During the period 1983-1988, a series of Land Mobile Satellite Service (LMSS) propagation experiments were performed. These experiments were implemented with transmitters on stratospheric balloons, remotely piloted aircraft, helicopters, and geostationary satellites. The earlier experiments were performed at UHF (870 mega-Hz) and the latter at both L band (1.5 giga-Hz) and UHF. The general objective of the above tests was to assess the impairment to propagation caused by trees and terrain for predominantly suburban and rural regions where cellular communication services are impractical. This paper presents an overview of the results derived from the above experiments

Goldhirsh, Julius

Vogel, Wolfhard J.

English

NASA Technical Reports Server

N92-24107
An Overview of Results Derived from
Mobile-Satellite Propagation Experiments
Julius Goldhirsh
The Johns Hopkins University, APL
Johns Hopkins Road, Laurel MD 20723-6099
Phone: 301-953-5042 FAX:301-953-1093
ABSTRACT
During the period 1983-1988, a series of Land
Mobile Satellite Service (LMSS) propagation
experiments were performed in Southern United
States (New Mexico to Alabama), Maryland,
Colorado, and South-Eastern Australia. These
experiments were implemented with transmit-
ters on stratospheric balloons, remotely piloted
aircraft, helicopters, and geostationary satel-
lites (INMARSAT B2, Japanese ETS-V, and
INMARSAT Pacific). The earlier experiments
were performed at UHF (870 MHz) and the
latter at both L Band (1.5 GHZ) and UHF.
The general objective of the above tests was to
assess the impairment to propagation caused
by trees and terrain for predominantly subur-
ban and rural regions where cellular communi-
cation services are impractical. In this paper
are presented an overview of the results de-
rived from the above experiments.
SINGLE TREE ATTENUATION-STATIC
CASE
Attenuation and attenuation coefficient
In Table 1 is given a summary of the sin-
gle tree attenuation results at 870 MHz (cir-
cularly polarized transmissions) based on the
measurements by Vogel and Goldhirsh [1] and
Goldhirsh and Vogel [2] who employed trans-
mitter platforms on remotely piloted aircraft
and helicopters and a receiving system on a
stationary vehicle.
Wolfhard J. Vogel
University of Texas, EERL
10100 Burnet Road, Austin TX, 78758-4497
L-Band versus UHF attenuation scaling
factor - static case
Ulaby et. al. [3] measured the attenua-
tion properties at 50 ° elevation associated with
propagation at 1.6 GHz through a canopy of
red pine foliage in Michigan at both horizon-
tal and vertical polarizations. Their measure-
ments gives rise to an average attenuation co-
efficient of approximately 1.8 dB/m. Com-
bining this result at L-band with the average
value of 1.3 dB/m at UHF given in Table 1
suggests the following
IfLF(fL) F(funv) fU-HnV (1)
where F(fL) is expressed in dB or dB/m. Si-
multaneous attenuation measurements by the
authors at 1.5 GHz and 870 MHz for the mo-
bile vehicle case showed consistency with the
expression (1).
Tree attenuation versus season and path
elevation angle
Figure 1 shows linear least square results of
attenuation versus path elevation angle derived
from measurements on the Callery Pear tree
in October 1985 (full foliage) and March 1986
(bare branches)[2,4]. The best linear fit results
in Figure 1 may be expressed as follows for 0
between 15 ° to 40 °
International Mobile Satellite Conference, Ottawa, t990
219
https://ntrs.nasa.gov/search.jsp?R=19920014864 2020-03-17T12:30:00+00:00Z
Full Foliage:
F,(O) = -0.480 + 26.2
Bare Tree:
(2)
(3)F2(0) = -0.350 + 19.2
where O is the elevation angle in degrees. The
percentage rms deviations of the data points
relative to the best fit expressions (2) and (3)
were 15.3% and 11.1% (1.7 and 1.2 dB), re-
spectively. We derive from (2) and (3) the
average condition for f = 870 MHz, and path
elevation between 15 ° and 35 °
F(full foliage) _ 1.35F(bare tree) (4)
which states that for the static case, the maxi-
mum attenuation contribution from trees with
leaves (at 870 MHz) is nominally 35% greater
than the attenuation of trees without leaves.
The rms deviation about the average for the
coefficient in the expression (4) is approximately
.o1%.
ATTENUATION DUE TO ROADSIDE
TREES - DYNAMIC CASE
Empirical fade distribution model
Cumulative fade distributions were system-
atically derived from helicopter-mobile [2,,1] and
satellite -mobile measurements [5] in the Cen-
tral Maryland region. This formulation re-
ferred to here as the MSS "Empirical Fade Dis-
tribution Equation" (EFDE) for P = 1 to 20%
is given by
F3(P,O) = -M(O)InP + B(O) (5)
where F3 is the fade in dB, P is the percent-
age of distance (or time) the fade is exceeded,
and 0 is tile path elevation angle to the satel-
lite. Least square fits of second and first order
polynomials in elevation angle 0 (deg) gener-
ated for M and B, respectively, result in
M(O) = a + bO + cO2 (6)
B(O)= dO+ e (7)
where
a = 3.44 b = .0975c=-0.002 d=-0.443 e=34.76 (8)
In Figure 2 are given a family of cumula-
tive distributions (percentage versus fade ex-
ceeded) for the indicated path elevation an-
gles.
L-Band versus UHF attenuation scaling
factor-dynamic case
Simultaneous mobile fade measurements by
the authors [2,41 at L-Band (1.5 GHz) and
UHF (870 MHz) have demonstrated that the
ratio of fades are approximately consistent with
the square root of the ratio of frequencies for-
mulation given by (1). The results demon-
strated that for fL = 1.5 GHz and fUHF =
870 MHz
F(fL) _ 1.31F(funv) (9)
The multiplying coefficient 1.31 was shown to
have an rms deviation of +/- 0.1 over a fade
exceedance range from 1% to 30%.
Seasonal effects-dynamic case
Seasonal measurements were performed by
the authors for the dynamic case in which the
vehicle was traveling along a tree-lined high-
way in Central Maryland (Route 295) along
which the propagation path was shadowed over
approximately 75% of the road distance [2,4].
Cumulative fade distributions were derived for
March 1986 during which the deciduous trees
were totally without foliage. These were com-
pared with similar distributions acquired in
October 1985 and June 1987, during which the
trees were approximately in 80% and full blos-
som stages, respectively. For the "dynamic
case" at a frequency f = 870 MHz and P =
1% to 30%
220
International Mobile Satellite Conference, Ottawa, 1990
F(full foliage) = 1.24F(no foliage) (10)
Fade reduction due to lane diversity
We examine the extent by which the fade
reduces (or increases) by switching lanes for
MSS configurations. For the case in which the
satellite path and the tree line is to the right of
the vehicle direction, the path length through
the canopies of roadside trees is greater when
the vehicle is in the right lane. A fade reduc-
tion should therefore be experienced by switch-
ing lanes from the right to the left side of
the road. The authors measured this effect
at UHF (870 MHz) and L Band (1.5 GHz)in
Central MD [2,4,5]. A quantity defined as the
"fade reduction, FR" is used to characterize
the increase in signal power gained by switch-
ing lanes. This quantity is obtained by differ-
encing equi-probability fade values from distri-
butions pertaining to right and left side driv-
ing. The fade reduction at L-Band is plotted
in Figure 3 for the indicated elevation angles
as a function of the maximum fade as derived
(for the example given) from right versus left
lane driving.
At each of the elevation angles, the indi-
vidual data points have been replaced by the
"best fit third order polynomial" which may
be expressed by
FR = Ao + AIF + A2F 2 + A3 F3 (11)
where FR (in dB) represents the fade reduc-
tion obtained in switching lanes from the greater
shadowing configuration to the lesser one. Also,
Ao, A1, A2, and A3 are tabulated in Table 2 for
L-band. The parameter F (in dB) represents
the maximum fade level value. The "best fit
polynomials" were observed to agree with FR
as derived from the measured distributions to
within 0.1 dB rms.
PROPAGATION IMPAIRMENT-LINE
OF SIGHT COMMUNICATIONS
Multipath for a mountain environment
The results described here were obtained from
MSS line of sight measurements in canyon passes
in North-Central Colorado [6]. The transmit-
ter was on a helicopter which, for each run,
flew behind a receiving mobile van and main-
tained a relatively fixed distance and path de-
pression angle relative to the receiving antenna.
The radiating antennas on the helicopter trans-
mitted simultaneous L-Band (1.5 GHz) and
UHF (870 MHz) cw signals.
Figure 4 shows four cumulative fade distri-
butions depicting "least square power curve
fits" for the above described multipath sce-
nario at a frequency of 870 MHz and 1.5 GHz
and path elevation angle 30 ° or 45 ° . The re-
sultant curves define the combined distribu-
tion corresponding to a driving distance of 87
km through canyon passes. Each of the best
fit power curves agree with the measured cu-
mulative distribution data points to within 0.1
dB rms. The distributions may be expressed
for P = 1% to 10% by
P = aF -s (12)
where a and b are tabulated in Table 3 at the
two frequencies and elevation angles.
Multipath Due to Roadside Trees
Similar type "line of sight measurements" as
described above for mountainous terrain were
also performed by the authors in Maryland
along tree lined roads [4]. The resultant dis-
tribution was found to follow the exponential
form for P = 1% to 50%
P=uexp(-vF) (13)
where u and v are tabulated in Table 4 and
the corresponding distributions are plotted in
international Mobile Satellite Conference, Ottawa, 1990
221
Figure 5. Since negligible differences in the
individual cumulative distributions existed for
O = 30 °, 45 °, and 60 °, they were combined in
the determination of (13).
OTHER PROPAGATION IMPAIRMENT
EFFECTS
The authors have characterized a number of
other propagation impairment effects for which
limited space here does not allow their char-
acterization [4,7,8]. These include distribu-
tions associated with "fade duration", "non-
fade duration", "antenna space diversity", "cross
polarization effects", and "high versus low an-
tenna gain effects".
REFERENCES
1. Vogel, W. J., and J. Goldhirsh. 1986.
Tree attenuation at 869 MHz derived from
remotely piloted aircraft measurements.
IEEE Trans. Antennas Propagat. AP-
34: 1460-1464.
2. Goldhirsh, J. and W. J. Vogel. 1987.
Roadside tree attenuation measurements
at UHF for land-mobile satellite systems.
IEEE Trans. Antennas Propagat. AP-
35: 589-596.
3. Ulaby, F. T., M. W. Whitt, and M.
C. Dobson. 1990. Measuring the prop-
agation properties of a forest canopy us-
ing a polarimetric scatterometer. IEEE
Trans. Antennas Propagat. AP-38: 251-
258.
4. Goldhirsh, J. and W. J. Vogel. 1989.
Mobile satellite system fade statistics for
shadowing and multipath from roadside
trees at UHF and L-band. IEEE Trans.
Antennas Propagat. AP-37: 489-498.
5. Vogel, W. J., and J. Goldhirsh. 1990.
Mobile satellite system propagation mea-
surments at L-band using MARECS-B2.
IEEE Trans. Antennas Propagat. AP-
38: 259-264.
6. Vogel, W. J., and J. Goldhirsh . 1988.
Fade measurements at L-band and UHF
in mountainous terrain for land mobile
satellite systems. IEEE Trans. Anten-
nas Propagat. vol. AP-36: 104-113.
7. Vogel, W. J., J. Goldhirsh, and Y.
Hase. 1989. Land-mobile-satellite prop-
agation measurements in Australia using
ETS- V and INMARSAT-Pacific. APL/JHU
Tech. Rep. S1R89U-037 (Laurel, MD; The
Johns Hopkins University, Applied Physics
Laboratory).
8. Hase, Y. W. J. Vogel, and J. Gold-
hirsh. 1990. Mobile-satellite measure-
ments of L-band fade durations derived
in Australia with ETS-V. APL/JHU Tech.
Rep. S1Rg0U-012. (Laurel, MD; The
Johns Hopkins University, Applied Physics
Laboratory).
20 ..............................
t_15-
Z
o
_10-
-
[.,,
5-
Full !Foliag_e t
'i _i 'I I p II I I
........ I"-- q'---
Bare uTree i "_ i i
b r I I I
_ _ 1 _ _ _ I I I,
,I t I
.... I ........ I- - - r - - "r - - -I- - -
I I I
I t I
t I I
t I I
I I
,,,I .... I ........ I ........ t .... t .... I ....
5
0 i
0 10 15 20 25 30 35 40 45
PATH ELEVATION ANGLE (deg)
Figure 1: Least square linear fits of attenu-
ation versus elevation angle for propagation
through the canopy of a Callery Pear Tree at
870 MHz.
222
International Mobile Satellite Conference, Ottawa, 1990
Table 1: Single Tree Attenuations at f = 870 MHz
Tree Type
Burr Oak*
Callery Pear
Holly*
Norway Maple
Pin Oak
Pin Oak*
Pine Grove
Sassafras
Scotch Pine
White Pine*
Attenuation (dB) Attenuation Coef. dB/m
Largest Average
13.9 11.1
18.4 10.6
19.9 12.1
10.8 10.0
8.4 6.3
18.4 13.1
17.2 15.4
16.1 9.8
7.7 6.6
12.1 10.6
14.3 10.6
Largest
1.0
1.7
2.3
3.5
0.85
1.85
1.3
3.2
0.9
1.5
Average
0.8
1.0
1.2
3.2
0.6
1.3
1.1
1.9
0.7
1.2
Overall Average 1.8 1.3
Table 2: Coefficients of fade reduction formulation (11) for lane diversity at
f = 1.5 GHz.
El. Angle 0 (deg)
30
45
60
AO
0.3931
-1.073
-0.1962
A1
0.2416
0.8816
0.2502
A2
-1.420 x 10 -2
-4.651 x 10 -2
5.244 x 10 -2
A3
-3.389 x 10 -4
7.942 x 10 -4
-2.047 x 10 -3
dB Range
3-26
3-17
3-16
Table 3: Coefficients a and b in best fit cumulative fade distribution formu-
lation (12) for multipath in mountainous terrain.
Frequency (Gtlz)
0.870
1.5
El = 30 ° El = 45 °
a b dB Range a b dB Range
34.52 1.855 2-7 31.64 2.464 2-4
33.19 1.710 2-8 39.95 2.321 2-5
Table 4: Coefficients u and v in formulation (13) describing best exponential
fit cumulative fade distributions for multipath for tree-lined roads.
Frequency (GHz) u
0.870 127.7
1.5 125.6
v Fade Range (dB)
0.8573 1-4.5
1.116 1-6
International Mobile Satellite Conference, Ottawa, 1990
223
1o T .... f .... - .... ? .... F .... f .... ,
............................. I I I [ I I60 deg
• I I I I I I 9-'_- .... L .... L .... L .... L .... L .... I
"_ I I I I I I I I I I I I
-1 I/
1 I I I I I _ I I / I I I• - _\A%-_kr _ -\- -_l[- -- _r - - r - --r ...... P .... i_ .... r ....
_= __!, ,',\\\\_\ \ X \ ;, " " " _ 85_.... "_.... "/_L__.....- --' I'_.... "_.... "l
I I I I I 7 .... L .... L .... L .... L .... I
' L/___L_' 'I I I I t I I I I I I10 -- - l.- ...... P- .... ;- .... I
I -- -- _- - -I- .... i- .... r I .... I _ _ .... L ....... L .... L .... II'/L' '''...........' '.... ....
r-< ..... P-- --_-- --P .... P .... l _t 5 L L L I
z 4+ .... L__ l__Y___L .... L-.... L.... +
l l ' I l _ J / /I I I I '
I I I I I i
30 deg
_ 3 .... L ........ L .... U --_+
..... _ p __ _ p...._....
= .... f - F- - f - -F .... f .... I
['_ I I I I I
i i + I I
I I t I I, , , , , , .... L.... L_
i j t ..... '
| I \ \I \ \ 1\40 \35 _ k k I d _ II II II II II II
/ , \ y \ \ i \ \ i\ 3o \2s _ i 1
II , , I , , I,\, \l \ \l\ \ _90DEG ')_l_l_m+ 7 0 .... ' .... I .... ' .... _ .... I .... II 0 5 10 15 20 25 30
0 5 I0 15 20 25 30 Maximum Fade (dB)
FADE DEPTH (dB)
Figure 2: Cumulative fade distributions at 1.5
GHz for family of path elevation angles de-
rived from the MSS Empirical Fade Distribu-
tion Equation (EFDE).
Figure 3: Best fit fade reduction at 1.5 GHz
versus equi-probability attenuation at path el-
evation angles of 30 ° , 45 ° , and 60 ° .
<
U
II
10 -
?.
i.
U
z +.
U
1
I ..............................
I i I
I I I
I t I
I I I
I I I
I I I
..... _--L----L---- L- -- -- L -- -- L ---- L ----L I I
....... ,_-.---,--,---.--,--.--
I I I F I I I--F-- -F--F--F-- --F-- F--I---
--.--,,-.--.--.--.--.--.--.--
_ _ L _ _ L\_\x_ L _ _ L _ _ L _ _L__L--L--L--
__P .... i_ X_ t- -- -- L- - -t---I----L---L----<-£--- 1.5 GHz, 30 _deg q i
--F--F -F--F--F--F--F--F--
, , , , , ,
I -- L I I _III II _ _i...._ _-- _X_L_ -- !I IL-_ _ L _ -- L -- -- L- -- --L -- -----_01 M_Z,I _01 IId_ III
__L _ _L - -tc-VL-_-_ x- _L _-L --L __L_ _
I 1 I I I I i
, : \\: , , ,
1.5 GHz, 45 del-_->_, I _ _ I I I
I I I \ I\ I _1 _ I I I
I I I I I I I
0 l 2 3 4 5 6 7 8 9 10
FADE DEPTH (dB)
0 I 2 3 4 5 6 7 8 9
FADE DEPTH (dB)
I0
Figure 4: Best power curve fit cumulative fade
distributions for line of sight configurations in
mountainous terrain.
Figure 5: Best exponential fit cumulative fade
distributions for line of sight configurations for
tree-lined roads.
224
International Mobile Satellite Conference, Ottawa, t990


An overview of results derived from mobile-satellite propagation experiments

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