
354 Chapter 15
W-CDMA Uplink Digital Modulation for Receiver Test
Understanding the PRACH
values or select an appropriate data part slot format.
The control part only has one slot format, so its configuration is static, see Figure 15-5.
Figure 15-5 Control Part Slot Format
Unlike the control part, the data part has multiple slot formats that enable it to transmit at
different data rates. This is shown in Figure 15-6.
Figure 15-6 Data Part Slot Format
Message Part Scrambling Codes
As stated in “Scrambling Codes” on page 352, the same code is used for both the message part
and the preamble. However the starting chip for the message part is shifted by 4096 chips
from the preamble code. The message part contains 38400 scrambling chips and they are
repeated every 10 ms (every radio frame). So a 20 ms message part would have two
repetitions of the same code.
Power Control
The PRACH power is controlled by setting the preamble and the message part power. The
PRACH power is determined by the component (preamble or message part) of the PRACH
that has the highest power level. If both components have the same power level, then both
components individually equal the PRACH power level. The message part power is comprised
of the absolute powers for the control part and data part. A PRACH power value can be
entered that exceeds the current displayed carrier power and vice versa. But in reality, the
PRACH power equals the carrier power; it cannot exceed it. When a PRACH over power
condition occurs, the ESG will automatically adjust the PRACH power or the carrier power to
keep them within limits. In the multiple PRACH mode, the ESG maintains an 18.06 dB offset
between the carrier power and the PRACH power level. This is so the ESG can accommodate
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