454 Chapter 16
W-CDMA Uplink Digital Modulation for Receiver Test
Understanding the PRACH
There are three areas that control the PRACH power level, the preamble power, the data part power, and the
control part power. Each of these areas are explained in the following sections. Figure 16-7 shows these
areas on the PRACH timing setup display while in the Pp-m power setup mode. Refer to “Power Control
Modes” on page 459 for more information on the power setup modes. The power control display is accessed
using the
PRACH Power Setup softkey.
Figure 16-7 PRACH Power Control Areas
Preamble Power
The preamble power is an absolute value (dBm) and is adjusted in the ESG by changing the value in the Max
Pwr field. Its value is used in determining the control part power level, which influences the total message
part power. See “Control Part Power” for more information.
The preamble power can be adjusted so that it exceeds the current carrier power. When this occurs, the ESG
will automatically adjust the carrier power. The reverse is also true when you enter a new carrier power.
Control Part Power
The control part power is an absolute value (dBm) that is set indirectly and with respect to the preamble. It is
derived from the sum of the highest preamble power and the Pp-m value.
The Pp-m is an offset value (dB) that determines the power difference between the control part and the
preamble powers (Pp-m = Cntl
dBm
- Pre
dBm
). (See Figure 16-8.) So by adjusting your Pp-m value, you
change the control part power with respect to the preamble.
Controls the Data Part Power
Controls the Control Part Power
Controls the Preamble Power
Pp-m Power Mode Selected
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