To Next Page

To Previous Page

2201R Mobile Tester User Guide

Chapter 3 Performing manual tests and measurements in GSM mode

47090/322

Performing 2201R-based receiver measurements

The 2201R Mobile Tester supports three different types of statistical measurements of the receiver performance: bit

error rate, residual bit error rate and fast bit error rate measurements. All of them allow you to judge the quality of

the mobile’s receiver, but in different ways.

Once a traffic channel has been set up (see instructions on either page 53 or page 55), push the BER Meas. soft key

to start the measurements, to change test parameters and to review the results of the receiver measurements. The

GSM BER Test menu appears.

For the purposes of these measurements, the 2201R commands the mobile phone to return all the bits received back

to the 2201R. For the time when the GSM BER Test menu is displayed, the speech loopback is therefore disabled and

a test loop is closed.

These measurements are typically performed at a very low power level at the mobile phone RF input, so the RF Output

Power should be set to –104 dBm for the measurements.

Bit error rate (BER) measurements are based on a statistical analysis over all the coded (and uncoded) bits. The bit

error rate is the number of the bits decoded incorrectly by the mobile relative to all bits received by it. The BER is

tested for all the different classes of speech and data bits; these are class Ia, class Ib and class II bits. Class Ia bits are

best protected against corruption on the air interface whereas class II bits are completely unprotected.

The residual bit error ratio (RBER) is similar to the BER, except that all frames that the mobile detects an error in, are

rejected and not used for the RBER. Thus, only those frames are included in the RBER measurement that were

accepted by the mobile. The RBER is calculated for bit classes Ib and II only.

In addition, 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.

The Fast BER is similar to a BER measurement on the class II bits. The main difference is that in Fast BER, all bits are

unprotected. To measure the FBER, a special loop function is used (the so-called type C loop).

A counter indicates how many results have already been produced since the start of the measurement, and indicates

the activity of the measurement.

COBHAM 2201R User Manual

Other manuals for COBHAM 2201R