ntwplan&optimi-presentation 2
TRANSCRIPT
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NETWORK PLANNINGNETWORK PLANNING
ANDANDOPTIMISATIONOPTIMISATION
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Multipath propogation
Shadowing
Terrain structures
Reflections
Inerferences
RADIO CHANNEL
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PROPOGATION LOSS
Basic loss formula
Clutter loss factors
Land usage classes
Usually stated in dB/decade
e.g. :
Free space 20 dB/dec
Open country side 25 dB/dec
Suburban areas 30 dB/dec
Urban areas 40 dB/dec
Historic city centre >45 dB/dec
L = Lo + E log(d) Losses are exponential with distance
Loss at reference point (e.g. 1km) EIRP level
Coupling loss
= Lo
reference
distance
40 dB/de
c30 dB/dec
20 dB/dec
0.1km 1km 10km
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SIGNAL ATTENUATION
Mixed land usage types on propagation path
25 dB/dec
30 dB/dec 20 dB/dec
40..50 dB/dec
Path loss
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MIXED PATH LOSS
Path loss
distance
Open : 25 dB/dec Urban : 40..50 dB/dec Open : 25 dB/dec
Signal
level
Open area curve
Urban curve
actual
signal level
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DIVERSITY TECHNIQUES=> USED TO COMBAT LOSSES
Time diversity
Frequency diversity
Space diversity
Polarisation diversity
Multipath diversity
interleaving
frequency hopping
multiple antennas
crosspolar antennas
equaliser,
rake receiver
t
f
Diversity techniques are used for improving coverage. Diversity gain
depends on environment
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PROPOGATION MODELS
Propagation models that are being used in planning tools:
Okumara Hata
The most commonly used statistical model
Walfish - Ikegami
Statistical model especially for urban environments
Juul - Nyholm
Same kind of a prediction tool as Hata, this model has different
equation for predictions beyond radio horizon (~20 km)
Ray - tracing
Deterministic prediction tool for micro cellular environments
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ANTENNA SYSTEMS
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ANTENNA CHARACTERISTICS
Directional antennas
Lobes
main lobes
side / back lobes
front-to-back ratioH-plane : 65-90 E-plane : 6-13
Half power beam-width
(3 dB- beam width)
Polarisation
Antenna impedance
Mechanical size (wind load)
Antenna down tilting
Mechanical / Electrical tilt (Electrical tilt is preferred due to good
backlobe suppression and dispersion control capability)
improves spot coverage and reduces interference
Typical characteristics VSWR : < 1.3
Impedance : 50 ohm
Front-to-back-ratio : >25 dB
Max. power : 500 W
Gain : 221 dBi
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INSTALLATION EXAMPLES
Flat panel antennas
sectorised sites Three-sector cell with RX
diversity
Horizontal / vertical separation
Horizontal Separation
needs approx. 5-15 lambda (2..4 m) separation for sufficient decoupling
and to avoid superimposing of antenna patterns
Horizontal decoupling distance depends on antenna gain and horizontal
radiation pattern
Vertical Separation needs approx. 1 lambda separation for sufficient decoupling
good for RX / TX decoupling
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ANTENNA CABLES
Cable types
Coaxial cables : 1/2, 7/8, 1 5/8
Losses approx. 10..4 dB/ 100m
power dissipiation is exponential with
cable length !!
Connector losses approx. 1 dB per connection(jumper cables etc..)
Thick antenna cables
lower losses per length
large bending radii
much more expensive
Keep antenna cables short
Jumper(2 m)
Jumper
(2 m)
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ANTENNA CABLES
Typical values for antenna cables
Typediameter
(mm)
900 MHz
dB/100m
1800 MHz
dB/100m
1/2
7/8
5/8
1 5/8
12.5
25
17
47
7
4
5
2
10
6
8
3
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NETWORK PLANNING
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OBJECTIVES OF NETWORKOBJECTIVES OF NETWORK
PLANNINGPLANNING
MAXIMIZE CAPACITY(Erl/KmMAXIMIZE CAPACITY(Erl/Km22) WITH) WITH
LIMITED FREQUENCY BANDLIMITED FREQUENCY BAND
MINIMIZEMINIMIZE
NETWORKNETWORKELEMENTS,ELEMENTS,
REDUCEREDUCE
COSTCOST
BETTER QoS,BETTER QoS,MINIMUMMINIMUM
INTERFERENCEINTERFERENCE
& CALL DROPS& CALL DROPS
MAXIMUM RADIO COVERAGEMAXIMUM RADIO COVERAGE
OBJECTIVES OF NETWORK PLANNINGOBJECTIVES OF NETWORK PLANNING
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CELLULAR PLANNING PRINCIPLE
5 steps of Network Planning
1. NW Dimensioning
2. Coverage /Capacity
Planning
3. Transmission Planning
4. Frequency Planning
5. ParameterPlanning
Initial NW
dimensioning
marketing
Coverage /
capacityplan
Freq & inte-
rferenceplan
Transmissionplan Trafficassumptions
Business
plan
Parameterplanning
Final NW
topology
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FACTORS GOVERNING NETWORK PLANNINGFACTORS GOVERNING NETWORK PLANNING
TOPOLOGY OF THE AREATOPOLOGY OF THE AREA
MORPHOLOGY OF THE AREAMORPHOLOGY OF THE AREA
DEMOGRAPHY OF THE AREADEMOGRAPHY OF THE AREA
While Morphology and Topology of an area play an
important role in coverage planning, Demographyplays an important role in capacity planning
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SITE SELECTION / LOCATION
Proper site location determines usefulnessof its cell
Sites are expensive
Sites are long-term investments
Site acquisition is a slow process
Hundreds of sites needed per network
Basestationsiteisa valuable long-termassetforthe operatorand accountsfor
majority ofthenetworkcost
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BAD SITE LOCATION
Avoid hill-top locations forBS Sites
Uncontrolled interferences
Interleaved coverage
Awkward HO behaviours
But : good location for
microwave links!
Wanted cellboundary
Uncontrolled, stronginterferences
Interleaved coverage areas:
Weak own signal, strong foreign signal
Prefer sites off hill-tops
Use hills to separate cells
Contiguous coverage area Needs only low antenna heights if
sites are slightly elevated above
valley bottom
Wanted cellboundary
GOOD SITE LOCATION
SITE LOCATION CRITERIA
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COVERAGE PLANNING
Initial NW dimensioning
TRX, cells, sitesbandwidth neededNW topology
Preliminary exercise
Site locationsCell parametersLink Budgeting
Preliminary Coverage
grid using search circles
Coverage simulation
using planning tool
Signal strengthArea of coverage
Sitepre-validation
Siteaccepted ?
Siteinspection
real cellplan
Cell size determination
usingTx-Rx.equipment
N
NPlanningcriteria fulfilled?
Fieldmeasurements
N
Go tofrequencyplanning
Createcell dataforBSC
External inputs
(traffic, subs. Forecast, Covg./ capacity requirements..)
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CELL SIZES
Achievable cell sizes depend on
Frequency band used(450, 900,1800 MHz)
Surroundings, environment
Link budget figures
Antenna types
Antenna positioning
Minimum required signal levels
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LINK BUDGET PLANNINGLINK BUDGET PLANNING
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LINK BUDGET LOSS FACTORS
At base station
connectors
cables
isolator
combiner
filter
At mobile station
body loss
polarisation of antenna
~ 3..5 dB losses
50..70% of signal energy is
lost before even reachingthe transmit antenna
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LINK BUDGET GAIN FACTORS
Antenna gain
Half-power beam width
Mechanical size
Antenna types
Diversity gain
Diversity can be implemented in many ways
Frequency hopping
Improves average link quality, but is not typically
taken into account in link budget calculations
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POWER BUDGET : DOWNLINK
Combiner
loss = 3 dB
Tx Power
43dBm(20W)
Feeder
loss = 4 dB
40 dBm
36 dBm AntennaGain = 16 dBi
52 dBm
Path loss = 154 dB
-102 dBm
Rx sensitivity
-102 dBm
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POWER BUDGET : UPLINK
Rx Sensitivity
-105 dB
Feeder
loss = 4 dB
-105 dBm
-101 dBm
DiversityGain = 4 dB
-121 dBm
Path loss = 154 dB
33 dBm
Tx Power
33 dBm (2W)
Antenna
Gain = 16dBi
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POWER CONTROL, PC
GSM : 15 power steps (2 dB each) BSC in command
Level or quality-driven or both
Use power control in both uplink & downlink
Doesnt affect the Link Balance
Minimise interference in network
Save battery life-time
PC not allowed
on BCCH carrier
Signallevel Target level
e.g. 85 dBm
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CAPACITY PLANNINGCAPACITY PLANNING
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WHAT IS ERLANG ?
Erlang is the name of a Danish researcher.
Erlang is the unit of traffic
1 Erlang is the max.traffic on one line.
The traffic is calculated using a simple formula:Erlangs =(calls per hour) x (average conversation time)
3600sec
There are two tables
Erlang B - for system that support no queuing Erlang C - for system that support queuing
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Cell capacity depends on No. ofTraffic Channels
No. ofTraffic Channelsisbased on:
Traffic in Cell = No. of Subscribers xTraffic per subscriber
Using thisTraffic figure,targeted GOSand Erlang BTable,
No. ofTraffic Channelsina Cell canbe calculated
TCH 7 15 22 30 37 45 53
Traffic 2.94 9.01 15 22 28 35.5 43
CELL CAPACITY
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TRAFFIC PATTERNS
Traffic is not evenly spread across the day (or week)
Dimensioning must be able to cope with peak loads
busy hour is typically twice the average hour load
8
A A A A
8
A A P
P
P
P
8
P
P
PEAK TIMEOFF-PEAK TIME
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TIMECOVERAGE BUILDING
ADDING TRX, CELL SPLITING
SOFT CAPACITY ( FH + UO )
CAPACITY
FLEXIBLE NETWORK EVOLUTION TO MEETFLEXIBLE NETWORK EVOLUTION TO MEET
THE CAPACITY DEMANDTHE CAPACITY DEMAND
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BASE BAND HOPPING (BB HOPPING)BASE BAND HOPPING (BB HOPPING)
0 4321 5 6 7RTSL
f1
f2
f3
f4
TRX-1
TRX-4
TRX-3
TRX-2
B
B = BCCH timeslot. It does not hop
Time slots 17 of all TRXshop over (f1,f2,f3,f4).
Time slot 0 of TRX-2,3,4 hop over f2,f3,f4.
BB hopping on 4 TRXs. The BCCHTRXis hopping except on RTSL-0.
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RF HOPPING (SYNTHESIZED HOPPING)RF HOPPING (SYNTHESIZED HOPPING)
B = BCCH timeslot. TRX1 does not hop
Non-BCCH TRXs are hopping overthe MA-list (f1,f2,f3,.fn) attached to the cell.
RFhopping in 3-TRXcell
TRX-2
TRX-1
TRX-3
B
f1,
f2,
f3,fn
f1,
f2,
f3,fn
....
f0 f0 f0 f0 f0 f0 f0
f0
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SUPER
SUPER
SUPER
REGULAR
BCCH
REGULARBCCH
REGULAR
BCCH
Co-channel and Adjacent channel interference is monitored continuously
Handover based on C/I Measurements
CONCEPT OF UNDERLAYCONCEPT OF UNDERLAY--OVERLAYOVERLAY
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BENCHMARKING THE QUALITY OF SERVICEBENCHMARKING THE QUALITY OF SERVICE
CALL SETCALL SET--UP RATEUP RATE
CALL DROP RATECALL DROP RATE
HANDOVER SUCCESS RATEHANDOVER SUCCESS RATE
INTERFERENCEINTERFERENCE
MARGINMARGIN
BLOCKED CALLBLOCKED CALL
QUALITY OF CALLQUALITY OF CALL
UPLINK INTERFERENCEUPLINK INTERFERENCE
95 TO 100 % CALL 95 TO 100 % CALL
< 6 SECWITHOUT< 6 SECWITHOUT
CONGESTIONCONGESTION
< 2 %
> 95 %> 95 %
COCO--CHANNEL 9 dBCHANNEL 9 dB
& ADJACENT& ADJACENT
CHANNELCHANNEL --9dB9dB
2% GRADE OF2% GRADE OF
SERVICESERVICE
97% OF CALLWITH IN QUALITY BAND97% OF CALLWITH IN QUALITY BAND--55
< 3% IN BAND< 3% IN BAND-- 0 (0 ( --110 TO110 TO --105 dBm).105 dBm).
QoSQoS
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INTERFERENCE
REDUC
TION
PROCESS OF NETWORK OPTIMISATIONPROCESS OF NETWORK OPTIMISATION
POWERCONTROLANTENNA TILTS
DISCONTINUOUS TX
FREQUENCY HOPPING
FREQUENCY
REALLOCATION
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A Pole Mounted BTS Site
GSM antennas
monuted on poles
Microwaveantennas
Cable tray /
ladder
Shelter(equipment)
room
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A Tower mounted BTS Site
Shelter with Security Guard