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7/27/2019 110793392 GSM RF Planning Concepts Ppt
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RF Network Design
Network Planning
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Introduction
The high level life cycle of the RF network planning process can
be summarised as follows :- To help theoperator toidentify their RFdesignrequirement
Optional
Discuss and agreeRF designparameters,assumptions andobjectives with thecustomer
Coveragerequirement Traffic requirement Various level of
design (ROM todetail RF design)
Issuing of searchring
Cand. assessment Site survey,
design, approval Drive test(optional)
Frequencyplan
Neighbour list
RF OMC data Optimisation
ComparativeAnalysis
RF Designrequirement
RF Design
SiteRealisation
RF Design
Implementation
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Comparative Analysis
This is an optional step
This is intended to :-o Help an existing operator in building/expanding their networko 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 :-o Identify all network that are competitors to the customero Design drive routes that take in the high density traffic areas of
interesto Include areas where the customer has no or poor service and the
competitors have service
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Comparative Analysis
The result of the analysis should include :-
For an existing operatoro All problems encountered in the customers networko All areas where the customer has no service and a competitor
doeso Recommendations for solving any coverage and quality problems
For a new operatoro Strengths and weaknesses in the competitors networko Problem encountered in the competitors network
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RF Network Design Inputs
The RF design inputs can be divided into :-o 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-carso Capacity requirements
Erlang per subscriber during the busy hour Quality of service for the air interface, in terms GoS Network capacity
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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 Thresholdso Indoor Coverage : Signal Level measured at street better than65 dBm.
Indoor coverage to be provided in commercial complexes,hotels,technology parks etc.
o In Car Coverage: Signal Level measured at street better than75 dBm.In Car coverage to be provided in residential areas, highways, touristspots etc.
o Outdoor Coverage : Signal level measured at street better than85dBm. All remaining areas to be covered with Outdoor coverage.
o These are general guidelines for planning , specific areas not provided.
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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
o Total No. of sites with configurationo Site details eg location(Lat-Long), Antenna height ,azimuth, etc.
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RF Network Design
There are 2 parts to the RF network design to meet the :-o Capacity requiremento Coverage requirement
For the RF Coverage Design
RFCoverage
Design
LinkBudget
PropagationModel
DigitisedDatabasesCW Drive
Testing
CustomerRequirements
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CW Drive Testing
CW drive test can be used for the following purposes :-
o Propagation model tuningo Assessment of the suitability of candidate sites, from both
coverage and interference aspect CW drive test process can be broken down to :-
TestPreparation
Propagation
Test
DataProcessing
Equipmentrequired BTS antenna
selection Channel selection
Power setting Drive route planning Test site selection
Transmittersetup
Receiversetup
Drive test Transmitter
dismantle
Measurementaveraging
Report generation
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CW Drive Testing - Test Preparation
Test Site Selection
For propagation model tuning, the test sites should be selected sothat :-o They are distributed within the clutter under studyo The height of the test site should be representative or typical for
the specific cluttero Preferably not in hilly areas
For candidate site testing/verification, the actual candidate siteconfiguration (height, location) should be used.
For proposed greenfield sites, a cherry-picker will be used.
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CW Drive Testing - Test Preparation
Frequency Channel Selectiono The necessary number of channels need to be identified from the
channels available With input from the customer
o The channels used should be free from occupation From the guard bands Other free channels according to the up-to-date frequency plan
o The channels selected will need to be verified by conducting apre-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 testA 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 isused
For candidate site testing, the transmit power of the testtransmitter is determined using the actual BTS link budget tosimulate the coverage
On sites with existing antenna system, it is recommended thatthe transmit power to be reduced to avoid interference or inter-modulation to other networks.
The amount of reduction is subject to the possibility if separatingthe test antenna from the existing antennas
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CW Drive Testing - Test Preparation
Drive Route Determinationo 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
o For propagation model tuning, each clutter is tested individually and thedrive route for each test site is planned to map the clutter under-study forthe respective sites.
o It is important to collect a statistically significant amount of data, typically
a minimum of 300 to 400 data points are required for each cluttercategory
o The data should be evenly distributed with respect to distance from thetransmitter
o In practice, the actual drive route will be modified according to the latestdevelopment 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 Setupo Test antenna location
Free from any nearby obstacle, to ensure free propagation in bothhorizontal and vertical dimension
For sites with existing antennas, precaution should be taken to avoidpossible interference and/or inter-modulation
o Transmitter installation
o A complete set of 360 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 Setupo 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 =
o It is recommended that :- Beside scanning the test channel, the neighbouring cells is also
monitored. This information can be used to check the coverageoverlap and potential interference
Check the field strength reading close to the test antenna beforestarting the test, it should approach the scanning receiver saturation
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CW Drive Testing - Propagation Test
Drive Testo Initiate a file to record the measurement with an agreed naming
conventiono Maintain the drive test vehicle speed according to the pre-set
scanning rateo Follow the pre-plan drive route as closely as possibleo Insert marker wherever necessary during the test to indicate
special locations such as perceived hot spot, potential interferer
etc.o Monitor the GPS signal and field strength level throughout the
test, any extraordinary reading should be inspected beforeresuming the test.
Dismantling Equipmento
It is recommended to re-confirm the transmit power (as the pre-setvalue) before dismantling the transmitter setup
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Measurement Data Processing
Data Averagingo This can be done during the drive testing or during the data
processing stage, depending on the scanner receiver and theassociated post-processing softwareo The bin size of the distance averaging depends on the size of the
human made structure in the test environment Report Generation
o For propagation model tuning, the measurement data is exported
into the planning tool (e.g. Asset)o Plots can also be generated using the processing tool or using
MapInfoo During the export of the measurement data, it is important to take
care of the coordinate system used, a conversion is necessary ifdifferent coordinate systems are used.
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Propagation Model Standard Macrocell Model for Asset
o Lp (dB) = K1 + K2 log(d) + K3 Hm + K4 log(Hm) + K5 log(Heff)o + K6 log(Heff) log(d) + K7 Diffraction + Clutter factoro where Lp, Diffraction, Clutter factor are in dBo d, Hm, Heff are in mo It is based on the Okumura-Hata empirical model, with a number of
additional features to enhance its flexibilityo Known to be valid for frequencies from 150MHz to 2GHzo Applies in condition :-
Base station height : 30 - 200 m Mobile height : 1 - 10 m Distance : 1 - 20 km
o An optional second intercept and slope (K1, K2) for the creation of a two-piece model with the slope changing at the specified breakpoint distance.
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Morphology Class
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Link Budget
Link Budget Element of a GSM Network
BTS Antenna Gain Max. Path Loss Fade Margin
LNA(optional)
Feeder Loss
DiversityGain
BTSReceiver
Sensitivity
ACELoss
BTSTransmit
Power
Penetration Loss
MS Antenna Gain,Body and Cable
Loss
MobileTransmit
Power
MobileReceiver
Sensitivity
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Li k B d t
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Link Budget
Mobile Transmit Powero GSM900 : Typical mobile class 4 (2W)o GSM1800 : Typical mobile class 1 (1W)
Mobile Receiver Sensitivityo The sensitivity of GSM900 and GSM1800 mobile = -102 dBm
Li k B d t
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Link Budget Diversity Gain
o Two common techniques used :- Space Polarisation
o Reduce the effect of multipath fading on the uplinko Common value of 3 to 4.5 dB being used
BTS Receiver Sensitivityo Depends on the type of propagation environment model used,
most commonly used TU50 modelo BTS :-
Receiver Sensitivity for GSM900 = -107 dBm
Li k B d t
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Link Budget
Feeder Losso Depends on the feeder type and feeder length
o The selection of the feeder type would depends on the feederlength, I.e. to try to limit to feeder loss to 3 -4dB.
BTS Antenna Gaino Antenna gain has a direct relationship to the cell sizeo The selection of the antenna type depends on :-
The morphology classes of the targeted area and coveragerequirements
Zoning and Local authority regulations/limitationso Common antenna types used :-
65, 90, omni-directional antennas with different gains
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Link Budget
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Link Budget
Penetration Losso Penetration loss depends on the building structure and materialo Penetration loss is included for in-building link budgeto Typical value used for Asia-Pacific environment (if country specific
information is not available) :- Dense Urban : 20 dB Urban : 18 dB
Suburban : 15 dB Rural : 9 dB
Body Losso Typical value of 3dB body loss is used
MS Antenna Gaino A typical mobile antenna gain of 2.2 dBi is used
Link Budget
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Link Budget
Link Budget Example (GSM900)
Antenna
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Antenna
Antenna Selectiono Gaino
Beamwidths in horizontal and vertical radiated planeso VSWRo Frequency rangeo Nominal impedanceo Radiated pattern (beamshape) in horizontal and vertical planeso Downtilt available (electrical, mechanical)o Polarisationo Connector types (DIN, N)o Height, weight, windload and physical dimensions
Antenna
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Antenna
The antenna selection processo
Identify system specifications such as polarisation, impedanceand bandwidtho Select the azimuth or horizontal plane pattern to obtain the
needed coverageo Select the elevation or vertical plane pattern to be as narrow as
possible, consistent with practical limitations of size, weight and
costo Check other parameters such as cost, power rating, size, weight,
mounting capabilities, wind loading, connector types, aestheticsand reliability to ensure that they meet system requirements
Antenna
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Antenna
System Specificationo Impedance and frequency bandwidth is normally associated with the
communication system usedo The polarisation would depends on if polarisation diversity is used
Horizontal Plane Patterno Three categories for the horizontal plane pattern :-
Omnidirectional Sectored (directional)
Narrow beam (highly directional) Elevation Plane Patterno Choosing the antenna with the smallest elevation plane beamwidth will
give maximum gain. However, beamwidth and size are inversely relatedo Electrical down tilto Null filling
Nominal RF Design
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Nominal RF Design
Link Budget
Maximumpath loss
Propagationmodel
Typical siteconfiguration
Site radius
Nominal RFDesign
(coverage)
Coveragerequirements
Nominal sitecount
Coverage sitecount
Transmit Power Antenna
configuration(type, height,azimuth)
Site type (sector,omni)
Trafficrequirements
Standard hexagonsite layout Friendly,
candidate sites Initial site survey
inputs
Traffic sitecount
Traffic > Cov.
Cov. > Traffic
Recalculate thesite radiususing the
number of sitesfrom the trafficrequirement
Repeat thenominal RFdesign
Trafficrequirements
Nominal RF Design
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Nominal RF Design
Calculation of cell radius
o A typical cell radius is calculated for each clutter environmento This cell radius is used as a guide for the site distance in the
respective clutter environmento The actual site distance could varies due to local terrain
Inputs for the cell radius calculation :-o Maximum pathloss (from the link budget)o Typical site configuration (for each clutter environment)o Propagation model
Nominal RF Design
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Nominal RF Design
There are different level of nominal RF design :-o Only using the cell radius/site distance calculated and placing
ideal hexagon cell layouto 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 COVERAGEREQUIREMENTS CELL COUNT BASED ON COVERAGE ISCALCULATED.
Nominal RF Design
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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 usingthe number of sites from the traffic requiremento Recalculating the cell radius for the high traffic density areaso The calculation steps are :-
Calculate the area to be covered per site
Calculate the maximum cell radius Calculate the site distance
Site Realisation
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Site Realisation
After completion of Nominal design based on cell count (coverage & capacity requirements) , search rings for each cellsite issued.
Nominal design is done , with the existing network inplace(existing BTS). Existing site location remain unchanged ,azimuth , tilts as per the new design requirements.
Based on the search ring form physical site survey isundertaken.
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Site Realisation
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Release ofSearch Ring
SuitableCandidates?
CandidatesApproved?
ArrangedCaravan
All partiesagreed atCaravan
Produce FinalRF Design
Caravan nextcandidate
Exhaustedcandidates
Additional sitesrequired
Cell splitrequired
Candidate
approved?
Driveby, RFsuggest possible
alternative
Nextcandidate
Problemidentifyingcandidate
Discussalternative with
customer
Issue designchange
Exhaustedcandidates
Y
N
Y Y
Y
Y
YY
NN
N
N
NN
YN
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Site Realisation-Site Survey Form
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y
Final RF Configuration Formo Base Station configuration
AzimuthAntenna heightAntenna type Down tiltAntenna location
Feeder type and length BTS type Transmit power Transceiver
configuration
Traffic Engineering
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g g
SpectrumAvailable
Reuse factor
Maximum numberof TRX per cell
No of TCH
availableTraffic offered
TrafficRequirement
Subscriber
supported
Channel
loading
Traffic Engineering
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Traffic Requirement
The Erlang per subscriber
Grade of Service (GoS)o
GoS is expressed as the percentage of call attempts that areblocked during peak traffico Most cellular systems are designed to a blocking rate of 1% to 5%
during busy hour
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Traffic Engineering
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Channel Loadingo As the number of TRX increases, the control channels required
increases accordinglyo The following channel loading is used for conventional GSM
networko For services such as cell broadcast, additional control channels
might be required
Traffic Engineering
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After determining the number of TCH available and the trafficrequirements, the traffic offered is calculated using the Erlang B table
o For example, for a 2% GoS and 3 TRX configuration, the traffic offered is14 Erlango If the traffic per subscriber is 50mE/subscriber, then the total subscribers
supported per sector = 280
For a uniform traffic distribution network, the number of sites requiredfor the traffic requirement is :-
Traffic Engineering
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Erlang B Table
Traffic Engineering
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If a traffic map is provided, the traffic engineering is done together withthe coverage design
After the individual sites are located, the estimated number ofsubscribers in each sector is calculated by :-o Calculating the physical area covered by each sectoro Multiply it by the average subscriber density per unit area in that regiono The overlap areas between the sectors should be included in each
sector because either sector is theoretically capable of serving the area The number of channels required is then determined by :-
o Calculating the total Erlangs by multiplying the area covered by theaverage load generated per subscriber during busy hour
o Determine the required number of TCH and then the required number ofTRXs
o If the number of TRXs required exceeded the number of TRXs supportedby the available spectrum, additional sites will be required
SWAP PLAN
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Why do we need a swap plan?To reduce mix of different vendor BTS within a large city/ area
o Reduce Inter MSC HO.o Better maintenance efficiency
Swap Strategyo No. of existing BTS sites with configuration knowno No. of new sites with configuration known.
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For Example BSNL UP(W) Circle
UP(W) Circle Network Diagram
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NokiaBTS
EriccssonBTS
All DHQ onNokia
Muzaffarnagar
Meerut
AligarhMathura
Agra
Noida
Etah
Ghaziabad
Bijnor
Rampur
Pilbhit
Etawah
Mainpuri
Budaun
Bulandshahr
Saharanpur
Moradabad
Bareilly
Delhi
NCR
Uttaranchal
Haryana
Haryana
RajasthanUP(E)
Nepal
UP(W) Circle Network Distribution Major Cities /SSAs to be deployed on Nokia BTS
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Major Cities /SSAs to be deployed on Nokia BTSo DHQ of all SSAso Meeruto Agrao Mathurao Noidao Ghaziabado Muzaffarnagaro Aligarho Bulandshahar
SSAs except DHQs deployed on Ericsson BTSo Bijnoro Bareillyo Moradabado Etaho Etawah
o Rampuro Pilbhito Badauno Mainpurio Saharanpur
HW & Rly Plan for UPW
NH 58
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Agra
Mathura
Mainpuri
Meerut
Muzaffarnagar
Saharanpur
Moradabad
Bulandshahar
BadaunPilbhit
Bareilly
Etawah
Aligarh
Bijnor
Rampur
Ghaziabad
Noida
Delhi
Etah
69 Ericsson HWSite
56 Nokia HW Site
National HW
Railways
State Highway
District Border
Uttaranchal
Haryana
Haryana
Rajasthan UP(E)
NH-58
NH-91
NH-24
NH-02
NH-03
Nepal
SWAPSUMMARYSl NO SSA PH-IV PLANNEDNOKIA
SWAPNOKIA WITHERICSSON
EXISTINGERICSSON
SWAPERICSSON
WITH NOKIA
TOTALNOKIA
TOTALERICSSON
HighwaysNokia
GRANDTOTAL
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A B C D E F G H
(A+D-B) (C-D+B) (E+F+G)
1 Agra 74 2 43 37 109 8 8 125
2 Aligarh 40 4 27 19 55 12 1 68
3 Badaun 16 10 11 3 9 18 1 28
4 Bareilly 45 11 27 17 51 21 2 74
5 Bijnor 39 32 16 3 10 45 0 55
6 Bulandshahar 27 3 17 12 36 8 1 45
7 Etah 17 12 10 3 8 19 3 30
8 Etawah 29 21 16 4 12 33 0 45
9 Ghaziabad 27 1 15 9 35 7 0 42
10 Mainpuri 22 17 12 2 7 27 0 34
11 Mathura 34 1 22 17 50 6 7 63
12 Meerut 68 5 30 26 89 9 11 109
13 Moradabad 73 35 33 16 54 52 9 115
14 Muzaffarnagar 48 10 17 13 51 14 3 68
15 Noida 12 0 8 6 18 2 0 20
16 Pilbhit 11 6 6 2 7 10 5 22
17 Rampur 20 13 11 3 10 21 0 31
18 Saharanpur 31 18 16 9 22 25 5 52
Total 633 201 337 201 633 337 56 1026
Before Swap 24volts (40) BTS
UP(W) Circle 24volt BTS Distribution
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Before Swap 24volt s (40) BTSstatuso Agra 9o Aligarh 2o Bareilly 5o Mathura 2o Meerut 3o Moradabad 6o Saharanpur 4o Bijnor 2o Bulandshahar 2o Etah 1o Etawah 3o Pilibhit 1
Out of 40 sites 31 have beenswapped too Bijnor 16o Moradabad 15
Out of 40 sites 9 left as it is (NoSwap)o Agra - 1o Moradabad 1o Saharanpur 1o Bijnor 1o Bulandshahr 1o Etah 1o Etawah 3
After Swap 24volts (40) BTS statuso Agra 1o Moradabad 16o Saharanpur 1
o Bijnor 17o Etah 1o Etawah 3o Bulandshahr 1
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Advanced Network Planning Steps
Parameter Planning
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Parameter planning means creating a default set of BSS parameters. The most important parameters to plan for:
o frequencieso BSIC
o LACo handover control parameterso adjacent cell definitions.
BSS Parameter
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Relevant BSS parameter for NW planningo frequency allocation plano transmit powero definition of neighbouring cellso definition of location areaso handover parameterso power control parameterso cell selection parameters
Handover Types
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Intracell same cell, other carrier or timeslot Intercell between cells (normal case)
Inter-BSC between BSC areas Inter-MSC between MSC areas Inter- PLMN e.g. between AMPS and GSM systems
intracell
intercell
inter-BSC
Handover Criteria
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1. Interference, UL and DL2. Bad C/I ratio3. Uplink Quality4. Downlink Quality5. Uplink Level6. Downlink Level
7. Distance8. Rapid Field Drop
9. MS Speed10. Better Cell, i.e. periodiccheck (Power Budget, UmbrellaHandovers)11. Good C/I ratio12. PC: Lower quality/levelthresholds (DL/UL)13. PC; Upper quality/levelthresholds (DL/UL)
Location Area Design 1/2
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Location updating affects all mobilesin networko LocUp in idle modeo LocUp after call completion
Location updating causes signallingand processing load within thenetwork (international LocUpdate !)
Avoid oscillating LocUpdate Trade-off between Paging load
and Location Update signalling
Location area 1
Location area 2
major road
Location Area Design 2/2
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Different MSC can not use the same LAC.
Location areas are important input for transmission plannerso should be planned as early as possible.
Never define location area borders along major roads! Dual band or microcellular networks require more attention on LAC
planningo co-located DCS and GSM cells are defined to the same LACo same MSC to avoid too much location updates which would
cause very high SDCCH blockings
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Network Optimisation
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What is network optimisation?
Network Optimisation is:
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Improving network quality from a subscribers point ofview.
Improving network quality from an operators point ofview.
p
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What is network quality?
H/W Failure Network
Configuration
Overall Network Quality
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OPE
RATOR
CUSTOMER
NETWORK
SERVICES
MOBILE
COST
Mail Box, Data,Fax, etc. Customer Care Faulty H/W or S/W Mobile Quality Misuse of
Equipment
g Network Traffic Spectrum
Efficiency
Coverage yes/no Service Probability Quality Call Set Up Time Call Success Rate Call Completion
Rate
H/W Costs
Subscription/AirtimecostsAdditional ServicesCosts
Network EquipmentCostsMaintenance Costs
Site Leasing Costs
Tools for Optimisation
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Cell Planning Tools
Prediction Simulation
Network Measurement Tools
Propagation Drive test
Network ManagementSystem Network configuration
BSS parameter data Network performance
Performance Feedback
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Network is under permanent changeo ==> detect problems and symptoms early!
OMC
field
tests
customercomplaints
Its far toolatewhen
customerscomplain!
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Optimize compared to what?
Key Performance Indicators, KPI
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KPIs are figures used to evaluate Networkperformance.o post processing of NMS data oro drive test measurements data
Usually one short term target and one long term target.o check the network evolution and which targets are
achieved KPIs calculated with NMS data
o network performance on the operator side. KPIs from drive test
o performance on the subscribers side Usually turn key projects are evaluated according to
some predefined KPIs figures like drop call rate
Network Performance Evaluation withNMS
Th t li bl KPI t l t th t k f ith
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The most reliable KPIs to evaluate the network performance withNMS are:o SDCCH and TCH congestiono Blocking percentage [%]o Drop call rate [%]o Handover failure and/or success rateo Call setup success rateo Average quality DL and UL
The targets are always defined by the customer but the followingfigures can be considered as satisfactory results:
Item limit Target Lowest acceptable Dropped calls: 98 % 96 %
Good Qual samples (0..5) >98 % 95 %
Drive Test Measurements
E l t t k f f th b ib i t f i
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Evaluate network performance from the subscriber point of view KPIs information:
o DL quality, call success rate, handover success rate, DL signallevel
o not statistically as reliable as NMS information Added value of drive test measurement :
o find out the geographical position of problems like bad DLquality to look for a possible interference source in the area
o compare the performance of different networkso display the signal level on the digital maps to individuate areas
with lack of coverage eventually improve the propagation modelo verify the neighbour list parameter plan
Optimisation Process
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There are not strict processes for optimization because the activity isdriven by the network evolution.
Optimisation Process: Young NetworkCase
In a young network the primary target is normally the coverage
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In a young network the primary target is normally the coverage. In this phase usually there is a massive use of drive test
measuremento check the signal ando the performance of the competitors
GPS
NMSX
MMAC
Optimisation Process: Mature NetworkCase In a mature network the primary targets are quality indicators
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p y g q yo drop call rate, average quality, handover failures.
Important use the information from NMSo a general view of the network performance.
Drive test measurements are still usedo but not in a massive wayo in areas where new sites are on airo where interference and similar problems are pointed out by NMS
data analysis.