ISSN: 1693-6930
TELKOMNIKA Vol. 8, No. 3, December 2010 : 319 – 326
322
3.3 Rain Attenuation
In this research, the rain rate measurements recorded for 2 years in Surabaya 7 13’ S,
112 43’ E, Indonesia are used. Rain rate statistic R
0.01
found from the measurement is 140 mmh, larger than that of 100 mmh suggested by ITU-R [9]. Rain attenuation was estimated by
using synthetic storm technique SST, which had been successfully tested for predicting long term statistics of fade duration [13]. Based on the rain attenuation estimates, it can be obtained
mean µ
and standard deviation σ
of logarithm of rain attenuation of various link lengths as shown in Table 3. It is well known that rain attenuation value
A
dB is approximately log- normally distributed. Therefore, the overall long-term pdf of rain attenuation along the link has
the form [12]:
≥
σ µ
− −
π σ
= ,
, ln
2 1
exp 2
1
2
a a
a a
a P
A
3 and the CCDF:
σ µ
− =
λ λ
= ≥
∫
∞
ln a
Q d
P a
A P
a A
4 where
µ and
σ are the mean and standard deviation of lnA. It can be obtained analytically
complementary cumulative distribution function CCDF of rain attenuation using 4. Figure 3 shows CCDFs of rain attenuation obtained using SST and analytically. The SST results can be
approximated by the analytical at least for exceedance probabilities above 0.01.
Table 3. Rain Attenuation Parameters of Mean and Standard Deviation
Rain attenuation parameters 1 km
2 km 3 km
4 km
µ
- 0.687 - 0.0255
0.347 0.603
σ
1.650 1.683
1.715 1.744
50 100
150 10
-2
10
-1
10 10
1
Attenuation dB P
ro b
.[ A
tt e
n u
a ti
o n
a b
s c
is s
a ]
1 km, SST 2 km, SST
3 km, SST 4 km, SST
1 km, analytic 2 km, analytic
3 km, analytic 4 km, analytic
Figure 3 CCDFs of rain attenuation for single link with 1-4 km link lengths
TELKOMNIKA ISSN: 1693-6930
An Adaptive Modulation of Millimeter-Wave Communication System for Tropical …. Suwadi 323
1 2
3 4
10
-3
10
-2
10
-1
10 10
1
Distance between transmitter and receiver km O
u ta
g e
p ro
b a
b ili
ty Adaptive modulation = 4-QAM, analytic
16-QAM, analytic 64-QAM, analytic
Adaptive modulation, simulation
Figure 4 Outage probability of various link lengths with transmit power 0 dBw
3.4 Outage Probability
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