rf planning and designing of air interface by using … atoll platform abinaya.m, sneka.a,...

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



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)



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:



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



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


ISSN : 2348 – 8549 www.internationaljournalssrg.org 9

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.


ISSN : 2348 – 8549 www.internationaljournalssrg.org 0

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.

rf planning and designing of air interface by using … atoll platform abinaya.m, sneka.a,...

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