PROJECT REPORT

ON

GSM

Submitted by

SONY

REGISTRATION NO:3460070068

PROGRAMME: B.TECH-MBA (ECE)

SECTION: D67T2

Department Of Electronics & Communication

Lovely School of Engineering & Computer Applications

Lovely Professional University, Phagwara

DECLARATION

I hereby declare that the project work entitled “” is an authentic record of my own work carried

out at “HFCL INFOTEL Ltd.,MOHALI” as requirements of Industry Internship project for

the award of degree of B.Tech-MBA (ECE), Lovely Professional University, Phagwara, under

the guidance of Er. Amit Wondraw and Mr. Amrinder singh, during July to December, 2010.

(Signature of student)

Name: MANINDER SINGH

Registration no:3460070068

Date: ___________________

Certified that the above statement made by the student is correct to the best of our knowledge

and belief.

Mr. Amrinder singh Er. Amit Wondraw

Faculty Coordinator Industry Coord.

PREFACE

During my B.Tech, as a part of it, I joined “ HFCL INFOTEL Ltd. MOHALI”, as a trainee

in 7th Semester. My assignment could be defined as development of Training Report In

SWITCH DEPARTMENT. Through this training I am working on CALLS ROUTING,

PATCHING, TRAFFIC ENGINEERING, POI’S…etc.

This report briefly describes the systematic approach adopted to develop the system by

efficiently using the latest facilities. The report follows the sequential actions of the different

phases in the system development life cycle.

INDEX:

Company profile

Service products

HFCL connectivity

What is switch

Types

Network Operation Centre(NOC)

E1’s

Feasibilities

Network Operation elements and Architecture

Anymedia

Home Location Register (HLR)

HLR Networking

HLR Features

HLR Structure

Traffic Engineering

Call Routing

Call Processing

Call Setup

Service provided by GSM

STP’s

Types

Linksets

Point codes

BICC

Bibliography

HFCL – COMPANY PROFILE

MANUFACTURING FACILITIES

RESEARCH & DEVELOPMENT

HFCL’S ASSOCIATED COMPANIES

SEVICES AND PRODUCTS

HITL NETWORK’S CONNECTIVITY

HFCL- COMPANY PROFILE

Established in 1987, Himachal Futuristic Communications has fast emerged as a leader in the

Indian Telecommunication sector. CONNECT, which is a prestigious venture of the Himachal

Futuristic Communications Limited Group has world class partners to support it in this

mammoth task.

Through the convergence of information, communication and entertainment, CONNECT

provides a world class telecom network to both the corporate and the common man of Punjab

and Chandigarh.

MANUFACTURING FACILITIES

HFCL's spirit manifests itself at the company's modern plants at Solan, Himachal Pradesh, Goa

and Chennai. The plants are modern with state-of- the-art production facilities. Quality and

reliability permeates the entire organization and company adheres to the highest quality

standards, including ISO 9002. It is the policy of the company to continuously improve its

performance.

Diversifying into exciting new areas, HFCL has extended its facilities to include a 10 million

optic fibre cable manufacturing unit in Goa. With a state- of- the-art plant at Goa, HFCL has set

new standards in capacity utilization with minimum wastage.

The R&D centre is the place where the HFCL Group creates future-efficient solutions and

products.

Since inception, HFCL has been innovating and developing state-of-art products for its

customers. The company has created an ISO 9001-2000 accredited Centre of Excellence in

Research & Development. The centre creates products which encompass future-ready

technologies in the telecom sphere.

HFCL’S ASSOCIATED COMPANIES

The core group today includes the following associate companies:

Microwave Communications Ltd. – Providing radio paging services under the brand name

of ‘Pagelink’ in 10 cities having more than 150k subscribers.

Himachal Exicom Communications Ltd.- Manufacturer of telephone instruments, SMPS

power plants.

HFCL Satellite Communications Ltd. – Providing DAMA based VSAT communication

services.

Consolidated Futuristic India Ltd. – Providing software services and software products.

This is joint venture with Kerry Packer Group.

Channel 9 India Ltd. – Broadcast Company. Also a joint venture with Kerry Packer

Group.

SERVICES & PRODUCTS

1. Basic Telephone Services:

CONNECT provides world class telephony service to the people of Punjab and Chandigarh.

You have the option to subscribe to national long distance (STD) and international long distance

(ISD) calls.

Network coverage :

Chandigarh

Ludhiana

Jalandhar

Amritsar

Patiala

Bathinda

Mohali

Ropar

Sangrur

Kapurthala

Khanna

Hoshiarpur

Nawanshahar

Rajpura

Barnala

Kotkapura

Pathankot

Mandi Gobindgarh

Jagraon

Phagwara

2. PCO Services:

To cater to the demands of various segments, CONNECT offers 3 types of PCOs

STD/ISD PCO - To call anywhere in India and the world

Punjab PCO - To call anywhere within Punjab on local calling facility, using “95 dialing”

Local PCO – To make calls within a city

3. Mobile Service:

CONNECT has launched its WLL Mobile service in Chandigarh, Ludhiana, Jalandhar and

Amritsar under the brand name CONNECT Mobile. This service enables the subscriber to be

mobile within an SDCA.

4. Phone Card:

CONNECT Phone card is a smart and convenient way of making phone calls. It is a prepaid

card that allows you to make STD/ISD & local calls from any CONNECT phone/ CONNECT

Phone Point. The CONNECT phone used by you does not get charged, instead your phone card

gets debited by the cost of call

For convenience of customers, HITL has installed CONNECT Phone Points in various cities in

Punjab. These phone points have a CONNECT Phone line thus enabling you to make calls using

CONNECT Phone card.

5. Internet Services :

COMECONNECT is brought to you by HFCL Infotel Ltd, a group company of Himachal

Futuristic Communication Ltd (HFCL). HFCL Infotel Ltd offers world-class telephony services

under the brand "CONNECT" and high performance Internet services under the brand

COMECONNECT to the people of Punjab and Chandigarh.

CONNECT ensures world class, uninterrupted and high-speed service to you through a state-

of-the-art intelligent broadband network with optic fiber backbone.

6. ISDN Services:

ISDN is a state of the art Digital switched Network, on which the subscriber can send and

receive voice, data image or a combination of any of these from his premises in an error free

digital form. The ISDN line terminates on customer premises equipment called Network

terminal. The subscriber can connect eight different ISDN Compatible Terminals (ISDN phone,

G4 FAX etc.) to the Network Terminal. One can use the existing analog customer premises

equipments (phone,G3 FAX etc.) using a terminal adapter.

7. Leased Lines:

A Leased Line is a dedicated line from one point to another facilitating instant and uninterrupted

connectivity between the users enabling enhanced efficiency and reduces communication costs.

The Leased line customer is charged only a flat yearly rental and no usage charges.

HFCL NETWORK’S CONNECTIVITY

WHAT IS A SWITCH:

to process calls from calling subscribers and make the connection to the called subscriber.

Flow of information from one subs to other subs via Electronic media.

As exchange handles thousands of calls at the same time, switch has to handle complex

relations between the Hardware and Software.

It connects two or more digital virtual circuits together.

TYPE OF SWITCHING

CIRCUIT SWITCHING

It creates a direct physical connection between two devices such as phones &computers . This

uses two type of technologies :

Space – division switch

Time -division switch

SPACE – DIVISION SWITCH

In space – division switching , the paths in the circuit are separated from each other spatially.

This technology was designed for use in analog networks but is used currently in both analog

&digital networks

.

Crossbar Switch

A crossbar switch connects n inputs to m outputs in a grid , using electronic micro switches . The

major limitation of this design is the no. of cross points required . Connecting n inputs to m

outputs using a crossbar switch requires n* m cross points .

Multistage switch

The solution to the limitations of the crossbar switch is the multistage switch, which combines

crossbar switches in several stages . In multistage switching devices are linked to switches that ,

in turn , are linked to other switches.

The design of a multistage switch depends on the no of stages & the no. of switches required in

each stage . The middle stages have fewer switches than do the first &last stages .Let us compare

the no. of cross points in a 15- by- 15single stage crossbar switch with the 15-by-15 multistage

witch, we need 225 cross points .In multistage switch, we need :

Three first stage switches, each with 10 cross points, for a total of 30 cross points at the

first stage.

Two second stage switches, each with 9 cross points, for a total of 18crosspoints at the

second stage.

Three third stage switches, each with 10 cross points, for a total of 30 cross points at the

last stage.

TIME- DIVISION SWITCH

Time –division switching uses time division multiplexing to achieve switching . There are

two methods :

Time- slot interchange(TSI)

TDM bus

Time- slot interchange(TSI)

A TSI consists of RAM (random access memory) with several memory locations. The size of

the each location is the same as the no. of inputs. The RAM fills up with incoming data from

time slots in the order received. Slots are then sent out in an order based on the decision of a

control unit.

TDM BUS

The input &output lines are connected to a high speed bus through input &output gates. Each

input gate is closed during one of the four time slots. During the same time slot, only one output

gate is closed. This pair of gate allows the burst of the data to be transferred from one specific

input line to one specific output line using the bus. The control unit opens &closes the gates

according to switching needs.

SPACE - AND TIME – DIVISION SWITCH COMBINATIONS

When we compare space – division and time division switching, some interesting facts emerge.

The advantage of space –division switching is that it is instantaneous. Its disadvantage is the no.

of cross points required to make space – division switching acceptable in terms of blocking.

The advantage of time – division switching is that it needs no cross points. Its disadvantage in

the case of TSI is that processing each connection creates delays.

In the third option we combine space –division & time division switching to take advantage of

the best of both. Multistage switch of this sort can be designed as time space –time (TST) time-

space-space – time (TSST) space-time-time-space (STTS).

A simple TST switch consists of two time stages &one space stage &has 12 inputs and 12

outputs. It divides the inputs into three groups and directs them to three time slot interchanges.

So average delay is one third of that which would result from using one time slot interchange to

handle all 12 inputs. The last image is mirror image of the first stage . The middle stage is a

space division switch that connects the TSI group to allow connectivity between all possible

input & output pairs.

NETWORK OPERATION CENTRE

A network operations center (or NOC, pronounced "nok," like the word "knock") is one or

more locations from which control is exercised over a computer, television broadcast, or

telecommunications network.

Large organizations may operate more than one NOC, either to manage different networks or to

provide geographic redundancy in the event of one site being unavailable or offline.

NOCs are responsible for monitoring the telecommunication network for alarms or certain

conditions that may require special attention to avoid impact on the network's performance. For

example, in a telecommunications environment, NOCs are responsible for monitoring for power

failures, communication line alarms (such as bit errors, framing errors, line coding errors, and

circuits down) and other performance issues that may affect the network. NOCs analyse

problems, perform troubleshooting, communicate with site technicians and other NOCs, and

track problems through resolution. If necessary, NOCs escalate problems to the appropriate

personnel. For severe conditions that are impossible to anticipate – such as a power failure or

optical fiber cable cut – NOCs have procedures in place to immediately contact technicians to

remedy the problem.

NOCs are frequently laid out with several rows of desks, all facing a video wall, which typically

shows details of highly significant alarms, ongoing incidents and general network performance; a

corner of the wall is sometimes used for showing a news or weather TV channel, as this can keep

the NOC technicians aware of current events which may have an impact on the network or

systems they are responsible for.

The back wall of the NOC is sometimes glazed; there may be a room attached to this wall which

is used by members of the team responsible for dealing with serious incidents to meet whilst still

able to watch events unfolding within the NOC.

Individual desks are generally assigned to a specific network, technology or area. A technician

may have several computer monitors on their desk, with the extra monitors used for monitoring

the systems or networks covered from that desk.

NOCs often escalate issues in a hierarchic manner, so if an issue is not resolved in a specific time

frame, the next level is informed to speed up problem remediation. Many NOCs have multiple

"tiers", which define how experienced/skilled a NOC technician is. A newly-hired NOC

technician might be considered a "tier 1", whereas a technician that has been there for several

years may be considered a "tier 3" or "tier 4". As such, some problems are escalated within a

NOC before a site technician or other network engineer is contacted.

Additionally, the NOC staff may perform extra duties; a network with equipment in public areas

(such as a mobile network Base Transceiver Station) may be required to have a telephone

number attached to the equipment for emergencies; as the NOC may be the only continuously

staffed part of the business, these calls will often be answered there.

The term NOC is normally used when referring to telecommunications providers, although a

growing number of other organizations such as public utilities (e.g., SCADA) and private

companies also have such centers, both to manage their internal networks and to provide

monitoring services.

The location housing a NOC may also contain many or all of the primary servers and other

equipment essential to running the network, although it is not uncommon for a single NOC to

monitor and control a number of geographically dispersed sites.

Lets study about E1’s…..

WHAT IS E1?

E1 is the media through which our data flows. Actually the data and signals travel from one

place to another through E1s.So we are having E1 cards at the node and the signal and data

travels from one end to other through these E1s.After that the E1 is dropped at the node end and

then it is carried to the customer through cards in ANYMEDIA. E1 has 32 time slots and each

time slot provides us the bandwidth of 64 kbps.

FEASIBILITIES:

Feasibilities means checking if the link is feasible at all ends. Our department have an important

and a responsible work assigned .We have to get checked the feasibility of the link at all the end

and then inform the responsible person for that and after that they proceed with the installation

of the link. Now how to proceed for getting feasibility depends on the technology used in that

link and the hardware required for that. After we get to know all the requirements we send the

feasibility to appropriate persons. Let me give the brief introduction for this and then all the

terms will be explained.

Brief overview:

Actually what happens is every station has a node where we have the whole set up for

transmission of the signal and data. So the person if wishing to have a connection goes to the

node. They will send us the request for feasibility and then we have to proceed with our work.

What we have to do is we have to forward that feasibility request to the persons which are

involved in this. Then they have to check the feasibility of that link from their ends and provide

us with the required information. If it is feasible at all ends then we have to release the work

order for that and after that installation is carried on. Now although we are nothing to do with

the installation but many things are involved in this like the technology used.

It can be of many types that will be discussed later on. Also we have to check where the request

for a selected link is to be sent. This depends on type of link whether it is point to point leased

line or internet leased line. We have to send the feasibility request at Data Group and Lac Group

of that station and also Data Group at Mohali end and if it is any link except point to point ,we

have to send that to ISP also. Now Data persons map the time slots according to the bandwidth

required at UMUX and they have to look after for the following requirements:

Hardware required for leased line provisioning like HDSL AP / ISDN AP /HDSL Modems(if

customer require modem from HFCL) at ANYMEDIA OR AN2000 OR UMUX.

Transmission limitations (if any) for provisioning E1’s .

And Lac Group have to provide us with the DP pair and also they have to look for Copper

available with them The concept behind this is explained below. Our data flows through E1.

LAC group has to take care of the following requirements:

Nearest node to customer premises

Availability of copper near customer premises

Distance from node to customer premises in case of fiber solution

Now let us start with the network diagram that will explain how our data is carried to the

customer end.

TECHNICAL FEASIBILITY

Is the prepared technology practical? Technical feasibility centers on the existing computer

system and to what extent it can support the proposed addition. But in this case since earlier all

the work was manual and there was no existing system, so the system proposed is technically

feasible. Also, the new system should be brought according to the specification of the product

being designed.

 OPERATIONAL FEASIBILITY:

Is the problem worth solving? Will the solution to problem work? The answer to the above

question is yes. As the problem is worth solving because the manual work is very inefficient and

from the statement of the problem gives us a clue that there is a solution to the problem and there

are pretty good chances that the solution will work.

ECONOMIC FEASIBILITY:

It is used to measure the cost effectiveness of a project which is commonly known as cost-

benefit analysis. The project is also economically feasible as the only requirement involving

expenses are related to the cost of buying a new system and a printer for the hard copies. And the

maintenance involved in this is only the maintenance of the computer and that does not cost

much. So according to the requirements the system is economically fit.

LEGAL FEASIBILITY:

Legal feasibility means that the software developed is legal; it is not violating any governmental

constraints and it is following all the legal laws. Since the project is developed for use within a

particular college only, it can by no mean violate any legal laws.

Therefore, it is said to be legally feasible too.

BEHAVIORAL FEASIBILITY:

Behavioral feasibility is an estimate of how strong reaction the user staff is likely to have

towards the development of a computer system. Since this project lightens the burden of the

manual work in the cell, so the end users of the software will always be encouraging towards the

use of computer. Also, no jobs are going to be replaced in this case.

For achieving the ISO-27001 standard we need to check the following information security

policy.

Security Policy,

Organization of information security,

Asset management, Human Resources security,

Physical and Environmental security,

Communications and Operations management,

Access control,

Information systems acquisition,

Development and maintenance,

Information security incident management,

Business continuity management,

Regulatory compliance.

External parties

Network security

Mobile computing and Tele working

Operating system access control

Security of system files

Cryptographic controls

NETWORK OPERATION ELEMENTS AND ARCHITECTURE:

* Mobile Station (MS)

* Base Station Subsystem (BSS)

* Network Switching Subsystem (NSS)

* Operation and Maintenance Subsystem (OMS)

* Enhanced Services Subsystem (ESS)

* Billing and Customer Care System (B&CCS)

MOBILE STATION (MS) :

Mobile Station, in fact, consists of two distinct entities. They are:

* Mobile Terminal or Equipment (MT)

* Subscriber Identity Module (SIM) Card

The mobile terminal is the actual hardware and is almost anonymous. Moibile equipment is

being manufactured by a number of vendors and a number of make and models are available in

the market. Each MT is identified by a number embedded in it by the manufacturer called

International Mobile Equipment Identity (IMEI). IMEI is useful to locate those mobile

phonesthat are reported stolen and also those manufactured without proper approval. IMEI is

also useful to route calls from MTs without SIM to emergency services. Mobile terminals are

distinguished mainly by their power class and application.

The SIM card is given by the service provider (PLMN Operator) when a customer enrolls

himself as a subscriber of that PLMN. SIM makes the MT operational and provides the

subscriber access to all his subscribed services. The subscriber information and provides

personal mobility. Each SIM is identified by a unique identifier called International Mobile

Subscriber Identity (IMSI). The SIM holds such vital information such as Authentication Key,

various algorithms, Cipher Key etc to ensure security of the subscription and privacy of the

conversation. Since SIM is such an important element of the personal subscription and can be

used in conjunction with any MT, it can be protected with a password of 4 to 8 digits long to

prevent misuase. Wrong entry of the password consecutively for 3 times would block the SIM

cards are classified on the basis of their operating voltage and the capacity of the Random

Access Memory (RAM).

BASE STATION SYBSYSTEM (BSS):

Base Station subsystem connects the MS to the rest of the network elements in the PLMN. It

provides all the digital radio interface functions. BSS comprises of three parts:

* Base transceiver Station (BTS)

* Base Station Controller (BSC)

* Transcoding and Rate Adoption Unit (XCDR/TRAU)

Base transceiver Station (BTS) : BTS houses the radio transeivers that define a cell. It transmits

to and receives signals from the MS. It handles the radio-link protocols with the Mobile Station

for call and mobility related activities on one side and with the BSC on the other side. Each

BTS can support a number of transceivers depending on the capacity of subscribers in the cell.

The BTS needs to be rugged, reliable, and portable to ensure reliable service and coverage.

The Base Station Controller (BSC) manages the radio resources of one or a group of BTSs.

BSC handles radio channel setup, performance improvement techniques such as control of the

RF power levels, etc and handovers. It establishes connection between the mobile station and

the MSC.

Transcoding and Rate adoption Unit (DCDR/TRAU) converts the transmission rate on the land

line to that compatible for transmission over the digital radio to and from the MS.

NETWORK SWITCHING SUBSYSTEM (NSS):

NSS manages the communication among the mobile users of the same PLMN and also with

other PLMN/PSTN users. It provides all the functionality needed to handle a mobile subscriber

such as:

* Registration

* Authentication and security

* Location updating

* Handovers and

* Routing to roaming subscribers

The central component in the NSS is the Mobile Switching Centre (MSC) that performs all the

switching functions of the network. Those MSCs that interface with other networks are called

Gateway MSC (GMSC). MSC realizes the above functions in conjunction with four intelligent

databases called:

* Home Location Register (HLR)

* Visitor Location Register (VLR)

* Authentication Centre (AuC)

* Equipment Identity Register (EIR)

Home Location Register (HLR)

HLR contains the administrative information of each of the subscriber registered in the network

and is the permanent copy of the subscriber data. Logically there will be one HLR per PLMN,

implemented as a centralized or distributed database. HLR maps each IMSI with a unique

mobile phone number called Mobile Subscriber ISDN (MSISDN). This is the number dialed by

others to access the mobile customer. HLR also holds most of the information held by the SIM

and also more importantly contains the pointer to the current location of the mobile customer in

order to gain access to him on an incoming call.

Visitor Location Register (VLR)

Each MSC has a VLR to holds the data relevant for handling calls from and to the MSs that are

currently located in its area.. The relevant data is downloaded from the home HLR when the

mobile subscriber switches on the mobile handset in the area of the visited MSC thereby

initiating the process of registration. VLR holds the exact location of the MS and keeps on

updating the location as the mobile move across its jurisdiction.

Authentication Centre (AuC)

Authentication Centre is a protected database used for security purposes. It is considered as part

of HLR and provides all the parameters needed for authentication of the subscriber and

encryption of voice/data over radio channel.

Equipment Identity Register (EIR)

Equipment Identity Register is a database that contains a list of all valid mobile equipment in the

network. It generates Valid, Suspect & Fraudulent lists (also called white list, grey list and

black list) of Mobile Hndsets through the use of International Mobile Equipment Identity

(IMEI). It forbid calls from unauthorized mobile terminals (non-standard and stolen terminals).

OPERATION AND MAINTENANCE SUBSYSTEM (OMS):

OMS is used to configure, control and monitor the GSM network. It comprises of two parts:

* Operation and Maintenance Centre - Switch

* Operation and Maintenance Centre - Radio

While OMC-S is used in conjunction with the NSS, OMCs-R is used in conunction with the

BSS. The OMC-R controls the traffic load on the various cells and performs automatic

reconfiguration of the transceivers to cope with the fluctuation of traffic, load caused due to the

mobility of the customers.

The OMCs also provide traffic data measurements, reporting and analysis. OMCs also store all

the data and software for the network elements and perform as the central maintenance control

point for all the network elements.

ENHANCED SERVICES SUBSYSTEM (ESS):

The ESS includes such elements as Unified Messaging System (UMS), Wireless Application

Protocol (WAP) System, Interlligent Network (IN) system, Content and Location Based

Services (C&LBS) system etc.

he first channel type carries speech and data and the other types control information (signaling)

The network attachment process consists of the following tasks :-

Cell Identification:-

When mobile station is switched on, it attempts to make contacts with a

GSM PLMN by performing the following tasks:-

Measure the BCCH channel

Search for a suitable cell

PLMN Selection :-

The particular PLMN to be contacted can be selected either in one of

 the following modes :- 

Automatic Mode

Manual Mode

 Cell Selection:-

The mobile station attempts to find a suitable cell by passing through

the list in descending order of received signal strength

It should be cell of the selected PLMN

It should not be ‘barred’.

The radio path laws between the MS and the selected BTS must be below a  threshold

set by the PLMN operator.

It should not be in ‘ forbidden LA’s for roaming ‘

No Suitable Cell Found:-

If the MS is unable to find a suitable cell to access, it attempts to access a cell irrespective of the

PLMN identity, and enters a ‘limited services’ state in which it can only attempt to make

emergency calls. 

ANYMEDIA: The Any Media Access System allows deployment of fiber deeper into the network and offers

simplified operations in any of its configurations. It is built on a new access interface platform.

It is basically acting as a MUX / DEMUX and also a node can be called an anymedia. We are

having different cards in ANYMEDIA which supports various technologies.

But the main point is that between two ANYMEDIAs we have E1 cards within which our data

travel from one place to other. There are many shelves in ANYMEDIA each having 16 cards.

Each card is supporting 12 subscribers minimum like an ISDN card supports 12 subscribers ,

POTS card support 32 subscribres and PCO card supports 24 subscribers etc. The output of

ANYMEDIA is extended to the MDF which is Main Distribution Frame. Two shelves of MDF

supports one shelf of ANYMEDIA means 16 cards.

From here we have underground Cu laid upto the customer end. In between we have DP’s which

is Distribution Panel. Each link has a DP number and then the copper is being taken to Customer

Premises. We can easily get every point cleared with the help of this network diagram.

NETWORK DIAGRAM FOR ANYMEDIA

UMUX

ISP

E1E1

L L

O E

M M I U F

E1 CARD

I

S

D

N

E1 CARD

I

S

D

N

ANYMEDIA

ROUTER ROUTER

HOME LOCATION REGISTER (HLR)

The Home Location Register (HLR) is a central database that contains details of each mobile

phone subscriber that is authorized to use the GSM core network. There can be several logical,

and physical, HLRs per public land mobile network (PLMN), though one international mobile

subscriber identity (IMSI)/MSISDN pair can be associated with only one logical HLR (which

can span several physical nodes) at a time.

The HLRs store details of every SIM card issued by the mobile phone operator. Each SIM has a

unique identifier called an IMSI which is the primary key to each HLR record.

The next important items of data associated with the SIM are the MSISDNs, which are the

telephone numbers used by mobile phones to make and receive calls. The primary MSISDN is

the number used for making and receiving voice calls and SMS, but it is possible for a SIM to

have other secondary MSISDNs associated with it for fax and data calls. Each MSISDN is also a

primary key to the HLR record. The HLR data is stored for as long as a subscriber remains with

the mobile phone operator

NT1 NT1

HLR NETWORKING:

FEATURES OF HLR

The main function of the HLR is to manage the fact that SIMs and phones move around a lot.

The following procedures are implemented to deal with this:

Manage the mobility of subscribers by means of updating their position in administrative areas

called 'location areas', which are identified with a LAC. The action of a user of moving from one

LA to another is followed by the HLR with a Location area update procedure.

Send the subscriber data to a VLR or SGSN when a subscriber first roams there.

Broker between the G-MSC or SMSC and the subscriber's current VLR in order to allow

incoming calls or text messages to be delivered.

Remove subscriber data from the previous VLR when a subscriber has roamed away from it.

HLR STRUCTURE:

TRAFFIC ENGINEERING

Traffic Parameters to Plan & administer a telecommunication System

Grade of Service (GoS)

Traffic Load

Number of Trunks

Grade of Service (GoS)

Defined as Percentage of calls that may encounter some form of blockage.

Generally taken as 1% to 5%.

Traffic load

• Expressed as quantity of traffic presented to a trunk group during the Busy Hour.

• It can be measured in minutes, hours or erlang. Generally measured in erlang.

• Traffic load is expressed as the relationship between the calling rate in busy hour (i.e., Busy

Hour Call Attempts- BHCA) and the length of an average call (i.e., Average Holding Time -

AHT)

• Erlang = (BHCA x AHT in Seconds) / 3600 Sec

Number of Trunks

• Based on GoS and Traffic load, the number of trunks are calculated based on traffic pattern i.e.,

user behavior

Traffic Pattern – User Behavior

• In traffic Engineering terms, the user behavior is described as:

– Blocked Calls Cleared

– Blocked Calls Held

– Blocked Calls Delayed

Blocked Calls Cleared

• This theory assumes that caller wait long enough before re-dialing when blockage is

encountered.

• The trunk serving this class of callers are designed using Erlang-B table.

Blocked Calls Held

• This theory assumes that caller keeps re-dialing, until the call is serviced, when blockage is

encountered.

• The trunk serving this class of callers are designed using Poisson table.

For this class of callers more trunks needs to be designed as compared to BCC.

Blocked Calls Delayed

• This theory assumes that caller is kept in queue and are held until the circuit is available to

service the call, when blockage is encountered.

• The trunk serving this class of callers are designed using Erlang-C table.

• For this class of callers, less trunks needs to be designed as compared to BCC.

CALL ROUTING

Routing is the process of selecting paths in a network along which to send network traffic.

Routing is performed for many kinds of networks, including the telephone network (Circuit

switching) , electronic data networks (such as the Internet), and transportation networks. This

article is concerned primarily with routing in electronic data networks using packet switching

technology.

In packet switching networks, routing directs packet forwarding, the transit of logically

addressed packets from their source toward their ultimate destination through intermediate

nodes, typically hardware devices called routers, bridges, gateways, firewalls, or switches.

General-purpose computers can also forward packets and perform routing, though they are not

specialized hardware and may suffer from limited performance. The routing process usually

directs forwarding on the basis of routing tables which maintain a record of the routes to various

network destinations. Thus, constructing routing tables, which are held in the router's memory,

is very important for efficient routing. Most routing algorithms use only one network path at a

time, but multipath routing techniques enable the use of multiple alternative paths.

Routing, in a more narrow sense of the term, is often contrasted with bridging in its assumption

that network addresses are structured and that similar addresses imply proximity within the

network. Because structured addresses allow a single routing table entry to represent the route to

a group of devices, structured addressing (routing, in the narrow sense) outperforms

unstructured addressing (bridging) in large networks, and has become the dominant form of

addressing on the Internet, though bridging is still widely used within localized environments.

Unlike routing in the fixed network, where a terminal is semi-permanently wired to a central

office, a GSM user can roam nationally and even internationally. The directory number dialed to

reach a mobile subscriber is called the Mobile Subscriber ISDN (MSISDN), which is defined by

the E.164 numbering plan. This number includes a country code and a National Destination

Code which identifies the subscriber's operator. The first few digits of the remaining subscriber

number may identify the subscriber's HLR within the home PLMN.

An incoming mobile terminating call is directed to the Gateway MSC (GMSC) function. The

GMSC is basically a switch, which is able to interrogate the subscriber's HLR to obtain routing

information, and thus contains a table linking MSISDNs to their corresponding HLR. A

simplification is to have a GSMC handle one specific PLMN. It should be noted that the GMSC

function is distinct from the MSC function, but is usually implemented in an MSC.

The routing information that is returned to the GMSC is the Mobile Station Roaming Number

(MSRN), which is also defined by the E.164 numbering plan. MSRNs are related to the

geographical numbering plan, and not assigned to subscribers, nor are they visible to

subscribers.

The most general routing procedure begins with the GMSC querying the called subscriber's

HLR for an MSRN. The HLR typically stores only the SS7 address of the subscriber's current

VLR, and does not have the MSRN (see the location updating section). The HLR must therefore

query the subscriber's current VLR, which will temporarily allocate an MSRN from its pool for

the call. This MSRN is returned to the HLR and back to the GMSC, which can then route the

call to the new MSC. At the new MSC, the IMSI corresponding to the MSRN is looked up, and

the mobile is paged in its current location area.

ROUTE MANAGEMENT

This function provides a means for rerouting traffic around failed or congested nodes. Route

management is a function of Level 3 and works together with link management. Route

management informs other nodes of the status of the affected node. It uses Message Signal Units

(MSUs) generated by adjacent nodes and is not usually generated by the affected nodes. (Link

management only informs adjacent nodes.)

TRAFFIC MANAGEMENT

This function provides flow control if a node has become congested. It allows the network to

control the flow of certain messages based on protocol. Traffic management deals with a specific

user part within an affected node. For example, if ISUP is not available at a particular node, a

traffic management message can be sent to adjacent nodes informing them that ISUP is not

available, without affecting TCAP messages on the same node.

MESSAGE ROUTING

Message discrimination in Level 3 will pass messages to message routing if it determines the

message is not local. Message routing reads the called and calling party addresses to determine

the physical address in the form of a point code. Every SS7 node must have its own unique point

code. Message routing determines the point code from an address contained in the routing table

CALL PROCESSING AND SMS :-

 Mobile originated (MO) call:

There are four types of distinct phase

Setup phase

Ringing phase

Conversation phase

Release phase

MOBILE CALL SETUP: -

Mobile call setup involves exchange of no. of message between the various elements in the

system. For setting up a mobile call following process is involved. It deals with two examples: -

Terminating call when the MS is in the HPLMN.

Terminating call when the MS is roaming.

The call set up broadly involves the following steps: -

PSTN subscriber dials MSISDN

Call is routed by PSTN network to GMSC of HPLMN of the dialed mobile subscriber.

GMSC interrogates HLR for verification of the access privileges profile and for obtaining the

location details if the call is permitted.

HLR directs the call to VLR of MSC area in which the mobile customer is currently located.

MSC interrogates VLR to obtain exact location of the MS.

VLR provides LAC to the MSC.

MSC translates the LAC code into BTS identity.

BSS pages all the BTSs identified by MSC within which MS is located using IMSI .

MS responds to the paging

Call is connected .

In case of roaming call MS will be located in a VPLMN

In such case steps are as follows:

On registration with VPLMN ,HLR will place a pointer in the data base for MS indicating the

current VLR address.

On interrogation by GMSC of the HPLMN ,HLR will in turn interrogate VLR of VPLMN using

the already stored pointer

VLR in VPLMN will assign a roaming number called in MSRN . To enable the HPLMN to

route the call to the VPLMN

Using MSRN , call is routed back from HPLMN to VPLMN and VMSC interrogates the VLR

VLR provides the LAC and call proceeds exactly in the same manner as for the call in.

CALL INITIATED BY A PPS SUBSCRIBER

Procedure:

1. The MSC a/VLR/SSP receives the call and according to Originating Camel Subscription

Information (O-CSI), triggers the service.

2. Put the area code of the MSC a/VLR/SSP in the Location Number parameter of IDP message

and send to the SCP a.

3. The SCP a, after receiving the IDP message, analyzes the calling party's user account. If the

user account is valid, it determines a call rate for the calling party according to the area code of

the calling party's visit location (Location Number within IDP message) and the called party's

HLR number, converts the balance to talk time, and then sends RRBE, AC, and FCI to the

MSCa/VLR/SSP.

4. When receiving Continue, the MSC a/VLR/SSP sends the SRI message to the called party's

HLRb and gets the called party's MSRN, and finally puts the call through.

5. After talking , the calling party or called party hangs up, and the MSC a/VLR/SSP sends the

charging report and Release event.

ORDINARY GSM SUBSCRIBER CALLS A PPS SUBSCRIBER

Procedure:

1. The MSC a/VLR/SSP receives the call originated by a GSM user. After judging that the

calling party is not a PPS user, it sends SRI to the called party and gets the called party's

subscription information T-CSI.

2. From T-CSI, the MSC a/VLR/SSP gets the called SCP b's address and sends the IDP message

to it. Area code of the originating MSC/VLR is put in the LocationNumber field in the IDP

message.

3. The SCP b, after receiving the IDP message, analyzes the called party's user account. If the

user account is valid, it determines a call rate for the called party according to the called party's

HLR number and current location, converts the balance to talk time, and then sends RRBE, AC,

and Connect to the MSCa/VLR/SSP.

4. Upon receiving Connect, the MSC a/VLR/SSP sends again the SRI message to the called

party's HLR and gets the called party's MSRN.

5. The MSC a/VLR/SSP finally puts the call through according to the called party's MSRN.

6. After the conversation, the calling or called party hangs up, and the MSC a/VLR/SSP sends

the charging report and Release event.

 MESSAGE FLOW IN CASE OF ANNOUNCEMENTS

SCP

MSC IP

idp

rrbcsm

etc

iamacm

anm

ari

pasrr

SMS MESSAGE FLOW (PRE-PAID IN HPLMN)

SERVICES PROVIDED BY GSM

Telecommunication services can be divided into bearer services, teleservices, and the

supplementary services.

The most basic teleservice supported by GSM is telephony. As with all other communications,

speech is digitally encoded and transmitted through the GSM network as a digital stream. There

is also an emergency service, where the nearest emergency-service provider is notified by

dialing three digits no. similar to 911

SCP

MSC IP

idp

rrbcsm

etc

iamacm

anm

ari

pasrr

A variety of data services is offered. GSM users can send and receive data, at rates up to 9600

bps, to users on POTS (Plain Old Telephone Service), ISDN, Packet Switched Public Data

Networks, and Circuit Switched Public Data Networks using a variety of access methods and

protocols, such as X.25 or X.32. Since GSM is a digital network, a modem is not required

between the user and GSM network, although an audio modem is required inside the GSM

network to interwork with POTS.

A unique feature of GSM, not found in older analog systems, is the Short Message Service

(SMS). SMS is a bi-directional service for short alphanumeric (up to 160 bytes) messages.

Messages are transported in a store-and-forward fashion. For point-to-point SMS, a message can

be sent to another subscriber to the service, and an acknowledgement of receipt is provided to

the sender. SMS can also be used in a cell-broadcast mode, for sending messages such as traffic

updates or news updates. Messages can also be stored in the SIM card for later retrieval.

Supplementary services are provided on top of teleservices or bearer services. In the current

(Phase I) specifications, they include several forms of call forward (such as call forwarding

when the mobile subscriber is unreachable by the network), and call barring of outgoing or

incoming calls, for example when roaming in another country. Many additional supplementary

services will be provided in the Phase 2 specifications, such as caller identification, call waiting,

multi-party conversations 

SS7 SIGNALING ARCHITECTURE

The SS7 signaling architecture consists of three essential components, interconnected via

signaling links. components and their associated symbols.

SS7 Network Signaling Components

Abbreviation Name Symbol

SSP Signal Switching Point

- or -

Service Switching Point

STP Signal Transfer Point

SCP Signal Control Point

- or -

Service Control Point

SIGNAL SWITCHING POINT

SSPs are switches that have SS7 software and terminating signaling links. An SSP can be a

combined voice/SS7 switch or an adjunct computer system (front end) connected to a voice

(Class 5 or tandem) switch. SSPs create packets (signal units) and send those messages to other

SSPs, as well as queries to remote shared databases to find out how to route calls. They can

originate, terminate, or switch calls. SSPs communicate with the voice switch via the use of

primitives and have the ability to send messages using ISUP (call setup and teardown) and

TCAP (database lookup) protocols. The SSP uses the calling party information (dialed digits) to

determine how to route the call. It looks up the dialed digits in the SSP routing table to find the

corresponding trunk circuit and terminating exchange. The SSP then sends an SS7 message out

to the adjacent exchange requesting a circuit connection on the trunk which was specified in the

routing table. The adjacent exchange sends an acknowledgement back, giving permission to use

that trunk. Using the calling party information contained in the setup info, the adjacent exchange

determines how to connect to the final destination. This might require several trunks to be set up

between several different exchanges.

SSP manages all of these connections until the destination is reached.

Signal Transfer Point

STPs are packet switches, and act like routers in the SS7 network. Messages are not usually

originated by an STP. An STP can act like a firewall, screening messages with other networks.

STPs route SS7 messages (based on information contained in the message format) to outgoing

signaling links over the SS7 network. They are the most versatile of all the SS7 entities, and are

a major component in the network.

There are three levels of STPs.

National Signal Transfer Point

International Signal Transfer Point

Gateway Signal Transfer Point

NATIONAL STP

A National STP exists within the national network (will vary with the country). It can transfer

messages that use the same national standard of protocol. Messages can be passed to an

International STP, but can not be converted by the National STP. Protocol converters often

interconnect a National and an International STP by converting from ANSI to ITU-TS.

INTERNATIONAL STP

An International STP functions within an international network. It provides for SS7

interconnection of all countries, using the ITU-TS standard protocol. All nodes connecting to an

International STP must use the ITU-TS protocol standard.

GATEWAY STP

A Gateway STP converts signaling data from one protocol to another. Gateway STPs are often

used as an access point to the international network. National protocols are converted to the

ITU-TS protocol standard. Depending on its location, the Gateway STP must be able to use both

the International and National protocol standards. Gateway STP also serves as an interface into

another network's databases, such as from an interexchange carrier (IXC) to an end office. The

Gateway STP can also be configured to screen for authorized users of the network. ateway STPs

also provide measurements of traffic and usage via the following means:

Traffic—Measures the peg counts of the type of messages entering or leaving the network.

Network events—Track events such as link out-of-service or local processor outage, for

maintenance purposes.

Usage—Provides peg counts of the record number of messages by message type. Usage counts

are sent to the Regional Accounting Office (RAO) for processing in Bell Networks. RAOs

invoice customers such as IXCs and independent telcos, charging for access into the SS7

network, to help offset the cost of deploying the network.

SIGNAL CONTROL POINT

An SCP is usually a computer used as a front end to a database system. It is an interface to telco

databases, not usually to other, application-specific databases

Telco databases are usually linked to SCPs by X.25 links. The SCP can provide protocol

conversion from X.25 to SS7, or can provide direct access to the database through the use of

primitives which support access from one level of protocol to another.

Note   Some new SCP applications are being implemented

in STPs.

The address of an SCP is a point code, and the address of the database it interfaces with is a

subsystem number. The database is an application entity which is accessed via the TCAP

protocol.

LINKSETS

Links are put into groups called linksets. Up to 16 links can be assigned to one linkset. All links

in a linkset must have the same adjacent node. Switches will alternate traffic across all links in a

linkset to ensure equal usage of all facilities in the network.

Linksets

LINKSET CHARACTERISTICS

If possible, links should be terrestrial. Satellite links can be used but are not preferred because of

the inherent delay.

Alternate linksets are set up to provide backup paths when congestion occurs in the network.

When a link fails, all other links within the linkset must take over.

Note   A maximum of 10 minutes downtime per year is allowed for any one linkset, to protect

network integrity.

If an SS7 entity such as an STP fails, its mate assumes the full traffic load. For this reason, SS7

entities are designed to send less than 40 percent of the traffic on any given link. If an entity

fails at 40-percent capacity, there is still enough room on its mate for it to carry the entire traffic

load of the mated pair.

PHYSICAL LINK INTERFACES

The signaling link interface type will depend on the type of equipment used with the links. The

V.35 interface is used to connect from the data service unit (DSU) to the signaling point. V.35

can also be used from a digital system cross-connect frame (DSX).

Note   V.35 needs a clock source. Data links are 56 or 64 Kbps.

The most commonly used interface is a DS0A, one 56/64 Kbps channel of a DS1. A channel

service unit (CSU) or DSU terminates the DS1 and separates DS0s from the T1 or E1 span

circuit.

ROUTES

The signal point must define linksets and routes in SS7 messaging. The following entities are

used in SS7 messaging:

Route—A collection of linksets to reach a particular destination. A linkset can belong to more

than one route.

Routeset—A collection of routes that are assigned to destinations and also provide alternate

routes.

Destination—An address entered into the routing table of a remote signaling point. A

destination need not be adjacent to the signaling point, but must be a point code that can be

reached by the signaling point.

ROUTE CONGESTION

POINT CODES

In SS7, addresses are assigned using a three-level hierarchy.

Member—A signaling point within a cluster.

Cluster—A collection of signaling points (members).

Network—Each cluster is defined as being part of a network.

Any node in the SS7 network can be addressed by the three-level number defined by its

network, cluster, and member numbers. Each of these numbers is an 8-bit number assigned a

value from 0 to 255. This three-level address is called the point code of the signaling point.

NETWORK NUMBERS

Network numbers are assigned on a nationwide basis. In North America, RBOCs, IXCs and

telcos already have network numbers assigned to them. etwork numbers are relatively scarce.

Companies are expected to meet size requirements in order to be assigned a network number.

Smaller networks can be assigned one or more clusters within network numbers 1, 2, 3 and 4.

The smallest networks are assigned point codes within network number 5. The cluster to which

they are assigned determines the state or province they are in.

BEARER INDEPENDENT CALL CONTROL

The Bearer Independent Call Control (BICC) is a signaling protocol based on N-ISUP that is

used for supporting narrowband ISDN service over a broadband backbone network. BICC is

designed to interwork with existing transport technologies. BICC is specified in ITU-T

recommendation Q.1901.

BICC signaling messages are nearly identical to those in ISUP; the main difference being that

the narrowband Circuit Identification Code (CIC) has been removed from the header. The BICC

architecture consists of interconnected Serving Nodes that provide the Call Service Function and

the Bearer Control Function. The Call Service Function uses BICC signaling for call setup and

may also interwork with ISUP. The Bearer Control Function receives directives from the Call

Service Function via BICC Bearer Control Protocol (ITU-T recommendation Q.1950) and is

responsible for setup and teardown of bearer paths on a set of physical transport links. Transport

links are most commonly TDM, ATM or IP.

According to the ITU, the completion of the BICC protocols is a historic step toward broadband

multimedia networks because it enables the seamless migration from circuit-switched TDM

networks to high-capacity broadband multimedia networks.

The Third Generation Partnership Project (3GPP) has included BICC CS 2 in the Universal

Mobile Telecommunications Service (UMTS) release 4.

CONCLUSION:

NOC is the heart beat of telecom system.

Packet switch is the next generation of switch.

Deregulation and fair competition in telecom field will promote tele density

at low cost to the customers.

BIBLIOGRAPHY

Paper/ Articles

1) General description of a GSM Public Land Mobile Network (PLMN) ‘Vol.19, No. 2

Books

2) Wireless Communication by Theodore s. Rappaport. 2nd Edition, Pearson Edition

Data Manuals

3) Connect Systra manual, connect infotel Ltd., Finland, 1998

4)Connect site GSM user base station manual, connect infotel Ltd. Finland, 1998

5) Connect Ultra site EDGE product description, connect infotel Ltd., Finland, 2001

6Connect infotel Ltd. customer training, connect infotel, Finland, 2003

Web Sites

7) www.mobile3G.com

8) www.connectinfotelltd.com

9) www.gsmworld.org

10) www.openmobilealliance.org