LOGARITHMIC SCALE Decibel (dB) is a convenient unit for expressing the ratio of two quantities. x = 10 log 10 ( P / P o ) where: x is in dB dB has no dimension 20 dB means 100:1 0 dB [ 1 / 1 ] 10 dB [ 10 / 1 ] 20 dB [ 100 / 1 ] - 3 dB [ 0.5 / 1 ] 3 dB [ 2 / 1 ] Review of Related Topics
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LOGARITHMIC SCALE
Decibel (dB) is a convenientunit for expressing the ratioof two quantities.
x = 10 log10 ( P / Po )
where:x is in dBdB has no dimension20 dB means 100:1
0 dB [ 1 / 1 ]
10 dB [ 10 / 1 ]
20 dB [ 100 / 1 ]
- 3 dB [ 0.5 / 1 ]
3 dB [ 2 / 1 ]
Review of Related Topics
dBm
dBm =Decibel unit in reference toa power unit which is 1mW. x = 10 log10 ( P / 1mW )
where:x is in dBm
0 dBm [ 1mW / 1mW ]
10 dBm [ 10mW / 1mW ]
20 dBm [ 0.1W / 1mW ]
- 3 dBm [ 0.5mW / 1mW ]
3 dBm [ 2mW / 1mW ]
30 dBm [ 1W / 1mW ]
- 50 dBm [ W / 1mW ]
- 75 dBm [ 0.032nW / 1mW ]
- 110 dBm [ 0.01pW / 1mW ]
Review of Related Topics
dBi vs dBd
dBi is a unit to measure antenna gainin reference to an isotropic antenna.An isotropic antenna has a power gain of unity; i.e., O dBi.
dBd is a unit to measure antenna gain inreference to a lossless half-wave dipole antenna. A lossless half-wave dipole antenna has a power gain of 0 dBd.
CONVERSION FACTOR:
dBi = dBd + 2.15 dB
id
Review of Related Topics
EFFECTIVE RADIATED POWERERP vs EiRP
ERP (Effective Radiated Power): is the radiated power (transmit power times antenna gain) with respect to a dipole antenna within a given geographic area.EiRP (Effective Isotropic Radiated Power): is the radiated power from an isotropic antenna.
EiRP = ERP + 2.15 (dB)
EiRPLp
SSdesign
Review of Related Topics
OBJECTIVES OF
LINK BUDGET ANALYSIS
to estimate the maximum allowable path loss to compute the required BS transmitter power
for a balanced path to estimate the coverage design threshold to evaluate technology performance
Tx Combiner Feeder
Feeder
RxTx
RxReceiverDivider
Feeder
FeederGdBTS
LcBTS LfBTS
GaBTS Lp
Lp
GaMS
LfMS
PinBTS
PoutBTS
LfBTS
GaBTS
PoutMS PinMS
RF PATH
WHY BALANCED PATH?
BS does nothear the MS
MS hears the BS
Strong SignalWeak Signal
UPLINK LIMITED:
DOWNLINK LIMITED:
BS hears the MSMS does nothear the BS
Weak SignalStrong Signal
HOW TO BALANCE PATH?
Coverage in a two-way radio communication system is decidedby the weakest transmission direction.
AssumeUplink Limited
Balance Path Compute BSTx Power Output
Path Loss in Uplink = Path Loss in Downlink
Balanced Path:
LINK BUDGET ANALYSIS
LBA ProcessorEngineer
INPUT OUTPUT
Rx SensitivityMS Max. Power
CoverageThresholdReliability
Equipment /Technology
Maximum Path Loss
CoverageThreshold
BS TX PowerOutput - Balanced
Path
Gain Loss
AntennaPA
Diversity
CombinerFeeder
Connectoretc
Cell Radiusand Count
INPUT TO LBA
LBA ProcessorEngineer
Rx SensitivityMS Max. Power
CoverageThresholdReliability
Equipment /Technology
Gain Loss
AntennaPA
Diversity
CombinerFeeder
Connectoretc
Rx SensitivityMS Max. Power
MS RX SENSITIVITY and BTS RX SENSITIVITY
Sensitivity
GSM900 MS RX SENSITIVITY
MS TYPE Sensitivity ValueEricsson MS - 104 dBmGSM900 Recommendation - 102 dBm
where SSreq = Required signal strengthLNFmarg(o) = Outdoor log normal fading marginLNFmarg(o+i) = Outdoor + indoor log normal fading marginCPL = Car penetration lossBPLmean = Mean building penetration loss
CoverageThresholdReliability
MARGINSEnvironmentDependent
Outdoor Log Normal Fading Margin
Outdoor + Indoor Log NormalFading Margin
Car Penetration Loss
Mean Building Penetration Loss
>THRESHOLD
LOG NORMAL FADING MARGIN
% AREA COVERAGE
% BORDER COVERAGE
JAKE’SFORMULAS
CoverageThresholdReliability
LOG NORMAL FADING MARGINS
90% AREA COVERAGE
50% BORDERCOVERAGE
threshold+ 4.5 dB
LNF Marginat 7 dB
standarddeviation
75% BORDERCOVERAGE
In order to plan for morethan 50% probability of signalstrength above a threshold, alog normal fading margin isadded to the threshold duringthe design process. (Ericsson)
(Nokia)
CoverageThresholdReliability
LOG NORMAL FADING MARGINS
Log NormalFading Marginin a Multi-CellEnvironment
Jakes’ formula does nottake the effect of manyservers into account.The presence of many serversat the cell borders will reducethe required log normal fadingmargin. (Ericsson)
CoverageThresholdReliability
OUTDOOR LOG NORMAL FADING MARGINS
% AREA COVERAGE
LNF(o) (dB) 75 85 90 95 99
6 -3 -1 1 3 7
8 -3 0 2 5 10
10 -3 0 3 6 12
12 -3 1 4 8 15
14 -3 1 4 9 17
Outdoor Log Normal Fading Margins (LNFmarg(o) ) in dB for different environments (LNF(o) ).
Suburban/Rural
Urban
Dense Urban
CoverageThresholdReliability
OUTDOOR + INDOORLOG NORMAL FADING MARGINS
% AREA COVERAGE
LNF(o+i) (dB) 75 85 90 95 99
10 -3 1 3 7 13
12 -3 1 4 8 15
14 -3 1 4 9 17
Outdoor + Indoor Log Normal Fading Margins(LNFmarg(o+i) ) in dB for differentenvironments (LNF(o+i) ).
Suburban
Urban
Dense Urban
CoverageThresholdReliability
MARGINSEnvironmentDependent
Outdoor Log Normal Fading Margin
Outdoor + Indoor Log NormalFading Margin
Car Penetration Loss
Mean Building Penetration Loss
CAR PENETRATION LOSS
CPL = 6 dB*
*based on Ericsson GSM900 RF GuidelinesLCC value is 4 to 10 dB CPL (portable)
CoverageThresholdReliability
MARGINSEnvironmentDependent
Outdoor Log Normal Fading Margin
Outdoor + Indoor Log NormalFading Margin
Car Penetration Loss
Mean Building Penetration Loss
BUILDING PENETRATION LOSS
BPLmean (dB)*
Dense Urban 18Urban 18Suburban 12
* based on Ericsson GSM900 RF GuidelinesLCC value is 10 - 20 dB
Equipment /Technology
BASE STATION RF COMPONENTS
LNA
PA RX1 RX2
Duplexer
Power AmpifierReceiver withsensitivity
ReceiverMulticoupler
Combiner
Bottom Jumper Cables
Main CableFeeder
Connector
Lightning Arrestor
Top JumperCables
RX1 TX/RX2
Equipment /Technology
RF COMPONENTS
GAINS LOSSES
MS BS MS BS
Antenna Antenna Feeder Main Cable/FeederPower Amp Power Amp Duplexer
Diversity CombinerLNA Jumper Cable
ConnectorLightning Arrestor
Gains
Losses
Equipment /Technology
BASE STATION ANTENNAS
Gains
OmniAntenna7- 11 dBi
DirectionalAntenna11- 17 dBi
Antenna gain plays avery important role inthe maximum allowablepath loss.
Equipment /Technology
MOBILE AND PORTABLE ANTENNAS
Gains
Portable antennastypically haveno gain
0 dBi
Mobile antenna gain1 - 4 dBi
Equipment /Technology
AMPLIFIERSTX Power Amplifier & Low Noise Amplifier
Gains
LNA
RX1 TX/RX2
TX PowerAmplifier
Low Noise Amplifiertypical gain up to 20 dB
TX Power Amplifier
System PA Output RangeGSM 2.5 - 32 WattsTACS 0.5 - 100 Watts
Equipment /Technology
DIVERSITY
Gains
LNA
RX1 TX/RX2
RX RX
Equipment /Technology
DIVERSITY SCHEMES
Gains
LNA
RX1 TX/RX2
•SPACE DIVERSITYd = 10 minimum according to LCCd = 12to 18 according to Ericsson
Smart uses 4 meters RX separation for GSM900/ETACS
•POLARIZATION DIVERSITY
For Ericsson, both schemes will give a gain of 3 to 6 dB.
For Nokia, the practical range is 0 to 5 dBdepending on environment and antennainstallation (separation). When BTS RX diversity is used,the default value is 4 dB for urban areas.
d
Equipment /Technology
DIVERSITY COMBINERS
Gains
RX RX
RXSelectiveCombining
SwitchedCombining
usually used in Mobiles
RX RX
+Maximal-RatioCombining
RX RX
+
Equal-GainCombining
commonlyused in BS’s
(S/N)ii=1
M
(Envelope)ii=1
M
Equipment /Technology
DIVERSITY GAIN TABLE
Gains
LNA
RX1 TX/RX2
Manufacturer Diversity Combining Diversity(Technology) Scheme Method Gain
Nokia MaximumGSM/DCS1800 Space Ratio 3.0 dB
Ericsson MaximumGSM/DCS1800 Space Ratio 3.0 dB
Equipment /Technology
another DIVERSITY SCHEMEFREQUENCY HOPPING for
Frequency Diversity
Gains
0.5 to 2.5 dB FH Gain
Equipment /Technology
CABLE LOSSES (BS)
Losses
LNA
RX1 TX/RX2Jumper CablesLDF4-501/2 inch Heliax Foam2.160 dB loss per 100 ft at 900 MHz
Main Cable / Feeder CableLDF5-507/8 inch Heliax Foam1.210 dB loss per 100 ft at 900 MHzrecommended use < 55 meters
Equipment /Technology
CONNECTOR LOSS (BS)
Losses
LNA
RX1 TX/RX2
Connectors connect RFcomponents and typicallyhave a loss of 0.1 dB each.
Equipment /Technology
LIGHTNING ARRESTOR LOSS (BS)
Losses
LNA
RX1 TX/RX2
LightningArrestor
Loss = 0.1 dB
Equipment /Technology
COMBINER LOSS (BS)
Losses
PA RX1 RX2
Duplexer
Characteristic Cavity Hybrid
Frequency Range 806-960 806-1000(MHz)
Continuous Input 150 150Power (Watts)
Insertion Loss (dB) 2 to 4.8 3.8 to 7.4
Maximum VSWR 1.5 : 1 1.5 : 1
Combiners
Equipment /Technology
DUPLEXER LOSS (BS & MS)
Losses
PA RX1 RX2
Duplexer
Duplexer Characteristic Value
Isolation (across all 3 ports, with >60 dBunused ports terminated at 50
whereLp = Path Loss in dBa(hm) = (1.1logf - 0.7)hm - (1.56logf - 0.8)f = carrier frequency in MHz (150-1000 MHz)hb = the base station antenna height in meter (30-200m)R = distance in km from the base station (1-20 km)hm = mobile antenna height in meter above ground (1-10m)
Cell Radiusand Count
Cell Radiusand Count
CELL RADIUS ESTIMATEBASED ON OKUMURA-HATA MODEL
d
R
MAPL - 69.55 - 26.16logf + 13.82loghb + a(hm)
44.9 - 6.55loghb
log R =
* urban area
Cell Radiusand Count
CELL COUNT ESTIMATION
CellCount
Estimate
TechnologyLBA
MAPLMobile TypeEnvironment
Area BoundariesType of Coverage
DemographicsTraffic Assumptions
ReUse Pattern
Required Input
d
R
Cell Radiusand Count
CRUDE CELL COUNT ESTIMATION
R
A
2.6 R2
Cell Count =
Cell Radius, R, from Okumura-Hata’s FormulaA = Market Area
LBA ProcessorEngineer
CONCLUSION1. What is receiver sensitivity?2. What is Fade Margin/Log-Normal Margin?3. Why do we care about coverage reliability?4. What is diversity?5. How many different kinds of diversity exist?6. Why balanced path?7. How does the environment affect LBA?