User`s guide

358 Chapter 15
W-CDMA Uplink Digital Modulation for Receiver Test
Understanding the PRACH
or data power will result in a ratio of one (0.00 dB). However the ESG gives you the flexibility
to set your relative power values to meet your testing needs. Which ever method you use, the
highest power value is used as your data part power reference relative to the control part
power.
NOTE When a random power value is used, the beta value is replaced by a hyphen,
since it cannot be defined by the beta values.
Using the relative power formula, a control beta of five would result in a relative control
power value of −9.54 dB. If the relative data power is 0.00 dB (beta of 15), this would mean
that the data part power is 9.54 dB higher than the control part power. If the relative data
power is
−9.54 dB and the relative control power is 0.00 dB, this would mean that the data
part power was 9.54 dB lower than the control part power. When the betas are the same
value, this means that the control part and data part powers are the same power levels. This
results in a 3 dB (two times the control part power) increase in the message part power.
To calculate the data part absolute power, perform the following steps where
1. Calculate the absolute power for the control part.
Cntl
dBm
= Pre
dBm
+ Pp-m
The preamble power is represented by the Max Pwr field on the ESG.
2. Calculate the relative power difference between the two relative power values.
Pwr
diff
= Data
pwr −
Cntl
pwr
3. Calculate the absolute power for the data part.
Data
dBm
= Cntl
dBm
+ Pwr
diff
Do not confuse the control power as a means of adjusting the control part power. Remember
the control part power is the sum of the preamble and the Pp-m values. The control power
merely serves as a reference for the data part power relative to the control part power. Figure
15-9 demonstrates the message part power when the data part has a greater influence.
Pwr
diff
= difference between relative power values Cntl
pwr
= relative control power
Data
pwr
= relative data power Cntl
dBm
= control part power
Data
dBm
= data part power Pre
dBm
= preamble power