines and 5500 trunks with 20 line BMs and 12 Trunks BMs. The trunk capacity can be increased by 450 at the cost of 2,000 subscriber or vice versa
(ii) MAX-L Ideal configuration to support 20,000 lines and 2700 trunks with 10 line BMs and 6 Trunk BMs. The trunk capacity can be increased by 450 at the cost of2,000 subscriber and vice versa.
3. Remote Switching Unit (RSU) 2,000 Subscriber Lines. Trunk interface at the
cost of subscriber lines.
4 Multi Base Module TAX 14,500 Trunks
Note : Out of the total equipment capacity, a maximum of 30,000 Lines may be Remote
Subscriber through RSUs in MAX-XL whereas 14000 lines.
SOFTWARE ORGANIZATION
The software is written in high level language ‘C’ & distributed over various processors
and is structured as a hierarchy of virtual machines. The software features are implemented by
communication processes. The operating system provides communication facilities such that
the processes are transparent to heir physical locations.
Resource are identified as ‘global’ or ‘local’ depending upon their distribution in the
system. The resource which depends upon the number of terminal are provided within the basic
growth module. The basic module processor are provide for handling call processing locally. In a
small system application , these processor independently support call processing, exchange
operation and maintenance functions. Central facilities are also provided to avoid repetition of
large data & memory intensive functions.
E.g., Processor architecture is characterized by distributed control & message based communication in order to achieve a loosely-coupled network for a flexible system architecture.
ROLE OF SOFTWARE IN C-DOT DSS
INTRODUCTION
The main feature of the software architecture of DSS-MAX is as:
Distributed architecture to ma the distributed control architecture
Layered architecture with loosely coupled modules & well defined message interfaces.
Use of high level language
Modular design with each layer providing higher of abstraction
These feature help in to achieve the following objectives:
Simplicity in design
Increased reliability due to fault tolerant software
Flexibility with option of up gradation to add feature & service
Efficiency and strict time check
Ease of Maintainability
C-DOT DSS MAX Layered Software Architecture
SOFTWARE SUBSYSTEMS
The main subsystem of C-DOT DSS MAX are as :
C-DOT real Time operating system
Peripheral Processors subsystem
Maintenance subsystem
Database subsystem
Administration subsystem
IOP subsystem
Call Processing subsystem
HARDWARE
These subsystem are responsible for providing the following basic services:
1. CDOS :
It is the operating system & provides the following function :
Process management
Resource management
Interrupt handling
Online & offline debugging
2. Peripheral Processor subsystem :
It controls all the telephony software. It also carries out the commands given by the
Base Processor for generating suitable telephony events. Another function is to carry out all
the maintenance related test function on hardware. It consists of 8-bit microprocessors
programmed in assembly language
3. Call processing subsystem:
It receives the information about telephony event that occur outside the exchange. It
processing this incoming information & gives commands to the peripheral processors for
interconnecting subscriber through the switching network. A special feature is to generate
Exhaustive Call Event Record for every call.
4. Maintenance subsystem:
It provides the following function:
Initialization
System integrity
Switch maintenance
Terminal interface
Human interface
5. Administration subsystem:
It consist of traffic, billing exchange performance measurement & human interface
functions. It also provides online software patching capability. It is responsible for
maintaining a large number of traffic records on the basis of information received by it
through Call Event Records. Over 200 man-machine commands are provided for these
operations.
6. Database Subsystem:
It provides for the management of global data.
The main objectives are:
(a) Easy access
(b) Quick access
(c) Transparency
(d) Consistency
(e) Security
(f) Synchronization
BASIC SERVICE IN DSS MAX
The most important function of a DSS switch is to process subscriber calls. Subscribers’
call can be classified as line-to-line, line-to-trunk, and trunk-to-trunk. A lint-to-line is a call that
starts on a line served by a DSS switch and terminates to another line served by the same
switch. The BMs involved in the call will perform almost 95% of the total call processing
function.
During a line-to-line call, the origination BM detects when a subscriber’s telephone
receiver as been picked up. The BM provides the dial Tone and then removes the Dail
Tone when first digit is dialed. It then collects and analyzes the dialed digits. Next, the
BM sends a request to the AM for a call path. The terminating BM locates the subscriber line for
the line-to-line call and provides ringing.
When AM has selected an available path. It alerts the CM to set up link between the
BM’s. The CM provides call paths between BM’s and carries all internal system communications.
The function of BM, AM, and CM in trunk-to-trunk call are basically the same as line-to-
line call described above except that the originating BM detect a trunk seizure rather than a
subscriber picking up the receiver. Also, the terminating BM locates as available trunk instead of
line.
The above scenarios may differ slightly, if the call involves both and trunk.
Lint-to-Line call can be of two types:
INTRA_BM: When both subscriber lines connected to same BM. This doesn’t require
use of CM.
INTER_BM: When both subscriber lines are to different BMs. This requires use of the
CM.
OTHER SERVICE PROVIDED BY MAX
The MAX provides the following features apart from processing of a telephone call:
Number identification Service:
Calling Line Identification Presentation (CLIP): The Calling Party’s details are given to the
user along with the incoming calls.
Calling Line Identification Restriction(CLIR): With this service the calling party may
restrict presentation of it’s number to the called party.
Calling Line Identification Restriction Override (CLIRO): The subscriber with this facility
receives the details of the calling party even if it has asked for it’s restriction.
Malicious Call Identification (MCID): During conversation the subscriber can use a
procedure to identify the malicious caller.
Call offering supplementary Service:
Call Forwarding ?Unconditional(CFU)L It allows the user to forward all incoming calls
to another number.
Call Forwarding Busy(CFB): It allows the user to forward all incoming calls to another
number if the user’s number is not free.
Call Forwarding No Reply (CFNR): It allows user to forward all incoming calls to
another number if the user doesn’t respond in a fixed number of rings.
Call completion Services:
Call Waiting: A Subscriber engaged in a call, is given an indication that another caller is
trying to call him up. The user can then talk to a caller by keeping the other holding.
Call Hold: This allows the user to put th call into wait for the being and initiate or accept
a new call. The user can retrieve the call put on hold whenever required.
Multi Party Services:
Three Party Conference: It enables the user to establish, participate in and control a
simultaneous communication involving the user and two other parties. The served user
can disconnect one party, disconnect the three-way conference or communicate
privately with one of the parties.
Multi Party Conference: It allows uses to establish and control a conference involving at
the most 6 users. The conference controller may add, drop, isolate, and reattach parties
from the conferences.
Misc. Service:
Hot Line(Timed): It allows the subscriber to establish calls to a pre-registered number.
After getting the dial tone, if the subscriber doesn’t dial any number for a minimum
amount of time, then he is connected to the pre-registered number. If the subscriber
dials a number, then normal connection is established.
Hot line(Without Time-Out): As soon as the subscriber lift the handset, the call to the pre
–registered number is established. Normal outgoing calls can’t be made.
Reminder Call/Alarm Services: The subscriber can receive a call by the exchange at a
specified time. This service is available in two forms: (i) Semiautomatic Form ,where the
booking is manual through an operator, or (ii) Automatic Form, where booking is done
automatically, through a control procedure.
Subscriber Controlled Call Restriction Service : In this service; the user can deny all call at
a time deny various levels of originations from a line. Outgoing calls can also be
restricted by the mean of a password.
Instruction Barring Service: With this service a subscriber can enjoy an uninterrupted
call, e.g., in case of data transmission.
POWER PLANT OF C-DOT DSS MAX
From the power supply bus bar power is tapped through cables to each suite separately. In this there is five modules, each having 200amp. As input. In this, AC is input and DC is output.
In this input is between 340-475 V and output is 48V. There are two batteries if one is not conduct than other is used. These are connected together if both are disconnected than till 15-20 minutes power is supplied. From the rectifier, which derives 48V DC from 440V AC. Power cables are terminated on the DC distribution panel (DCDP). From the DCDP, power cables run along the cable runways and ladders and terminated on the power distribution panel(PDP). Distribution panel consists of two bus bars for –48V, one each for copy 0 and copy 1 equipment. Similarly there are two bus bars for ground.
For each base module cabinet, the power i.e.-48V is tapped twice one for each plane
through a fuse. Whenever the fuse blows off the LED, which is connected in parallel glows on
the FBI card, and an audio alarm is given at a centrally located point.
SUMMARY
C-DOT DSS is a modular and flexible Digital Switching System which provides economical means of serving metropolitan, urban and rural environment. It incorporated all important feature and mandatory service, required by the user with option of up gradation to add new features and service in future. The architecture for the C-DOT DSS is such that it is possible to upgrade a working C-DOT SBM or MBM exchange to provide ISDN service by adding minimum addition hardware modules while retaining existing hardware units.
C-DOT DSS MAX is a universal digital switch which can be Configured for different application as local, transit, or integrated local and transit switch. The design of C-DOT DSS MAX has envisaged a family concept. The advantages of family concept are standardized components, commonality in hardware, documentation, training, installation and field support for all product and minimization of inventory of spares. Infact this Modular design has been consciously achieved by employing appropriate hardware, software, and equipment practices.
Software is written in high level language ‘C’ and distributed over various processor and is structured as a hierarchy of virtual machines. It can be distributed over appropriate controllers. The Software failures are implemented by communicating processes.
REFERENCES
C-DOT Library
C-DOT DSS MAX General Description
www.cdot.com
A Book Digital Switching System by Saied Ali