1 RF Network Design Network Planning 2 Introduction • The high level life cycle of the RF network planning process can be summarised as follows :- • To help the operator to identify their RF design requirement • Optional • Discuss and agree RF design parameters, assumptions and objectives with the customer • Coverage requirement • Traffic requirement • Various level of design (ROM to detail RF design) • Issuing of search ring • Cand. assessment • Site survey, design, approval • Drive test (optional) • Frequency plan • Neighbour list • RF OMC data • Optimisation Comparative Analysis RF Design requirement RF Design Site Realisation RF Design Implementation
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1
RF Network Design
Network Planning
2
Introduction
• The high level life cycle of the RF network planning process can be summarised as follows :-
• To help the operator to identify their RF design requirement
• Optional
• Discuss and agree RF design parameters, assumptions and objectives with the customer
• Coverage requirement• Traffic requirement• Various level of design (ROM to detail RF design)
• Issuing of search ring• Cand. assessment• Site survey, design, approval
• Drive test (optional)
• Frequency plan• Neighbour list• RF OMC data• Optimisation
Comparative Analysis
RF Design requirement
RF Design
Site Realisation
RF Design
Implementation
3
Comparative Analysis
• This is an optional step
• This is intended to :-
• Help an existing operator in building/expanding their network
• Help a new operator in identifying their RF network requirement, e.g.
where their network should be built
• For the comparative analysis, we would need to :-
• Identify all network that are competitors to the customer
• Design drive routes that take in the high density traffic areas of interest
• Include areas where the customer has no or poor service and the
competitors have service
4
Comparative Analysis
• The result of the analysis should include :-
• For an existing operator
• All problems encountered in the customer’s network
• All areas where the customer has no service and a competitor does
• Recommendations for solving any coverage and quality problems
• For a new operator
• Strengths and weaknesses in the competitors network
• Problem encountered in the competitors network
5
RF Network Design Inputs
• The RF design inputs can be divided into :-
• Coverage requirements
• Target coverage areas
• Service types for the target coverage areas. These should be
marked geographically
• Coverage area probability
• Penetration Loss of buildings and in-cars
• Capacity requirements
• Erlang per subscriber during the busy hour
• Quality of service for the air interface, in terms GoS
• Network capacity
6
RF Network Design Inputs
• Available spectrum and frequency usage restriction, if any
• List of available, existing and/or friendly sites that should be included in
the RF design
• Limitation of the quantity of sites and radios, if any
• Quality of Network (C/I values)
• Related network features (FH, DTX, etc.)
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Coverage Design Inputs by BSNL
• Coverage Thresholds
• Indoor Coverage : Signal Level measured at street better than –65 dBm.
Indoor coverage to be provided in commercial complexes,
hotels,technology parks etc.
• In Car Coverage: Signal Level measured at street better than –75 dBm. In
Car coverage to be provided in residential areas, highways, tourist spots
etc.
• Outdoor Coverage : Signal level measured at street better than –85 dBm.
All remaining areas to be covered with Outdoor coverage.
• These are general guidelines for planning , specific areas not provided.
8
Capacity Design Inputs by BSNL
• Frequency spectrum available 6.2 MHz (31 channels).
• Average traffic per sub for RF design : 50 mErlang.
• Synthesizer frequency hopping can be used.
• GOS: 2%
• Existing network Database
• Total No. of sites with configuration
• Site details eg location(Lat-Long), Antenna height ,azimuth, etc.
9
RF Network Design
• There are 2 parts to the RF network design to meet the :-
• Capacity requirement
• Coverage requirement
• For the RF Coverage Design
RF
Coverage
Design
Link
BudgetPropagation
Model
Digitised
DatabasesCW Drive
Testing
Customer
Requirements
10
CW Drive Testing
• CW drive test can be used for the following purposes :-
• Propagation model tuning
• Assessment of the suitability of candidate sites, from both coverage and interference aspect
• CW drive test process can be broken down to :-
Test
Preparation
Propagation
Test
Data
Processing
• Equipment required
• BTS antenna selection
• Channel selection
• Power setting
• Drive route planning
• Test site selection
• Transmitter setup
• Receiver setup
• Drive test
• Transmitter dismantle
• Measurement averaging
• Report generation
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CW Drive Testing - Test Preparation
• The test equipment required for the CW drive testing :-
• Receiver with fast scanner
• Example : HP7475A, EXP2000 (LCC) etc.
• The receiver scanner rate should conform to the Lee Criteria of 36
to 50 sample per 40 wavelength
• CW Transmitter
• Example : Gator Transmitter (BVS), LMW Series Transmitter
(CHASE), TX-1500 (LCC) etc.
• Base Station test antenna
• DB806Y (Decibel-GSM900), 7640 (Jaybeam-GSM1800) etc.
• Accessories
• Including flexible coaxial cable/jumper, Power meter, extended
power cord, GPS, compass, altimeter
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CW Drive Testing - Test Preparation
• Base Station Antenna Selection
• The selection depends on the purpose of the test
• For propagation model tuning, an omni-directional antenna is preferred
• For candidate site testing or verification, the choice of antenna depends
on the type of BTS site that the test is trying to simulate.
• For Omni BTS :
• Omni antennas with similar vertical beamwidth
• For sectorised BTS
• Utilising the same type of antenna is preferred
• Omni antenna can also be used, together with the special
feature in the post processing software like CMA (LCC)
where different antenna pattern can be masked on over the
measurement data from an omni antenna
13
CW Drive Testing - Test Preparation
• Test Site Selection
• For propagation model tuning, the test sites should be selected so that
:-
• They are distributed within the clutter under study
• The height of the test site should be representative or typical for the
specific clutter
• Preferably not in hilly areas
• For candidate site testing/verification, the actual candidate site
configuration (height, location) should be used.
• For proposed greenfield sites, a “cherry-picker” will be used.
14
CW Drive Testing - Test Preparation
• Frequency Channel Selection
• The necessary number of channels need to be identified from the
channels available
• With input from the customer
• The channels used should be free from occupation
• From the guard bands
• Other free channels according to the up-to-date frequency plan
• The channels selected will need to be verified by conducting a pre-test
drive
• It should always precede the actual CW drive test to verify the
exact free frequency to be used
• It should cover the same route of the actual propagation test
• A field strength plot is generated on the collected data to confirm
the channel suitability
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CW Drive Testing - Test Preparation
• Transmit Power Setting
• For propagation model tuning, the maximum transmit power is
used
• For candidate site testing, the transmit power of the test
transmitter is determined using the actual BTS link budget to
simulate the coverage
• On sites with existing antenna system, it is recommended that the
transmit power to be reduced to avoid interference or inter-
modulation to other networks.
• The amount of reduction is subject to the possibility if separating
the test antenna from the existing antennas
16
CW Drive Testing - Test Preparation
• Drive Route Determination
• The drive route of the data collection is planned prior to the drive test using a
detail road map
• Eliminate duplicate route to reduce the testing time
• For propagation model tuning, each clutter is tested individually and the drive
route for each test site is planned to map the clutter under-study for the
respective sites.
• It is important to collect a statistically significant amount of data, typically a
minimum of 300 to 400 data points are required for each clutter category
• The data should be evenly distributed with respect to distance from the
transmitter
• In practice, the actual drive route will be modified according to the latest
development which was not shown on the map. The actual drive route taken
should be marked on a map for record purposes.
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• Transmitter Equipment Setup
• Test antenna location
• Free from any nearby obstacle, to ensure free propagation in both horizontal
and vertical dimension
• For sites with existing antennas, precaution should be taken to avoid possible
interference and/or inter-modulation
• Transmitter installation
• A complete set of 360º photographs of the test location (at the test height) and the
antenna setup should be taken for record
CW Drive Testing - Propagation Test
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CW Drive Testing - Propagation Test
• Scanning Receiver Setup - HP 7475A Receiver Example
HP 7475A Receiver
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CW Drive Testing - Propagation Test
• Scanning Receiver Setup
• The scanning rate of the receiver should always be set to allow at least 36
sample per 40 wavelength to average out the Rayleigh Fading effect.
• For example: scanning rate = 100 sample/s
• test frequency = 1800 MHz
• therefore, to achieve 36 sample/40 wavelength, the max. speed is =
•
• It is recommended that :-
• Beside scanning the test channel, the neighbouring cells is also monitored.
This information can be used to check the coverage overlap and potential
interference
• Check the field strength reading close to the test antenna before starting
the test, it should approach the scanning receiver saturation
hkmsm36/100
0.166740/67.66/52.18
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CW Drive Testing - Propagation Test
• Drive Test
• Initiate a file to record the measurement with an agreed naming
convention
• Maintain the drive test vehicle speed according to the pre-set scanning
rate
• Follow the pre-plan drive route as closely as possible
• Insert marker wherever necessary during the test to indicate special
locations such as perceived hot spot, potential interferer etc.
• Monitor the GPS signal and field strength level throughout the test, any
extraordinary reading should be inspected before resuming the test.
• Dismantling Equipment
• It is recommended to re-confirm the transmit power (as the pre-set
value) before dismantling the transmitter setup
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Measurement Data Processing
• Data Averaging
• This can be done during the drive testing or during the data processing
stage, depending on the scanner receiver and the associated post-
processing software
• The bin size of the distance averaging depends on the size of the
human made structure in the test environment
• Report Generation
• For propagation model tuning, the measurement data is exported into
the planning tool (e.g. Asset)
• Plots can also be generated using the processing tool or using MapInfo
• During the export of the measurement data, it is important to take care
of the coordinate system used, a conversion is necessary if different
coordinate systems are used.
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Propagation Model• Standard Macrocell Model for Asset
• A typical mobile antenna gain of 2.2 dBi is used
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Link Budget
• Link Budget Example (GSM900)
UPLINK DOWNLINKMS Transmit Power 33 dBm BTS Transmit Power 46 dBm
Cable Loss 0 dB ACE Loss ZMS Antenna Gain 2.2 dBi Feeder Loss 2 dB
Body Loss 2 dB LNA Gain 0 dB
Penetration Loss W BTS Antenna Gain 18 dBi
Slow Fade Margin X Max. Path Loss YMax. Path Loss Y Slow Fade Margin XBTS Antenna Gain 18 dBi Penetration Loss WLNA Gain 0 dB Body Loss 2 dB
Feeder Loss 2 dB MS Antenna Gain 2.2 dBi
ACE Loss 0 dB Cable Loss 0 dB
Diversity Gain 4 dB Diversity Gain 0 dB
BTS Receiver Sensitivity -107 dBm MS Receiver Sensitivity -102 dBm
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Antenna
• Antenna Selection
• Gain
• Beamwidths in horizontal and vertical radiated planes
• VSWR
• Frequency range
• Nominal impedance
• Radiated pattern (beamshape) in horizontal and vertical planes
• Downtilt available (electrical, mechanical)
• Polarisation
• Connector types (DIN, N)
• Height, weight, windload and physical dimensions
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Antenna
• The antenna selection process
• Identify system specifications such as polarisation, impedance and
bandwidth
• Select the azimuth or horizontal plane pattern to obtain the needed
coverage
• Select the elevation or vertical plane pattern to be as narrow as
possible, consistent with practical limitations of size, weight and cost
• Check other parameters such as cost, power rating, size, weight,
mounting capabilities, wind loading, connector types, aesthetics and
reliability to ensure that they meet system requirements
34
Antenna
• System Specification
• Impedance and frequency bandwidth is normally associated with the
communication system used
• The polarisation would depends on if polarisation diversity is used
• Horizontal Plane Pattern
• Three categories for the horizontal plane pattern :-
• Omnidirectional
• Sectored (directional)
• Narrow beam (highly directional)
• Elevation Plane Pattern
• Choosing the antenna with the smallest elevation plane beamwidth will give
maximum gain. However, beamwidth and size are inversely related
• Electrical down tilt
• Null filling
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Nominal RF Design
Link Budget
Maximum
path loss
Propagation
model
Typical site
configuration
Site radius
Nominal RF
Design
(coverage)
Coverage
requirements
Nominal site
count
Coverage site
count
• Transmit Power
• Antenna configuration
(type, height, azimuth)
• Site type (sector, omni)
Traffic
requirements
• Standard hexagon site
layout
• Friendly, candidate sites
• Initial site survey inputs
Traffic site
count
Traffic > Cov.
Cov. > Traffic
• Recalculate the site
radius using the
number of sites from
the traffic requirement
• Repeat the nominal
RF design
Traffic
requirements
36
Nominal RF Design
• Calculation of cell radius
• A typical cell radius is calculated for each clutter environment
• This cell radius is used as a guide for the site distance in the respective
clutter environment
• The actual site distance could varies due to local terrain
• Inputs for the cell radius calculation :-
• Maximum pathloss (from the link budget)
• Typical site configuration (for each clutter environment)
• Propagation model
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Nominal RF Design
• There are different level of nominal RF design :-
• Only using the cell radius/site distance calculated and placing ideal
hexagon cell layout
• Using the combination of the calculated cell radius and the
existing/friendly sites from the customer
The site distance also depends on the required capacity
•In most mobile network, the traffic density is highest within the CBD area and major routes/intersections
•The cell radius would need to be reduce in this area to meet the traffic requirements
•BASED ON THE SITE DISTANCE & THE COVERAGE REQUIREMENTS CELL COUNT BASED ON COVERAGE IS CALCULATED.
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Nominal RF Design
• Cell count based on traffic is derived based on capacity inputs:-
• Capacity requirements
• GOS
• Spectrum availability
• Freq. Hopping techniques
• If the total sites for the traffic requirement is more than the sites required for coverage, the nominal RF design is repeated using the number of sites from the traffic requirement
• Recalculating the cell radius for the high traffic density areas
• The calculation steps are :-
• Calculate the area to be covered per site
• Calculate the maximum cell radius
• Calculate the site distance
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Site Realisation
• After completion of Nominal design based on cell count ( coverage & capacity requirements) , search rings for each cell site issued.
• Nominal design is done , with the existing network in place(existing BTS). Existing site location remain unchanged , azimuth , tilts as per the new design requirements.
• Based on the search ring form physical site survey is undertaken.
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Site Realisation
Search Ring Form
• Site ID
• Site Name
• Latitude/Longitude
• Project name
• Issue Number and date
• Ground height
• Clutter environment
• Preliminary configuration
• Number of sector
• Azimuth
• Antenna type
• Antenna height
• Location Map & SR radius
• Search ring objective
• Approvals
Spheroid:
Coordinates: (GPS)
o ' ''N
o ' ''E
Site AGL (m): 30 Antenna Type: 65 deg Vertical polarised
• Evaluate network performance from the subscriber point of view
• KPIs information: • DL quality, call success rate, handover success rate, DL signal level• not statistically as reliable as NMS information
• Added value of drive test measurement :• find out the geographical position of problems like bad DL quality to
look for a possible interference source in the area• compare the performance of different networks • display the signal level on the digital maps to individuate areas with
lack of coverage eventually improve the propagation model • verify the neighbour list parameter plan
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Optimisation Process
• There are not strict processes for optimization because the activity is driven by the network evolution.
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Optimisation Process: Young Network Case
• In a young network the primary target is normally the coverage.
• In this phase usually there is a massive use of drive test measurement • check the signal and • the performance of the competitors
GPS
NMSX
MMAC
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Optimisation Process: Mature Network Case
• In a mature network the primary targets are quality indicators• drop call rate, average quality, handover failures.
• Important use the information from NMS• a general view of the network performance.
• Drive test measurements are still used • but not in a massive way• in areas where new sites are on air• where interference and similar problems are pointed out by NMS data