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RF Planning and Optimization in GSM and
UMTS Networks
A Graduate Project Report submitted to Manipal University in partial
fulfilment of the requirement for the award of the degree of
BACHELOR OF TECHNOLOGY
In
Electronics and Communication Engineering
Submitted by
Apurv Agrawal
Reg. No: 140907700
Under the guidance of
DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING
MANIPAL INSTITUTE OF TECHNOLOGY
(A Constituent Institution of Manipal Academy of Higher Education)
MANIPAL – 576104, KARNATAKA, INDIA
2
ABSTRACT
As we have seen over course of time that GSM was superior to analogue mobile networks. When the
standardization work for GSM began in 1982, CEPT ( conference Europeenne des Postes et Telecommunications) ,
could use experiences from analogue networks such as NMT ( Nordic Mobile Telephone) and TACS ( Total
Access Communication System) to create a better digital network. Still today, standardization continues to specify
new features for GSM networks.
Then 3G (Third Generation) network technologies are also already, specified and in many parts of the world
operational. The 3G version in Europe is named UMTS (Universal Mobile Telecommunications System). Its air
interface will be based on WCDMA (Wideband Code Division Multiple Access) transmission. 3G networks
provide substantially higher capabilities than 2G.
RF PLANNING stands for “Radio Frequency & Planning”. Achieving maximum capacity while maintaining an
acceptable grade of service and good speech quality is the main issue for the network planning. RF Planning is the
process of assigning frequencies, transmitter locations and parameters of a wireless communications system to
ovide sufficient coverage and capacity for the services required. The RF plan of a cellular communication system
has two objectives: coverage and capacity.
With the proper RF planning we not only save the huge wastage of the money spent in putting up the Transceiver
setup but also provide a QOS with the current network. The basic approach to RF planning is to first analyse the
present quality of network and then providing a proper recommendation to improve QOS.
3
❖ LIST OF FIGURES
Figure No Figure Title Page No
2.1.1 Cell sectoring 10
2.1.2 Cluster size 4 12
2.2.1 GSM frequency spectrum 14
2.3 GSM architecture 15
2.3.1 Radio Sub system overview 16
2.4 UMTS architecture 17
2.5 BTS architecture 18
2.5.1 RRU 19
2.5.2 BBU unit 21
3.2.1.1 Cluster of sites 25
3.2.1.2 Radio parameter during drive test 26
3.2.1.3 Mapinfo report 27
3.2.1.4 Site mapped on google earth 28
3.2.2 a)-power link calculation
b)- findind LOS
30
31
3.2.3 a)- e-tilt calculation
b)-netact coverage plot
32
33
3.2.5 a)-7/21 frequency cluster re-use
b)- first and second layer cells
33
35
3.3.1 a)- fault window in netnumen
b)-BSNL backhaul connectivity
c)-device power alarm
39
40
42
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Contents
Page No
Abstract 4
Chapter 1 INTRODUCTION
1.1 Introduction 5
1.2 Objective 5
1.3 Organization of Report 6
Chapter 2 BACKGROUND THEORY
2.1 Cellular Network Architecture 10
2.2 Frequency Spectrum 13
2.3 GSM Architecture 14
2.4 UMTS Architecture 17
2.5 BTS Architecture 18
Chapter 3 METHODOLOGY
3.1 Introduction 23
3.2 RF Network Planning 23
3.3 Maintenance and Optimization 36
3.4 Tools used 46
Chapter 4 RESULT ANALYSIS
4.2 Project Goals 47
4.1 Project Result Analysis 48
Chapter 5 CONCLUSION AND FUTURE SCOPE 50
REFERENCES 51
ANNEXURES 52
PROJECT DETAILS 56
5
CHAPTER 1
INTRODUCTION
In telecommunication the whole geographical coverage area is divided into different sized
cells namely micro and macro and each cell is responsible for serving multiple users. This
communication takes place on a certain band of frequencies also known as channels. The
channels are broadly divided into 2 types uplink and downlink depending on flow of data
between BTS and MS. The communication is done through radio waves which are electro-
magnetic in nature and the power varies with the distance. RF PLANNING stands for “Radio
Frequency & Planning”. Achieving maximum capacity while maintaining an acceptable
grade of service and good speech quality is the main issue for the network planning. RF
Planning is the process of assigning frequencies, transmitter locations and parameters of a
wireless communications system to provide sufficient coverage and capacity for the services
required .It is the main duty of a mobile service providers to subject their networks to
continuous monitoring and optimization in order to maintain their business flow and ensure
growth of the company. Optimization means keep a check of the present network by
extracting various statistical reports from drive test as well as OMC software to ensure that it
can be expanded to meet the growing demands of the users as well as the network can be
enhanced to support the new users. The optimization also plays a major role in troubleshoot
of the network.
1.2 OBJECTIVE
Network planning is a complicated process consisting of several phases. The final target
for the network planning process is to define the network design, which is then built as a
cellular network. The network design can be an extension of the existing GSM, 3G
network or a new network [4G] to be launched. The difficulty in network planning is to
combine all of the requirements in an optimal way and to design a cost-effective network.
The network after being planned and optimised should have good signal coverage area at
both macro and micro sites. Rx quality level should be good and there should be minimal
co channel interference.
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1.3 ORGANIZATION OF THE REPORT
The report can be understood as a step by step roll out process flow. It starts with giving a
brief description about the networks which is needed to understand how communication line
is established and the media flows. The next part gives a little overview of the current
network including location of all BTS, the backhaul connectivity to the BSC and other
parameters. Then towards the later part the report emphasis on 2 major steps in the project
which includes the maintenance of the current network which include continuous monitoring
of the present network and the other part focus on the expansion of the network by
installation of new BTS to improve the network. Due to the resources constraints bases
stations need to be managed in groups also known as clusters which are processed together in
order to get a exact knowledge of how a particular BTS is dealing with the interferences from
the nearby networks, whether the handovers are successfully administered and various
neighbouring params.. The steps in the process are phased and designed carefully to ensure
that the project is completed in the given time.
The RF network team is responsible for providing the best QoS to its users which the team
achieves by changing the radio parameters as well as proposing new site. Once the team has
decide the new location of site based on multiple factors which are discussed further in report
the data is handed to the administration block for funds allocation , lease and various other
works. The site location can vary from an existing building to a mast, which has to be built
purposely.
7
CHAPTER 2
BACKGROUND THEORY
Till now we have 4 major distinct generations of mobile which can be classified based on
transport technologies but when we go towards depth of the mobile communication we can
see that with each upgraded generations the users have been given more functionalities and
for this sole reason we do not define the generations based on the frequency but rather on the
basis of functionality offered.
• 1st
generation- provided basic mobile services which is calling with limited mobility. This
technology was based on analog cellular technology.
• 2nd
generation – the only longest serving technology which is still used in many parts
of India . This generation revolutionized the mobile industry by using digital cellular
technology which laid the very foundation of all the major advances in mobile
communication . This technology focused on better utilization of mobile spectrum
and also has added ciphering benefits. This technology made the users familiar with
the concept of Internet as well as provided them with far better telephonic services
than 1 G. This generation also invented the concept of roaming which led to increased
mobility for the users. The GSM was so successful that in 2004 it acquired a user base
of 1 Billion customers.
• 3rd
generation : This generation which arrived in India on Oct 2001 by docomo is
characterized by its ability to carry data at a very high speed compared to its previous
generation which carried at 9.6 kbps. The average downlink data speed in this generation was
around 64kbps which made this tech perfect for youngsters, as well as major it firms. 3G uses
WCDMA access technique which means that each user has been given a unique access code
which is mixed with the signal and tranfsered to ensure that data sent is protected from any
potential theft and leaks. This generation gave a boon to the digital industry.
• 4th
generation:- Launched in 2009 in Ohio , this generation is also called LTE which stands
for long term evolution and is recorded to provide a peak uplink data speed of 500Mbps.
The key to this high speed provided by this generation is its ability to high efficient
utilization of the spectrum using MIMO techniques.It also provides high reliability with a
very long range communication using spatial multiplexing techniques and unlike 3g which
uses both data and voice it is fully data based.
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2.1 CELLULAR NETWORK ARCHITECTURE
The basic idea of a cellular network is to divide a geographical area into small divisions or
cells , Proposed by Bell Labs 1971 these cells would be in a hexagon shape and each cell will
be served by one base station rather than only one for entire city. During the years the
technology has been changed but the base concept is still intact. Now a days operators vary
cell size, power, frequencies to make reliable use of the limited BTS and also now cell
phones are designed for minimal power transmission and hence the concept of frequency
reuse came into play. These cells are further connected to a common BSC through
controllers, switches, cables and routers.
There are few major concepts which are used in designing of cellular network:-
2.1.1 Sectoring
Cells sectoring means to replace a omnidirectional gsm antenna with a sector
antenna in order to reduce co-channel interference and also increase the no. of
user one cell can serve with omni directional antenna. One cell can be portioned
into 3 , 6 , 9…n sectors and now these new sectors acts as individual cells with
individual antenna which provide better signal to mobile users based in individual
sectors. The sectoring also comes with the load in the processing ability of a BTS
as well as BSC because sectoring leads to a huge increase in the no. of handovers
a user will experience.
Fig 2.1.1 – cells with no sector , 6 sectors , 3 sectors
2.1.2 Frequency re use-
Every network operator has limited bandwidth and it is absolutely essential to
plan properly how to use that band of frequency in order to give frequency to all
9
its cell in that particular state. At BSNL Sikkim we have a band of roughly 40
unique frequencies which are to be assigned to total of 360 cells in the area , so
here the concept of frequency use takes place where we allocate same frequencies
to cells which are at a particular distance d [reuse distance] . The cells are
grouped together into clusters of size K with the rule that all the cells in a cluster
will have unique frequencies this helps the RF team to allocate frequencies to the
cells outside a particular reference cluster. The difficult part for any network
engineer is to find the value of K/ re-use pattern.
And the value of K is first calculated by the undermentioned value and then checked whether it
satisfies the I,j relation.
C/I – coverage to interference ration and at BSNL Sikkim we take it as 8db while planning
for cluster.
Alpha - is path loss coefficient taken as 4 for urban areas.
10
Fig 2.1.2 – showing frequency re use pattern for a cluster size of 4
13
GSM uplink – 810-915 = 25 Mhz
25M/200K = 125 channels
Total AFRCN in GSM 900 = 125 which are numbered from 0-124
2.2 Frequency Spectrum :-
2.2.1 GSM-
GSM uses 2 bands one for uplink and other for downlink and for each link there is a set
of frequencies allocated by TRAI . The uplink band is from 890-915Mhz and downlink
is 925-960Mhz and each of these frequencies is separated from the other using a guard-
band of BW – 200Khz and these bands of 200Khz form the channels on which
communication takes place and each channel is further divided into 8 time slots to
ensure the proper utilization of frequency. These channels of BW 200Khz are given
unique numbers and this number is termed as ARFCN – Absolute Radio Frequency
Channel Number.
At BSNL Sikkim we have been given a BW of 5MHZ in both uplink and downlink
bands and AFRCN from 63-87 Similarly each operator buys particular BW in both
uplink and downlink bands.
2.2.2 UMTS/3G-
3G has multiple bands but the band which is used by mobile
operators is 2100 band. The uplink and downlink frequencies
are 1920-1980Mhz and 2110-2170Mhz with same carrier
separation of 200Khz
UARFCN = 50M/200K = 250 which is twice of 2G
14
Fig 2.2.1 – GSM frequency spectrum overview
2.3 GSM Architecture -
Since cellular network are made up of cells so similarly GSM also has cells which together
form the full geographical coverage area. In GSM each cell is assigned a particular identity
number also abbreviated as CGI .This CGI helps the mobile equipment to identify the serving
cell. CGI has 4 parts
• Mobile country code – 404 for India
• Mobile network code – 74 for BSNL
• Local area code- each operator, group the cells into various LAC based on their
distance from BSC
• Cell identity- cell no. given to particular cell which is unique to each cell like 54272
governor house(BSNL)
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Figure 2.3: GSM ARCHITECTURE
The GSM network architecture is made up of 3 subsystems which are discussed below.
2.3.1 Radio Subsystem: -
This system is responsible for allocating resources to the mobile users. All the transmission
of voice, channel allocation, data services are provided by this subsystem only. The RSS
consists of 3 components.
1. Mobile Station
2. Transcoder and Rate Adaptation Unit (TRAU)
3. Base Station Subsystem
a) Base Transceiver Station(BTS)
b) Base Station Controller(BSC)
It also controls the major air interfaces of mobile communication which are Um(MS-BTS)
and Abis (BTS-BSC) interfaces. The interfaces are used to transmit signalling information
and the traffic volume between 2 points of the system. All the transfer protocols like FTP(file
transfer) , LAP(link access protocol) and various others are controlled by interfaces only. The
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AUTHENTICATION
CENTRE (AC)
EQUIPMENT
IDENTITY
REGISTER (EIR)
VISITOR
LOCATION
REGISTER (VLR)
HOME LOCATION
REGISTER (HLR)
MOBILE
SWITCHING
CENTRE (MSC)
NSS
RSS is also responsible for all signal processing function like modulation, speech transcoding
and rate adaptation for both full rate and half rate which is done by TRAU unit.
Fig 2.3.1 – Radio subsystem overview
2.3.2 Network Switching Subsystem-
It forms the heart of GSM network. It is responsible for mobility and calling options only for
roaming users. It doesn’t control the calling functions of the local mobile users as local
functions are controlled by BSC which is part of RSS. It is used for communication between
different networks like public switched telephone network and the local home network. It has
following components: -
MSC controls many BSC and is used to communication between different MSC as well as
different BSCs , for example if a user wants to make a STD call then the BSC will
communicate with the MSC and MSC will check if dialed number is under control of BSC of
same MSC or different MSC controlled BSC and after that MSC ensures end to end
17
communication between both users. MSC is also used to manage the calls in and out of the
network like a call to PSTN even if controlled by same BSC will have to go through MSC in-
order to use channel. Similarly EIR is used to monitor particular mobile numbers as directed
by police/any other government agency. HLR is a register which contains a record of all the
mobile numbers which come under 1 MSC and it also has job to keep updating the location
of user in case it goes into roaming mode and similarly when in roaming same users SIM
information is stored in VLR to ensure that the user is able to use the roaming network
efficiently.
2.3.3 Operation Maintenance Centre-
It is the part of the GSM network which is responsible for proper functioning of all the entire
network including BTS, BSC,MSC as well as the transmission part including the fibre
connectivity , micro link connectivity and satellite communication. The other major function
of OMC is to take care of all billing related queries including post paid and pre-paid. It is also
responsible for maintenance of all network hardware components like antenna, routers ,
switches etc.
2.4 UMTS Architecture -
UMTS architecture is quite similar to GSM except with a few new terminologies like BTS in
UMTS is called NODE and BSC in UMTS is RNC (radio network controller) and different
Fig 2.4- UMTS architecture
18
air interfaces compared to GSM. Except that the working and function of both the
architecture is pretty much same.
2.5 BTS Architecture-
Base transceiver system is responsible primarily for receiving and transmitting radio signal to
and from the mobile unit . It is responsible for transmitting various signaling information to
the mobile unit. Any communication done between MS and BSC takes place through BTS.
BTS also regularly sends time and frequency correction signals to both mobile unit and BSC
to make sure that all the clocks are properly synchronized in order to prevent any packet loss
or time delay. It holds the media card which are responsible for traffic channels and also BTS
has its unique Base Station Code which is used by mobile users to detect the serving BTS.
Typically a BTS has antennas for radiation , transceivers , equipment for encryption and
various other interfacing equipment’s for communication between BSC and MS along with
equipment’s for traffic control . But to generalize it the BTS is made of 2 components :-
➢ Radio Resource Unit
➢ Base Band Unit
Fig 2.5 – hardware architecture of ZTE BTS at BSNL
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2.5.1 Radio Remote Unit(RRU)
It is the distributed and integrated frequency unit that connects to an operators network with
the User Equipment's (UE's) like Cell Phone and mobile devices. The RRU is connected to
the base station via the fiber optic link which is bi-directional link. The optical interface link
is also known as CPRI (Common Public Radio Interface). CPRI is a interface protocol
developed by combination of major telecom equipment's manufacturing company. The RRU
helps to provide flexibility at cellular sites. Undoubtedly, this helps in upgrading to new
equipment's and devices more easily.
Fig 2.5.1 – Radio resource unit
RRU Functions:
1) Acts as a transceiver: transmit and receive the user signals to the base station and vice-
versa.
2) Provides back to back support and connectivity between user equipment's like power,
delay, etc.
3) Control and process the EM signals received from the Antenna via Jumper(Hollow Guide).
4) Provide interface between two physical link: Optical and EM(Electromagnetic).
20
5) Provide Controlling support of the Auxiliary equipment's like RCU (Remote Control
Unit) for electrical tilt adjustment generally known as RET(Remote Electrical Tilt).
6) Generate and sends the different signals like VSWR.
Fig 2.5.1.1 – RRU hardware architecture showing 3 major parts 1 ,2 3
1) CPRI Port: There is 2 port generally named as CPRI0 and CPRI1. However there
may be 1's in some model. The name at suffix may vary. Its function is to connect to
BBU.
2) RF Port: We say it as a Jumper port. The number of jumper port may vary with
model and company's architecture. At least there is 2 jumper port, one of which is for
Tx and another for Tx/Rx. The RF port is connected to the Antenna via Jumper
Cable.
3) RET Port: There is at least one RET port for connection to RCU. The connector is
mostly DB9 in ZTE and may vary with other company's. RCU is connected to the
Antenna. RET cable connects the RCU and RRU.
2.5.2 Base Band unit-
Also referred to as BB card which is used to process original unmodulated frequency
signal. It has in built signal processors which is responsible for between AC and Dc
signals because the connectivity between BSC and BTS is analog signals and the signal
21
sent to RRU is also analog signal so the conversion is mandatory to ensure
communication between MS , BTS and BSC and that’s why it is referred to as heart of a
BTs.
Fig 2.5.2 – full BBU unit at BSNL site “Balwakhani”
BBU has following important components:
1. Control & Clock Board:- This is also know as cc card which is used for clock
synchronization, alarm monitoring ports for environment monitoring, and an Ethernet
port which can be used by Rf engineer to monitor the status of BTS. It is also
responsible for Abis Interface protocol processing and also acts as ethernet switch
for signaling and media transmission.
2. Base Band Processing board:- this is the heart of BBU unit as it is responsible for
providing traffic channels on which networking takes place. It also has dedicated
common radio resource ports as well as optical links for communication with RRUs
22
and processes uplink and downlink baseband signals. The zte bts used at BSNL is
capable of providing 60 TRx and has capacity to serve 24 cells at one time.
3. Fan :- It is responsible to dissipates heat from the BBU unit . It can be monitored and
controlled from BSC from where we can control the rotation speed of the fan and see
the inlet temperature of room . The current BBU unit in BSNL is made of 6 fans in
total and is responsible all the overheating alarms raised at BTS.
4. Power Module Board :- it is responsible for power to be delivered to both BBU and
RRU unit. It consists of 16 internal interfaces for +12v - +24V load power.
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CHAPTER 3
METHODOLOGY
3.1 INTRODUCTION
RF PLANNING stands for “Radio Frequency & Planning”. As we know that in cellular
network the coverage and quality of network are almost inversely proportional as when
coverage increases it degrades the quality so the main objective of RF team is to achieve the
maximum capacity for a network while providing acceptable quality of service to the users.
The Rf team also ensure adequate network capacity as well as flexibility to be provided to the
network to support the increases traffic requirements and at last it has to be cost effective.
The RF part of any network deals with all the parameters related to radio waves which
include frequency planning, antennas location, tilt of antenna, height, location and continuous
optimization of the network. The RF plan of a cellular communication system has two
objectives: coverage and capacity. Coverage relates to the geographical footprint within the
system that has sufficient RF signal strength to provide for a call/data session. Capacity
relates to the capability of the system to sustain a given number of subscribers. Capacity and
coverage are interrelated. To improve coverage, capacity has to be sacrificed, while to
improve capacity, coverage will have to be sacrificed.
The RF team has 2 major responsibilities to adhere to:-
1. Network planning for the new site
2. Maintenance and optimization of the present network
3.2 Network planning for the new site:-
The network planning for new sites includes analysis of drive test results , data from OMC ,
frequency planning , post-optimization of site , site location , antenna tilt , antenna height ,
power budget calculation , transmission planning , the neighboring cells definition , coverage
area and many other aspects are also considered while planning a new site.
24
The question that RF team tries to answer before submitting the report for the new site are:-
• Area of coverage required?
• Can some site be optimized to provide coverge instead of new site?
• Height of antenna?
• Whether site be a stand alone or a cluster site?
• Calculate coverage proababilities using drive test?
The major focus on planning of new site include:-
1. Site location
2. Antenna height calculation
3. Antenna tilt calculation
4. Transmission planning
5. Frequency planning
3.2.1 Site location:-
A normal BTS has a installation cost of around 12-15lac and annual maintenance cost of
around 2 lac . So , it is not feasible to just randomly plant a BTS without proper planning
because if a BTS installed at a wrong location will not only degrade a network by creating
un-necessary interference to the nearby BTS but also not generating the required revenue
needed by the operators. The location of BTS is properly decided after careful examination of
the results obtained from drive test. The various steps involved in basic planning of the
location of site are listed below
3.2.1.1 Grouping of sites into clusters:-
25
It is not feasible to view a cellular network pint by point so the sites this step requires to be
familiar with the terrain of the place as well the LAC code , Range and the technology
partner of BTS ( Ericsson and Nortel and ZTE ) so that all the sites(60) can be divided into
various clusters(18) and Standalone sites to make it convenient for the Drive Test. The sites
are first mapped into software “MAPINFO” from database maintained at BSC and once the
plotting of sites with proper azimuth are done, the clusters are defined. The basic rule
followed by the Rf team at BSNL is that the if the nearest neighbor of site is within 2-3 km it
will be in a cluster with the neighboring sites while other would be a Standalone Site.
Fig 3.2.1.1:- SITES GROUPED IN CLUSTER
3.2.1.2 Drive Testing:-
It is a method of measuring and assessing the coverage, capacity and Quality of
Service (QoS) of a mobile radio network. The technique consists of using a car
containing mobile equipment which is used to detect and record a wide variety of the radio
parameters of network in a given geographical area. The DT engineer has to constantly keep
an eye on the Radio parameters to make sure that the cell which is being served is having a
unique BCCH and BSIC no. in-order to avoid call failure. The scripts for both Long calls
26
(30min) , short calls(2 min) and FTTP download have to run in Idle , dedicated and packet
switched mode on the mobile equipment. TEMS is the software used for this testing. The
engineer has to keep an eye on event window of the software to report alarming errors like
call barred , missing neighbor , high frequency of handover. The algorithm for scripts have
been attached at end of report.
Fig 3.2.1.2:- Radio parameter 2G and Event window of cluster
7 during drive test
3.2.1.3 Mapping of Drive test report into Map info –
Once the drive test of the cluster is completed, the log file is exported with following
parameters and then a final report is generated which is analyzed to improve the network.
1. 2G – Rx level and quality (Full/Sub) , Co-channel Interference , Handover
success rate , Call drop rate , Call attempted ,SDCCH rate , Call blocked and
a full event window for better understanding
3G
2G
2. 3G – RSCP( received energy) , INTER-RAT handover , RRC establishment
rate , HSDPA Throughput , Interference per chip symbol , Primary Scrambling
code
Based on these reports we can analyze the coverage area of the present sites and whether a
new site is required to ensure a proper coverage to users.
Fig 3.2.1.3 – Mapinfo report showing the received signal strength in 2G and 3G of the BTS
27 ranipool
28
3.2.1.4 Viewing of the demographics , terrain on google earth-
After the above 2 steps we can get approximate area as to where a site is to be needed but in
order to pin-point the exact location of the site the network is analyzed on google earth to
check for the population density , the terrain of the area , the exact latitude and longitude of
the place because we generally want the site to be installed at the highest point in the area to
ensure best signal propagation and these all are planned based on google earth pro.
Fig 3.2.1.4 google earth images of the site
3.2.1.5 Manual survey of the site:-
Once the exact location has been pin-pointed the RF team visits the site for a survey
to ensure that the location is feasible for setting up the BTS as well for the
maintenance of the BTS in future.
3.2.2 Antenna height calculation: -
The antenna used for mobile communication is a radio antenna and the waves are radio
waves so the it is important to know the type of propagation model which will be used to find
29
the path loss in the environment. many times the mobile user and BTS are not in LOS but still
the waves reach to the mobile user propagating through the building, that means the mobile
communication is a reason of multipath propagation of waves so for this sole reason a proper
propagation model needs to be chosen to get a estimate of a path loss incurred. The model
used for GSM in BSNL is Okumura–Hata model.
4 Lu is the path loss for urban area in db
5 F is frequency in Mhz
6 HB and hM are base station and mobile antenna height.
As we can see that in the above equation we have 4 variable which are path loss , distance ,
height of mobile , height of base station. For this we take some standard assumption.
1. Mobile height (hM ) – 1.5m
2. Distance (d)- geographical distance from its nearby neighbor boundary coverage area
and cell radius = d/2
3. Path loss- it is found using power link budget calculation
Power link budget Calculation:-
Power link is used to quantify a radio link performance. It basically includes all gains and
losses incurred by the wave travelling from transmitter to receiver through a medium. The
power link budget calculation is done in telecom industry to get a estimate of maximum
allowable path loss which is further used to determine the base antenna height.
30
Fig 3.2.2 (A) – TRAI specified calculation for power link calculation for ZTE bts and Power link budget for 100m feeder
cable suggests that maximum path loss allowed should of 158.6 dB
Now after you calculate the maximum path loss use it in the hata equation to find the
minimum height of BTS which can be used. Like for the above example when the hata model
is used we can found that the height of antenna > 40m
And once the minimum threshold height is found we use software “wireless networkplanner”
to see the effect of height variation with respect to the path obstacles like tall buildings, hills
or any other obstacle. For this software we set a point at distance of d from BTS to check the
blockage caused by all the obstacles in the way and a height is chosen which causes
minimum blockage with the maximum allowed height to be 60m.
31
Fig 3.2.2 (b) – finding LOS for various heights of BTS
Similarly for 3G model used is COST Hata Model with C=0.
3.2.3 Antenna Tilt Calculation :-
The efficiency of a BTS depends on correct configuration of its antenna and one of the most
important part of optimization of network is its antenna tilt. Cell tower Antenna has a
radiation pattern with the primary lobe pointed towards horizon. Down tilting the antenna
limits its range by reducing strength in horizon and redirecting the radiated power towards the
cell the antenna is serving. A increase in down tilt of antenna will reduce the coverage area
but gives a higher signal strength and a lesser tilt might cause the BTS to overshoot the
signals and cause interference with the other site. It is the goal of Rf engineer to provide the
highest signal strength for the coverage area of cell decided. The tilt of antenna is a 2 step
process which is e-tilt calculation and Net Act simulator report.
32
1. In this tilt is calculated using basic law of trigonometry. A point at distance d is selected
which is generally the last coverage point of the BTS and then on Wireless network tool
we do the calculation taking the height variations of hill and BTS.
Fig 3.2.3 (a) – the step by step calculation of tilt of antenna
2. Net Act is one of the most powerful tools used in planning of BTS sites. The survey
engineer brings the survey reports. The new site as well as the nearby sites are mapped
onto the Net Act tool with input variables as tilt of antenna , power of antenna , height of
antenna , ARFCN and PSC of sites . Now, based on these inputs the software gives a
virtual coverage area .TheNetActtoolalsogivesusthesignalstrengthinDbaroundthesite
andthisisrepresented bythevariouscolors. Thus,wecheckthetiltoftheantenna, soasto
prevent the overlap of the signals and accordingly we adjust the tilt of antenna ranging
from 00
-70
.
33
Fig 3.2.3(b) – Net act window to show the received signal around a BTS which help in tilt optimization
3.2.4 Transmission planning: -
Transmission plays an important part in the mobile communication. The transmission
planning involves connectivity of the site with BSC. the site could be directly connected to
BSC or it can be connected to a neighbor site which is further connected to the BSC. This
inter connectivity is achieved using 2 ways either by mini-link or by optical fibre cable. The
basic rule of mini-link connectivity is that the both the sites should be in the perfect LOS. So
it is important to understand and analyze the neighbors of site to understand how the
connectivity would be planned.
3.2.5 Frequency planning:-
As we know that in cellular network each operator has a limited band-width that means it will
have limited carrier frequencies. In cellular communication the frequency re-use concept is
used for efficient allocation of BCCH number which is unique to a cell in a cluster and all the
34
signaling and communication information are done through this channel only. As we have
discussed in previous sections that cells are divided into cluster for frequency reuse and
cluster can be of size 3,4,7…etc. The common notation used in telecom industry to show the
frequency reuse is n/m where n is the re-use factor or cluster size and m is no. of unique
carrier frequency no.
At BSNL, Sikkim the re-use pattern used is 7/21 which means that a total of 7 sites with 3
sectors use have been given 21 unique BCCH frequencies to use. So, frequency allocation is
done within these 21 frequencies.
Fig 3.2.5(A) :- 7/21 cluster re-use pattern
For manual frequency allocation there are certain steps to be followed:-
Step1:- write the 21 BCCH site wise in a pre-defined IMT format , frequencies are assigned
in sequence to cells A1-G3 and BCCH allotted to BSNL is from 65-96 , where the last 10 are
used for various govt secure establishments.
A
1
B
1
C
1
D
1
E
1
F
1
G
1
A
2
B
2
C
2
D
2
E
2
F
2
G
2
A
3
B
3
C
3
D
3
E
3
F
3
G
3
35
FRE
Q
NO
1 2 3 4 5 6 7 8 9 1
0
1
1
1
2
1
3
1
4
1
5
1
6
1
7
1
8
1
9
2
0
2
1
BC
CH
6
5
6
6
6
7
6
8
6
9
7
0
7
1
7
2
7
3
7
4
7
5
7
6
7
7
7
8
7
9
8
0
8
1
8
2
8
3
8
4
8
5
So it is clear from this pattern that site A will be allotted BCCH – 65,72,79 similarly we can
find which pair of frequencies to be allotted to a site based on its alphabet.
Step 2:- identifying the neighbors of the siteand grouping them into 1st
and 2nd
layer cells
based on the interference interference level which is decided on basis of the distance from the
new site.
Theoretically site which are at a fixed distance from reference site say within 1km are termed
as first layer cells and sites which are at a distance of 3km are termed as 2nd
layer cells. Due
to less distance from the reference site , the interference caused by first layer cells is way
more and hence the planning of frequency is done in such a manner to reduce the first layer
cell interference by allocating them unique frequencies and second layer cells are also
considered in case after frequency planning the data reports from drive tests shows high
interference at the reference site. This dividing of cells into various layers becomes difficult
while implementing it in practical use as the sites are not at equal distance so to get the best
results we use a range estimation.
• First layer cell – 1-2Km
• Second layer cells- 2-5Km
Fig 3.2.5(b) – all the first and second layer cells from target site
36
Step 3 :- The next step involves finding the BCCH of the first and second layer neighbor cells
so that they can be assigned a alphabet from A-G based on BCCH range as discussed in step
1. Once the neighbor sites are labelled we can see which alphabet to be assigned to the new
site to minimize interference from first layer cells and if we have multiple alphabet can be
assigned to the new site , the distance from second layer cells is considered minimize
interference.
Step 4:- post drive test to be done to check the interference caused by the new site and the
interference caused in the target cell.
3.3 Maintenance and Optimization of present network:-
The cellular networks requires a continuous monitoring and optimization to make sure that
good quality of service is achieved throughout the geographical coverage area without any
data holes. This process is done by Operation and Maintenance unit of the network. The OMC
works intwodifferent areas namelyRADIOandSWITCH.TheOMCprocesscanbedividedinto
followingfivetypes.
▪ FaultManagement:
▪ Configuration Management
▪ Database Management.
▪ Performance Management
▪ SecurityManagement
This OMC unit is nothing but a generalized software developed by a manufacture which can
remotely control all the BTS installed in the area. In BSNL Sikkim we have 2 software.
1. Net Numen for ZTE BTS
2. Winfoil for Errison BTS
Net Numen:-
To allow carriers to cope with the modern challenges of managing multi-technology networks
while keeping pace with the evolution of full-service operations, NetNumenTM
U31 is
designed to provide end-to-end capability for high O&M efficiency. It is basically a unified
37
management interface for telecom industry that lets the RF team view the current status of all
the BTS within one BSC. Few of its functionality are noted down below:-
Fault Management: The fault management helps the operation and maintenance personnel
know in time all abnormal running conditions in the CDMA network and helps them to
locate causes and positions, so that the user can find, handle and solve the system faults as
soon as possible and ensure normal running of the network. Alarm correlation analysis
helps eliminate redundant alarm information and alarm storm, locate and eliminate fault
causes.
Performance Management: it is responsible for monitoring and analyzing performance of
the network and NEs. With various performance data collected from the NEs, the OMC
knows network running conditions, provides the operation and maintenance personnel
with detailed information that can offer guidance to the planning and adjustment of the
network engineering and improve the network quality.
Configuration Management: The configuration management presents configurations for
all kinds of equipment resources and settings of important parameters in the CDMA
network, so that the user can know easily the configuration and usage of the key network
resources, make related statistics, improve management, and maximize profits.
Additionally, it also provides necessary reference data for performance management and
fault management.
Security Management: The security management can protect and prevent unauthorized
OMC users from accessing or destructing the OMC and its NE system, and legal users
from ultra vires action. It records all security operation information for review and
ensures legal use of the system.
Topology Management: The topology management provides a topology view for the
whole network. It provides key information management, including the geographic
location, alarm, and KPI.
Log Management: The log management completes management of all kinds of system
logs that records information about all events and operations in the system. With the logs,
38
the user can know whether the system runs normally or not, locate the cause of the fault,
and trace back and review important events.
3.3.1 Maintenance of network:-
Due to hilly terrain maintaining the network is really difficult in the area. The first step of
network maintenance is to make sure that the BTS is up and functional which is monitored
using fault management of net numen. The fault management lets you visualize the whole
network including all nodes to see which BTS is non-operational as we can see in the above
figure that BTS with a red cross tells that the BTS is non-functional at the time.
The software works on the method of alarm raising where all the alarms raised within a BTS
are classified into 3 categories:-
➢ Critical alarms:- these alarms are of utmost priority as these directly affect the
services of BTS terminating all the services and making BTS go in shut down mode
➢ Major alarms:- these alarms may or may not affect BTS in near future so they come
second in priority list and are monitored continuously to ensure that they do not block
any of BTS services
➢ Minor alarms:- these alarsm are more like warning alarms which do not affect the
BTS functionalities and are not monitored until there priorirty is changed to major or
critical.
39
Fig 3.3.1 (a) – fault management window of Net Numen
The RF team keeps a continuous eye on these alarms and based on the action taken by RF
team the alarm state is changed to Acknowledged , Unacknowledged and cleared. Once a
BTS is down RF team check the alarm code to know the possible problem. There are various
alarm codes which help engineer to know the possible cause. Few of alarms code and
handling solutions are mentioned below:-
➢ Link between omm and ne broken – one of the most common alarm codes at is
raised at the BTS which means that there has been lost in connectivity between the BTS
and BSC with the possible cause of either power failure or fibre link/micro-link broken.
The next step of troubleshoot for this alarm is to see the back haul connectivity diagram
of BSNL Sikkim in order to trace the connectivity back to BTS. Then with this diagram
we trace the various intermediate nodes and check their status if they all are perfectly
functional then we can rule out the possibility of fibre break from BSC. Once this step is
taken we run a query to check the history of the alarm which gives us a idea for how long
the alarm has been on. If a alarm has been raised for a longer than 6-7 hrs it is possible
that there has been a fibre break between the BTS and the next intermediate node
40
because power failure for that long is very rare and the issue is raised to transmission
team to rectify the fibre.
Fig 3.3.1(b) – back haul BSNL connectivity
Abnormal voltage:- this alarm is raised at BBU unit of a BTS which causes BTS to
continuously turn ON/OFF , it is a critical alarm which has to be solved immediately as it
posses direct risk to the BTS life. The handling suggestion for this BTS is to change the
power relay in the power module of BTS. Once this alarm is raised it is directed to the
field electrician to replace the relay from the store.
VSWR critical:- Voltage Standing Wave Ratio represents a ratio between the
transmitted power to received power through a transmission medium. It is also a measure
of efficiency of a transmission link. The allowed VSWR in mobile communication is 1.2
and as soon as value crosses 1.4 the alarm is raised thereby shutting the BTS. The
handling solution for this alarm is to check the co-ax cable between bbu-rru or there
might be moisture in attenuator attached to BBU due to heavy rains. For this RF team go
to site and check the cable and attenuator manually.
41
➢ Overheat Alarm:- each BTS has 2 mode of heat dissipation the first is the internal fan
panel of BTS and other is centralized air conditioning for the whole equipment’s like BTS
, power supply and routers. The problem is solved by manual visit to site and replace the
faulty part.
RRU-BBU link broken:- this alarm is raised when the co-axial cable between RRU
and BBU is broken which makes RRU and antenna inactive and hence no communication
in that frequency spectrum is not possible in that area. If 2g link is broken 3G will still
serve the area. For more detailed information we open up alarm description to know
which link is broken RRU-BBU(900 gsm) or RRU-BBU(2100 3G) and that particular
cable is replaced.
Device Power down:- this is critical alarm which can be caused by either power
failure to BP card of BTS , CC card may be non-functional , antenna power might be
down , RRU power link broken . to diagnose this open up the rack chart of BTS to locate
the actual problem and as it can be seen in the image below that there is a red warning on
RRU S900 in the rack chart that means the 900 spectrum GSM antenna is not receiving
power and it is rectified by checking RRU power supply attached to BBU unit.
42
fic at each cell. This report is the most important for process ofFig 3.3.1(d) -rru power supply
Fig 3.3.1©- device power down alarm
3.3.2 Analyze BBH report:-
Busy Bouncy hour report is nothing but the network report of the busiest hour or the hour
with the highest traf
optimization as this report helps the team to understand various Key performance indicators
based on which the further optimization of network takes place . The BBH report is generated
in Netnumen software by running a query in history performance template and is auto-mailed
to the head of the BSNL for that telecom district. Key Performance Index is the set of
parameterswhichareconstantly observedtocheckthe performanceofthenetwork.Thisincludes
SDBlock,SDDrop,TCHBlock,TCHDropandHOSR.
43
Fig 3.3.2:- BBH report
The various parameters and there thresholds are given below:
▪ SDBlock <0.5%
▪ SDDrop <2.5%
▪ TCHDrop <3.5%
▪ HOSR >85%
SD Block: -
❖ SDCCH is a bidirectional logical channel used indifferent ways:
-Registration: periodic location update.
-Call setup: immediate assignment.
-SMS to/from MS in dedicated mode.
SD blocking means that you are not getting SD resource for the call origination. When MS
connects with BTS then RACH(random access channel) and SDCCH( stand alone dedicated
control channel) are provided but when MS doesn’t receive SDCCH channel due to some
44
problem it results in SD drop. In this case the MS is not able to initiate the call. The SD drop
is also a measure of Call Set up Success rate.
CSSR = 100-SD drp
Removal of SD block:-
1. Problem with BP/Media card which is responsible for channel allocation
2. Overshooting which can be caused due to reflection from hills may lead the MS
connect to a far away cell which might cause the drop and to rectify it go for DT to
verify which cell id is the mobile equipment
TCH drop :- it is also known as call drop which happens when the mobile station is
already having channels and somehow the call gets disconnected. It is measured by TCH
drop parameter of OMC report .The major reasons of call drop are
• Poor received signal
• Late handover reducing the serving signal strength less than threshold value.
• Co-channel Interference
TCH drop troubleshoot solutions:-
1. Check the BCCH frequency of the cell as well as the nearby cells to check for
45
interference
2. Poor coverage quality in the cells which can be rectified by reorientation of the
tilt of antenna
3. Check the allotted power to BTS if it is low increase it to max of 43db as
specified by TRAI
➢ HOSR: it refers to handover success rate , HO activity is performed to maintain – Call
continuity and call quality . The inputs that the BSC uses for making a handover
decision, from the received MRs from the MS is the DL signal strength, DL quality, and
the signal strength of the six best reported neighbours. From the serving BTS, for the
same MS the BSC will use UL signal strength, UL quality and TA.
• If HOSR will be good TCH drop will also be good.
• If Handover success rate degrades call drop rate will take place.
PROCESS for Optimization:
1. Take the detailed report showing cause & target cell
2. Check congestion; hardware Alarm; Quality; Rx level
3. Missing neighbour – Best server is not in there in neighbour list
4. BCCH Missing
5. Same BCCH & BSIC combination
➢ SDCCH Drop:- it is an important KPI which largely affects subscriber
service quality. When MS is already on SDCCH and in-between communication
with Base station SDCCH channel got disconnected abruptly then SDCCH Drop
has occurred.
PROCESS for Optimization:
1. Check the hardware alarm
2. Calculate the number of traffic channels required based on traffic erlang
3. Check the neighbour sites data to find which site is causing interference
4. Check for Neighbour Relations and correct if it is not proper
5. High VSWR(1.05-1.3) due to feeders generally leads to high SDCCH drop rate
46
Few of problems from field and actions taken:-
I. Problem code : 22685A
Description:- high SDCCH drop rate at site 2516A , the net numen shows PA
power alarm
Action taken:- Replace the Power cable.
II. Problem code : 03312B
Description:- high SDCCH drop rate is recorded at site “balwakhani A”
Action taken:- had the wrong BCCH so BCCH changed from 70-77
3.4 TOOLS USED:-
The whole RF planning and optimization is done using the following software/applications
• TEMS investigation 18.1:- one of the major tool which is widely used by
all mobile operators to analyze the network condition. The tool provides
with coverage related information like Received signal quality, Co-
interference, Handovers.
• MAPINFO Professional 5.1:- this tool is used to virtually plot the present
location of all the serving BTS and also plotting the new proposed sites.
• GOOGLE EARTH:- this tool is used to see the geographical information
about the place which includes population , buildings , roads , mountains.
• SALTLAKE by ERISSON:- the tool is heart and soul of Operation And
Maintenance center of the network and is used to change various radio
parameters like power , frequencies , channels and many more.
• NETNUMEN by ZTE:- it works the same as SALTLAKE but it is used for
all ZTE BTS.
47
CHAPTER 4
RESULT ANALYSIS
4.1 PROJECT GOALS
Network planning is a complicated process consisting of several phases. The final target for
the network planning process is to define the network design, which is then built as a cellular
network. The network design can be an extension of the existing GSM network or a new
network to be launched. The difficulty in network planning is to combine all of the
requirements in an optimal way and to design a cost-effective network.
Pre-planning contains network dimensioning and system configuration without any site
location information. Information on amount of base station and transmission equipment
divided on area basis. Business plan should be available. Basic requirements from the customer
and authorities and selection of equipment must be taken into account. This procedure is under
continuous updating as new technologies appear. In pre planning/ dimensioning phase, we
dimension the network elements based on the capacity and coverage calculations. The
calculations for capacity and coverage are based on the customer requirements and decided
planning criteria. These calculations give a rough idea how many BTSs and TRXs are needed
for the specified area . Network specific Planning guideline defines the network design criteria
and thus the maximum amount of connections between transmission equipment using different
topologies (point to point, chain, star and loop) is known and thus it is ensured that the planned
transmission network fulfils items defined in the planning guideline. Information of possible
existing transmission network with different transmission media are also gathered and
investigated during the pre-planning process. The pre-planning is prepared to be used as a basis
for the preparing the network configuration plan. Current network performance and traffic
should be evaluated by OSS reports and by performance measurements. After this evaluation
we should have enough information to point out the problem areas and the main targets of
interest in the existing network. Also we need to consider location of hot spots and cluster
areas.
Initial frequency plan strategy must be studied already during the dimensioning
this leads to estimations of market share in the beginning and objectives for the future. More
detailed estimations are needed on how much each user of a certain type is using the services
48
provided. The needed capacity for each service and onwards for the whole network can be
calculated from the estimated average usage. The basic requirements for the cellular network
are to meet coverage and quality targets. These requirements are also related to how the end
user experiences the network. Coverage targets firstly mean the geographic area the network is
covering with an agreed location probability, i.e. the probability to get service. The
requirements also specify the signal strength values that need to be met inside different area
types. The quality targets are related to factors such as the success of the call, the drop call
ratio, which should not exceed the agreed value, and the success ratio for the call setup and for
handovers.
4.2PROJECT RESULT ANALYSIS
During the course of the project I worked on two phases of the projects .My first phase of the
project included the layout and testing of the 90 sites across Sikkim with my my major phase
focus is on the changing radio parameters to cut down the need for installation of new BTS
and the second phase From the very initial stages of planning and testing our work was to
ensure that those sites are properly worked upon and in the end ensure whether or not the
work on the sites are managed properly.
There are two types of sites, first is the new site, which deals with the making the site from
the very beginning, starting from raw material collection to planning then to testing and later
evaluation. The other type of site is the upgradation, this deals with the site, which is already
set up and needs few upgradations whether it be the change of broadcasting frequencies, the
new technology, addition of more TRX , addition of sectors , changing the tilt or azimuth of
antennas.. In this the major factor we make certain changes, thus submitting to DOT.
During my time at BSNL , I have successfully reduced the SDCCH drop rate from >3% to
almost at 1.5% without suggesting the set-up of the new BTS. In many remote sites which are
surrounded by hills a little adjustment of about 1-2 units in electrical and magnetic tilt we
were able to increase the coverage area of the site. In army sites due to huge traffic
congestion , there was a significant call drop rate which is reduced to an average of 1% from
critical rate of >5% which was achieved by addition of Media card in BTS racks. The
continuous monitoring of the bts sites through software net numen has reduced the no. of
49
non-functional sites to about 5% from 20% of the total sites and careful use of frequency re-
use concept has helped to reduce the co-channel interference. The total of 7 new sites which
are to be planned have been allocated the latitude and longitude by analyzing the results from
drive test and location of sites including the co-ordinates as well as azimuth , the height of
antenna have already been forwarded to the top management team for final approval.
Cell
ID
LA
C
SITE
NAM
E
Longi
tude
Latit
ude
BCC
H
BS
IC
AZI
MU
TH
PS
C
TYPE
OF
SITE
BTS
heig
ht
Transmission
connectivity
tilt
541
51
54
SICH
EY
88.60
61
27.3
458
70,77
,84
25
20/1
20/2
40
2G
30m Ofc link-
BSC-sichey
0
541
40
54
6TH
MILE
88.68
85
27.3
751
111 20
40/2
70/3
20
212
ARMY
IP
20m OFC link-
BSC-
ganjulama
dwar_6th
mile
3
197
62
119 Cipla
88.55
066
27.1
850
8
71,78
,85 21
50/2
35/3
00 198
2G+3G
40m Microwave
link BSC
GTK
2
192
51
119
-2G
,
160
17-
3G
Gayzi
ng 1
88.25
806
27.2
929
4 20
0/12
0/24
0
96
2G
NORT
EL
+3G
ERICS
SON
36m Ofc link –
BSC -
penengla-
damthang-
gayzing1
5
432
15 119 Aritar
88.67
03
27.1
869
69,76
,83 24
0/12
0/24
0
100 ZTE
45m Ofc link
BSC-upper
chandmari_m
icrowave link
to Aritar
3
478
594 54
Bager
khola
88.49
6
27.9
3
71,78
,85 23
10/1
20/2
70 ZTE
30m Ofc link –
BSC-
bagerkhola
1
119
,54
Assa
m
linze
88.496
4
27.1
913
75,82
,89
2-
1
0/12
0/24
0
ZTE
40
m
Microwave
link BSC to
Nmachi-
OFC link to
assam linze
4
Table 4.1:- New site database including all the parameters
50
CHAPTER 5
CONCLUSION AND FUTURE SCOPE OF WORK
I would like to conclude that RF planning in mobile communication is one of fastest growing
field which the newly under-grad students should consider as it will lead them to a long term
sucess.
And with the advances in the mobile technology and a huge competition among the mobile
operators the QOS to be provided to user is a real game changer. Since with the bandwidth
constraints it has become absolutely necessary to plan and implement a efficient network
which has expoansion capabilities and a adaptive nature to cope up with the new mobile
generations.
It is mandatory for the next-generation mobile cellular system to achieve the performance
that any present IMT-2000 system cannot, the next generation key focus would be on a much
higher throughput , data speed in Gbps , much lower latency , ability to support very larger
user base and much higher spectrum utilization efficiency. As it is been in trend to use a
laregr bandwidth with each new generation we can expect a exponential increase in the
bandwidth channel however with a higher bandwidth channel some major advances has to be
done in ciphering and deciphering techniques to prevent data breach. Radio access
technologies for the XG cellular system is gonna inherit the present technologies of the 4G
systems, and introduce new technologies to meet challenges in cellular networks.
Characteristics of a broader channel bandwidth, and by increased performance requirements.
Keeping the leadership in radio access technologies, NTT DoCoMo proposes VSF-OFCDM
and VSCRF-CDMA for XG broadband radio access. The proposed technologies evolve
CDMA-related technologies by introducing new technologies, such as multicarrier and chip
repetition to meet the performance requirements of next-generation cellular systems.
As we have seen that 3G architecture was both IP based and voice based due to which there
was limitation both at level of network architecture as well as on the service architecture and
then $g came which was all IP architecture so judging by trend we can predict that the XG
will be all IP based but with some innovative and lucrative services. .
Architecture, believing that this division of the architecture into four distinct layers, with
different degrees of coupling, provides a foundation for providing local control to niche
markets while ensuring that the system as a whole retains key control and coordination points
51
for third-party services. Aside from a coherent long-range architectural framework, we have
developed research results in the areas of mobility management, security and cryptography,
network programmability and support for value-added services that are among the key
enablers for the XG architecture
52
REFERENCES
[1] Theodore S Rappaport, Wireless Communication, 2nd ed., MA MIT Press, 1986.
[2] C.Y. Lee, Cellular Mobile communication, 4th ed., Eds. Princeton, NJ: Princeton
Univ. Press, 1985, pp107-125.
[3] Sanjay Sharma, Cellular Mobile communication, vol, 5, IIT Bombay, Mumbai
Canavad press, 2006, pp145-189.
[4] Web: www.coai/subject topics/ data trends.com
53
ANNEXURES
6.1 Annexure 1
7 Algorithm for short call used in drive testing
8 Algorithm for FTP up and down link rate to check data speed
54
6.2 Annexure 2
9 Flow diagram for TCH Drop rate analysis
10 Flow diagram for high Handover Failure rate analysis
55
Handoverfailure
rate
incorrect
parameters
Co-BCCH
BSIC
Missing
neighbours
Too many
neigbours
with high
power
TCH
congestion
TCHDroprate
low
strength dl
highTA
rx quality
sub
hardware
faults
handover
failure
less defined
channels
high
interferance
56
PROJECT DETAILS

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RF Planning and Optimization in GSM and UMTS Networks

  • 1. 1 RF Planning and Optimization in GSM and UMTS Networks A Graduate Project Report submitted to Manipal University in partial fulfilment of the requirement for the award of the degree of BACHELOR OF TECHNOLOGY In Electronics and Communication Engineering Submitted by Apurv Agrawal Reg. No: 140907700 Under the guidance of DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING MANIPAL INSTITUTE OF TECHNOLOGY (A Constituent Institution of Manipal Academy of Higher Education) MANIPAL – 576104, KARNATAKA, INDIA
  • 2. 2 ABSTRACT As we have seen over course of time that GSM was superior to analogue mobile networks. When the standardization work for GSM began in 1982, CEPT ( conference Europeenne des Postes et Telecommunications) , could use experiences from analogue networks such as NMT ( Nordic Mobile Telephone) and TACS ( Total Access Communication System) to create a better digital network. Still today, standardization continues to specify new features for GSM networks. Then 3G (Third Generation) network technologies are also already, specified and in many parts of the world operational. The 3G version in Europe is named UMTS (Universal Mobile Telecommunications System). Its air interface will be based on WCDMA (Wideband Code Division Multiple Access) transmission. 3G networks provide substantially higher capabilities than 2G. RF PLANNING stands for “Radio Frequency & Planning”. Achieving maximum capacity while maintaining an acceptable grade of service and good speech quality is the main issue for the network planning. RF Planning is the process of assigning frequencies, transmitter locations and parameters of a wireless communications system to ovide sufficient coverage and capacity for the services required. The RF plan of a cellular communication system has two objectives: coverage and capacity. With the proper RF planning we not only save the huge wastage of the money spent in putting up the Transceiver setup but also provide a QOS with the current network. The basic approach to RF planning is to first analyse the present quality of network and then providing a proper recommendation to improve QOS.
  • 3. 3 ❖ LIST OF FIGURES Figure No Figure Title Page No 2.1.1 Cell sectoring 10 2.1.2 Cluster size 4 12 2.2.1 GSM frequency spectrum 14 2.3 GSM architecture 15 2.3.1 Radio Sub system overview 16 2.4 UMTS architecture 17 2.5 BTS architecture 18 2.5.1 RRU 19 2.5.2 BBU unit 21 3.2.1.1 Cluster of sites 25 3.2.1.2 Radio parameter during drive test 26 3.2.1.3 Mapinfo report 27 3.2.1.4 Site mapped on google earth 28 3.2.2 a)-power link calculation b)- findind LOS 30 31 3.2.3 a)- e-tilt calculation b)-netact coverage plot 32 33 3.2.5 a)-7/21 frequency cluster re-use b)- first and second layer cells 33 35 3.3.1 a)- fault window in netnumen b)-BSNL backhaul connectivity c)-device power alarm 39 40 42
  • 4. 4 Contents Page No Abstract 4 Chapter 1 INTRODUCTION 1.1 Introduction 5 1.2 Objective 5 1.3 Organization of Report 6 Chapter 2 BACKGROUND THEORY 2.1 Cellular Network Architecture 10 2.2 Frequency Spectrum 13 2.3 GSM Architecture 14 2.4 UMTS Architecture 17 2.5 BTS Architecture 18 Chapter 3 METHODOLOGY 3.1 Introduction 23 3.2 RF Network Planning 23 3.3 Maintenance and Optimization 36 3.4 Tools used 46 Chapter 4 RESULT ANALYSIS 4.2 Project Goals 47 4.1 Project Result Analysis 48 Chapter 5 CONCLUSION AND FUTURE SCOPE 50 REFERENCES 51 ANNEXURES 52 PROJECT DETAILS 56
  • 5. 5 CHAPTER 1 INTRODUCTION In telecommunication the whole geographical coverage area is divided into different sized cells namely micro and macro and each cell is responsible for serving multiple users. This communication takes place on a certain band of frequencies also known as channels. The channels are broadly divided into 2 types uplink and downlink depending on flow of data between BTS and MS. The communication is done through radio waves which are electro- magnetic in nature and the power varies with the distance. RF PLANNING stands for “Radio Frequency & Planning”. Achieving maximum capacity while maintaining an acceptable grade of service and good speech quality is the main issue for the network planning. RF Planning is the process of assigning frequencies, transmitter locations and parameters of a wireless communications system to provide sufficient coverage and capacity for the services required .It is the main duty of a mobile service providers to subject their networks to continuous monitoring and optimization in order to maintain their business flow and ensure growth of the company. Optimization means keep a check of the present network by extracting various statistical reports from drive test as well as OMC software to ensure that it can be expanded to meet the growing demands of the users as well as the network can be enhanced to support the new users. The optimization also plays a major role in troubleshoot of the network. 1.2 OBJECTIVE Network planning is a complicated process consisting of several phases. The final target for the network planning process is to define the network design, which is then built as a cellular network. The network design can be an extension of the existing GSM, 3G network or a new network [4G] to be launched. The difficulty in network planning is to combine all of the requirements in an optimal way and to design a cost-effective network. The network after being planned and optimised should have good signal coverage area at both macro and micro sites. Rx quality level should be good and there should be minimal co channel interference.
  • 6. 6 1.3 ORGANIZATION OF THE REPORT The report can be understood as a step by step roll out process flow. It starts with giving a brief description about the networks which is needed to understand how communication line is established and the media flows. The next part gives a little overview of the current network including location of all BTS, the backhaul connectivity to the BSC and other parameters. Then towards the later part the report emphasis on 2 major steps in the project which includes the maintenance of the current network which include continuous monitoring of the present network and the other part focus on the expansion of the network by installation of new BTS to improve the network. Due to the resources constraints bases stations need to be managed in groups also known as clusters which are processed together in order to get a exact knowledge of how a particular BTS is dealing with the interferences from the nearby networks, whether the handovers are successfully administered and various neighbouring params.. The steps in the process are phased and designed carefully to ensure that the project is completed in the given time. The RF network team is responsible for providing the best QoS to its users which the team achieves by changing the radio parameters as well as proposing new site. Once the team has decide the new location of site based on multiple factors which are discussed further in report the data is handed to the administration block for funds allocation , lease and various other works. The site location can vary from an existing building to a mast, which has to be built purposely.
  • 7. 7 CHAPTER 2 BACKGROUND THEORY Till now we have 4 major distinct generations of mobile which can be classified based on transport technologies but when we go towards depth of the mobile communication we can see that with each upgraded generations the users have been given more functionalities and for this sole reason we do not define the generations based on the frequency but rather on the basis of functionality offered. • 1st generation- provided basic mobile services which is calling with limited mobility. This technology was based on analog cellular technology. • 2nd generation – the only longest serving technology which is still used in many parts of India . This generation revolutionized the mobile industry by using digital cellular technology which laid the very foundation of all the major advances in mobile communication . This technology focused on better utilization of mobile spectrum and also has added ciphering benefits. This technology made the users familiar with the concept of Internet as well as provided them with far better telephonic services than 1 G. This generation also invented the concept of roaming which led to increased mobility for the users. The GSM was so successful that in 2004 it acquired a user base of 1 Billion customers. • 3rd generation : This generation which arrived in India on Oct 2001 by docomo is characterized by its ability to carry data at a very high speed compared to its previous generation which carried at 9.6 kbps. The average downlink data speed in this generation was around 64kbps which made this tech perfect for youngsters, as well as major it firms. 3G uses WCDMA access technique which means that each user has been given a unique access code which is mixed with the signal and tranfsered to ensure that data sent is protected from any potential theft and leaks. This generation gave a boon to the digital industry. • 4th generation:- Launched in 2009 in Ohio , this generation is also called LTE which stands for long term evolution and is recorded to provide a peak uplink data speed of 500Mbps. The key to this high speed provided by this generation is its ability to high efficient utilization of the spectrum using MIMO techniques.It also provides high reliability with a very long range communication using spatial multiplexing techniques and unlike 3g which uses both data and voice it is fully data based.
  • 8. 8 2.1 CELLULAR NETWORK ARCHITECTURE The basic idea of a cellular network is to divide a geographical area into small divisions or cells , Proposed by Bell Labs 1971 these cells would be in a hexagon shape and each cell will be served by one base station rather than only one for entire city. During the years the technology has been changed but the base concept is still intact. Now a days operators vary cell size, power, frequencies to make reliable use of the limited BTS and also now cell phones are designed for minimal power transmission and hence the concept of frequency reuse came into play. These cells are further connected to a common BSC through controllers, switches, cables and routers. There are few major concepts which are used in designing of cellular network:- 2.1.1 Sectoring Cells sectoring means to replace a omnidirectional gsm antenna with a sector antenna in order to reduce co-channel interference and also increase the no. of user one cell can serve with omni directional antenna. One cell can be portioned into 3 , 6 , 9…n sectors and now these new sectors acts as individual cells with individual antenna which provide better signal to mobile users based in individual sectors. The sectoring also comes with the load in the processing ability of a BTS as well as BSC because sectoring leads to a huge increase in the no. of handovers a user will experience. Fig 2.1.1 – cells with no sector , 6 sectors , 3 sectors 2.1.2 Frequency re use- Every network operator has limited bandwidth and it is absolutely essential to plan properly how to use that band of frequency in order to give frequency to all
  • 9. 9 its cell in that particular state. At BSNL Sikkim we have a band of roughly 40 unique frequencies which are to be assigned to total of 360 cells in the area , so here the concept of frequency use takes place where we allocate same frequencies to cells which are at a particular distance d [reuse distance] . The cells are grouped together into clusters of size K with the rule that all the cells in a cluster will have unique frequencies this helps the RF team to allocate frequencies to the cells outside a particular reference cluster. The difficult part for any network engineer is to find the value of K/ re-use pattern. And the value of K is first calculated by the undermentioned value and then checked whether it satisfies the I,j relation. C/I – coverage to interference ration and at BSNL Sikkim we take it as 8db while planning for cluster. Alpha - is path loss coefficient taken as 4 for urban areas.
  • 10. 10 Fig 2.1.2 – showing frequency re use pattern for a cluster size of 4
  • 11. 13 GSM uplink – 810-915 = 25 Mhz 25M/200K = 125 channels Total AFRCN in GSM 900 = 125 which are numbered from 0-124 2.2 Frequency Spectrum :- 2.2.1 GSM- GSM uses 2 bands one for uplink and other for downlink and for each link there is a set of frequencies allocated by TRAI . The uplink band is from 890-915Mhz and downlink is 925-960Mhz and each of these frequencies is separated from the other using a guard- band of BW – 200Khz and these bands of 200Khz form the channels on which communication takes place and each channel is further divided into 8 time slots to ensure the proper utilization of frequency. These channels of BW 200Khz are given unique numbers and this number is termed as ARFCN – Absolute Radio Frequency Channel Number. At BSNL Sikkim we have been given a BW of 5MHZ in both uplink and downlink bands and AFRCN from 63-87 Similarly each operator buys particular BW in both uplink and downlink bands. 2.2.2 UMTS/3G- 3G has multiple bands but the band which is used by mobile operators is 2100 band. The uplink and downlink frequencies are 1920-1980Mhz and 2110-2170Mhz with same carrier separation of 200Khz UARFCN = 50M/200K = 250 which is twice of 2G
  • 12. 14 Fig 2.2.1 – GSM frequency spectrum overview 2.3 GSM Architecture - Since cellular network are made up of cells so similarly GSM also has cells which together form the full geographical coverage area. In GSM each cell is assigned a particular identity number also abbreviated as CGI .This CGI helps the mobile equipment to identify the serving cell. CGI has 4 parts • Mobile country code – 404 for India • Mobile network code – 74 for BSNL • Local area code- each operator, group the cells into various LAC based on their distance from BSC • Cell identity- cell no. given to particular cell which is unique to each cell like 54272 governor house(BSNL)
  • 13. 15 Figure 2.3: GSM ARCHITECTURE The GSM network architecture is made up of 3 subsystems which are discussed below. 2.3.1 Radio Subsystem: - This system is responsible for allocating resources to the mobile users. All the transmission of voice, channel allocation, data services are provided by this subsystem only. The RSS consists of 3 components. 1. Mobile Station 2. Transcoder and Rate Adaptation Unit (TRAU) 3. Base Station Subsystem a) Base Transceiver Station(BTS) b) Base Station Controller(BSC) It also controls the major air interfaces of mobile communication which are Um(MS-BTS) and Abis (BTS-BSC) interfaces. The interfaces are used to transmit signalling information and the traffic volume between 2 points of the system. All the transfer protocols like FTP(file transfer) , LAP(link access protocol) and various others are controlled by interfaces only. The
  • 14. 16 AUTHENTICATION CENTRE (AC) EQUIPMENT IDENTITY REGISTER (EIR) VISITOR LOCATION REGISTER (VLR) HOME LOCATION REGISTER (HLR) MOBILE SWITCHING CENTRE (MSC) NSS RSS is also responsible for all signal processing function like modulation, speech transcoding and rate adaptation for both full rate and half rate which is done by TRAU unit. Fig 2.3.1 – Radio subsystem overview 2.3.2 Network Switching Subsystem- It forms the heart of GSM network. It is responsible for mobility and calling options only for roaming users. It doesn’t control the calling functions of the local mobile users as local functions are controlled by BSC which is part of RSS. It is used for communication between different networks like public switched telephone network and the local home network. It has following components: - MSC controls many BSC and is used to communication between different MSC as well as different BSCs , for example if a user wants to make a STD call then the BSC will communicate with the MSC and MSC will check if dialed number is under control of BSC of same MSC or different MSC controlled BSC and after that MSC ensures end to end
  • 15. 17 communication between both users. MSC is also used to manage the calls in and out of the network like a call to PSTN even if controlled by same BSC will have to go through MSC in- order to use channel. Similarly EIR is used to monitor particular mobile numbers as directed by police/any other government agency. HLR is a register which contains a record of all the mobile numbers which come under 1 MSC and it also has job to keep updating the location of user in case it goes into roaming mode and similarly when in roaming same users SIM information is stored in VLR to ensure that the user is able to use the roaming network efficiently. 2.3.3 Operation Maintenance Centre- It is the part of the GSM network which is responsible for proper functioning of all the entire network including BTS, BSC,MSC as well as the transmission part including the fibre connectivity , micro link connectivity and satellite communication. The other major function of OMC is to take care of all billing related queries including post paid and pre-paid. It is also responsible for maintenance of all network hardware components like antenna, routers , switches etc. 2.4 UMTS Architecture - UMTS architecture is quite similar to GSM except with a few new terminologies like BTS in UMTS is called NODE and BSC in UMTS is RNC (radio network controller) and different Fig 2.4- UMTS architecture
  • 16. 18 air interfaces compared to GSM. Except that the working and function of both the architecture is pretty much same. 2.5 BTS Architecture- Base transceiver system is responsible primarily for receiving and transmitting radio signal to and from the mobile unit . It is responsible for transmitting various signaling information to the mobile unit. Any communication done between MS and BSC takes place through BTS. BTS also regularly sends time and frequency correction signals to both mobile unit and BSC to make sure that all the clocks are properly synchronized in order to prevent any packet loss or time delay. It holds the media card which are responsible for traffic channels and also BTS has its unique Base Station Code which is used by mobile users to detect the serving BTS. Typically a BTS has antennas for radiation , transceivers , equipment for encryption and various other interfacing equipment’s for communication between BSC and MS along with equipment’s for traffic control . But to generalize it the BTS is made of 2 components :- ➢ Radio Resource Unit ➢ Base Band Unit Fig 2.5 – hardware architecture of ZTE BTS at BSNL
  • 17. 19 2.5.1 Radio Remote Unit(RRU) It is the distributed and integrated frequency unit that connects to an operators network with the User Equipment's (UE's) like Cell Phone and mobile devices. The RRU is connected to the base station via the fiber optic link which is bi-directional link. The optical interface link is also known as CPRI (Common Public Radio Interface). CPRI is a interface protocol developed by combination of major telecom equipment's manufacturing company. The RRU helps to provide flexibility at cellular sites. Undoubtedly, this helps in upgrading to new equipment's and devices more easily. Fig 2.5.1 – Radio resource unit RRU Functions: 1) Acts as a transceiver: transmit and receive the user signals to the base station and vice- versa. 2) Provides back to back support and connectivity between user equipment's like power, delay, etc. 3) Control and process the EM signals received from the Antenna via Jumper(Hollow Guide). 4) Provide interface between two physical link: Optical and EM(Electromagnetic).
  • 18. 20 5) Provide Controlling support of the Auxiliary equipment's like RCU (Remote Control Unit) for electrical tilt adjustment generally known as RET(Remote Electrical Tilt). 6) Generate and sends the different signals like VSWR. Fig 2.5.1.1 – RRU hardware architecture showing 3 major parts 1 ,2 3 1) CPRI Port: There is 2 port generally named as CPRI0 and CPRI1. However there may be 1's in some model. The name at suffix may vary. Its function is to connect to BBU. 2) RF Port: We say it as a Jumper port. The number of jumper port may vary with model and company's architecture. At least there is 2 jumper port, one of which is for Tx and another for Tx/Rx. The RF port is connected to the Antenna via Jumper Cable. 3) RET Port: There is at least one RET port for connection to RCU. The connector is mostly DB9 in ZTE and may vary with other company's. RCU is connected to the Antenna. RET cable connects the RCU and RRU. 2.5.2 Base Band unit- Also referred to as BB card which is used to process original unmodulated frequency signal. It has in built signal processors which is responsible for between AC and Dc signals because the connectivity between BSC and BTS is analog signals and the signal
  • 19. 21 sent to RRU is also analog signal so the conversion is mandatory to ensure communication between MS , BTS and BSC and that’s why it is referred to as heart of a BTs. Fig 2.5.2 – full BBU unit at BSNL site “Balwakhani” BBU has following important components: 1. Control & Clock Board:- This is also know as cc card which is used for clock synchronization, alarm monitoring ports for environment monitoring, and an Ethernet port which can be used by Rf engineer to monitor the status of BTS. It is also responsible for Abis Interface protocol processing and also acts as ethernet switch for signaling and media transmission. 2. Base Band Processing board:- this is the heart of BBU unit as it is responsible for providing traffic channels on which networking takes place. It also has dedicated common radio resource ports as well as optical links for communication with RRUs
  • 20. 22 and processes uplink and downlink baseband signals. The zte bts used at BSNL is capable of providing 60 TRx and has capacity to serve 24 cells at one time. 3. Fan :- It is responsible to dissipates heat from the BBU unit . It can be monitored and controlled from BSC from where we can control the rotation speed of the fan and see the inlet temperature of room . The current BBU unit in BSNL is made of 6 fans in total and is responsible all the overheating alarms raised at BTS. 4. Power Module Board :- it is responsible for power to be delivered to both BBU and RRU unit. It consists of 16 internal interfaces for +12v - +24V load power.
  • 21. 23 CHAPTER 3 METHODOLOGY 3.1 INTRODUCTION RF PLANNING stands for “Radio Frequency & Planning”. As we know that in cellular network the coverage and quality of network are almost inversely proportional as when coverage increases it degrades the quality so the main objective of RF team is to achieve the maximum capacity for a network while providing acceptable quality of service to the users. The Rf team also ensure adequate network capacity as well as flexibility to be provided to the network to support the increases traffic requirements and at last it has to be cost effective. The RF part of any network deals with all the parameters related to radio waves which include frequency planning, antennas location, tilt of antenna, height, location and continuous optimization of the network. The RF plan of a cellular communication system has two objectives: coverage and capacity. Coverage relates to the geographical footprint within the system that has sufficient RF signal strength to provide for a call/data session. Capacity relates to the capability of the system to sustain a given number of subscribers. Capacity and coverage are interrelated. To improve coverage, capacity has to be sacrificed, while to improve capacity, coverage will have to be sacrificed. The RF team has 2 major responsibilities to adhere to:- 1. Network planning for the new site 2. Maintenance and optimization of the present network 3.2 Network planning for the new site:- The network planning for new sites includes analysis of drive test results , data from OMC , frequency planning , post-optimization of site , site location , antenna tilt , antenna height , power budget calculation , transmission planning , the neighboring cells definition , coverage area and many other aspects are also considered while planning a new site.
  • 22. 24 The question that RF team tries to answer before submitting the report for the new site are:- • Area of coverage required? • Can some site be optimized to provide coverge instead of new site? • Height of antenna? • Whether site be a stand alone or a cluster site? • Calculate coverage proababilities using drive test? The major focus on planning of new site include:- 1. Site location 2. Antenna height calculation 3. Antenna tilt calculation 4. Transmission planning 5. Frequency planning 3.2.1 Site location:- A normal BTS has a installation cost of around 12-15lac and annual maintenance cost of around 2 lac . So , it is not feasible to just randomly plant a BTS without proper planning because if a BTS installed at a wrong location will not only degrade a network by creating un-necessary interference to the nearby BTS but also not generating the required revenue needed by the operators. The location of BTS is properly decided after careful examination of the results obtained from drive test. The various steps involved in basic planning of the location of site are listed below 3.2.1.1 Grouping of sites into clusters:-
  • 23. 25 It is not feasible to view a cellular network pint by point so the sites this step requires to be familiar with the terrain of the place as well the LAC code , Range and the technology partner of BTS ( Ericsson and Nortel and ZTE ) so that all the sites(60) can be divided into various clusters(18) and Standalone sites to make it convenient for the Drive Test. The sites are first mapped into software “MAPINFO” from database maintained at BSC and once the plotting of sites with proper azimuth are done, the clusters are defined. The basic rule followed by the Rf team at BSNL is that the if the nearest neighbor of site is within 2-3 km it will be in a cluster with the neighboring sites while other would be a Standalone Site. Fig 3.2.1.1:- SITES GROUPED IN CLUSTER 3.2.1.2 Drive Testing:- It is a method of measuring and assessing the coverage, capacity and Quality of Service (QoS) of a mobile radio network. The technique consists of using a car containing mobile equipment which is used to detect and record a wide variety of the radio parameters of network in a given geographical area. The DT engineer has to constantly keep an eye on the Radio parameters to make sure that the cell which is being served is having a unique BCCH and BSIC no. in-order to avoid call failure. The scripts for both Long calls
  • 24. 26 (30min) , short calls(2 min) and FTTP download have to run in Idle , dedicated and packet switched mode on the mobile equipment. TEMS is the software used for this testing. The engineer has to keep an eye on event window of the software to report alarming errors like call barred , missing neighbor , high frequency of handover. The algorithm for scripts have been attached at end of report. Fig 3.2.1.2:- Radio parameter 2G and Event window of cluster 7 during drive test 3.2.1.3 Mapping of Drive test report into Map info – Once the drive test of the cluster is completed, the log file is exported with following parameters and then a final report is generated which is analyzed to improve the network. 1. 2G – Rx level and quality (Full/Sub) , Co-channel Interference , Handover success rate , Call drop rate , Call attempted ,SDCCH rate , Call blocked and a full event window for better understanding
  • 25. 3G 2G 2. 3G – RSCP( received energy) , INTER-RAT handover , RRC establishment rate , HSDPA Throughput , Interference per chip symbol , Primary Scrambling code Based on these reports we can analyze the coverage area of the present sites and whether a new site is required to ensure a proper coverage to users. Fig 3.2.1.3 – Mapinfo report showing the received signal strength in 2G and 3G of the BTS 27 ranipool
  • 26. 28 3.2.1.4 Viewing of the demographics , terrain on google earth- After the above 2 steps we can get approximate area as to where a site is to be needed but in order to pin-point the exact location of the site the network is analyzed on google earth to check for the population density , the terrain of the area , the exact latitude and longitude of the place because we generally want the site to be installed at the highest point in the area to ensure best signal propagation and these all are planned based on google earth pro. Fig 3.2.1.4 google earth images of the site 3.2.1.5 Manual survey of the site:- Once the exact location has been pin-pointed the RF team visits the site for a survey to ensure that the location is feasible for setting up the BTS as well for the maintenance of the BTS in future. 3.2.2 Antenna height calculation: - The antenna used for mobile communication is a radio antenna and the waves are radio waves so the it is important to know the type of propagation model which will be used to find
  • 27. 29 the path loss in the environment. many times the mobile user and BTS are not in LOS but still the waves reach to the mobile user propagating through the building, that means the mobile communication is a reason of multipath propagation of waves so for this sole reason a proper propagation model needs to be chosen to get a estimate of a path loss incurred. The model used for GSM in BSNL is Okumura–Hata model. 4 Lu is the path loss for urban area in db 5 F is frequency in Mhz 6 HB and hM are base station and mobile antenna height. As we can see that in the above equation we have 4 variable which are path loss , distance , height of mobile , height of base station. For this we take some standard assumption. 1. Mobile height (hM ) – 1.5m 2. Distance (d)- geographical distance from its nearby neighbor boundary coverage area and cell radius = d/2 3. Path loss- it is found using power link budget calculation Power link budget Calculation:- Power link is used to quantify a radio link performance. It basically includes all gains and losses incurred by the wave travelling from transmitter to receiver through a medium. The power link budget calculation is done in telecom industry to get a estimate of maximum allowable path loss which is further used to determine the base antenna height.
  • 28. 30 Fig 3.2.2 (A) – TRAI specified calculation for power link calculation for ZTE bts and Power link budget for 100m feeder cable suggests that maximum path loss allowed should of 158.6 dB Now after you calculate the maximum path loss use it in the hata equation to find the minimum height of BTS which can be used. Like for the above example when the hata model is used we can found that the height of antenna > 40m And once the minimum threshold height is found we use software “wireless networkplanner” to see the effect of height variation with respect to the path obstacles like tall buildings, hills or any other obstacle. For this software we set a point at distance of d from BTS to check the blockage caused by all the obstacles in the way and a height is chosen which causes minimum blockage with the maximum allowed height to be 60m.
  • 29. 31 Fig 3.2.2 (b) – finding LOS for various heights of BTS Similarly for 3G model used is COST Hata Model with C=0. 3.2.3 Antenna Tilt Calculation :- The efficiency of a BTS depends on correct configuration of its antenna and one of the most important part of optimization of network is its antenna tilt. Cell tower Antenna has a radiation pattern with the primary lobe pointed towards horizon. Down tilting the antenna limits its range by reducing strength in horizon and redirecting the radiated power towards the cell the antenna is serving. A increase in down tilt of antenna will reduce the coverage area but gives a higher signal strength and a lesser tilt might cause the BTS to overshoot the signals and cause interference with the other site. It is the goal of Rf engineer to provide the highest signal strength for the coverage area of cell decided. The tilt of antenna is a 2 step process which is e-tilt calculation and Net Act simulator report.
  • 30. 32 1. In this tilt is calculated using basic law of trigonometry. A point at distance d is selected which is generally the last coverage point of the BTS and then on Wireless network tool we do the calculation taking the height variations of hill and BTS. Fig 3.2.3 (a) – the step by step calculation of tilt of antenna 2. Net Act is one of the most powerful tools used in planning of BTS sites. The survey engineer brings the survey reports. The new site as well as the nearby sites are mapped onto the Net Act tool with input variables as tilt of antenna , power of antenna , height of antenna , ARFCN and PSC of sites . Now, based on these inputs the software gives a virtual coverage area .TheNetActtoolalsogivesusthesignalstrengthinDbaroundthesite andthisisrepresented bythevariouscolors. Thus,wecheckthetiltoftheantenna, soasto prevent the overlap of the signals and accordingly we adjust the tilt of antenna ranging from 00 -70 .
  • 31. 33 Fig 3.2.3(b) – Net act window to show the received signal around a BTS which help in tilt optimization 3.2.4 Transmission planning: - Transmission plays an important part in the mobile communication. The transmission planning involves connectivity of the site with BSC. the site could be directly connected to BSC or it can be connected to a neighbor site which is further connected to the BSC. This inter connectivity is achieved using 2 ways either by mini-link or by optical fibre cable. The basic rule of mini-link connectivity is that the both the sites should be in the perfect LOS. So it is important to understand and analyze the neighbors of site to understand how the connectivity would be planned. 3.2.5 Frequency planning:- As we know that in cellular network each operator has a limited band-width that means it will have limited carrier frequencies. In cellular communication the frequency re-use concept is used for efficient allocation of BCCH number which is unique to a cell in a cluster and all the
  • 32. 34 signaling and communication information are done through this channel only. As we have discussed in previous sections that cells are divided into cluster for frequency reuse and cluster can be of size 3,4,7…etc. The common notation used in telecom industry to show the frequency reuse is n/m where n is the re-use factor or cluster size and m is no. of unique carrier frequency no. At BSNL, Sikkim the re-use pattern used is 7/21 which means that a total of 7 sites with 3 sectors use have been given 21 unique BCCH frequencies to use. So, frequency allocation is done within these 21 frequencies. Fig 3.2.5(A) :- 7/21 cluster re-use pattern For manual frequency allocation there are certain steps to be followed:- Step1:- write the 21 BCCH site wise in a pre-defined IMT format , frequencies are assigned in sequence to cells A1-G3 and BCCH allotted to BSNL is from 65-96 , where the last 10 are used for various govt secure establishments. A 1 B 1 C 1 D 1 E 1 F 1 G 1 A 2 B 2 C 2 D 2 E 2 F 2 G 2 A 3 B 3 C 3 D 3 E 3 F 3 G 3
  • 33. 35 FRE Q NO 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0 2 1 BC CH 6 5 6 6 6 7 6 8 6 9 7 0 7 1 7 2 7 3 7 4 7 5 7 6 7 7 7 8 7 9 8 0 8 1 8 2 8 3 8 4 8 5 So it is clear from this pattern that site A will be allotted BCCH – 65,72,79 similarly we can find which pair of frequencies to be allotted to a site based on its alphabet. Step 2:- identifying the neighbors of the siteand grouping them into 1st and 2nd layer cells based on the interference interference level which is decided on basis of the distance from the new site. Theoretically site which are at a fixed distance from reference site say within 1km are termed as first layer cells and sites which are at a distance of 3km are termed as 2nd layer cells. Due to less distance from the reference site , the interference caused by first layer cells is way more and hence the planning of frequency is done in such a manner to reduce the first layer cell interference by allocating them unique frequencies and second layer cells are also considered in case after frequency planning the data reports from drive tests shows high interference at the reference site. This dividing of cells into various layers becomes difficult while implementing it in practical use as the sites are not at equal distance so to get the best results we use a range estimation. • First layer cell – 1-2Km • Second layer cells- 2-5Km Fig 3.2.5(b) – all the first and second layer cells from target site
  • 34. 36 Step 3 :- The next step involves finding the BCCH of the first and second layer neighbor cells so that they can be assigned a alphabet from A-G based on BCCH range as discussed in step 1. Once the neighbor sites are labelled we can see which alphabet to be assigned to the new site to minimize interference from first layer cells and if we have multiple alphabet can be assigned to the new site , the distance from second layer cells is considered minimize interference. Step 4:- post drive test to be done to check the interference caused by the new site and the interference caused in the target cell. 3.3 Maintenance and Optimization of present network:- The cellular networks requires a continuous monitoring and optimization to make sure that good quality of service is achieved throughout the geographical coverage area without any data holes. This process is done by Operation and Maintenance unit of the network. The OMC works intwodifferent areas namelyRADIOandSWITCH.TheOMCprocesscanbedividedinto followingfivetypes. ▪ FaultManagement: ▪ Configuration Management ▪ Database Management. ▪ Performance Management ▪ SecurityManagement This OMC unit is nothing but a generalized software developed by a manufacture which can remotely control all the BTS installed in the area. In BSNL Sikkim we have 2 software. 1. Net Numen for ZTE BTS 2. Winfoil for Errison BTS Net Numen:- To allow carriers to cope with the modern challenges of managing multi-technology networks while keeping pace with the evolution of full-service operations, NetNumenTM U31 is designed to provide end-to-end capability for high O&M efficiency. It is basically a unified
  • 35. 37 management interface for telecom industry that lets the RF team view the current status of all the BTS within one BSC. Few of its functionality are noted down below:- Fault Management: The fault management helps the operation and maintenance personnel know in time all abnormal running conditions in the CDMA network and helps them to locate causes and positions, so that the user can find, handle and solve the system faults as soon as possible and ensure normal running of the network. Alarm correlation analysis helps eliminate redundant alarm information and alarm storm, locate and eliminate fault causes. Performance Management: it is responsible for monitoring and analyzing performance of the network and NEs. With various performance data collected from the NEs, the OMC knows network running conditions, provides the operation and maintenance personnel with detailed information that can offer guidance to the planning and adjustment of the network engineering and improve the network quality. Configuration Management: The configuration management presents configurations for all kinds of equipment resources and settings of important parameters in the CDMA network, so that the user can know easily the configuration and usage of the key network resources, make related statistics, improve management, and maximize profits. Additionally, it also provides necessary reference data for performance management and fault management. Security Management: The security management can protect and prevent unauthorized OMC users from accessing or destructing the OMC and its NE system, and legal users from ultra vires action. It records all security operation information for review and ensures legal use of the system. Topology Management: The topology management provides a topology view for the whole network. It provides key information management, including the geographic location, alarm, and KPI. Log Management: The log management completes management of all kinds of system logs that records information about all events and operations in the system. With the logs,
  • 36. 38 the user can know whether the system runs normally or not, locate the cause of the fault, and trace back and review important events. 3.3.1 Maintenance of network:- Due to hilly terrain maintaining the network is really difficult in the area. The first step of network maintenance is to make sure that the BTS is up and functional which is monitored using fault management of net numen. The fault management lets you visualize the whole network including all nodes to see which BTS is non-operational as we can see in the above figure that BTS with a red cross tells that the BTS is non-functional at the time. The software works on the method of alarm raising where all the alarms raised within a BTS are classified into 3 categories:- ➢ Critical alarms:- these alarms are of utmost priority as these directly affect the services of BTS terminating all the services and making BTS go in shut down mode ➢ Major alarms:- these alarms may or may not affect BTS in near future so they come second in priority list and are monitored continuously to ensure that they do not block any of BTS services ➢ Minor alarms:- these alarsm are more like warning alarms which do not affect the BTS functionalities and are not monitored until there priorirty is changed to major or critical.
  • 37. 39 Fig 3.3.1 (a) – fault management window of Net Numen The RF team keeps a continuous eye on these alarms and based on the action taken by RF team the alarm state is changed to Acknowledged , Unacknowledged and cleared. Once a BTS is down RF team check the alarm code to know the possible problem. There are various alarm codes which help engineer to know the possible cause. Few of alarms code and handling solutions are mentioned below:- ➢ Link between omm and ne broken – one of the most common alarm codes at is raised at the BTS which means that there has been lost in connectivity between the BTS and BSC with the possible cause of either power failure or fibre link/micro-link broken. The next step of troubleshoot for this alarm is to see the back haul connectivity diagram of BSNL Sikkim in order to trace the connectivity back to BTS. Then with this diagram we trace the various intermediate nodes and check their status if they all are perfectly functional then we can rule out the possibility of fibre break from BSC. Once this step is taken we run a query to check the history of the alarm which gives us a idea for how long the alarm has been on. If a alarm has been raised for a longer than 6-7 hrs it is possible that there has been a fibre break between the BTS and the next intermediate node
  • 38. 40 because power failure for that long is very rare and the issue is raised to transmission team to rectify the fibre. Fig 3.3.1(b) – back haul BSNL connectivity Abnormal voltage:- this alarm is raised at BBU unit of a BTS which causes BTS to continuously turn ON/OFF , it is a critical alarm which has to be solved immediately as it posses direct risk to the BTS life. The handling suggestion for this BTS is to change the power relay in the power module of BTS. Once this alarm is raised it is directed to the field electrician to replace the relay from the store. VSWR critical:- Voltage Standing Wave Ratio represents a ratio between the transmitted power to received power through a transmission medium. It is also a measure of efficiency of a transmission link. The allowed VSWR in mobile communication is 1.2 and as soon as value crosses 1.4 the alarm is raised thereby shutting the BTS. The handling solution for this alarm is to check the co-ax cable between bbu-rru or there might be moisture in attenuator attached to BBU due to heavy rains. For this RF team go to site and check the cable and attenuator manually.
  • 39. 41 ➢ Overheat Alarm:- each BTS has 2 mode of heat dissipation the first is the internal fan panel of BTS and other is centralized air conditioning for the whole equipment’s like BTS , power supply and routers. The problem is solved by manual visit to site and replace the faulty part. RRU-BBU link broken:- this alarm is raised when the co-axial cable between RRU and BBU is broken which makes RRU and antenna inactive and hence no communication in that frequency spectrum is not possible in that area. If 2g link is broken 3G will still serve the area. For more detailed information we open up alarm description to know which link is broken RRU-BBU(900 gsm) or RRU-BBU(2100 3G) and that particular cable is replaced. Device Power down:- this is critical alarm which can be caused by either power failure to BP card of BTS , CC card may be non-functional , antenna power might be down , RRU power link broken . to diagnose this open up the rack chart of BTS to locate the actual problem and as it can be seen in the image below that there is a red warning on RRU S900 in the rack chart that means the 900 spectrum GSM antenna is not receiving power and it is rectified by checking RRU power supply attached to BBU unit.
  • 40. 42 fic at each cell. This report is the most important for process ofFig 3.3.1(d) -rru power supply Fig 3.3.1©- device power down alarm 3.3.2 Analyze BBH report:- Busy Bouncy hour report is nothing but the network report of the busiest hour or the hour with the highest traf optimization as this report helps the team to understand various Key performance indicators based on which the further optimization of network takes place . The BBH report is generated in Netnumen software by running a query in history performance template and is auto-mailed to the head of the BSNL for that telecom district. Key Performance Index is the set of parameterswhichareconstantly observedtocheckthe performanceofthenetwork.Thisincludes SDBlock,SDDrop,TCHBlock,TCHDropandHOSR.
  • 41. 43 Fig 3.3.2:- BBH report The various parameters and there thresholds are given below: ▪ SDBlock <0.5% ▪ SDDrop <2.5% ▪ TCHDrop <3.5% ▪ HOSR >85% SD Block: - ❖ SDCCH is a bidirectional logical channel used indifferent ways: -Registration: periodic location update. -Call setup: immediate assignment. -SMS to/from MS in dedicated mode. SD blocking means that you are not getting SD resource for the call origination. When MS connects with BTS then RACH(random access channel) and SDCCH( stand alone dedicated control channel) are provided but when MS doesn’t receive SDCCH channel due to some
  • 42. 44 problem it results in SD drop. In this case the MS is not able to initiate the call. The SD drop is also a measure of Call Set up Success rate. CSSR = 100-SD drp Removal of SD block:- 1. Problem with BP/Media card which is responsible for channel allocation 2. Overshooting which can be caused due to reflection from hills may lead the MS connect to a far away cell which might cause the drop and to rectify it go for DT to verify which cell id is the mobile equipment TCH drop :- it is also known as call drop which happens when the mobile station is already having channels and somehow the call gets disconnected. It is measured by TCH drop parameter of OMC report .The major reasons of call drop are • Poor received signal • Late handover reducing the serving signal strength less than threshold value. • Co-channel Interference TCH drop troubleshoot solutions:- 1. Check the BCCH frequency of the cell as well as the nearby cells to check for
  • 43. 45 interference 2. Poor coverage quality in the cells which can be rectified by reorientation of the tilt of antenna 3. Check the allotted power to BTS if it is low increase it to max of 43db as specified by TRAI ➢ HOSR: it refers to handover success rate , HO activity is performed to maintain – Call continuity and call quality . The inputs that the BSC uses for making a handover decision, from the received MRs from the MS is the DL signal strength, DL quality, and the signal strength of the six best reported neighbours. From the serving BTS, for the same MS the BSC will use UL signal strength, UL quality and TA. • If HOSR will be good TCH drop will also be good. • If Handover success rate degrades call drop rate will take place. PROCESS for Optimization: 1. Take the detailed report showing cause & target cell 2. Check congestion; hardware Alarm; Quality; Rx level 3. Missing neighbour – Best server is not in there in neighbour list 4. BCCH Missing 5. Same BCCH & BSIC combination ➢ SDCCH Drop:- it is an important KPI which largely affects subscriber service quality. When MS is already on SDCCH and in-between communication with Base station SDCCH channel got disconnected abruptly then SDCCH Drop has occurred. PROCESS for Optimization: 1. Check the hardware alarm 2. Calculate the number of traffic channels required based on traffic erlang 3. Check the neighbour sites data to find which site is causing interference 4. Check for Neighbour Relations and correct if it is not proper 5. High VSWR(1.05-1.3) due to feeders generally leads to high SDCCH drop rate
  • 44. 46 Few of problems from field and actions taken:- I. Problem code : 22685A Description:- high SDCCH drop rate at site 2516A , the net numen shows PA power alarm Action taken:- Replace the Power cable. II. Problem code : 03312B Description:- high SDCCH drop rate is recorded at site “balwakhani A” Action taken:- had the wrong BCCH so BCCH changed from 70-77 3.4 TOOLS USED:- The whole RF planning and optimization is done using the following software/applications • TEMS investigation 18.1:- one of the major tool which is widely used by all mobile operators to analyze the network condition. The tool provides with coverage related information like Received signal quality, Co- interference, Handovers. • MAPINFO Professional 5.1:- this tool is used to virtually plot the present location of all the serving BTS and also plotting the new proposed sites. • GOOGLE EARTH:- this tool is used to see the geographical information about the place which includes population , buildings , roads , mountains. • SALTLAKE by ERISSON:- the tool is heart and soul of Operation And Maintenance center of the network and is used to change various radio parameters like power , frequencies , channels and many more. • NETNUMEN by ZTE:- it works the same as SALTLAKE but it is used for all ZTE BTS.
  • 45. 47 CHAPTER 4 RESULT ANALYSIS 4.1 PROJECT GOALS Network planning is a complicated process consisting of several phases. The final target for the network planning process is to define the network design, which is then built as a cellular network. The network design can be an extension of the existing GSM network or a new network to be launched. The difficulty in network planning is to combine all of the requirements in an optimal way and to design a cost-effective network. Pre-planning contains network dimensioning and system configuration without any site location information. Information on amount of base station and transmission equipment divided on area basis. Business plan should be available. Basic requirements from the customer and authorities and selection of equipment must be taken into account. This procedure is under continuous updating as new technologies appear. In pre planning/ dimensioning phase, we dimension the network elements based on the capacity and coverage calculations. The calculations for capacity and coverage are based on the customer requirements and decided planning criteria. These calculations give a rough idea how many BTSs and TRXs are needed for the specified area . Network specific Planning guideline defines the network design criteria and thus the maximum amount of connections between transmission equipment using different topologies (point to point, chain, star and loop) is known and thus it is ensured that the planned transmission network fulfils items defined in the planning guideline. Information of possible existing transmission network with different transmission media are also gathered and investigated during the pre-planning process. The pre-planning is prepared to be used as a basis for the preparing the network configuration plan. Current network performance and traffic should be evaluated by OSS reports and by performance measurements. After this evaluation we should have enough information to point out the problem areas and the main targets of interest in the existing network. Also we need to consider location of hot spots and cluster areas. Initial frequency plan strategy must be studied already during the dimensioning this leads to estimations of market share in the beginning and objectives for the future. More detailed estimations are needed on how much each user of a certain type is using the services
  • 46. 48 provided. The needed capacity for each service and onwards for the whole network can be calculated from the estimated average usage. The basic requirements for the cellular network are to meet coverage and quality targets. These requirements are also related to how the end user experiences the network. Coverage targets firstly mean the geographic area the network is covering with an agreed location probability, i.e. the probability to get service. The requirements also specify the signal strength values that need to be met inside different area types. The quality targets are related to factors such as the success of the call, the drop call ratio, which should not exceed the agreed value, and the success ratio for the call setup and for handovers. 4.2PROJECT RESULT ANALYSIS During the course of the project I worked on two phases of the projects .My first phase of the project included the layout and testing of the 90 sites across Sikkim with my my major phase focus is on the changing radio parameters to cut down the need for installation of new BTS and the second phase From the very initial stages of planning and testing our work was to ensure that those sites are properly worked upon and in the end ensure whether or not the work on the sites are managed properly. There are two types of sites, first is the new site, which deals with the making the site from the very beginning, starting from raw material collection to planning then to testing and later evaluation. The other type of site is the upgradation, this deals with the site, which is already set up and needs few upgradations whether it be the change of broadcasting frequencies, the new technology, addition of more TRX , addition of sectors , changing the tilt or azimuth of antennas.. In this the major factor we make certain changes, thus submitting to DOT. During my time at BSNL , I have successfully reduced the SDCCH drop rate from >3% to almost at 1.5% without suggesting the set-up of the new BTS. In many remote sites which are surrounded by hills a little adjustment of about 1-2 units in electrical and magnetic tilt we were able to increase the coverage area of the site. In army sites due to huge traffic congestion , there was a significant call drop rate which is reduced to an average of 1% from critical rate of >5% which was achieved by addition of Media card in BTS racks. The continuous monitoring of the bts sites through software net numen has reduced the no. of
  • 47. 49 non-functional sites to about 5% from 20% of the total sites and careful use of frequency re- use concept has helped to reduce the co-channel interference. The total of 7 new sites which are to be planned have been allocated the latitude and longitude by analyzing the results from drive test and location of sites including the co-ordinates as well as azimuth , the height of antenna have already been forwarded to the top management team for final approval. Cell ID LA C SITE NAM E Longi tude Latit ude BCC H BS IC AZI MU TH PS C TYPE OF SITE BTS heig ht Transmission connectivity tilt 541 51 54 SICH EY 88.60 61 27.3 458 70,77 ,84 25 20/1 20/2 40 2G 30m Ofc link- BSC-sichey 0 541 40 54 6TH MILE 88.68 85 27.3 751 111 20 40/2 70/3 20 212 ARMY IP 20m OFC link- BSC- ganjulama dwar_6th mile 3 197 62 119 Cipla 88.55 066 27.1 850 8 71,78 ,85 21 50/2 35/3 00 198 2G+3G 40m Microwave link BSC GTK 2 192 51 119 -2G , 160 17- 3G Gayzi ng 1 88.25 806 27.2 929 4 20 0/12 0/24 0 96 2G NORT EL +3G ERICS SON 36m Ofc link – BSC - penengla- damthang- gayzing1 5 432 15 119 Aritar 88.67 03 27.1 869 69,76 ,83 24 0/12 0/24 0 100 ZTE 45m Ofc link BSC-upper chandmari_m icrowave link to Aritar 3 478 594 54 Bager khola 88.49 6 27.9 3 71,78 ,85 23 10/1 20/2 70 ZTE 30m Ofc link – BSC- bagerkhola 1 119 ,54 Assa m linze 88.496 4 27.1 913 75,82 ,89 2- 1 0/12 0/24 0 ZTE 40 m Microwave link BSC to Nmachi- OFC link to assam linze 4 Table 4.1:- New site database including all the parameters
  • 48. 50 CHAPTER 5 CONCLUSION AND FUTURE SCOPE OF WORK I would like to conclude that RF planning in mobile communication is one of fastest growing field which the newly under-grad students should consider as it will lead them to a long term sucess. And with the advances in the mobile technology and a huge competition among the mobile operators the QOS to be provided to user is a real game changer. Since with the bandwidth constraints it has become absolutely necessary to plan and implement a efficient network which has expoansion capabilities and a adaptive nature to cope up with the new mobile generations. It is mandatory for the next-generation mobile cellular system to achieve the performance that any present IMT-2000 system cannot, the next generation key focus would be on a much higher throughput , data speed in Gbps , much lower latency , ability to support very larger user base and much higher spectrum utilization efficiency. As it is been in trend to use a laregr bandwidth with each new generation we can expect a exponential increase in the bandwidth channel however with a higher bandwidth channel some major advances has to be done in ciphering and deciphering techniques to prevent data breach. Radio access technologies for the XG cellular system is gonna inherit the present technologies of the 4G systems, and introduce new technologies to meet challenges in cellular networks. Characteristics of a broader channel bandwidth, and by increased performance requirements. Keeping the leadership in radio access technologies, NTT DoCoMo proposes VSF-OFCDM and VSCRF-CDMA for XG broadband radio access. The proposed technologies evolve CDMA-related technologies by introducing new technologies, such as multicarrier and chip repetition to meet the performance requirements of next-generation cellular systems. As we have seen that 3G architecture was both IP based and voice based due to which there was limitation both at level of network architecture as well as on the service architecture and then $g came which was all IP architecture so judging by trend we can predict that the XG will be all IP based but with some innovative and lucrative services. . Architecture, believing that this division of the architecture into four distinct layers, with different degrees of coupling, provides a foundation for providing local control to niche markets while ensuring that the system as a whole retains key control and coordination points
  • 49. 51 for third-party services. Aside from a coherent long-range architectural framework, we have developed research results in the areas of mobility management, security and cryptography, network programmability and support for value-added services that are among the key enablers for the XG architecture
  • 50. 52 REFERENCES [1] Theodore S Rappaport, Wireless Communication, 2nd ed., MA MIT Press, 1986. [2] C.Y. Lee, Cellular Mobile communication, 4th ed., Eds. Princeton, NJ: Princeton Univ. Press, 1985, pp107-125. [3] Sanjay Sharma, Cellular Mobile communication, vol, 5, IIT Bombay, Mumbai Canavad press, 2006, pp145-189. [4] Web: www.coai/subject topics/ data trends.com
  • 51. 53 ANNEXURES 6.1 Annexure 1 7 Algorithm for short call used in drive testing 8 Algorithm for FTP up and down link rate to check data speed
  • 52. 54 6.2 Annexure 2 9 Flow diagram for TCH Drop rate analysis 10 Flow diagram for high Handover Failure rate analysis
  • 53. 55 Handoverfailure rate incorrect parameters Co-BCCH BSIC Missing neighbours Too many neigbours with high power TCH congestion TCHDroprate low strength dl highTA rx quality sub hardware faults handover failure less defined channels high interferance