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ECE 5221 Personal Communication Systems
Prepared by:
Dr. Ivica Kostanic
Lecture 5: Example of a macroscopic
propagation model (Lee model)
Spring 2011
Florida Institute of technologies
Outline
Lee model equation
Propagation prediction over terrain database
Nominal cell radius calculation
Examples
Important note: Slides present summary of the results. Detailed
derivations are given in notes.
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Macroscopic propagation modeling
 More input descriptors – more accurate
models
Log distance path loss model
 d 

PL  PL 0  m log 
d 0 

    
X

log normal shadowing
Distance dependent mean
 As the models become more accurate,
the standard deviation of the unexplained
portion of path loss becomes smaller
 The unexplained portion still retains log
normal character
More general models
PL  F  d , hTX , h Rx , f , clutter, obstructio ns,   
             
X

Unexplaine d portion of path loss
Distance dependent mean
 Some popular macroscopic propagation models
o Lee model
o Hata-Okumura
o COST 231
o Longley-Rice
o Walfish-Ikagami, etc.
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Lee model
 Prediction conducted in two steps
 Developed by W.C.Y Lee in 1970s
 Statistical, empirical model
 Popular due to is simplicity and relatively good
accuracy
 Valid for frequencies 800-2000MHz
 Straight forward extension of log distance path
loss model
 Expected model accuracy: 6-9dB standard
deviation of the prediction error
 Model introduces reference conditions
Parameter
Reference value
Transmit power
10W (40dBm)
BS antenna height
100 ft (30m)
BS antenna gain
6dB
MS antenna height
10 ft (3m)
MS antenna gain
0dB
Reference distance
1 mile (or 1km)
o Step 1. Predict the propagation path losses for
standard conditions
o Step 2. Correct the prediction for all
differences between actual and standard
conditions
 Parameters of the environment are specified
for standard conditions
 Two parameters of the environment are given
o Slope of the path loss in dB/dec (m)
o Reference distance intercept in dBm (or
reference distance path loss in dB)
Illustration of Lee model reference
conditions
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Lee model – RSL form
Form 1: RSL form
Parameter explanations:
 d 

PR  RSL 0  m log 

 d0 
RLS0 – reference distance intercept (dBm)
m – slope (dB/dec)
h 
 h 
 PT  40   C log  te   F log  r  
 h rr 
 h tr 
G T
 6 Gm
PT – transmit power (dBm)
hte – effective antenna height of the transmitter
hr – height of the receiver
GT – transmit antenna gain
Correction coefficients have default values
Gm – mobile antenna gain
d – distance between transmitter and receiver
C = 15dB
F = 10dB
Frequency correction:
• slope stays the same
• intercept adjusted as
RSL 0  f 2   RSL 0  f 1   20 log  f 1 / f 2 
Environment
@ f=850MHz
Intercept (dBm)
Slope (dB/dec)
Open area
-54.5
43.5
Suburban
-63.0
38.4
Urban
-67.0
40.0
Dense urban
-77.0
43.1
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Lee model – path loss form
Form 2: PL form
Parameter explanations:
 d 

PL  PL 0  m log 

 d0 
PL0 – reference distance path loss (dB)
m – slope (dB/dec)
h 
 h 
 C log  te   F log  r  
 h rr 
 h tr 
G T
 6 Gm
hte – effective antenna height of the transmitter
hr – height of the receiver
GT – transmit antenna gain
Gm – mobile antenna gain
Correction coefficients have default values
d – distance between transmitter and receiver
C = 15dB
F = 10dB
Frequency correction:
• slope stays the same
• PL0 adjusted as
PL 0  f 2   PL 0  f 1   20 log  f 2 / f 1 
Environment
@ f=850MHz
Intercept (dBm)
Slope (dB/dec)
Open area
100.5
43.5
Suburban
109
38.4
Urban
113
40.0
Dense urban
124
43.1
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Effective antenna height – slope method
 Lee model uses slope method for effective
antenna height calculation
 Slope of the local terrain of the receiver –
extended
 Effective antenna height – determined by
intersection of the slope and the vertical
through TX antenna
 Two cases
o Up-sloping terrain – effective height
greater than actual height
o Down sloping terrain – effective
height smaller then effective height
 Effective antenna height is a local
parameter, i.e. it is different for every point
within coverage region
Note: calculation of effective height requires knowledge of terrain
elevations with the coverage area
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Diffraction losses
 Diffraction losses – additional losses due to
terrain blockage
 Terrain obstacle – replaced by knife edge
 Two steps for additional loss calculation
o Step 1. Calculate Fresnel-Kirchoff
parameter
vh
2d1  d 2 
d1 d 2
o Step 2. Estimate losses using
diffraction formulas
Illustration of KED calculations
1 v
L0
0  v 1
L   20 log 0 . 5  0 . 62 v 
1  v  0
L   20 log 0 . 5 exp 0 . 95 v 
 2 .4  v  1
v   2 .4
L   20 log  0 . 4 

2
0 . 1184  0 . 1v  0 . 38  

 0 . 225 
L   20 log  

v 

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Propagation over terrain
Terrain data
 Terrain database – fundamental input
into propagation modeling
 Accuracy of terrain database – bin size
 Typical bin size 30-100m
 Using terrain -> radio profile is generated
 Through radio profile 3D propagation
problem becomes 2D problem
 Radio profile is used by propagation
model to estimate path loss
 Path loss is calculated between the
transmitter and every bin within
surrounding region
Example of radio profile
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Example 1
Consider a transmitter located in suburban environment. The effective height of the
transmitter is 45m, its power is 20W and the gain of the transmit antenna is 8dB.
Calculate the path loss and RSL at the mobile located at distance of 5miles. The gain
of the mobile antenna is 0dB and its height is 1.5m. The frequency of operation is
850MHz. Use Lee model.
Answers:
RSL = -85.2dBm
PL = 136.2dB
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Example 2
Consider a system deployed in urban environment. Assume that the operating frequency is 1900Mhz
and that the minimum RSL at the receiver is -95dBm. The base station has ERP of 50dBm and
effective height of 40m. The mobile height is 1.5m and its antenna gain is 0dB. The error of
propagation modeling is characterized by standard deviation of 8dB.
a)
Determine the contour for 90% are reliability.
b)
Using Lee model estimate distance to contour calculated in part a)
c)
Repeat a) and b) for reliability of 95%
d)
Estimate increase of the cell site count that corresponds to the increase of reliability requirement.
Answers:
a) RSLp=-89.96dBm
b) d = 3 miles
c) RSLp = -86.6dBm, d = 2.43 mile
d) 95% reliability requires 50% more cells
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