MAHANAGAR TELEPHONE NIGAM Ltd.(MTNL)MAHANAGAR TELEPHONE NIGAM Ltd.(MTNL)

MTNL(Mahanagar Telephone Nigam Ltd.) was constituted in the year April,1986. Previously it was a government organisation under the department of Telecommunication.

The basic of MTNL is to provide best and fault free telephone services to the subscribers so that they are satisfied with what they get.

MTNL is fast emerging as a global giant in the telecom sector in its

endeavour to provide world class telecom services, MTNL is equipping itself with the ‘state-of-art’ machines and acquiring the latest gadgets to achieve the target of office automation.

MTNL is pioneering the introduction of information technology in the telecom-sector through human resource development, capacity building, computerization of consumer services like telephone directory, integrated computer networks, computer based scanning and signature recognition of subscribers, internet and customer service management etc.

The perceived threat of the Y2K problem was addressed effectively on a war footing. In addition, the Information Technology Division of MTNL is constantly keeping at bay hackers and attacks from viruses such as the recent “ I LOVE YOU ” bug.

For an organisation like MTNL, the customer support services like billing, Directory Enquiry, IVRS, FRS, commercial etc. are very important. It plays an important role in the implementation of these support services. Directory enquiry service is an essential customer care service being provided by telecommunication service provider, It helps the customers to find out the whereabouts of their associates. It comes to their rescue in times of emergencies. MTNL New Delhi is regularly updating telephone directory on CDROM. For national directory services also, MTNL was the first to integrate and start the service. Presently directory enquiry services system is being accused by nearly 250 cities of India.

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HISTORICAL DEVELOPMENT OF DELHI HISTORICAL DEVELOPMENT OF DELHI TELEPHONESTELEPHONES

1911 : Establishment of Delhi Telephones system with manual exchange

1926 : Opening of first automatic exchange (Lothian Exchange) 1972 : X-Bar (31) Janpath-1 exchange commissioned. Delhi

telephone crosses 1 lac lines 1973 : Opening of X-Bar (67) Chanakya Puri exchange. 1975 : X-Bar Janpath-IV (34) exchange commissioned. X- Bar

Shahdara East (20) exchange commissioned. 1976 : Shakti Nagar (74) exchange commissioned. Idgah-II (52)

X-Bar exchange inaugurated by Fakhuruddin Ali Ahmed, President of India, on 28.8.76 and presided over by Mr. S.D. Sharma (Minister of communications). Opening of Shahdara East (20) Extension-I, X-Bar exchange on 31.8.76. It was inaugurated by Mr. H.K.L. Bhagat (Minister of State for Works and Housing) and Mr. S.D. Sharma (Minister of communications). Opening of Hauz Khas (65) X-Bar exchange on 18.10.76

1991-92:Commissioning of gross switching capacity of 1,18,000 lines. Interactive graphics system (IGS) for computerization of outdoor network plant installed. I-NET services installed.

1992-93: 83,558 new telephone connections provided. Morning wake up call facility introduced free to all electronic exchange customers. Voice Mail Services introduced.

1993-94: Commissioning of gross switching capacity of 1,69,250 lines out of which 100500 lines of new technology. Waiting list under OYT & Special category made current in most areas.

1994-95: Record commission of gross switching capacity of 226000 lines.

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1995-96 : Record commission of gross switching capacity 323200 lines. Automatic Changed Number Announcement Service 1951/1952 using Interactive Voice Response System (IVRS) introduced. Fault Repair Service of all major exchanges computerized. Multimedia center with video conferencing facility opened.

1996-97 : Commissioning of gross switching capacity of 241028 lines and provision of 203100 lines in one year which is an all-time high. The waiting list almost completed except few pockets. ISDN services introduced commercially.

1997 : Wireless in local loop (WILL) phone system introduced.

SERVICES BY MTNLSERVICES BY MTNL

CUSTOMER SERVICE CENTER (CSC)

The various service centers provided are as follows :

Area Customer Service Centers {Located at the headquarters of the Area General Manager}

Sub-Area Customer Service Centers {Located at the office of Dy.General Manager of the respective

division} Divisional Customer Service Centers

{Located at the office of the Divisional Engineer(Outdoor)of the respective division}

Mobile Customer Service Centers

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CUSTOMER SERVICE MANAGEMENT SYSTEM (CSMS)

A fully computerized single window facility for all telephone related work, covering from registration of new phones to billing services and fault repair services.

I. Computerized booking of complaint 198/2198II. Helpline serviceIII. Voice Mail Fault Repair Service(VMFRS)

DIRECTORY INFORMATION SERVICES

I. Computerized Directory EnquiryII. On-line Directory Information ServiceIII. Directory Dial up ServiceIV. Directory service for I-NET SubscribersV. Know your billing cycle/bill date

VOLUNTARY DEPOSIT SCHEME(VDS)

Under this scheme, the customer may make an advance deposit to MTNL based on his average billing and this deposit will be adjusted in the future telephone bills.

INTELLIGENT NETWORK

Intelligent Network Service( IN-Service ) e.g. free phone, premium rate service, tele voting, virtual private network, universal access network and Virtual Calling Card or Account Calling Card.

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Virtual Calling Card This service allows customers to make a call from any tone telephone in the networks of Delhi and Mumbai to any destination-local, national or international even if the telephone from where the

call is made is without STD facility.

Account Calling Card This service also provides the same facility as VCC. As in the case of VCC, here also there is no need of a telephone connection.

HOTLINE

For instant connection to your most often called number this facility is quite useful. With this facility one can connect the phone to any one pre-determined number.

CALL FORWARDING/ CALL TRANSFER

With this facility, incoming calls can be forwarded to any other telephone number within the same local area by availing this facility.

TELEPHONE SERVICES

Voice Plain old telephone services through distinguished Public Switched Telephone Network with variety of phones plus services and direct-in-dialing facility of PABXs connected to the PSTN.

Dolphin Cellular services provided by MTNL.

Garuda Wireless in Local loop (WLL) : Service offered are both in fixed mode as well as portable mode (mobile).

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ISP (INTERNET SERVICE PROVIDER)

Various features of internet service provided are as follows :

I. Single access numberII. Faster accessIII. Uninterrupted serviceIV. E-commerceV. Online telephone directory( www.mtnl.net.in|)VI. Hourly News updateVII. Login package CDs available for 199/250/500 hoursVIII.No registration charges

ATM SERVICES CUSTOMER CARE SERVICES

I. New telephone registration, bill payment and complaint registration through internet

II. Smart Card for payphoneIII. Meditation Billing Customer Care in GSM MobileIV. Data Ware HousingV. Call Center

VOICE MAIL SERVICES

I-NET

Data Service through X.25 based Packet Switched Public Data Network is called I-NET.

ISDN 6

Integrated Service Digital Network (ISDN) to meet the requirements of customer for data, voice and video on one line, both in Basic Rate Access(64 kbps) and Primary Rate Access(2Mbps).

OTHER SERVICES OFFERED BY MTNL TO THE SUBSCRIBERS

I. Telax-operational on local and international levelII. Leased LineIII. Telephone directory of MTNL is available on CD-ROM as

well as on the internetIV. Single window computerized customer service centers

introduced to provide solution to all telephone related mattersV. Introduction of electronic bill clearence scheme : Bill

presentment and online electronic bill payment of telephone bills by MTNL subscribers implemented for Delhi subscribers.

VI. Call Waiting : 118 (Activation)VII. Abbreviation Dialing : 110+directory no.+xxVIII.Call Diversion : 114+Telephone no.(Activation) 115+ Telephone no. (Deactivation)IX. Morning Alarm : 116 (Activation), 117 (Cancellation)X. Dynamic Lock : 123-abcd-abcd (Registration) 124-abcd-1 (Lock) 124-abcd-3 (Open)XI. Absent Subscriber (Abs)XII. Caller Line Identification

XIII.Hotline

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TELEPHONIC COMMUNICATION TELEPHONIC COMMUNICATION

Telephony is the branch of line communication which deals with the transmission of spoken message. Telephony is the most widely used and common for telecommunication. Speech from one subscriber is converted into electrical signals in the telephone instrument which are transmitted over wires to the telephone exchange for being conveyed to another subscriber’s instrument where the electrical signals are converted back into sound energy. The telephone exchange serves the essential purpose of interconnecting different subscribers.

TELEPHONE

A Telephone is a device which transmits and receives speech at a distance. The conversion between two speakers across a distance is due to the sound waves carried by the intervening medium that is air these sound waves are generated by the human voice. When these waves exert pressure on the diaphragm of the human ear, he receives the speech, although the audio frequencies range from 16 to 20,000Hz , a human voice or a musical instrument does not always produce all these frequencies. On the other hand they generate much narrower band of frequencies.

TELEPHONE TRANSMITTER

It is a transducer converting sound energy into electrical energy. The type of transmitter most widely used in telephone hand-sets of today is the carbon granule transmitter. It consists of a carbon granule chamber within which there are two carbon electrodes F and M. One of them that is F is fixed and the other that is M is movable along the conical diaphragm D.

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When the diaphragm moves to and fro due to the impinging sound waves, the pressure on the carbon granule varies.The electrical resistance offered by the carbon granule varies according to the pressure and the current in an external circuit having these carbon

granules as variable will vary.

TELEPHONE RECEIVER

This does the reverse function of a transmitter. It is a transducer which converts electrical energy into sound energy. The coming voice frequency current passes through a coil producing magnetic flux in the magnetic path consisting the iron path of the permanent magnet, the pole pieces and the diaphragm.

SYSTEM FUNCTIONING

The function of the whole system (connection between subscriber and the exchange) is quite simple. Two or more telephone exchange can also communicate with each other by sing optical fibre cables(OFC), this method adopts in such a case when the subscribers communicate indirectly to the another exchange. Suppose an exchange have the capacity of five thousands subscriber but there is more than five thousand subscribers under that exchange so in that condition this exchange communicates with other one. Other many conditions are also used for communication links of exchanges which is not described here.

Another essential component required for transmission and reception of speech of a system is the dial. The dial is used to send specific impulses over the subscriber line, when the subscriber lifts his hand-set, the dc loop between subscriber and the exchange is closed and steady current flows through the loop. The impulsing spring of the dial which is connected in series with the line breaks the loops as many times as the number is dialed.

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The two contacts doc1 and doc2 are called dial of normal contacts and close as soon as the finger plate of the dial is displaced from its normal position. When impulses are being sent by successive closing and opening of the impulsing spring s-1 contacts doc1 and doc2 are in closed position and the loop current flows through these contacts, the bell, the transmitter and the receiver all remaining shunted.

NETWORKS

Networks play an important role to run, connect and communicate between exchanges or subscribers. In the telephone departments, there are these networks as given below:

I. Cable NetworkII. Transmission NetworkIII. Switching Network

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SUBSCRIBER LINE SUBSCRIBER LINE

CONFIGURATIONCONFIGURATION

SUBSCRIBER LINE CONFIGURATION is divided into two parts :

Outdoor Part It further consists of :

I. TelephoneII. Distribution Point (D.P.) - 10/20 pairIII. Cabinet

Indoor Part

It further consists of :

I. Main Distribution Frame (MDF)II. Switch Room

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SWITCHING SYSTEMSSWITCHING SYSTEMS

There are many switching systems used such as :

MEC X BAR FETAX SPC E10B C-DOT OCB 283 CDMA EWSD 5ESS

FETAX, SPC, E10B, OCB 283 are based on FRANCE technology.C-DOT is based on INDIAN technology.CDMA used in mobiles is based on CHINESE technology.EWSD is a SIEMENS make.5ESS is an AT&T (Bell Lab. USA) make.

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5ESS SWITCH5ESS SWITCH

“5ESS” stands for :

5 : 5th generation product as assigned by LUCENT TECHNOLOGY

E : Electronic S : Switching S : System

The 5ESS switch is a digital exchange that can serve as a local(lines), toll(trunks), tandem(lines and trunks) or international gateway exchange depending upon the type of switch. It can serve a small community with fewer than 100 subscribers or large metropolitan area more than 100,000 subscribers.

The 5ESS switch is the most flexible digital exchange for use in the global switching network. It switches ISDN voice and data, local voice and long distance calls, internet access, wireless PCS, advanced intelligent network services, interactive video and multimedia services--- moving any kind of traffic(voice, data, video) on the public switched telephone network(PSTN). For service providers who need packet technology, the 7R/E Packet Driver converts your 5ESS Switch into a packet switch. The 5ESS Switch can transform your network into a multi-functional network, meeting your needs as well as those of your residential and business subscribers. The 5ESS is a digital switching system with distributed processing. Distributed processing means that multiple processors handle all call processing functions.

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Many processors are distributed throughout to handle second-to –second decisions that must be made to process a call.Call processing, self-maintenance and testing are performed independently in each module. Processors communicate with each other via an internal digital network that links the module together.

5ESS ACCESS TANDEM SWITCH

A high-capacity, high speed trunk switch that provides communication links between multiple regions and networks. It stores sufficient routing data to access a particular switch in another service provider’s network and vice-versa. Eliminating the need for each end office to store routing information provides faster call transfer, results in administrative cost savings and gains access charge revenues.

The Tandem Switch is a high capacity, high speed switch that connects geographically dispersed networks. Local end office switches are linked to each other via access tandem switches. Each access tandem switch aggregates voice and data calls from several local switches, then connects to a tandem switch in another area’s network to move calls from one region to another. Typically, the tandem switch receives toll traffic and uses its trunks to process and route the traffic to and from another service provider’s end office switch.

Tandem switches have only trunks, not lines, which allow faster call transfer nationwide. This multi-use, flexible switch eliminates the need for each end office switch to store multitudes of routing information, provides faster call transfer and results in cost savings as well as gaining regulatory access charge revenues.

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5ESS SWITCH HARDWARE

The 5ESS Switch hardware is subdivided into three major types of equipment modules with each of them involved in varying degrees in setting up and tearing down of every call :

Switching Module (SM) It connects the customer. Communication Module (CM)

It provides a path for control and data messages.

Administrative Module (AM) It collects the call completion data for engineering and billing.

Each module performs the assigned functions that contribute to the total operation of the 4ESS switch. The SM connects all the lines and trunks to the 5ESS switch. It performs the call processing functions. There can be many SMs per 5ESS switch. The CM provides communication between SM and AM. There is one CM per 5ESS switch.

M O D U L A R D I S T R I B U T E D D E S I G N

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AM

SM SMCM

NCT links

DSCH

NCT links

SM

FEATURES OF 5ESS SWITCH

High Reliability The 5ESS switch has the latest amount of downtime of any switch in its class, according to analysis of the latest U.S. FCC quality reports. The reports reveal that among four major switch vendors, the 5ESS switch is in four standard performance categories and set new in two key areas.

Multiple Applications The 5ESS switch is the only switch in the market today that can deliver any media of the same switch. The 5ESS can deploy all types and combinations of services from a single platform including wireline, wireless, voice and data. Together with the 7R/E Packet Driver, the 5ESS switch integrates IP/ATM networks and circuit switching. Therefore, service providers can offer the latest data services by building on their current switch investment.

Modular Design This feature distinguishes the 5ESS switch from all others because its intelligence is distributed into modules. This unique architecture allows growth in increments simply by adding modules, which can be dedicated to specific services, such as long distance and data services. Therefore, adding new services when and where the service provider needs them becomes quick and easy. Also, remote switch modules can be located upto 600 miles from the host switch, making it easy to enter new categories. Basically, the switch supports any network strategy without locking the service provider into a specific future and without interrupting current services.

Market Leadership With an embedded base of more than 108 million lines and 48 million trunks served by 4000 host switches in more than 52 countries. The 5ESS switch product family includes a range of switches in varying sizes to meet diverse communication needs. The

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5ESS switch is a market leader. A full-sized as the most reliable 5ESS switch serves upto 250,000 subscriber lines and over 100,000 trunk lines, with the flexibility to meet the most diverse business needs.

5ESS Supports Wireless The 5ESS switch continues Lucent Technology’s leadership role in the wireless area providing advanced wireless services such as FDMA/TDMA/CDMA on the 5ESS Switch Very Compact Digital Exchange (VCDX). This low cost service application eliminates the “pops and clicks” of call hand-offs between cells over a large geographic areas. It improves billing for cellular customers to increase revenue and improve customer satisfaction and offers multiple grades of service to provide pricing flexibility for targeting different customers in the wireless market.

5ESS Switch Configurations Several switch configurations are available to serve differing networking functions and needs. The 5ESS switch innovative modular design assures network operators of complete flexibility in planning switch deployment and network growth.

BENEFITS OF 5ESS SWITCH

I. The only media switch in the market today providing wireless, wireline, voice and data on a single platform.

II. A high density switch, reducing floor space requirements and power consumption.

III. A high capacity switch allowing fewer layers in the network providing network efficiency and reduced operational costs

IV. #1 in reliability according to U.S. FCC Automatic Reporting Management and Information (ARMIS) Report

V. Capable of evolving to the 7R/E Packet Solutions.

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5ESS SWITCH APPLICATIONS

Current applications supported by the system are as follows :

I. Local ExchangeII. Toll ExchangeIII. Gateway ExchangeIV. OSPS (Operator Service Position System)V. ISDN (Integrated Services Digital Network)VI. STP (Signaling Transfer Point) VII. SSP (Services Switching Point or Action Control Point)VIII.MSC (Mobile Switching Center or Wireless)

Local Exchange Local subscribers gain access to the local exchange through lines. The exchange switches a call from an internal subscriber to another subscriber directly or through a trunk circuit to a subscriber in another exchange. A trunk circuit (or trunk) connects a local exchange to a local exchange or a toll exchange. A local exchange has high percentage of lines and a small percentage of trunks.

Toll Exchange A Toll Exchange or Trunk tandem Exchange connects a local exchange

to another local exchange or to a gateway exchange. A Toll exchange has high percentage of trunks but low percentage of lines, if any.

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Gateway Exchange

There is one international network consisting of interconnected gateway exchanges. Each country (A and B) in this network has its own gateway exchange, an international toll exchange. International calls enter or leave the country from this exchange.

Operator Service Position System The 5ESS-2000 offers automatic operator services via the OSPS. OSPS applications are directory enquiry to supply directory numbers to calling subscriber. Traffic Assistance allows operators to complete calls and respond to enquiries for subscriber. The OSPS uses a special SM called PSM (Position Switching Module).

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T O L L L O C A L

G W 2

G W 1

L O C A L

Integrated Service Digital Network Another type of 5ESS-2000 switch application is the ISDN. It offers new voice and data services and allows features such as OSPS. It also allows voice, data and signaling information to travel over the same digital subscriber line. It lets all three components use the same transmission path simultaneously.

Two people with ISDN can make phone calls and use their computer terminals to access one or more computers at the same time. ISDN service is fully compatible with POTS service. ISDN service requires specific ISDN hardware and software in the SM.

Signaling Transfer Point The STP is an exchange application that sends signaling message on the way to the proper destination over a different path than voice circuit. TPs are associated with the CSS7 (common channel signaling 7) network. This application allows for more efficient use of trunk circuits.

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Service Switch Point The SSP, also called ACP (action control panel) is a 5ESS-2000 switch application that is a part of IN (intelligent network) configuration. IN technology allows the introduction of advanced services, primarily through software updates, with minimal network rearrangements and minimal service disruption. The SSP is able to recognize the incoming IN calls, process them or request call handling instructions by use of a remote database that is accessed by many switches in the IN.

Mobile Switching Center The MSC (Mobile Switching Center) perform the switching function for wireless systems. This 5ESS-2000 switch application monitors subscriber mobility manages resources, communicates with other networks, performs call routing and control functions. The MSC configuration includes the AM, CM, SMs, WGSM (wireless global switching module), at least one WSM (wireless switching module) and possibly a WRSM (wireless remote switching module) or multimodule.

GROWTH AND DEGROWTH

Modular architecture makes it easy to increase or decrease the capacity of the exchange. Increase in the capacity of the switch is called growth. Decrease in the capacity of the switch is called degrowth. The SM is the primary module for growth and degrowth is accomplished by changing the number of SM in a switch or the number of units within the SM.

SWITCHING MODULE SWITCHING MODULE 21

The primary job of the switching module is to connect subscriber lines and inter-office trunks to the 5ESS switch. A switching module is a multi-unit component and is located in a variable number of cabinets. The switching modules are available in two models :

SM configuration Each SM contains a duplicated MCTSI, duplicated DLIs and two LDSU DSUs. All other hardware components are configured according to office requirements.

SM-2000 configuration Each SM-2000 contains a duplicated MCTSI, duplicated NLIs and LDSF DSCs. All other hardware components are configured according to office requirements which can handle more calls with less equipment.

Switching Module(SM) is the most essential and vital part of a switching system. Originally SMs were called IMs (Interface Modules). With in a switch it performs the 90% of all the call processing functions as well as the circuit maintenance functions. The main function which constitute the process of call processing are :

I. Line scanning for tone originationsII. Dial tone generationIII. Digit collection and analysisIV. Call supervision

An SM terminates analog lines, analog trunks and digital trunks and lines. Within the switch architecture, SMs perform the time division switching functions. SM communicates with the AM for maintenance purpose or for obtaining routing information.

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TYPES OF SM

LSM (Local Switching Module) This type of SM serves local lines & ISDN users. The LSM is usually referred as SM.

HSM (Host Switching Module) This type of SM provides normal LSM subscriber interfaces and also one or more RSMs (Remote Switching Module).

RSM (Remote Switching Module)

This type of SM is designed to meet the needs of those communities that are too small to be served by their own 5ESS switch in a remote area. This can be done by having the RSM connected to a HSM. This HSM can be far away as 242km. From host upto 4 RSMs, called a MMRSM (Multi mode RSM), can be interconnected to serve.

PSM (Position Switching Module) This type of SM supports OSPS features.

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SM COMPONENTS

HERE : SMP – It is used for processing the calls. TSI – Time Slot Interchanger. LDSU – Local Digital Service Unit. GDSU – Global Digital Service Unit. PSU – Packet Switch Unit.

SM can be broadly classified into two categories :

SMC LTP

The three main functional areas that exist in an SM are :

I. Interface UnitII. Control UnitIII. Service Unit

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CONTROL UNITS

MCTSI

SMP TSI

AIU

PSU

SERVICE UNITS

DIU

TSI TSI

LDSU GDSU

DSU 2

TSI TSI

SM INTERFACE UNITS

The interface units interface the telephone lines with the system. There are various types of interfaces needed to convert the telephone signaling systems into the format of the internal digit format needed by the exchange. Interface units exist for all the types of analog and digital lines and trunks, as well as for transmission systems between central offices. Every setup of a speech connection is started with detection in one of the interface units. Each interface unit has circuits that are developed for a particular type of signaling. After converting these signal into internal format of the exchange it transmits them to control unit which acts on them and make a connection from the interface unit to the service unit. In the service unit, tone detectors and tone generators are present. Detected tones are decoded and then the decoded value is transmitted to the control unit. Upon command from the control unit, call processing and signaling tones can be generated (by the LDSU) and transmitted to the interface units. In this way, the control unit receives the information for digit analysis and is able to respond according to the signaling type.

There are various types of SM interface units which are as follows :

Line Unit It is the interface to the analog subscribers of various signaling types. The concentration ratio can vary from 4:1 to 10:1 depending on how the line units are equipped. The speech output per line is 64 time slots which enables a line unit to interface a maximum of 640 subscribers (10:1). A line unit is divided into two service groups, each processing 32 of the 64 time slots output by the line unit. It ensures that if an error has occurred in one service group then only maximum 32 calls within a line unit will be affected.

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Integrated Service Line Unit-version 2 (ISLU2) This interface unit is designed to meet the ITU-T requirements for an ISDN. It can interface with both analog as well as digital subscriber lines. The digital interface includes the U-DSL (digital subscriber lines). An ISLU2 can upto a maximum of 1024 analog and digital lines.

A version of ISLU2 is RISLU2 (Remote ISLU) which may be located on the subscriber’s premises when a large number of lines are to be interfaced from the same location. Since it is capable of performing line concentration, it can be used as pair gain system. It’s an economical way for remote units.

Analog Trunk Unit It is an interface unit to the analog trunks. In this unit after conversion to the internal format of the exchange, the trunk traffic is transmitted to the control unit without any concentration factor. Since the trunk unit has 64 time slots available, every trunk unit can interfere with 64 analog trunks. These are grouped in pair of 32-32 trunks each. An error would affect a service group of trunks maximum.

Digital Line Trunk Unit (DLU) It is the interface unit to the digital trunks. A DLU is equipped with DFI (digital facility interface) circuits. With a 30 channel digital inter-exchange transmission facilities, each DFI can interface with a digital link carrying 30 data channels plus 2 signaling channels. In case of common channel signaling (CCS) DFI can interface with a digital transmission facility carrying 31 data channel and 1 signaling channel.

Any combinations of interface unit may be installed as long as the capacity of standard control unit of SM200 is not exceeded. The signaling requirements of the interface units are handled under the control of the switching module control unit.All these interfaces support the signaling specifications from ITU-T.

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SM CONTROL UNITS

The control units control the operation of the SM and perform the time switching of a speech sample. A speech sample can be switched either between two subscribers connected to the same switching module or between two subscribers on different SM2000’s via the CM. The control units are fully duplicated in an active/standby configuration. Both of them receive the output signals of interface units, but the response of only active mode is acknowledged.

SM Control Unit & SMC Cabinet

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A control unit is based on the following components :

Module Controller Time Slot Interchanger (MCTSI) This is made up of sub-components like Switching Module Processor Unit (SMPU), Time Slot Interchanger Unit (TSIU) etc.

The primary jobs of the SMPU are :

I. Controls call processing activities for the peripheral units in the switching module.

II. Handles maintenance activities for the switching module.III. Monitors and reports all switching module activities to the

AM to generate hardware status reportsIV. Handles subscriber data and control messages from the

switching module peripherals and CM.V. Performs a “bootstrapper function” which enables the 5ESS

switch to rapidly reload memory in the SMP.

Network Link Interface (NLI) The Network Link Interface (NLI) is a one paddle board component. The NLI is located in the backplane of the TSIU shelf in an SMC cabinet of an SM-2000. The main functions of NLI are :

I. Connect MCTSI to the Time Multiplexed Switch (TMS) part of CM.

II. Convert subscriber data and control messages.

Dual Link Interface The Dual Link Interface (DLI) is a one circuit pack component.The DLI is located in the MCTU shelf of the SMC cabinet of a SM. The primary job of the DLI is to connect the MCTSI to the TMS.

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Apart from the above main components of Control Unit, RSMs contain :

Facility Interface Unit It is located in shelf of RSM and contains components, the remote link interface. The primary jab of the RLI is to transmit subscriber data and control messages between a SM at a host site and a SM at a remote site. It also generates clock pulses for the RSM when the RSM is operating in a stand alone mode.

Remote Clock Unit (RCLKU) It has the following sub-parts :

I. RCLK Oscillator :During a normal operation state, the RCLK oscillator provides a synchronizer with a source to remove jitter from the clock pulses that are received from the SM at the host site. During isolation from the host office the RCLK oscillator generates clock pulses for the RSM.

II. RCLK Synchronizer :During a normal operation state the RCLK synchronizer removes jitter from the clock pulses.

SM SERVICE UNITS

Service Unit performs all tone detection and generation functions. Service Unit also provides test functions and call processing function such as three-party or six-party conferencing. It is composed of following sub-units :

Packet Switch Unit The Packet Switch Unit Model 2 (PSU2) is a one to five shelf unit. The PSU2 is located in an LTP cabinet of a SM. The primary job of the PSU2 is to route packets of control messages & subscriber

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data to ISDN lines & C7 signaling trunks. The C7 signals are used to provide a path to set up and tear down trunk calls.

Service Announcement System

It provides general recorder announcements like “The following number has been changed ” or “ This number does not exists ” and others.

Global Digital Service Function The Global Digital Service Function is a one circuit pack component. The GDSF is located in SMPU or DSU shelf of a SM-2000 cabinet, or CSU shelf of a SM cabinet. It receives and control message from MCTSI through PICB and tone generation and analysis through PIDB.

The primary job of the GDSF are :

I. Perform three and six port conference callingII. Perform transmission testIII. Perform integrated system testIV. Generate an measure various tones to test POTS and ISDN

subscriber lines and trunks

Global Digital Service Unit The Global Digital Service Unit is a multi-circuit pack component. The GDSU is located in a cabinet of SM. The primary jobs of the GDSU are to :

I. Perform three to six user conferencingII. Perform transmission tests on subscriber loops and trunks

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Local Digital Service Unit (LDSU) It is one of the important parts of service unit which is connected through PICB to Control Interface (CI ) of MCTSI and through LDSUB to Data Interface (DI). Through PICB transmission of control messages occur to the SMP and through LDSUB tones are send and receive the TSI.

The functions of LDSU are :

I. Generates call processing tones for digit and call progress alerts in an SM.

II. Decodes call processing tones for routing calls in an SM.

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COMMUNICATION MODULECOMMUNICATION MODULE

Communication Module performs several critical functions within 5ESS switch. It provides the space switching of data type slots between SMs. It switched control line slots between SMs and between AM and SMs. The CM contains part of hardware needed to fast pump an SM. Finally, because it is switching hub of the system the CM contains the NCLK network clock and distributes timing signal to all switch units.

COMMUNICATION MODULE CABINET

CM configurations depend on the number of equipped SMs. The CM consists of two cabinets. The CM uses duplex controllers side 0 and 1. The CM operates in an active / standby configuration. Both sides of the CM receive the same inputs, and output the same information; however, only information from active is accepted at

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SM

CM

TMS

TMS

NC

MI

ONTC

MMP

MMP

MMP

MMP

MSC

MSGS

SM

DLI

NCT LINKS

FUSE / FILTER

GROWTH

MESSAGESWITCH

PERIPHERALUNIT MODEL 3

MESSAGESWITCH

CONTROLUNIT MODEL 2

TMSU 2

CMCU

TMSU 2

FAM UNIT

BAY 06

the destination. Switching between the active and standby controllers is under the control of AM. The CM can perform limited self maintenance routines; overall control operations are provided by AM.

The basic two cabinet configuration can handle a maximum of 30 SMs or 32 SMs with a combination of SMs and RSMs with atleast 2 being RSMs. Each SM has 2 NCT links connected to each side of CM.

COMMUNICATION MODULE SUB-UNITS

CM 05 CM 06

MSPU MSPU

MSCU MSCU

TMSU TMSU

CMCU CMCU

TMSU TMSU

SIDE 0 SIDE 1

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TMSU’sTMS

CMCU

NCT LINKS

MSPU’S

MSCU

AM

MSGS

COMMUNICATION MODULE CONTROL UNIT (CMCU)

There are four CMCU sub-units :

I. TMC (Time Multiplexed Switch Controller)II. DMI (Dual Message Interface)III. NCLK (Network Clock)IV. E-BUS UNIT

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CDAL CONTROL

MIBDATA

MIBDATA

L II NN TK E

RFACE

FABRIC

#

FAB CONTROL

SUB

SM1 1

TMSUTO E-BUS

CMCU

SM2 1

TO E - BUS

CONTROLTIME

SLOTS

DM1

TMC

NCLK

CONTROL

MMP

MMP

MMP

MMP

TO MSCU

TO MSCU

CDAL

Time Multiplexed Switch controller (TMC) The TMC controls the TMSUs. Using information received from the AM, the TMC configures the switching fabric path on a time slot by slot basis. The TMC also monitors the interrupts from each of the TMSUs and reports these error indicators to the AM. Finally, the TMC has the ability to perform low level maintenance activity such as generating data test pattern on the serial address or data stream to the TMSUs.

I. Dual Message Interface (DMI) :The DMI is the interface for the routing of control information between the TMSU and the MSPU. The DMI operates the control of the AM receiving its commands over the CDAL (control and diagnostic access links).

II. Network Clock (NCLK) :The NCLK provides the 5ESS switch with the high stability clock for the synchronization purposes.

III. Emitter-Coupled Logic Bus Units (E-BUS UNITS) :E-Bus Units are found only in the growth cabinets of the CM. Their purpose is to interface the expansion buses from the CMCU to the growth TMSUs in the growth cabinets, thus linking the fabric packs together into a complete space switching matrix. Each fabric pack has access to transmit and receive time slots on the E-Bus.

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IV. Time Multiplexed Switch Unit (TMSU) :The TMSU switches control time slots (inter-module messages) from the AM to SM modules and between SMs. It also switches data time slots (telephone calls) between SMs.

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L II NN TK E

RFACE

FABRIC

#

FAB CONTROL

SUB

SM 1

SM X

CMCU

CMCU

NCT

There are two NCT links interface between the SMs and CM 0 and CM 1. There are two NCT links connected between each DLI of a SM and each LI (Link Interface) of the TMSU. These NCT links are duplicated but not cross-connected to TMSU 0 and TMSU 1. Time slots send and receive by the standby TMSU are indicated to those sent and received by the active TMSU.

The TMSU consists of the following :

1) LINK INTERFACE (LI)

The NCT links from the SMs are connected to LI boards at the TMSU. Each LI interfaces maximum of 32 NCT links from 32 different switching modules. In a maximum configuration of 6 TMSUs per CM side, the link interface will connect 192 (6 x 32) NCT links. The total number of SMs that can be connected is reduced by two (to 190); however, one LI connection is reserve for an internal link to the CMCU and another for a special test link.

The limitation of 190 SM or 192 SMs and RSMs are : RSMs do not have NCT link connection with the TMSU. Instead their control time slots are sent using data time slots location on the host SMs NCT links. Therefore if there are at least two RSMs, the full 182 CTS switching capacity of the CM can be used even though there are only 190 CM to SM NCT link connection.

2) FABRIC BOARD (FAB)

The FAB performs the space switching of the time slots received over the NCT links from the SMs. The space switch size depends on the number of equipped SMs.

3) SHELF UTILITY BOARD (SUB)The CMCU controls the entire CMSU shelf through the SUB.

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4) FABRIC CONTROL

The fabric control receives the CMCU commands through the SUB and sets up the connections in the FAB.

The main functions of the TMS are as follows :

I. TMS Switching of the time slots :These contain control messages as well as speech samples. At the maximum configurations, the TMS contains a dual 192 by 192 switching fabric made up of six pairs of TMS units. The I/Os are divided over a maximum of 190 SMs, the link from the message switch and a special test link under the direction of the time multiplex controller, TMS unit switches the content of a certain time slot from a source input to a destination output, Any combination of input and output can be connected at the same time.

II. For a speech connection, the two path through the TMS unit need to be setup. One from the source SM to the destination SM and vice versa. In this way a full duplex connection is built.

III. Control messages destined for the SMs are received from the message switch, these control messages are switched by the multiplex switch unit to the control time slot of the network control and timing link to the correct SM.

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TMS MAINTENANCE

Within the message switch, the same maintenance philosophy is supported as in the SM. Error checks are used to detect errors and errors are reported while the system tries to minimize the impact of the error. Diagnostic software is used to determine the faculty circuit pack.

Additionally, a special test link is present. Via this test link, test patterns are switched through the TMS and transmitted to a destination where the test patterns are compared with the expected patterns. When both the patterns are found not to be identical, an error signal will result.

Message Switch Peripheral Unit (MSPU)

An SM in A 5ESS switch exchange is connected to each site of the CM by two bi-directional NCT links. One of the two NCT links is used for even number time slots and the other for odd numbered time slots. One time slot on each link is assigned as CTS (Control Time Slots). These CTS will never be used to carry data (telephone calls) but are reserved for communications from SM to SM, SM to AM or AM to SM. The CTS assignments are actually made using DIP (dual in – line package) switch is located on the back of the SM DLI circuit pack. Thus SM 24 might be hardware assigned CTS 40 and 41 and SM 3 might be assigned CTS 18 and 19.

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No other SMs will be assigned those CTS and the CTS numbers become unique SM addresses. If SM 24 wishes to setup a call with

SM 3, it will send a control message on either CTS 40 or 41, with destination CTS 18 or 19 SM3 will reply with a message directed to either CTS 40 or 41.

The MSPU (message switch peripheral unit) contains the circuitry (Module Message processor) that provides switching of a control message from one unit's CTS to another unit's CTS. Control

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MIBDATA

SM1

CONTROLTIME

SLOTS

CDAL CONTROL

MIBDATA

L II NN TK E

RFACE

FABRIC

#

FAB CONTROL

SUB

TMSUTO E-BUS

CMCU

SMX 1

TO E - BUS

DM1

TMC

NCLK

CONTROL

MMP

MMP

MMP

MMP

CDAL

message from AM to SM or SM to AM are sent via an MMP (Module Message Processor).

One MSPU has four MMP. The group of four MMPs in a MSPU is referred to as an MMP community. There are two MMP communities (side 0 and side 1) in a minimum MMP configuration and 12 communities in a maximum MMP configurations.

The MMPs in the M8PU act as buffers, receiving and temporarily storing CTS messages in RAM until they can be routed out on the appropriate destination CTS. Although each SM has two CTS, one CTS is sufficient to handle its control message traffic. This provides redundancy in case of a failure of equipment or software associated with a CTS. When one MMP fails, the MMP at the other can still handle all control messages via one control time slot. For a system with a fewer than 96 SM, even control time slots are assigned to side 0, and odd control time slots are assigned to side 1.

Message Switch Control Unit (MSCU) The MSCU is provided only in the basic (05 and 06) CM cabinets.

The MSCU consists of the following subunits :

I. DDSBS (duplex and dual serial bus selector)II. BIC (bus interface controller)III. PIC (peripheral interface controller)IV. FPC (foundation peripheral controller)PPC (pump peripheral controller)

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MESSAGE SWITCH CONTROL UNIT

42

CDAL CONTROL

SM1

CONTROLTIME

SLOTS

CDAL CONTROL

MIBDATA

L II NN TK E

RFACE

FABRIC

#

FAB CONTROL

SUB

TMSU

TO E-BUS

CMCU

SMX

TO E - BUS

DM1

TMC

NCLK

CONTROL

MMP

MMP

MMP

MMP

CDAL

PPC

FPC

PIC

EXTERNAL REFERENCE

DSCHAM

MSPU

The MSCU performs the following functions :

I. Provides the interface to the AM.II. Controls MSPU activity.III. Provides fast pump capability for rapid transfer of large

amounts of data from the AM to the SM.

OPERATION OF CM The CM handles subscriber data and control messages between the switching modules.

Stage 1: The CM receives subscriber data and control messages from switching modules via the NCT/NCT2 links.

Stage 2:When the message is data-specific then the CM sends the subscriber data to a switching module via the NCT/NCT2 links.

When the message is control-specific then the CM either:

I. Executes the control message.II. Routes the message to the switching module via the

NCT/NCT2 links.III. Routes the message to the AM via the DSCH.

The CM handles control messages from the AM.

Stage 1:The CM receives control messages from the AM via the DSCH.

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Stage 2:The CM either:

I. Executes the control messages.II. Routes the message to the switching module via the

NCT/NCT2 links.

The CM handles external timing references.

Stage 1:The CM receives a timing signal via the external clock leads.

Stage 2:The CM:

I. Adjusts the internal clock to synchronize with the timing signal.

II. Generates clock pulses.III. Distributes the clock pulse to the switching modules.

COMMUNICATION MODULE FUNCTIONS In the switch, the AM and SMs are not directly connected to each other. The CM routes messages between each module so they all work together. The following are provided by the CM for the 5ESS switch :

Call Switching The CM interconnects the path between switching modules to complete telephone calls and to reply data. The space switch in the CM TMS (Time-Multiplexed Switch) switches calls between SMs. Calls between SMs are known as inter-module call.

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Network Timing The CM provides the accurate timing and synchronization for the 5ESS-2000 Switch. Timing signals are generated by the CM and distributed to each of the SMs synchronize communication between modules.

Message Switching The CM provides the paths to send information between processors to process calls, maintain records and perform system tasks. The CM MSGS (Message Switch) provides inter-module communication between SMs and between the SMs and the AM. The CM acts as a routing facility (MSGS) and switching facility (TMS) for switching messages between these modules. The AM controls the CM maintenance and network operations by sending messages to the CM.

Fast Pump The CM provides resources to quickly download (pump) software from the AM to ANSM if needed. Fast pump is a feature of the 5ESS switch that quickly initializes SM memory. The SM contains the rest of the hardware.

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CONTROL UNIT

INPUTOUTPUT

UNIT

DISK FILE CONTROLLER

ASM CM

ADMINISTRATIVE MODULE ADMINISTRATIVE MODULE

In the 5ESS-2000 switch, the AM is a switch equipment module which has the overall of the entire 5ESS-2000 switch. The AM controls the CM and communicates with all the SMs through the CM. The AM monitors itself and the CM for malfunctions. Maintenance tasks performed system stability. It has the overall control of the entire exchange.

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ADMINISTRATIVE MODULE COMPONENTS

There are three main units located in the AM :

I. Control Unit (CU)II. Input/Output Processor (IOP)III. Disk File Controller (DFC)

The CU monitors overall system operation. The IOP interfaces with the MCC (Master Control Center). The CU contains the CC (Central Control), which is responsible for the ROP (Receive Only Printer) and other peripheral devices. The DFC controls the TD (Tape Drive) and the DD (Disk Drive). The CU also contains the MAS (Main Store), which contains the program data and instruction to be used by CC. All programs must be located into MAS before they can be executed.

The main store, input/output and disk file controller units are used to access additional memory from disk. When additional memory must be loaded into the MAS, the memory is “swapped” or copied into MAS from the disk copies.

The port switch unit (located Bay 0) ensure that MCC terminal is connected to active IOP (0 or 1). For example, if IOP 0 becomes OOS (out of service) the port switch automatically switches the MCC to IOP 1.The tape/disk cabinet houses the magnetic tape unit and a maximum of four disk drive units, in the 340 MB SMD configuration.

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ADMINISTRATIVE MODULE DIRECT MEMORY ACCESS

48

CCD Bus MSB

CC MMMSB

DIRECT MEMORY ACCESS

DSCH DSCH DSCH DSCH

ASM IOP DFC CM

ADMINISTRATIVE MODULE MAIN MEMORY

AM Control Unit

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CENTRAL CONTROL CU

DMADMA

Main Store Update Bus

EAIBUS

Main Store

Update Bus

MAIN MEMORY

CC

DMA

EAI BUS

MSUB

MSUB

Control unit is the actual 32-bit processor. The control unit is used for the extension of the software via which the control of the system is performed. Another function of control unit is the storage of data and software which is directly needed.

UNITS OF CONTROL UNIT

Central Main Store Direct Memory Maintenance Control (It is the memory (It performs i/o (It is used for (It executes of the control for control unit) maintenancethe instructions) unit) purpose)

Main functions of the Control Unit are :

I. Execution of software : It is accomplished in central control, has 32 bit word format and retrieves the software instructions from the main store bus. Via execution of these software instructions, the control of the system is performed. The instructions are decoded and executed. The results of the execution are either stored in the main store or output via the maintenance channel or the direct memory access controller.

II. Data Storage : It is executed by main store. Under control of the central control and the software, a data base is maintained containing all data needed for normal operation. In order to increase the reliability of the main store, an additional hamming code is used with every data word.

III. Input/output to the rest of the system : The central control will use the central control input/output bus to send a command to the direct memory access controller. This controller will receive a message from the main store and transmit the message via one of the dual serial channel buses.

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Disk File Controller

Disk File Controller is an independent processor used for control of the disk units. The disk units perform the backup memory functions. Data and software that is not directly needed is stored on the disk units.The SCSI is an ANSI (American National Standard Institute) standard interface for computer input/output devices. Currently the only peripheral that is accessible over the interface is disk drives.

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CU

DFC

DISKS TAPE DRIVE

SCSI BUS

DSCH BUS

SCSI hardware components are :

I. SCSI Disk File Controller (SDFC) provides connection between the CU and MAS and the fixed Media disk drive units through a SCSI standard bus.

II. SCSI Disk Unit Package (DUP) is made up of two parts : Disk Drive is an industry standard internal 5.25 inch winchester type drive with a built in processor to accept messages from the SDFC through the SCSI bus.

III. Power supply designed by AT&T for the purpose of converting 48v to 5v for the SFC and SCSI bus.

The functions of the SCSI (Small Computer System Interface) disk drive are as follows :

I. Stores copies of software used in the 5ESS-2000 switch. If data in the MM is lost it is restored from the disk copy.

II. Stores hardware configuration data. Information on the disk defines the configuration of hardware and line and trunk terminations.

III. Stores billing data. Disk has a temporary area for billing data. The data is stored until it is requested by the host collector or dumped to tape.

UNITS OF DISK FILE CONTROLLER

Disk File Controller Interface Peripheral Disk

Via dual series channel buses, the active control unit will transmit the block of data to the active disk file controller. The disk file controller interface accepts these blocks. The blocks will be checked for transmission errors and converted to a format that can be accepted by the peripheral disk interface.

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After receiving a command to retrieve data from disk units, the disk file controller executes the command via peripheral disk interface. The peripheral disk interface will retrieve the data blocks and transmit these blocks to the disk file controller interface. The disk file controller interface will then interrupt the control unit and after the reception of the appropriate command, will send the data to the control unit.

Input/Output Processor Input/output processor is the unit which performs the input/output to the utility equipment within the AM. It is an independent processor used for control of the other utility equipment. Via this equipment, the input/output functions are performed as well as the alarm signaling and tape storage functions.

UNITS OF INPUT/OUTPUT PROCESSOR

Input/Output Processor Peripheral Controller Community

The main functions of the I/O Processor are :

I. Input/Output : Data that is input at the terminal will cause the maintenance tele-typewriter controller (peripheral controller) to be interrupted, after which the data is retrieved from the terminal. The data then loaded in the input/output processor controller and transmitted to the control unit.

II. Data Storage on Tape : The tape controller (peripheral unit) is in the control of the tape unit and converts the received data from the input/output processor controller into the appropriate tape format. The tape controller is also in control of the

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positioning of the tape to the correct position for loading or retrieving the information.

III. Data Link Control : The data link controller interfaces to a connected data link. Via this data link, system can be remotely controlled. Commands from remote canter arrived at an asynchronous line controller. In the controller, information is converted into correct format and transmitted to control unit via I/O processor controller.

IV. Alarm Signaling and Guarding Point Scanning : Scanner/Signal distributor controller is used to transmit the necessary information to the I/O processor controller. This input/output processor controller will transmit information of certain conditions to scanner/ signal distributor controller that will light the appropriate lamp.

ADMINISTRATIVE MODULE FUNCTIONS

The AM has a minimum of one cabinet and can have a maximum of three cabinets. The AM performs resource allocation and processing functions that are done more efficiently on a centralized basis such as :

I. Call routing for inter-module and intra-module calls.II. Administrative data processing/billing data.III. Traffic measurement reports/system performance reports.IV. Memory management.V. System management.VI. Maintaining file records of changes to the system software release.VII. Personnel interface/system monitoring.VIII.Allocating trunks for call processing.

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As the AM consists of both hardware and software so the main functions performed are :

I. Route Selection : SMs are able to provide route selection for most intra-exchange call, but the AM becomes involved in route selection for intra-exchange calls which involves shared equipment (conference circuits), and for inter-exchange calls. It is the AM that record available trunks in the exchange. Under various conditions the AM is also involved in aspects of RSM (Remote- Switching Module) and MMRSM (Multimode Remote Switching Module) call routing. The AM provides inter-exchange trunk selection for an MMRSM, for example: If a hunt group is spread over more than one MMRSM, the AM provides the hunting. The routing data necessary to complete calls within an MMRSM are stored in the AM and in each RSM of the MMRSM.

II. Assigning time slots : The AM monitors and assigns all network time slots connections.

III. System Maintenance : The AM is responsible for system maintenance or itself and the CM. SM maintenance is done by the SM under control of AM. System maintenance includes performing diagnostics, reconfiguration and initialization.

IV. Exchange maintenance : The AM provides monitoring and maintenance access to switch through the MCC, (Master Control Center) and ROP (Receive-Only Printer) and additional terminals and printers located at the switch or at remote locations.

V. Managing billing information : The AM process billing information collected by the SMs and stores it on the disk and /or type for further processing at a billing center.

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Operation of AM

I. Receives orders from users through the ASM via the DSCH and the Input/Output peripherals via the metallic wires.

II. Sends the orders to the AM components, CWP and ASM via the DSCHs.

III. Sends messages (data, address, select and control) to the CM, CMP and ASM via the DSCHs.

IV. Receives messages (data and response) from the CM, CMP and ASM via the DSCHs.

CALL PROCESSINGCALL PROCESSING

------------------------------------ Calling Subscriber Called Subscriber

Call handling is the processing of calls from calling subscribers to the called subscribers. In all exchanges the basic function is to process a call i.e. to assign a suitable path between the calling and called subscriber and thus ensure a faithful communication between the two. In 5ESS switch the 90% of call processing is done in SM Unit.

A call processing may occur between following types of communications systems :

I. Public Switched Telephone Network (PSTN) : A tele-communication network set up by an administration to perform telephonic services for public subscribers. The main characteristics of PSTN is that most PSTN subscribers have analog access to the network.

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II. Integrated Services Digital Network (ISDN) : A network which provides end-to-end digital connectivity to support a wide variety of services. Users of ISDN have access to a limited set of standard, multipurpose customer interfaces.

III. Global System for Mobile Communication (GSM) : A cellular network based on digital technology with international coverage for mobile telephony.

IV. Intelligent Network (IN) : A network that is organized in such a way that telephone calls, received by the IN are interrupted in query a database. The database has the capability to handle the call based on a number of predefined conditions.

V. Personal Handyphone System (PHS) : A cellular network which offers low cost telephone service with low speed mobility.

STAGES OF CALL PROCESSING FOR PSTN

Digit Dialing Screening Index Digit AnalysisRouting Charging Termination

Origination/Incoming A call enters the exchange over a line (origination) or a trunk (incoming).

Digit Collection The collection of digits from the incoming line or trunk.

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Digit collection is responsible for :

I. Collecting dialed digits from incoming trunks or lines.II. Supporting the signaling protocol of the incoming trunk or

line.III. Performing dial timing requirements.

Digit Analysis The digits collected by digit collection are analysed to determine routing.

Digit analysis is responsible for :

I. Identification of the call type (normal call, dialed service, emergency number).

II. Interdigit timing requirements (for example determine the minimum number of digits that are required to route the call).

III. Generation of routing request data (for example destination index).

Carrier Selection Enables network subscribers to select the carrier used for a call. The carriers other than the access provider are called Other Licensed Operators (OLOs).

Input and Output The input for digit collection and digit analysis are the incoming digits. The output from the digit collection and digit analysis is for instance :

I. The Screening IndexII. The Destination IndexIII. Charging Information

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ROUTING

Routing is defined as the process of selecting the correct circuit path for a message. It translates the destination data received from digit analysis into the physical port that leads to the dialed destination (an outgoing trunk or line).

Route

A possible trunk group (or multiple hunt group) leaving the exchange and leading to (but not necessarily connected to) the specified destination. The actual trunk (or line) must be found by “hunting” the group for an idle member.

Data associated with a route includes :

I. The trunk group (or multiple hunt group) member.II. The type of route (hunted, reorder, congestion, maintenance,

etc.).III. Digit deleting and prefixing database.IV. The alternate (or next) route if the specified trunk group (or

multiple hunt group) is busy.

Any route can be associated with one and only one trunk group. However the same trunk group can be busy by more than one route.

TERMINAL ALLOCATION

Terminal allocation is connecting the correct circuit path for a message to the incoming trunk or line.

Route Index An arbitrary number assigned by the telephone administration to uniquely identify one route out of the exchange. Route indices can also be assigned to specific announcements or tones.

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Alternate Route Index It defines the next or alternate. An Alternate Route Index (ARI) can be used if the current route's trunk group (or multiple hunt group) is busy.

Screening Index An arbitrary number assigned by the telephone administration to uniquely identify the source of the originating line or incoming trunk call for routing and charging purposes. A screening index allows the same call type dialed to the same destination to be routed or charged differently, based on who originated the call. Screen Indices are obtained from line or trunk port data.

Destination Index An arbitrary number assigned by the telephone administration to uniquely identify each destination that can be reached for routing and charging purposes. Destination indices are obtained as an output of digit analysis.

Types of terminations are :

I. Line Termination (for the route types line and DSL)II. Multi-Line Hunt TerminationIII. Trunk Termination

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COMMON HARDWARE AND SOFTWARE Hardware

The hardware used in the call processing is SM, AM and CM that is in a hierarchy given below-

Each module in switch has specified functions to perform in setting up and tearing down calls. All 3 modules are involved to varying degrees in every call.

Software

The software used in the call processing is-

I. Peripheral Control (PC)II. Feature POTS(Plain Old Telephone Service) ; (FP)III. Feature Control (FC)IV. Routing and Terminal Allocation (RTA)

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CHARGINGCHARGING

Charging is the function that assesses the cost of the usage of switching capacity and that passes on that assessment to the billing center.

Currently two charging methods can be distinguished:

I. Automatic Message Accounting (AMA)II. Multimetering (MM), also known as Periodic Pulse Metering

(PPM).

In an exchange either method can be used or in combination.

AMA

Automatic Message Accounting (AMA) is a method of charging whereby for each call, records are generated for billing purposes. The records contain the information needed to generate a detailed subscriber bill, for example call start time, call end time, call duration, calling party number, called party number, and so on.

Advantages :

I. Allows detailed billing per call type or even per individual callII. Does not require tariff intelligence to be present in the exchange

Disadvantages :

I. Requires large amounts of charging data to be collected and processed.

II. Requires alternative methods to drive home meters and payphones.

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MM

Multimetering (MM) is a method of charging whereby a call is charged in terms of charge units. The number of units to be charged is based on the distance (or route) of the call, the date and the time of day. All this information yields a charge rate which determines how many charge units are applied over a set time interval. Each time this interval expires during the call the calling party is charged the pre-determined number of units.

Advantages :

I. Only requires the number of imposed charge units to perform billing.

II. Uses the charge units to generate meter pulses (to drive home meters and payphones or to transmit charging information to other exchanges).

Disadvantages :

I. On accumulates charge units.II. No history is kept, so no detailed billing is possible.

What is charged?

I. Basic analog Public Switched Telephone Network (PSTN) calls.

II. Basic digital Integrated Services Digital network (ISDN) Calls.

III. Basic wireless calls (mobile originations and terminations), location updates and Home Location Register (HLR) interrogations.

IV. ISDN data packet calls.

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V. Subscriber programming actions for PSTN, ISDN and wireless supplementary services, for example activation, deactivation and interrogation.

VI. Exchange executable services like Alarm Call Service (ACS). The subscriber is charged when the service is executed by the system.

VII. All answered and unanswered calls that complete a Service Control Point (SCP) query, using the Intelligent Network (IN)

VIII. PBX trunk originations.

Who is charged?

I. Individual subscribers (PSTN and ISDN), mobile subscribers, individual PBX lines and PBXs

II. Other administrations (to share revenues)

III. Intelligent Network (IN) service providers.

Types of output

Normally the charging data is sent to a billing center. A billing center is a system, external to the exchange that performs the billing.

The charging data is sent to the billing center using:

I. Magnetic tapeII. Direct data link to remote billing center.

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CHARGING PROCESSCHARGING PROCESS

The charging process consists of a number of stages. Some of these stages are charging method dependent.

Process flow

The following process stages can be distinguished in the charging process:

I. Collect charging data in Switching Module (SM) :

This stage is charging method dependent :

AMA

At the start of the call it is determined whether the call is chargeable, what AMA call type is to be used and what type of AMA output record needs to created. The call processing software in the originating SM is responsible for the collection of all necessary charging data during thelifetime of a call. At completion of the call the basic call record is populated with all the information required for detailed billing.

MM

At the start of the call the charge rate is determined, consisting of number of charge units on answer, length of charge interval and number of charge units per interval. On answer and each time the charge interval expires, the relevant number of charge units is added to the temporary charging register in the SM. Each time a rate change occurs, one or more of the charge rate values are subject to change.

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II. Format charging data in SM

This stage is charging method dependent:

AMA

At the end of the call the AMA Call Accounting Record (CAR) is populated based on the information in the basic call record. During the creation of each CAR the charging data is verified. If an invalid value is detected the corresponding field in the CAR is filled with a dummy value. Some of the fields will cause an assert to be fired to indicate the fault.

MM

The charge units accumulated in the temporary charging register are transferred to the MM Call Accounting Record (CAR), also in the SM.

The CARs are placed in dedicated fixed size message buffers in the SM.

III. Transfer charging data to AM :

The following main steps can be distinguished:

a) Send interprocessor message from SM to AM :Periodically or when the message buffer is full, an interprocessor message is sent to the AM containing charging data for several calls. What happens if the communication with the AM is down is described in the topic “Stand-alone SMs”.

b) Store charging data in AM memory :In the AM the Call Accounting Records (CARs) are stored in an AM memory buffer, called the Shared Data Segment (SDS). Both charging methods have their own dedicated section in the SDS. The SDS is one of the Protected Application Segments (PAS).

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These segments are projected from any system failure other than the highest manual system initialization.

In case of MM, a multimetering system process in the AM takes the register increments from the CARs and updates the related permanent Subscriber Charge Registers (SCRs).

c) Back up charging data to disk :Periodically or after a specific number of blocks of data (defined using RC) is filled in the SDS, the charging data is backed up to disk, in unformatted files.When Real Time Billing (RTB) is active, the charging data is transferred to disk immediately in order to meet the one minute real time transfer requirement.

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MAINTENANCE TOOLSMAINTENANCE TOOLS

A maintenance staff responsible for maintaining a 5ESS switch uses the following maintenance tools :

I. Master Control Center (MCC)II. Trunk and Line Workstation (TLWS)III. Recent Change and Verify (RC/V)IV. Diagnostic ProgramsV. Documentation

MCC The MCC is the most important maintenance tool. Almost all the maintenance tasks can be performed from MCC. It uses a full-colour video display terminal as a window to the system. By entering poke commands selected from menus on the terminal screen or man machine language commands selected from the 5ESS-2000. Switch commands and report manual, maintenance personnel can diagnose equipment, remove equipment from service, restore equipment to service, test lines and trunks, modify the database and service features for customers. The ROP (Receive- only Printer) provides a printed copy of reports from the MCC.

The primary functions of the MCC are to provide the following :

I. Visual Display of the system status and alarm information.II. The means to control, test and reconfigure the system.III. The means to manually recover the system.IV. Access to exchange data.

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TLWS It is a software function and is not related to a specific piece of equipment. As the name implies, the TLWS function is used to test trunks and lines (subscribers). Its functions can be performed from the MCC terminals known as supplementary TLWS positions.

RC/V It is also a software function. It is used to make addition, deletion , insertion, updation or changes to the database of the system. For instance, adding subscriber lines, changing the digit analysis, deleting trunks and so on are performed using the RC/V function. For example : update the subscriber class from Local to STD. Updb-sbldn : directory no. , SBclass=STD ;

Diagnostics Programs When a piece of equipment is faulty, the maintenance technician can run a specific diagnostic on that piece of equipment. The switch has the ability to tell the maintenance staff which circuit pack is most likely the faulty one and must be changed. The accuracy of the diagnostic process is quite impressive, more than 95% of system faults can be pinpointed, correctly. For example : for diagnostic of Line Ckt.— Dgn – AIU : LC= xxx-xxx-xx-xx ;

Documentation It plays a very important role in troubleshooting. Since a procedure may change over time, always refer to the documentation at the switch. Updating documentation must be performed whenever changes in new equipments are made.

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