Rohde & Schwarz CMU-K20, Руководство по эксплуатации

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CMU-K20/K21/K22/K23/K24
GPRS Signalling and EGPRS
1115.6088.12 4.195 E-12
Fig. 4-87 Connection Control – Connection (TBF Established)
RF Signals of the MS (Connection Control – MS Signal)
The
MS Signal
tab configures the operating mode and the RF traffic channel signal of the MS under
test. For packet data transfer the following parameters can be set:
•
The
Main Timeslot
and the remaining timeslots
(Slot Configuration)
that are used in downlink and
uplink direction
•
The RF levels and power control parameters in all timeslots
GPRS Uplink Power Control
Power control of the MS is important for spectral efficiency in the cellular system as well as for the reduction of
power consumption of the mobile station. In circuit switched mode, where a continuous two way connection
between the BTS and the MS is maintained,
closed loop
power control is used: The BTS measures the received
signal level from the MS and dynamically adapts the MS output power in 2-dB steps using a fixed scale of Power
Control Levels (PCL).
In
open loop
power control, the path loss in downlink and in uplink is assumed to be identical. If the MS detects a
reduction of the received signal level C, it tries to compensate for the changed propagation conditions by
increasing its own output power P
CH
by the same amount: The sum of P
CH
+ C is always kept constant. This fast
but inaccurate power control mode is useful at the beginning of a packet transmission.
For a discontinuous, packet oriented GPRS connection, a combination of open loop and closed loop power control
is used (GSM 11.10). The RF output power P
CH
on each individual uplink PDCH shall be:
) P ), 48 (C ( min P
MAX CH 0 CH
+ − Γ − Γ =
α
where
Γ
0
is a network-specific constant (+39 dBm for GSM400, GSM850 and GSM900, +36 dBm for GSM 1800
and GSM1900, i.e. the maximum nominal output power of an MS in the network),
Γ
CH
is a power control parameter
depending on the MS and channel (analogous to the PCL in circuit switched mode), and
α
represents a system
parameter. Both
Γ
CH
and
α
are controlled by the BTS. P
CH
must not exceed the maximum allowed output power in
the cell P
MAX
.
A pure open loop power control is achieved by setting
α
= 1 and keeping
Γ
CH
constant. A closed loop is achieved
by setting
α
= 0. The CMU is able to set the individual power control parameters
Γ
CH
for all uplink timeslots
whereas the system parameter
α
is always set to 0.
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