Shaheed udham singh college of engeneering & technology

Tangori(mohali)

Midterm report

6 month training

From: TELCOMA TECHNOLOGIES,Mohali

ON ADVANCED TELECOMMUNICATION

TRAINING DURATION:july to december 2011

Submitted to: Submitted by:

Mrs Charu Tandon SHASHANK DUBEY

(H.O.D ECE) ECE-B 5TH sem

81003108158

INTRODUCTION OF ORAGNISATION:

Telcoma Technologies (ISO 9001:2008 Certified) is a provider of Telecommunication and IT based solutions, including software, equipment and systems integration services. Telcoma Technologies develops and provides products, solutions, and professional services primarily for Telecommunications/IT companies.  The business paradigm of Telcoma Technologies includes the following areas –

1. Telecommunications

Network Solutions

Next Generation Networks Wireless Broadband Service Data Transmission Mobile Networks Value-added Systems and Intelligent Networks Network Deployment and Integration New Technologies

Operation & Business Support

Network Monitoring Network and Service Management Fulfillment Billing and Customer Care Management

2. Customized software development - Telcoma Technologies develops customized software solutions for its clients. Our expertise includes Java programming, Apple iPhone/Google Android applications, PHP/MySQL, Ajax and Ruby on Rails.

3. Web development and Internet/Intranet based Solutions - Telcoma Technologies has completed many web projects catering to niche segment of internet fraternity, which include social networking sites, content management portals, dynamic websites, multimedia rich interactive websites with Flash and Intranet based solutions for Business Automation. The sites and portals generate a run-of-the-network traffic and a significant business every month for our clients.  

4. 4. Corporate Training and IT/Telecom Education - Telcoma Technologies has also launched various initiatives in the area of corporate training and IT education introducing the emerging technologies training solutions at affordable price.

The team at Telcoma Technologies is well-qualified and strongly motivated and committed to providing the high level of personal service and customer satisfaction. All processes within Telcoma Technologies are aligned towards the highest quality standards and formally certified to ISO 9001:2008. We "Believe in the Best", be it people, products or services. Our approach to everything emanates from this corporate philosophy. With every new day the quest for acquiring new competencies continues. Forever searching, experimenting, innovating, learning, moving ahead with our sincere efforts and dedication, shaping the future, and challenging our competencies to create new opportunities, is a never-ending process.

Corporate training modules

1. GSM Basic

2. GSM Protocols and Signaling

3. GSM Network Planning

4. RF Optimization

5. GPRS and EDGE

6. UMTS Basics

7. WCDMA Planning

Contact :

Telecoma Technologies SCO 123 Phase 3B-2, Above Dominos Mohali, Punjab, India.Landline :0172 4010731Mobile 9814145471Email : info@telcoma.in

INDEX

S.NO. TOPIC PAGE NO1. Department in telecom industry 1

2. Introduction 3

3. OSI Reference model 7

4. GSM introduction 10

5. GSM architecture 34

6. GSM channel 50

7. Handover 62

8. Number plan 74

9. project:radio frequency optimisation

DEPARTMENT IN TELECOM INDUSTRY

Department of Telecom industry provides 24 hours Network availability, with optimized

performance, to all the customers of worldwide. This department has six sections:

1. NSS (Network Switching Centre)

2. BSS (Base Station System)

3. OMC-R (Operations and Maintenance for Radio)

4. EFD (Engineering Front Desk)

5. Planning

6. Performance

NETWORK SWITCHING CENTRE- This is involved in the maintenance of the Switch, over

which all the calls of the SPICE customers are routed in the Network.

BASE STATION SUBSYSTEM- This department is involved in the maintenance of the GSM

Network. It involves all daily routines like Preventive Maintenance, Weather proofing, Site

Expenditures, Fuel availability, Power availability, etc. These people if required also do any

reconfiguration.

OPERATIONS AND MAINTENANCE FOR RADIO- It is there for the maintenance and

operations of the radio. Any alarms in the Network are raised in OMCR, notification for which are

then are sent to the concerned regions.

ENGINEERING FRONT DESK- This department is the front desk for the Engineering

department. Any customer complaints or queries from any other department have to go through

this for evaluation.

PLANNING- This Department is involved in the planning of the sites, drive tests, etc.

PERFORMANCE- This department is there to keep a check on the Network performance and to

enhance the performance whenever required time by time.

INTRODUCTION:

Telecommunication is the transmission of information over significant distances to communicate. In earlier times, telecommunications involved the use of visual signals, such as beacons, smoke signals, semaphore telegraphs, signal flags, and optical heliographs, or audio messages via coded drumbeats, lung-blown horns, or sent by loud whistles, for example. In the modern age of electricity and electronics, telecommunications now also includes the use of electrical devices such as telegraphs, telephones, and teleprinters, the use of radio and microwave communications, as well as fiber optics and their associated electronics, plus the use of the orbiting satellites and the Internet.

Basic elements:

A basic telecommunication system consists of three primary units that are always present in some form:

A transmitter that takes information and converts it to a signal. A transmission medium, also called the "physical channel" that carries the signal. A receiver that takes the signal from the channel and converts it back into usable

information.

Telecommunication over telephone lines is called point-to-point communication because it is between one transmitter and one receiver. Telecommunication through radio broadcasts is called broadcast communication because it is between one powerful transmitter and numerous low-power but sensitive radio receivers.

Telecommunications in which multiple transmitters and multiple receivers have been designed to cooperate and to share the same physical channel are called multiplex systems.

Generation of telecommunication:

FIRST GENERATION:

1G (or 1-G) refers to the first-generation of wireless telephone technology, mobile telecommunications. These are the analog telecommunications standards that were introduced in the 1980s and continued until being replaced by 2G digital telecommunications. The main difference between two succeeding mobile telephone systems, 1G and 2G, is that the radio signals that 1G networks use are analog, while 2G networks are digital.

Although both systems use digital signaling to connect the radio towers (which listen to the handsets) to the rest of the telephone system, the voice itself during a call is encoded to digital signals in 2G whereas 1G is only modulated to higher frequency, typically 150 MHz and up.

One such standard is NMT (Nordic Mobile Telephone), used in Nordic countries, Switzerland, Netherlands, Eastern Europe and Russia. Others include AMPS (Advanced Mobile Phone System) used in the North America and Australia.

SECOND GENERATION:

2G (or 2-G) is short for second-generation wireless telephone technology. Second generation 2G cellular telecom networks were commercially launched on the GSM standard in Finland in 1991. Three primary benefits of 2G networks over their predecessors were that phone conversations were digitally encrypted; 2G systems were significantly more efficient on the spectrum allowing for far greater mobile phone penetration levels; and 2G introduced data services for mobile, starting with SMS text messages.

After 2G was launched, the previous mobile telephone systems were retrospectively dubbed 1G. While radio signals on 1G networks are analog, radio signals on 2G networks are digital. Both systems use digital signaling to connect the radio towers (which listen to the handsets) to the rest of the telephone system.

Advantages:

The lower power emissions helped address health concerns. Going all-digital allowed for the introduction of digital data services, such as SMS and

email. Greatly reduced fraud. With analog systems it was possible to have two or more "cloned"

handsets that had the same phone number. Enhanced privacy

2.5 GENERATION (GPRS):

2.5G is a stepping stone between 2G and 3G cellular wireless technologies. The term "second and a half generation" is used to describe 2G-systems that have implemented a packet switched domain in addition to the circuit switched domain. It does not necessarily provide faster services because bundling of timeslots is used for circuit switched data services (HSCSD) as well.

The first major step in the evolution of GSM networks to 3G occurred with the introduction of General Packet Radio Service (GPRS). CDMA2000 networks similarly evolved through the introduction of 1xRTT. The combination of these capabilities came to be known as 2.5G.

GPRS could provide data rates from 56 kbit/s up to 115 kbit/s. It can be used for services such as Wireless Application Protocol (WAP) access, Multimedia Messaging Service (MMS), and for Internet communication services such as email and World Wide Web access. GPRS data transfer is typically charged per megabyte of traffic transferred, while data communication via traditional circuit switching is billed per minute of connection time, independent of whether the user actually is utilizing the capacity or is in an idle state.

2.75 GENERATION (EDGE):

GPRS networks evolved to EDGE networks with the introduction of 8PSK encoding. Enhanced Data rates for GSM Evolution (EDGE), Enhanced GPRS (EGPRS), or IMT Single Carrier (IMT-SC) is a backward-compatible digital mobile phone technology that allows improved data transmission rates, as an extension on top of standard GSM. EDGE was deployed on GSM networks beginning in 2003—initially by Cingular (now AT&T) in the United States.

EDGE is standardized by 3GPP as part of the GSM family and it is an upgrade that provides a potential three-fold increase in capacity of GSM/GPRS networks. The specification achieves higher data-rates (up to 236.8 kbit/s) by switching to more sophisticated methods of coding (8PSK), within existing GSM timeslots.

3- GENERATION:

3G or 3rd generation mobile telecommunications is a generation of standards for mobile phones and mobile telecommunication services fulfilling the International Mobile Telecommunications-2000 (IMT-2000) specifications by the International Telecommunication Union. Application services include wide-area wireless voice telephone, mobile Internet access, video calls and mobile TV, all in a mobile environment. To meet the IMT-2000 standards, a system is required to provide peak data rates of at least 200 kbit/s. Recent 3G releases, often denoted 3.5G and 3.75G, also provide mobile broadband access of several Mbit/s to smart phones and mobile modems in laptop computers.

The following standards are typically branded 3G:

The UMTS system, the cell phones are typically UMTS and GSM hybrids.

The CDMA2000 system, the cell phones are typically CDMA2000 and IS-95 hybrids. The latest release EVDO Rev B offers peak rates of 14.7 Mbit/s downstream.

Applications of 3G:

The bandwidth and location information available to 3G devices gives rise to applications not previously available to mobile phone users. Some of the applications are:

Mobile TV Video on demand Videoconferencing Telemedicine Location-based services

OSI REFERENCE MODEL:

Osi model is applicable in many areas, it is used mostly in the areas communication between computer. Its purpose is to organize and formalize the communication method. the basic idea of osi model is to separate the various part, in their totality, form a communication process.

LAYER 1: THE PHYSICAL LAYER:

LAYER 2: DATA LINK LAYER

LAYER 3: THE NETWORK LAYER

LAYER 4 TRANSPORT LAYER:

LAYER 5:SESSION LAYER:

LAYER 6: PRESENTATION LAYER:

LAYER 7: THE APPLICATION LAYER:

GSM introduction:

History of GSM:

When the acronym GSM was used for the first time in 1982, it stood for Groupe Spéciale Mobile , a committee under the umbrella of Conférence Européenne des Postes et Télécommunications (CEPT), the European standardization organization. The task of GSM was to define a new standard for mobile communications in the 900 MHz range. It was decided to use digital technology. In the course of time, CEPT evolved into a new organization, the European Telecommunications Standard Institute (ETSI).The Global System of mobile communication (GSM) is an ETSI (European telecommunication standard institute) standard for 2G pan digital cellular with international roaming. The main purpose of 2G is to resolve roaming problem in the six existing different 1G analog system in Europe. In 1986, the task force was formed, and in 1987 a memorandum of understanding (mou) was signed. In 1989, ETSI include GSM in its domain. In 1991 the specification of the standard was completed, in 1992, the first deployment started. By the year 1993, thirty two operators in 22 countries adopted the GSM standard, and in 2001, close to 150 countries had adopted GSM for cellular adaption.

Benefits of GSM:

GSM became popular very quickly because it provided improved speech quality and, through a uniform international standard, made it possible to use a single telephone number and mobile unit around the world. The European Telecommunications Standardization Institute (ETSI) adoptedthe GSM standard in 1991, and GSM is now used in 135 countries.

The benefits of GSM include: Support for international roaming Distinction between user and device identification Excellent speech quality Wide range of services Interworking (e.g. with ISDN, DECT) Extensive security features

GSM also stands out from other technologies with its wide range ofServices

Telephony Access to packet data network (X.25) Telematic services (SMS, fax, videotext, etc.) Many value-added features (call forwarding, caller ID, voice mailbox) E-mail and Internet connections

GSM Architecture:

A GSM network can be divided into three groups (see Fig.): The mobile station (MS), the base station subsystem (BSS) and the network subsystem(NSS).

The mobile station:A mobile station may be referred to as a handset, a mobile, a port- (MS) able terminal or mobile equipment ME). It also includes a subscriber identity module (SIM) that is normally removable and comes in two sizes. Each SIM card has a unique identification number called IMSI(International mobile subscriber identity). In addition, each MS is as- signed a unique hardware identification called IMEI (international mobile equipment identity). In some of the newer applications (data communications in particular), an MS can also be a terminal that acts as a GSM interface, e.g. for a laptop computer. In this new application the MS does not look like a normal GSM telephone. The seemingly low price of a mobile phone can give the (false) impression that the product is not of high quality. Besides providing a transceiver (TRX) for transmission and reception of voice and data, the mobile also performs a number of very demanding tasks such asauthentication, handover, encoding and channel encoding.

The base stationThe base station subsystem (BSS) is made up of the base station subsystem (BSS) controller (BSC) and the base transceiver station (BTS). The base transceiver station (BTS): GSM uses a series of radio transmitters called BTSs to connect the mobiles to a cellular network. Their tasks include channel coding/decoding and encryption/decryption. A BTS is comprised of radio transmitters and receivers, antennas, the in- terface to the PCM facility, etc. The BTS may contain one or more transceivers to provide the required call handling capacity. A cell site may be omnidirectional or split into typically three directional cells. The base station controller (BSC): A group of BTSs are connected to a particular BSC which manages the radio resources for them.Today's new and intelligent BTSs have taken over many tasks that were previously handled by the BSCs. The primary function of the BSC is call maintenance. The mobile stations normally send a report of their received signal strength to the BSC every 480 ms. With this information the BSC decides to initiate handovers to other cells, change the BTS transmitter power, etc. Ultra BTS can support max. of 12 TRx (transceivers), while Flexi can support max. of 24 TRx.

BSS = BSC + BTS

BTS:

One BTS operate with some components or a whole site consist mainly:

Shelter or AC room DC generator(DG) Tower(including antenna)

Shelter or AC room

Tower

Tower two types: Roof Top tower Ground base tower

Tower components: Microwave antenna Jumper & feeder cable RF antenna

Microwave antenna

Jumpers and feeders:

BTS has 4 functional parts: Transmission unit Control functions TRX Combiner

Transmission unit: The task of the transmission unit is to connect the BTS to the the Abis interface and, in doing so, create different types of transmission techniques. All nokia Bts have integrated transmission unit. Transmission unit are monitored by the operation and maintenance unit by means of an internal bus Q1.

Control function:It split into four individual functions:a) Operation and maintenance: The O&M processor controls and supervises the operation of all BTS units alone or in co-operation with other processors. It is the main interface for local O&M and controls and supervises the other units as well as delivers all status information to BSC by means of the O&M signaling link, which manages. It stores SW as well as downloads SW to the other units.

b) External alarms and control:It can be used to monitor environmental conditions at the BTS site as well as monitor the state of units, which do not have a processor of their own. External alarm might be an intruder alarm or smoke detector.

c) Master clock:The master clock generates the exact 13MHZ time base for the BTS.Most of the time BTS operate & tune itself to the clock signal from 2Mbit/s link, though in many cases it can also function in plesiochronous mode.

d) Frequency hopping control:It controls the frequency hopping functions of BTS by calculating the frequency hopping algorithm.

Transceiver(TRX):it is the transmitter / receiver unit for the BTS i,e it is the one generating the channel for user / BTS communication. it is divided to 8 time slots. Contains variable oscillator to be able to change the carrier frequency if needed.The TRX can also contain a varying number of plug-in units depend on the BTS.The TRX can basically be thought of in terms of two functional parts: The base band part and radio part. The radio part can also be split into a transmitter part (TX) and receiver (Rx).The Rx part may also be configured to support antenna diversity.The functions of TRX can be divided into two categories: O&M and telecommunication control. One of the most important functions relative to O&M is to download the software and configuration information received from the main O&M processor.

Combiner/coupler(antenna filter):It rejects the band pass filtering signal. Which are not in the received band. It also couples common transmitter signals to common antenna. The coupler also performs degree of transmission loss by

calculating VSWR.The coupler function is to split the received signal to different receiving TRX as well as to amplify the signal. In case of duplexing used it combines both transmitted and received signals to antenna.

Network subsystem:The mobile switching center (MSC): Acts like a standard exchange in a fixed network and additionally provide all the functionality needed to handle a mobile subscriber. The main functions are registration, authentication, location updating, handovers and call routing to a roaming subscriber. The signaling between functional entities (registers) in the network subsystem uses Signaling System 7 (SS7). If the MSC also has a gateway function for communicating with other networks, it is called Gateway MSC (GMSC). The home location registers (HLR): A data base used for management of mobile subscribers. It stores the international mobile subscriber identity (IMSI), mobile station ISDNnumber (MSISDN) and current visitor location register (VLR) address. The main information stored there concerns the location of each mobile station in order to be able to route calls to the mobile subscribers managed by each HLR. One HLR can serve several MSCs.

Home location register (HLR): it is centralized network database which contains all the information about the mobile subscription belonging to specific operator.

Subscriber identity Subscriber supplementary services Location information Authentication information

The visitor location register (VLR): Contains the current location of the MS and selected administrative information from the HLR, necessary for call control and provision of the subscribed services, for each mobile currently located in the geographical area controlled by theVLR. A VLR is connected to one MSC and is normally integrated into the MSC's hardware.

The authentication center (AuC): A protected database that holds a copy of the secret key stored in each subscriber's SIM card, which is used for authentication and encryption over the radio channel. The AuC provides additional security against fraud. It is normally locatedclose to each HLR within a GSM network.

The equipment identity register (EIR): The EIR is a database that contains a list of all valid mobile station equipment within the network, where each mobile station is identified by its international mobile equipment identity (IMEI). The EIR has three databases:

White list: for all known, good IMEIs Black list: for bad or stolen handsets Grey list: for handsets/IMEIs that are uncertain

Operation and Maintenance centre:The OMC is a management system that oversees the GSM functional blocks. The OMC assists the network operator in maintaining satisfactory operation of the GSM network. Hardware redundancy and intelligent error detection mechanisms help prevent network down-time. The OMC is responsible for controlling and maintaining the MSC, BSC and BTS. It can be in charge of an entire public land mobile network (PLMN) or just some parts of the PLMN.

GSM CHANNELS:

Since radio spectrum is a limited resource shared by all users, a method was devised to divide the bandwidth among as many users as possible. The method chosen by GSM is a combination of time- and frequency-division multiple access (TDMA/FDMA). The FDMA part involves the division by frequency of the (maximum) 25 MHz allocated bandwidth into 124 carrier frequencies spaced 200 kHz apart. One or more carrier frequencies are assigned to each base station. Each of these carrier frequencies is then divided in time, using a TDMA scheme. The fundamental unit of time in this TDMA scheme is called a burst period and it lasts approx. 0.577 ms. Eight burst periods are grouped into a TDMA frame (approx. 4.615 ms), which forms the basic unit for the definition of logical channels. One physical channel is one burst period per TDMA frame.

Traffic channels:A traffic channel (TCH) is used to carry speech and data traffic. Traffic on the air inters- channels are defined using a 26-frame multiframe, or group of 26 TDMA face frames. The length of a 26-frame multiframe is 120 ms, which is how the length of a burst period is defined (120 ms divided by 26 frames divided by 8 burst periods per frame). Out of the 26 frames, 24 are used for traffic, 1 is used for the slow associated control channel (SACCH) and 1 is currently unused (see Fig. 5). TCHs for the uplink and downlink are separated in time by 3 burst periods, so that the mobile station does not have to transmit and receive simultaneously, thereby simplifying the electronic circuitry. This method permits complex antenna duplex filters to be avoided and thus helps to cut power consumption.

In addition to these full-rate TCHs (TCH/F, 22.8 kbit/s), half-rate TCHs (TCH/H, 11.4 kbit/s) are also defined. Half-rate TCHs double the capacity of a system effectively by making it possible to transmit two calls in a single channel. If a TCH/F is used for data communications, the usable data rate drops to 9.6 kbit/s (in TCH/H: max. 4.8 kbit/s) due to the enhanced security algorithms. Eighth-rate TCHs are also specified, and are used for signaling. In the GSM Recommendations, they are called stand-alone dedicated control channels (SDCCH).

Signaling:The signaling channels on the air interface are used for call establishment, paging, call maintenance, synchronization, etc. There are 3 groups air interface of signaling channels:

The broadcast channels (BCH): Carry only downlink information and are responsible mainly for synchronization and frequency correction. This is the only channel type enabling point-to-multipoint communications in which short messages are simultaneously transmitted to several mobiles. The BCHs include the following channels:

The broadcast control channel (BCCH): General information, cell- specific; e.g. local area code (LAC), network operator, access parameters, list of neighboring cells, etc. The MS receives signals via the BCCH from many BTSs within the same network and/or different networks.

The frequency correction channel (FCCH): Downlink only; correction of MS frequencies; transmission of frequency standard to MS; it is also used for synchronization of

an acquisition by providing the boundaries between timeslots and the position of the first time-slot of a TDMA frame.

The synchronization channel (SCH): Downlink only; frame synchronization (TDMA frame number) and identification of base station. The valid reception of one SCH burst will provide the MS with all the information needed to synchronize with a BTS.

The common control channels (CCCH): A group of uplink and downlink channels between the MS card and the BTS. These channels are used to convey information from the network to MSs and provide access to the network. The CCCHs include the following channels:

The paging channel (PCH): Downlink only; the MS is informed by the BTS for incoming calls via the PCH.

The access grant channel (AGCH): Downlink only; BTS allocates a TCH or SDCCH to the MS, thus allowing the MS access to the network.

The random access channel (RACH): Uplink only; allows the MS to request an SDCCH in response to a page or due to a call; the MS chooses a random time to send on this channel. This creates a possibility of collisions with transmissions from other MSs.

The PCH and AGCH are transmitted in one channel called the paging and access grant channel (PAGCH). They are separated by time. The dedicated control channels (DCCH): Responsible for e.g. roaming, handovers, encryption, etc. The DCCHs include the following channels:

The stand-alone dedicated control channel (SDCCH): Communications channel between MS and the BTS; signaling during call setup before a traffic channel (TCH) is allocated;

The slow associated control channel (SACCH): Transmits continuous measurement reports (e.g. field strengths) in parallel to operation of a TCH or SDCCH; needed, e.g. for handover decisions; always allocated to a TCH or SDCCH; needed for ªnon-urgentº procedures, e.g. for radio measurement data, power control (down link only), timing advance, etc.; always used in parallel to a TCH or SDCCH.

The fast associated control channel (FACCH): Similar to the SDCCH, but used in parallel to operation of the TCH; if the data rate of the SACCH is insufficient, ªborrowing mode is used: Additional bandwidth is borrowed from the TCH; this happens for messages associated with call establishment authentication of the subscriber, handover decisions, etc.

HANDOVER:

In cellular telecommunications, the term handover or handoff refers to the process of transferring an ongoing call or data session from one channel connected to the core network to another.

Purpose:

In telecommunications there may be different reasons why a handover might be conducted:

When the phone is moving away from the area covered by one cell and entering the area covered by another cell the call is transferred to the second cell in order to avoid call termination when the phone gets outside the range of the first cell.

in non-CDMA networks when the channel used by the phone becomes interfered by another phone using the same channel in a different cell, the call is transferred to a different channel in the same cell or to a different channel in another cell in order to avoid the interference;

again in non-CDMA networks when the user behavior changes, e.g. when a fast-travelling user, connected to a large, umbrella-type of cell, stops then the call may be transferred to a smaller macro cell or even to a micro cell in order to free capacity on the umbrella cell for other fast-traveling users and to reduce the potential interference to other cells or users (this works in reverse too, when a user is detected to be moving faster than a certain threshold, the call can be transferred to a larger umbrella-type of cell in order to minimize the frequency of the handovers due to this movement);

in CDMA networks a (see further down) may be induced in order to reduce the interference to a smaller neighboring cell due to the "near-far" effect even when the phone still has an excellent connection to its current cell;

The most basic form of handover is when a phone call in progress is redirected from its current cell (called source) and its used channel in that cell to a new cell (called target) and a new channel. In terrestrial networks the source and the target cells may be served from two different cell sites or from one and the same cell site (in the latter case the two cells are usually referred to as two sectors on that cell site). Such a handover, in which the source and the target are different cells (even if they are on the same cell site) is called inter-cell handover. The purpose of inter-cell handover is to maintain the call as the subscriber is moving out of the area covered by the source cell and entering the area of the target cell.

A special case is possible, in which the source and the target are one and the same cell and only the used channel is changed during the handover. Such a handover, in which the cell is not changed, is called intra-cell handover. The purpose of intra-cell handover is to change one channel, which may be interfered or fading with a new clearer or less fading channel.

Types of handover:

In addition to the above classification of inter-cell and intra-cell classification of handovers, they also can be divided into hard and soft handovers:

A hard handover is one in which the channel in the source cell is released and only then the channel in the target cell is engaged. Thus the connection to the source is broken before or 'as' the connection to the target is made—for this reason such handovers are also known as break-before-make. Hard handovers are intended to be instantaneous in order to minimize the disruption to the call. A hard handover is perceived by network engineers as an event during the call. It requires the least processing by the network providing service. When the mobile is between base stations, then the mobile can switch with any of the base

stations, so the base stations bounce the link with the mobile back and forth. This is called ping-ponging.

A soft handover is one in which the channel in the source cell is retained and used for a while in parallel with the channel in the target cell. In this case the connection to the target is established before the connection to the source is broken, hence this handover is called make-before-break. The interval, during which the two connections are used in parallel, may be brief or substantial. For this reason the soft handover is perceived by network engineers as a state of the call, rather than a brief event. Soft handovers may involve using connections to more than two cells: connections to three, four or more cells can be maintained by one phone at the same time. When a call is in a state of soft handover, the signal of the best of all used channels can be

Used for the call at a given moment or all the signals can be combined to produce a clearer copy of the signal. The latter is more advantageous, and when such combining is performed both in the downlink (forward link) and the uplink (reverse link) the handover is termed as softer. Softer handovers are possible when the cells involved in the handovers have a single cell site.

NUMBER PLAN:

ISDN number (MSISDN) of mobile subscriber:

• A MSISDN number is the number dialed by the caller subscriber in PLMN.

• Composition of a MSISDN number.

International mobile subscriber identification number (IMSI):

IMSI is an unique number that can identify a mobile subscriber in the PLMN network. Composition of an IMSI number:

Mobile country code+mobile network code+mobile subscriber identification number

Temporary mobile subscriber identification number (TMSI):

TMSI is an identification number assigned temporarily to a visiting mobile subscriber by VLR for the secrecy of IMSI. It is a 4-byte BCD code, used only locally, and assigned by each MSC/VLR independently

International mobile equipment identification number (IMEI):

IMEI is a unique number that can identify a mobile device in the GSM network.

Location area identification number (LAI):

LAI is used to identify the location area. Its number structure is:

Mobile country code+ mobile network code+location area code

Mobile subscriber roaming number (MSRN) :

MSRN is a number temporarily assigned by VLR to a called mobile subscriber which it registers in according to the request of HLR (of called party) in each call for the network to re-route.

Hand-over number (HON) :

HON is a number assigned to a mobile subscriber by the destination MSC/VLR temporarily for routing during inter-office handover. This number is part of a MSRN number. It is used only during inter-office handover of a mobile subscriber. After the connection, it is released and used by other subscribers.

PROJECT: RADIO FREQUENCY OPTIMISATION

1.1INTRODUCTION

Optimization is the process of the identification and rectification of performance affecting problems within the constraints of an existing network infrastructure. Network Optimization can be defined as a continuous process of improving overall network quality.

Every live Network needs to be under continuous control to maintain/improve the performance. Optimization is basically the only way to keep track of the network by looking deep into statistics and collecting/analyzing drive test data. It is keeping an eye on its growth and modifying it for the future capacity enhancements. It also helps operation and maintenance for troubleshooting.

Successful Optimization requires:

Recognition and understanding of common reasons for call failure. Capture of RF and digital parameters of the call prior to drop. Analysis of call flow, checking messages on both forward and reverse links to establish

“what happened”, where, why

The optimization is to intend providing the best network quality using available spectrum as efficient as possible. The scope will consists of all below

Finding and correcting an existing problem after site implementation and integration.

Meeting the network quality criteria agreed in the contact.

Optimization will be continuous process of improving overall network quality.

Optimization cannot reduce the performance of the rest of the network.

Area of interest is divided in smaller areas called cluster to make optimization and follow up processes easier to handle

1.2 REQIREMENTS FOR OPTIMISATION

The requirements for optimization are:

Perceived reduction in network quality Maximizing the use of existing infrastructure Introduction of new services Change in original design parameters

1.3 TYPES OF REPORTS:

Daily Report:they are used to check cell level, Rapid fault identification, Parameters like TCH, congestion, SDCCH, TCH drop rate

Weekly Report:it tell us about the Cell Level,Performance Trend,Traffic trend,Cell detention Cell accessibility

Monthly Report: it tell us about the TCH Utilization, BSC level, Performance trend, Processor Loading,BSS call set up.

THINGS TO INVESTIGATE :

1) Non working sites and TRX2) Inactive radio network features like freq hopping3) Disable/Enable GPRS4) Overshooting sites5) Coverage hole6) High interference spots7) Drop calls8) Capacity problem9) Missing neighbors10) One way neighbors11) Ping Pong HO12) HO not defined

13) KPI for accessibility and retain ability 14) Equipment performance 15) Faulty installations.

2.1 RADIO PARAMETERS

At the deployment phase, operators tend to use standard parameter templates, as thousands of GSM parameter exist. However, due to differences between cells (propagation and interference environment), it is necessary to fine-tune some parameters on a cell-by-cell or adjacency-by-adjacency basis in order to get optimum performance. The essential idea behind optimization is how to find the correct value for a specific parameter applied to a specific cell. Even this task, which requires optimization expertise and is time consuming, can be automated.

2.2 Roles of Network Identification Parameters

Enable the MS to correctly identify the ID of the current network so that it can correctly select the network the user (or telecom operator) wants to access to in any conditions.

Enable the network to be real time informed of the correct geographical location of the MS so that the network can normally connect various service requests with the MS as the terminal.

Enable the MS to report correctly the adjacent cell information during the conversation process so that the network can hand-over the calls when necessary to ensure the continuity of the conversation.

2.3 Types of parameters

1. Network Identification Parameters( CGI, BSIC) 2. System Control Parameters (RLT, CBA, CBQ, etc) 3. Cell Selection Parameters (C1, C2) 4. Network Functional Parameters (INTAVE, LIMITn, etc)

2.4 RF Design parameters

When a Network is designed benchmarking is done for Network quality, capacity, failure and congestion parameters. Whenever the Network is unable to comply with any of the RF design parameters, optimization process needs to be initiated.

OMC Alarm

Any problem in the Network results in a alarm at the OMC.

Whenever a alarm is observed at the OMC it must be carefully analyzed to determine if there is a network problem and if it is required to initiate optimization process.

The alarm can be due to faulty hardware which can create problems in the network.

DRIVE Testing

Drive testing is done continually to monitor the health of the network.

It is a normal procedure to define drive test routes and have them drive tested daily to monitor the network.

All sites and sectors should be tested within the drive test routes at least once.

Following care should be taken while defining the routes

– All major roads and highways should be tested at least twice per week within the agreed routes.

– All cells should be tested for handout and hand-in within the routes if possible.

– The routes should be approximately 2 - 3 hours in duration. This is required to manage the data collected for analysis, routes longer than this can be difficult to analyze and transfer from P.C to P.C due to the files being too large.

Customer Feedback

A procedure to feed back customer information on the performance and coverage of the network can be extremely useful.

The received information is used to target areas requiring optimization and to verify coverage against the RF design.

The information fed back is also used in assessing the growth of the network by identifying areas of high traffic volumes.

2.5 Call Drop Reasons: There are many reasons for call drop. It is important to reduce these reasons for the

performance of a network. These reasons are investigated during the drive test for a call drop.

1). PCH drop > 2% (showcase) > 2.5% (non showcase

2).Drop due to HO failure 3).Interference on target cell 4).In correct serving cell 5).Low signal level and quality 6).Long TA 7).MS enter on high attenuation area like tunnel or building 8).High co channel and adjacent channel interference 9).Extraneous Interference 10).Link Imbalance.

2.6 SDCCH Drop Reasons:

1) Interference (from neighboring cell): The SDCCH will drop if the interference is more and the capacity of network is very low.

If the interferences is occur from the neighboring cell. This is the responsibility of the drive test engineer to allot a different

frequency to each cell. 2) Lack of capacity:

The another reasons is the lack of capacity of a network. Because the lack of a capacity of network the chances of call drop are introduced more. 3) SDCCH time slot:

When the SDCCH time slot is not provided then the call will not be established. 4) High signaling load:

This another reason of call drop when the signaling load is very high.

2.7 HO Failure Reasons:

1) HO not defined 2) BSIC, BCCH same 3) Cable swap 4) TCH not available in neighbor cell 5) Fading 6) Interference 7) HO margin not properly defined 8) LAC not properly defined 9) Faulty hardware 10) E1 terminal swap 11) Lack of dominant server 12) One way neighbor defined

2.8 Rectifying The Major Problems:

1) Traffic:Sometimes SDCCH allocated to the time slots are not sufficient for signaling and presence of more users cause congestion or unavailability of signaling channel to them. So more SDCCH can be allotted to the time slots.Even if 1 TRX card if filled, few time slots of other card can be given to SDCCH.At the time of congestion in TCH, there are some solutions which can be taken to help away with traffic:More time slots can be provided to TCH more users to latch in.Even new TRX cards can be added to increase the capacity

2) Temporary Congestion:Suppose in particular area BTS is established according to the clutter but due to some occasion or anything more number of users make calls in that area few steps can be taken to avoid any congestion or call drops.SDCCH can be allotted to the user by same BTS under which it is latched but TCH of some other neighbor BTS.We can change the Rx level i.e. by increasing the Rx level from -100db of the particular BTS near the crowded area and decreasing Rx level from -100db of some other nearby BTS so that the crowd could latch to those BTS and

calls can be established.3) Alarm:

In case of occurrence of alarm the technical dept is informed and for the time being SDCCH and TCH are allotted some other slots or other TRX.4. Wrongly Define LAC:

LAC can be made same for the nearby two BSCs to remove congestion and frequent communication.

5. NCC and BCC

In the connection mode (during conversation), the MS must measure the signals in the adjacent cells and report the result to the network. As each measurement report sent by the MS can only contain the contents of six cells, so it is necessary to control the MS so as to only report the information of cells factually related to the cell concerned. The high 3 bits (i.e. NCC) in the BSIC serve this purpose.

6. BA

When a MS is turned on, it will scan from the BA (Adjacent cell BCCH table) it remembered when turned off last time. The MS will first search carriers from this table and if none is found it will turns to find any of 30 carriers with highest levels, and then try to decode BCCH carriers one by one according to their level sequences.

7. Remedy For Frequency for Optimization

1. Antenna Down tilt2. Freq Hopping

8. Remedy For Overshooting

1. Tilt2. Power3. Antenna Height

3.1. NETWORK AUDIT PHASE OF OPTIMISATION

The network audit phase serves two primary purposes. First is a review of existing network hardware and software (Inc database) configurations to determine the both validity and consistency across the network. Analysis of data gathered from performance-related network monitoring in order to identify weaknesses or sub-optimal operating performance levels.

3.1.1 DECIDING ON KPIs, MEASUREMENT STRATEGY AND TOOLS

This step in the process is normally only implemented when these elements do not exist within the network. A mature network should already have its KPIs and measurement strategy in place, together with tools to support this process. However, in such cases, part of the network audit process would be to validate these measurement counters and procedures.

3.1.2 MEASURING PERFORMANCE AND ESTABLISHING BENCHMARKS

In mature networks, benchmarks would have already been established. Measuring performance is an ongoing process. However, if a network audit is to carried out as an independent process, a review of existing performance parameters and benchmarks will be required to ensure their validity and applicability to the audit taking place.

3.1.3 PERFORMANCE REVIEW

Having established benchmarks and validated performance parameters, a review of performance is carried out. A possible structure of such a review is as shown in the slide below. The performance Review is not intended to provide all the answers to all the problems, but to highlight the major issues and provide all the necessary background for further analysis, investigation and in-depth troubleshooting of the major performance-impacting problems in the network. It is important that any network performance audit should follow a methodical process and should be systematic in its approach to data collection.