![](bg5.png)
If we define
and use equation 2.23, we
obtain equation 2.29 from 2.21
mp
TTT −=
1
222
0
0
1
1
22
)1(2
)(log200
dqp
d
low
W
gK
p
N
T
c
d
f
e
σσσ
α
σ
+++
⎥
⎦
⎤
⎢
⎣
⎡
+
+
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
−−∆
−
2.29
3 SIMULATION RESULTS
We simulated the BER of received signal at base
station when user number was 5 ~ 30 persons.
Simulation circumstance was assumed to be
pedestrian(5 km/h), urban vehicle(40 km/h),
highway and railroad(100 km/h), KTX(300 km/h),
and upgraded KTX(350 km/h).
BER was calculated from equation 2.20. m
r
and
σ
r
of equation 2.20 was calculated from equation
2.17 and 2.18. m
k
and
σ
k
was calculated from
equation 2.12 and 2.13. We used the lower bound of
equation 2.28 when calculating equation 2.12 and
2.13. Figure 1 and 2 shows user number and BER
when mobile speed is 5 km/h, 40 km/h, 100 km/h,
300 km/h, and 350 km/h. We assumed R
b
= 4.8 kbps,
W = 1.2288 MHz, d = 4 km,
α
= 0.1, T
1
= 100 us,
N
o
/p
o
= 5 us,
σ
o
2
= 3.9 (dB)
2
. Figure 1 and 2 shows
increase of mobile speed degrades the BER of
received signal. This means the reverse link capacity
decreases to maintain the quality of service. Figure 1
and 2 shows the result when interference constant g
is 0.3 and 0.634, respectively. Larger interference
constant increases the receiver sensitivity with user
number. (a) and (b) of each Figure shows the results
in the case of
dqp
σ
and
dqp
. High speed enlarges the
Doppler shift in equation 2.22. Doppler shift
increases the lower bound of error variance in
equation 2.29. This increases the BER and degrades
the quality of service.
2222
)(5.0dB=++
σσ
σσσ
as well as
coverage for cellular network planning.
A.M
l. 42, No. 2/3/4,
B.
y users,” Pro. IEEE
N.C
unications, vol. 43, No. 12, pp. 2869-2873, Dec.
M.B
tions, vol. COM-25, No. 8, pp. 795-799,
J.M
munications, vol. 40, No. 3, pp.
C.C
Proc.-Commun., vol. 143, pp.
R.N s
D. network,”
internal communication.
2222
)(5.1dB=++
In urban vehicular (40 km/h) condition, BER
increase by Doppler shift was negligible. BER
degradation was not severe even though highway
and railroad (100 km/h) condition. We could plan
the cellular network assuming constant capacity with
mobile speed before KTX service. However, BER
was dramatically increased in KTX circumstance.
User number in KTX was limited to 17 ~ 26 persons
to maintain BER lower than 1 %.
4 CONCLUSION
We measured the coverage of CDMA2000 1X
network experimentally and simulated the capacity
in KTX condition. Although coverage was not
decreased, capacity was reduced severely in high
mobile speed of 300 km/h. We don’t have to
consider the mobile velocity in cell-planning
because capacity reduction is negligible in highway
and railroad. However, capacity is severely reduced
in KTX for its high velocity. We must consider the
number of passenger carried by KTX when opposite
train is met. Cell-planning without considering
capacity can make the burst error in high traffic
intensity. It causes not only quality degrade but also
call drop. We must consider capacity
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CDMA2000 1X CAPACITY DECREASE BY POWER CONTROL ERROR IN HIGH SPEED TRAIN ENVIRONMENT
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