2201R Mobile Tester User Guide
Chapter 3 Performing manual tests and measurements in GSM mode
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Class Ib, II
The Residual BER section displays the results for the class Ib and class II bits. The limits can be defined in the
GSM/GPRS Limits menu.
FER
In addition to the class Ib and class II bits, the frame erasure ratio (FER) is measured. This is defined as the ratio of
the frames rejected by the mobile in relation to all frames transmitted. A frame is marked as ‘erased’ and rejected by
the mobile when its error detector finds an error. To do so, the mobile uses the checksum provided with the class Ia
bits.
Round Trip Delay
This is the number of frames that the mobile phone takes to return a speech frame.
This value is for information purposes only. It is not a required test with any test limits.
Interpreting FBER measurement results
In the Fast BER measurement, the bit stream is not encoded and decoded at all, so all the bits are unprotected as the
class II bits in the BER measurement. This is a fast way to measure the true bit rate (without the effect of channel
decoding) over a larger number of samples.
FBER
The Fast BER section displays the results for all the bits being sent to the mobile phone and returned to the 2201R
Mobile Tester.
The limits can be defined in the GSM/GPRS Limits menu. It is advisable to use the same limits as for the class II bits
in the BER Speech measurements.
Note
The round trip delay may differ between the types of statistical measurements, but should be stable
within one measurement type.
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