RF planning and designing of air interface by using … ATOLL Platform Abinaya.M, Sneka.A,...
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SSRG International Journal of Electronics and Communication Engineering - (ICRTECITA-2017) - Special Issue - March 2017
ISSN : 2348 – 8549 www.internationaljournalssrg.org Page 64
RF planning and designing of air interface by
using ATOLL Platform Abinaya.M, Sneka.A, Chandradevi.R, Grace Mabel Timothy
Department of electronics and communication,
Mr.S.Maheshwaran.M.E.,
Assistant professor of electronics and communication engineering,
PonnaiyahRamajayam College of Engineering and Technology,
Thanjavur-613403, India
ABSTRACT:The cellular industry is growing day to day. Rapid increase in the demand for data services has
pushed wireless operators to invest in new technologies. Operators capitalize a major portion of their money in
their network infrastructure to be able to offer new services with high quality and lower rates. To survive in such a
competitive market, they look for network planning tools which can design with low cost and good coverage. But at
the same time the customer looking for the good coverage without interference. Here we use ATOLL software to
design and plan the capacity, coverage and frequency analysis of radio network .which was performed to prepare a
radio planning sketch considering possibility of network realization of the surrounding in Vallam, Thanjavur.
KEYWORDS:RF planning, ATOLL platform, frequency reuse, C/S calculation, C/I calculation.
1. Introduction:
Designing of air interface inGSMis one of the vital.
Parts in GSM planning thisproject involves in a study
of how the air interfacein mobile environment is
planned and engineered. Global system for mobile
communication (GSM) standard for digital cellular
communication wasintroduced in 1982 to create a
common Europeanmobile telephone .GSM Network
is comprised of amobile Station (MS) which is
connected to the BaseTransceiver Station (BTS) via
air interface.
Inadditionto other hardware, BTS contains the
equipment calledTransceiver (TRx), which is
responsible for thetransmission and reception of
several radio frequency(RF) signals to/from the end
user. BTS is thenconnected to the base station
controller (BSC). BSC usually handles radio resource
management and handovers of the calls from one BTS
(cell/sector) to the other BTS (cell/sector) equipped in
it.
BSC is then connected to Mobile Switching Centre
(MSC).However, some ideas had not implemented in
live GSM network. In this paper, the analysisof
signal flow is made and RF planning is done using
ATOLL tool to a particular range of area. The results
are shown using ATOLL tool as
comparativescreenshots between existingand
designed areas depicts the architecture model and
description of the network layout and rules of
planning. The followingparameters such as coverage,
capacity, quality and cost for planning are considered
during planning process.
2. Radio Network Planning:
The radio network planning isusually a comparative
process and requires an initial baseline of KPI’s.
Networks must bedimensioned to support user
demands. Coverage is the most important quality
determining.
Parameter in a radio network. A system with
goodcoverage will always be superior to a system
with less
Good coverage. An area is referred to as being
covered if the signal strength received by an MS in
that area is higher than a certain minimum value. A
typical valuein this case is around ‐95dBm.
However, coverage in a two‐way radio
communication system is determined by the weakest
link. In addition to this, factors such as receiver
sensitivity and different margins are considered.
Power budget implies that thecoverage of the
downlink is equal to the coverage ofthe uplink. The
power budget shows whether the uplink or the
downlink is the weak link. When thedownlink is
stronger, the EIRP used in the predictionshould be
based on the balanced BTS output power.When the
uplink is stronger, the maximum BTS output power
is used instead. Practice indicates that incases where
the downlink is the stronger it is advantageous to
have a somewhat (2‐3 dB) higher base EIRP than the
one strictly calculated from powerbalance
considerations. Defining the radio network
parameters is the final stepin the design of a radio
network. There are a numberof parameters that has
to be specified for each cell. The parameters could
be divided into four differentcategories that are
Common cell data
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SSRG International Journal of Electronics and Communication Engineering - (ICRTECITA-2017) - Special Issue - March 2017
ISSN : 2348 – 8549 www.internationaljournalssrg.org Page 65
Example: Cell Identity, Power setting, Channel
Numbers
Neighboring cell relation data
Example: Neighboring Cell relation, Hysteresis,
Offset
Locating and idle mode behavior
Example: Paging properties, Signal strengthcriteria,
Quality thresholds.
Feature control parameters
Example: Settings to control the behavior of e.g.
Frequency Hopping and Dynamic Power Control.
The volume of traffic received determines the
number of nodes used and capacity provisioned
between nodes, whilst the nature of traffic has a
bearing on the type of nodes deployed as well as
allowing the planner to forecast traffic trends.
2.1 Planning process:
2.1.1 Capacity planning:
The capacity that a network can handleis measured
in terms of the subscribers or the traffic load. Here,
the Erlang is calculated for 20 BTS coverage area,
which gives the number of traffic channels for
different number of carriers.
: Subscriber growth playing a main roll while
considering the capacity of the channel Customer
migration and increasing traffic can affect the
capacity of the channel.The connection between BTS
and BSC given below
Fig 1: AbisInterface (E1) between BTS and
BSC.
For voice =30 logical channel.
For signaling =1 logical channel
For synchronization=1 logical channel.
Totally 32 logical channel is dedicated for abis
interface.
1 physical channel=32 logical channel.
1 physical channel =64kbps
= (16+16+16+16)kbps.
The physical channel split into 4 logical channel
groups.
Total number =no.of voice * no. of channel
channelchannel group
Total number of channel =30*4=120 channels
Cell Sector Number of channel
1/1/1 8/8/8 =24
2/2/2 16/16/16 =48
3/3/3 24/24/24 =72
4/4/4 32/32/32 =96
5/5/5 40/40/40 =120
Table 1: capacity calculation
The total capacity of the channel is 120.but 96
channels are capable to use, because if you use full
capacity the channel get full load and it affect the
communication. So that the traffic density is 96 per
one physical channel.
Traffic Density: Users per cell site calculated below
in urban are.
• 1.5 Average call holding time(practical)
• 1.5/60 = 0.025 E traffic per user for
1h.(approx.).
• traffic per sector = 2.94/0.025 = 120 users
for
Bandwidth Channel Grade of
service
1 8 2.94
2 16 9.8
Table.2 Erlang table
Traffic per cell site ≈ 3 * 120 = 360 user per hour.
2.1. 2Coverage planning:
The objective of coverage planningphase is to find a
minimum amount of cell sites with optimum
locations for producing the required coverage for the
target area. It is normally performed with prediction
modules on digital map database.
• Number of sites required for
• coverage in urban area = Total
coverage area
Coverage area per site
1. Uplink Power Budget:
The uplink power budget is calculated to determine
the maximum path loss. This calculation is done first
because: The MS transmit power is fixed The BTS
receiver sensitivity is fixed The MS has less transmit
power than the BTS.
BTS BSC ABIS Interface(E1)
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SSRG International Journal of Electronics and Communication Engineering - (ICRTECITA-2017) - Special Issue - March 2017
ISSN : 2348 – 8549 www.internationaljournalssrg.org Page 66
Table.3 uplink power budget
2. Downlink Power Budget:
• After the maximum path loss is calculated
in the uplink power budget, the BTS
transmit power needs to be determined
using the downlink power budget.
• After the maximum path loss is calculated
in the uplink power budget, the BTS
transmit power needs to be determined
using the downlink power budget.
Example
The table below gives an example for an downlink
power budget.
Table.4 downlink power budget
2.1.3 Frequency planning:
The radio frequency spectrum for GSM is limited,
the most significant challenge is to use the radio
frequency as efficient as possible. This topic
discusses how the allocated frequencies can be
distributed over the cells from the interference point
of view.
2.1.4 Living Plan
The frequency plan is a living plan. Changes have to
be made continuously due to:
Network growth
Traffic growth
Detection of interference.
2.2Different Ways to Plan
The frequency plan can be made in different ways:
Fixed cluster configuration
Flexible assignment
Mixture of both.
2.2.1 Fixed Cluster Configuration
Using the reuse factor. Frequencies that can be used
within a cluster can be determined. For example a
cluster size of K=21 cells will use at least 21
frequencies. This fixed frequency planning can be
done manually. It is simple but not particularly
efficient.
2.2.2 Flexible assignment
The flexible assignment is based upon an
interference matrix using an automatic tool. This
method can lead to a more efficient frequency use.
For example 18 frequencies are needed to have the
same level of coverage quality as manual assigned
21 frequencies.
2. 3Interference Analysis
The assignment of frequencies to cells is based upon
the interference requirements. The input for the
frequency assignment is the interference matrix.
2.3.1 Interference Matrix
The interference matrix shows the minimum
frequency spacing that should be used between to
cells to have minimum interference.
2.3.2 Calculation Tools
It is almost impossible to calculate the interference
relationship for every cell by hand. In practice, cell-
planning tools are used to calculate the interference
matrix.
2.4 Minimum Frequency Spacing
When the interference relations between cells are
known, the resulting minimum frequency spacing for
each pair of cells is noted in the compatibility matrix
by a 0, 1, 2, or 3 as follows:
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SSRG International Journal of Electronics and Communication Engineering - (ICRTECITA-2017) - Special Issue - March 2017
ISSN : 2348 – 8549 www.internationaljournalssrg.org Page 67
Number Allowed
channel
Spacing(khz)
0 Co-channel 0
1 1st adjacent
channel
200
2 2nd adjacent
channel
400
3 3rd adjacent
channel
600
Table.1 channel allocation
2.4.1 Extensionsand Frequency Changes:
Revision of Frequency Plan:
When the network is to be extended, e.g. by
increasing the cell density in order to improve the
traffic capacity and the coverage quality, a revised
frequency plan is necessary. The revision process
should consider the following points:
• To minimize the retuning, the already
operational base stations should be left
unchanged as much as possible.
• The TRX and combiners are remotely
controllable from the OMC. Retuning is not
a technical difficulty Changing a frequency
will interrupt service and may momentarily
cause higher interference because not all
basestations can be retuned simultaneously
from the OMC.
• The pre-assigned frequencies of the cell
cliques that will change significantly should
be abandoned in favor of new
frequencies(cells B1, C5, and D1 in the
figure below).This figure shows an example
of network growth by cell splitting:
Fig.2 clusters formation
Fig.1 cellular concept
3. Frequency Hopping:
Frequency hopping is the dynamic switching of radio
links from one carrier frequency to another.
Frequency hopping changes the frequency used by a
radio link every new TDMA frame in a regular
pattern.
3.1. Types of Frequency Hopping
Two types:
ETSI defines two type of frequency hopping:
1. Baseband hopping
2. Synthesizer hopping
3.1.1. Baseband Hopping:
The transceiver within a BTS operates on fixed
frequencies. The speech signal generated at the
channel coder is switched between the transceivers
before transmission. Each frame of eight time slots is
input to a different transceiver and so to a different
frequency. The transceiver does not retune to
different frequencies, but each channel hops over the
available frequencies.
3.1.2. Synthesizer Hopping:
The each transceiver retunes to a different frequency
before transmitting a frame. This allows each
transceiver to hop over as many frequencies as
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SSRG International Journal of Electronics and Communication Engineering - (ICRTECITA-2017) - Special Issue - March 2017
ISSN : 2348 – 8549 www.internationaljournalssrg.org Page 68
desired (with a maximum of 18), regardless of the
number of transceivers in the cell.
4. Atoll planning tool:
Atoll Planning Tool was used in this research;
open, scalable, and flexible multi-technology
and optimization platform that supports.
4.1. Atoll General Features
1) Multi technology tool
Dedicated Project Templates & Propagation
all supported technology
2) User friendly GUI
• Windows based tools
• Easy to export/ import all required data
• Simply support copy/paste all data
3) Flexibility in data management
Display, Sorts & Filter
4) Working systems
Stand alone .atl documents.
4.2 Simulation Steps:
: Here we take a Vallam area in Thanjavur as a
reference. Effective radio network planning is
obviously a big challenge here with the optimal
utilization of limited resources.In this part of the
work, coverage analysis-link level simulation result
along with link budget preparation and capacity
analysis system level simulation have been
performed. As a result, it can be included for the
complete part of Vallam area radio planning
performing the simulations with planning tool like
Atoll.
Fig 3: Import the map in ATOLL window
4.2.1Place a towers on the map
Fig 4: Fix towers on the selected area.
4.2.2Cluster class properties
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SSRG International Journal of Electronics and Communication Engineering - (ICRTECITA-2017) - Special Issue - March 2017
ISSN : 2348 – 8549 www.internationaljournalssrg.org Page 69
Fig7: Cluster class properties.
4.3Cost hata model
The cost hata model is a radio propagation
model that extends the urban Hata model (which in
turn is based on the Okumura hata model) to cover a
more elaborated range of frequencies.
Planning parameters:
Frequency: 1500–2000 MHz
• Mobile station antenna height: 1–10 m
• Base station antenna height: 30–200
m
• Link distance: 1–20 km
• Propagationmodel: costhata
Name: urban low density.
Path loss {L50(urban)} = 46.3 + 33.9 log fc – 13.82
log hte – a (hre) + (44.9 – 6.55 log hte) log d + Cm
4.3.1Range of parameters:
i. f : 1500–2000 MHz
ii. hte :30m to 200m
iii. hre:l0m to lm
iv. d :lkm to 20 km
4.3.2Coverage by signal level
Fig 5: Coverage by signal level
The signal coverage is designated in to best signal
which is represented by the color yellow, good signal
which is represented by the color green. Worst signal
which is represented blue.
C/I Calculation for finding interference
Fig6: C/I Calculation
If any interference occurred due to poor frequency
allotment can be find out by this c/i calculation.
Table3: C/I Values
4.3.3.Finished model
Fig:Finished design
This paper proposing a designing of network in a
vallam area, Thanjavur.
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SSRG International Journal of Electronics and Communication Engineering - (ICRTECITA-2017) - Special Issue - March 2017
ISSN : 2348 – 8549 www.internationaljournalssrg.org Page 70
5. Conclusion and feature work:
The success of LTE network depends on its three
factors:
Coverage: The required coverage for the target area
and performed with prediction modules on digital
map.
Capacity: Capacity is based on an assessment of
dropped calls.
Quality: Quality has been improved by eliminating
interference from both external and internal sources.
In future, work must be provided for improvement of
LTE by using planning software.
7.Reference:
[1] Prabhjot Singh, Mithilesh Kumar, Ambarish
Das,“Effective Frequency Planning to Achieve
Improved KPI'S, TCH and SDCCH drops for a real
GSM Cellular Network,” IEEE Trans.2014.
[2] U S Rahman, M. A. Matin, M R Rahman, “A
Practical Approach of Planning and Optimizationfor
Efficient Usage of GSM Network,”International
Journal of Communications (IJC)Volume 1 Issue 1,
December 2012.
[3] Christer Johansson Jonas Naslund, Magnus
Madfors, “Adaptive Frequency Allocation of
BCCH Frequencies in GSM,”IEEE Trans. on
Communications, Vol. 39, No. 12, 1995.
[4] Kuthadi, V. M, R. Selvaraj, and C. Rajendra.
"A Study of Security Challenges in Wireless
Sensor Networks." Journal of Theoretical and
applied information technology 20.1 (2009): 39-44
[5] Prabhjot Singh, Mithilesh Kumar, Ambarish
Das, “A Design Approach to Maximize Handover
Performance Success rate and Enhancement of
voice quality Samples for a GSM CellularNetwork,”
IEEE Trans 2014.
[6] Bilal Haider, M. Zafrullah and M. K. Islam
'Radio Frequency Optimization &QoS Evaluation
in Operational GSM Network', in the Proceedings
of the World Congress on Engineering and
Computer Science 2009 Vol WCECS 2009,
October 20-22,2009, San Francisco, USA.