Making The Transmitter Power Measurement; Purpose; Measurement Method - Agilent Technologies E4404B Operation Manual

Making GSM Base Station Measurements

Making the Transmitter Power Measurement

Making the Transmitter Power Measurement

Purpose

Transmitter Power is the measure of in-channel power for GSM
systems. Mobile stations and base transceiver stations must transmit
enough power, with sufficient modulation accuracy, to maintain a call of
acceptable quality without leaking into frequency channels or timeslots
allocated for others. GSM systems use dynamic power control to ensure
that each link is maintained with minimum power. This gives two
fundamental benefits: overall system interference is kept to a minimum
and, in the case of mobile stations, battery life is maximized.
The Transmitter Power measurement determines the average power for
a RF signal burst at or above a specified threshold value. The threshold
value may be absolute, or relative to the peak value of the signal.
At the base transceiver station, the purpose of the Transmitter Power
measurement is to determine the power delivered to the antenna
system on the radio-frequency channel under test. The Transmitter
Power measurement verifies the accuracy of the mean transmitted RF
carrier power. This can be done across the frequency range and at each
power step.

Measurement Method

The instrument acquires a GSM signal in the time domain. The average
power level above the threshold is then computed and displayed. This
measurement uses the "power-above-threshold" method instead of the
"useful part of the burst" method defined in the GSM standards. The
measured Transmitter Carrier Power will be very nearly the same for
these two methods. The power-above-threshold method has the
advantages of being faster and allows power measurements to be made
at somewhat lower power levels. It also has the advantage of not
requiring the carrier to have a valid TSC (Training Sequence Code).
Note that this measurement does not provide a way to specify which
timeslot is to be measured. Therefore if multiple timeslots are on, they
should all be set at the same power level, or the levels of those timeslots
to be excluded need to be kept below the threshold level. If you want to
measure Transmitter Carrier Power using the GSM specified useful
part of the burst method, use the Power vs Time measurement, which
also measures the power ramping of the burst.
Chapter 3 3-19