5.3.
System productivity calculation taking into account features of the standard
DVB-T2.
The communication quality depends on many parameters, such as gain of the
transmitting and receiving antennas, the transmitter power and receiver noise figure.
All these parameters are controlled by the system designer and can be modified to
optimize the system.
One option, however, is not under the control of the system designer. This option
– propagation loss in wireless channel.
The signal attenuation calculation, system productivity, BER value dependency
from distance, propagation zones range and other parameters are held by using the
Okamura-Khata spatial model [20], using DVB-T2 parameters for MSDS.
Signal attenuation by Okamura-Khata model calculated by the following formula:
()=
0
()+(,)−(ℎ
)−(ℎ
)−
, (16)
where
– the propagation distance (km),
0
() – signal in free space
attenuation,
(,) – signal attenuation in city in respect of attenuation in free space at the base
station antenna height
ℎ
=50m and mobile station antenna height
ℎ
=1.6m,
(ℎ
) – base station antenna gain (dB), (ℎ
) – mobile station antenna gain (dB),
– attenuation factor for any terrain type.
In (16) the value
0
() is calculated, and all others are determined by the
chart constructed on the basis of experimental data.
The gain based on stations heights are defined as follows:
(ℎ
)=20⋅log (
ℎ
200
),при 100 > ℎ
> 10,
(17)
(ℎ
)=10⋅(
ℎ
3
),при 3 > ℎ
,
(18)
(ℎ
)=20⋅(
ℎ
3
),при 10 > ℎ
,
(19)
Signal attenuation in free space is calculated by formula (20):
0
()=32,4+20∙ (∙) ,
(20)
where d is given by a range of 1 to 10 km, and F is calculated as
=
10
6
and the
frequency range
=3 GHz.
Signal power estimation is calculated according to the energy balance of equation
(21):
=
+
−
+
,
(21)
wherein
– the radiation power of BS (W).
Then it’s necessary to construct a graph matching BER to distance d based on the
estimated signal power. The QPSK, QAM-16, QAM-64 and QAM-256 are used in
calculations – as they are used in the DVB-T2 standard.
The energy potential is directly proportional to transmitter power, and is inversely
proportional to the spectral noise density and bit rate.
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