Rohde & Schwarz CMU-K20, Operating Manual

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Non Signalling: Power Measurements CMU-K20/K21/K22/K23/K24
1115.6088.12 4.32 E-11
P/t Multislot –
Info Box The Info Box parameter switches the info boxes for all displayed timeslots on or off.
Remote control
No command, display configuration only
P/Slot Table –
Slot Count
The input field Slot Count defines the total number of slots measured in the P/Slot
Table application.
Remote control
CONFigure:POWer:XSLot:SCOunt
P/Frame –
Frame Count
The input field Frame Count defines the total number of consecutive TDMA frames
measured in the P/Frame Table application. One timeslot is measured in each
frame. One TDMA frame has a duration of approx. 4.6 ms. A smaller number of
frames reduces the measurement time.
Remote control
CONFigure:POWer:FRAMe:FCOunt
Limit lines (Power Configuration – Limit Lines)
The Limit Lines tab defines the limit lines for the burst power vs. time measurements (applications P/t
Norm. GMSK , P/t Norm. 8PSK, and P/t Multislot ).
Burst structure in
the GSM mobile
radio network:
GMSK modulation
In the GSM mobile radio network, all radio channels are divided into frames with 8 timeslots,
each with a duration of 15/26 ms
≈
577
µ
s. In this time mask, bursts with various types of bit
patterns are transferred:
Normal burst Used for data transmission on the traffic channel and on the control
channels except RACH.
Access burst Used by the mobile (MS) for initial random access to the nework and for
handover.
Other burst types Dummy burst, frequency correction burst, synchronization burst, are only
used by the BTS.
The basic GSM modulation scheme is GMSK modulation. With this modulation scheme, the
transmission rate is 270.833 ksymbols/s (where each symbol codes one data bit), resulting in
a bit duration/symbol duration of 3.69
µ
s/symbol. The structure of the GSM bursts is shown in
Fig. 4-33
. Compared to a normal burst, the access burst has a longer guard period (68.25
symbols instead of 8.25 symbols) whereas the length of the useful part of the burst (useful
duration) is shortened by 60 symbols. The extended guard period is needed since timing
advance is not known at initial random access and handover.
The tolerance template for normal (NB) and access bursts (AB) can be divided into different
areas. These areas are used as a basis for the definition of the limit lines and are shown in
the following diagram (
Fig. 4-11
).
Note that in upper areas 2 and 7, the limit lines depend on the PCL of the mobile phone. In
the CMU, this can be taken into account by defining a PCL-dependent, dynamic correction to
the static limit lines, which is explained in the
Limit Lines section of the Signalling mode (see
p.
4.111
).
Note: In Non Signalling mode, only normal bursts can be measured. The access bursts
transmitted by the mobile phone to initiate a location update can be analyzed in Signalling
mode; see section
Power Measurements on page 4.97 ff. The reference level (0 dB line) is
equal to the received transmitter carrier power, i.e. the average value of the transmitter
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