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Practical measurements

In practice, there are really two values of sensitivity, compliance sensitivity and

absolute sensitivity. To verify compliance sensitivity, a GSM modulated signal

with a power level of –104 dBm is applied to the receiver and RBER class II is

verified to be below 2%.

To verify absolute sensitivity, a GSM modulated signal is applied at a nominal

level (–90 dBm) and decreased until the specified BER occurs. This sensitivity

level contributes enormously to overall system performance. Sensitivity is the

network equipment manufacturerís most important specification. A few dB of

added sensitivity performance can reduce the mobile stations required transmit

power, or reduce the number of dropped calls in a hostile environment.

When to use the measurement

Sensitivity measurements are performed in every phase of the BTS lifecycle.

In final manufacturing tests, BER, RBER, and FER are typically verified at

bottom, middle, and top frequencies using a traffic channel. During full type

approval, a thorough list of different channel configurations and specification

limits are used to verify performance.

Base station

GSM signal source

Channel simulator

(optional)

GSM receiver

and BERT

Figure 26. BER results shown on Agilent ESG E4433B, digital RF signal generator

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Agilent Technologies Switch/Measure Manual do Utilizador Página 30