Appendix
TETRA power levels and power control
Each TETRA MS belongs to a power class, which defines the maximum RF
output power capability. In addition, the MS is capable of adapting its power level
in 5-dB steps to the external requirements. Two mechanisms are available: Open
loop and closed loop power control.
In open loop power control, the MS adjusts its transmit power based on the signal
quality it receives on the downlink from the BS. The weaker the signal from the
BS, the more RF power is transmitted by the MS. If the BS signal gets stronger,
the MS reduces its RF power again. So don’t be surprised to find the MS change
its output power when you change the STABILOCK’s one!
"
On a traffic channel, reducing the STABILOCK’s power level might be the right
way to change the power transmitted by the mobile station.
In closed loop power control, the base station measures the strength of the signal
it receives from the MS. It may decide to instruct the MS to change its power level
by a multiple of 5 dB. Of course, the MS cannot obey if it is instructed to send
more or less RF power than it is capable.
"
The TETRA option of the STABILOCK does not yet support this mechanism to
control the RF output power level of the MS under test. It is planned, however, to
add this feature in a future software version.
10
Appendix TETRA MS Test
10-45
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