484 Chapter 16
W-CDMA Uplink Digital Modulation for Receiver Test
Setting Up a Multiple PRACH Signal
You will notice the PRACH Trigger Source Immedi Trigger and the PRACH Trigger are located on several
softkey menus. This was done so you could provide the trigger or make a different trigger choice without
having to return to any one particular menu. Pressing the
PRACH Trigger softkey is a manual trigger
action. You can also provide an external trigger signal for the PRACH transmission.
3. Press the
PRACH Trigger Source Immedi Trigger softkey until Immedi is highlighted.
The Immedi choice lets the W-CDMA signal transmission start as soon as the modulation format is
turned on. Since the format is already on, selecting Immedi will enable the immediate transmission of
the currently configured signal.
Configuring the Message Part Transmission
1. Choose whether or not to transmit the message part
a. Highlight the Message Part field.
b. Press the
Edit Item softkey.
Two softkeys are displayed,
ON and OFF. When you select OFF, the message part is not transmitted
leaving only the preamble as the PRACH transmission.
c. Press the
ON softkey since we will be transmitting the PRACH with both the preamble and message
part.
2. Select the transmission time for the message part.
a. Highlight the TTI (transmit time interval) field.
b. Press
10 > msec.
There are two valid entries for this field, 10 or 20 ms. The values can be entered using decimal
notation (0.01 or 0.02 seconds) or millisecond units (10 or 20 ms).
The 10 ms setting equates to 7.5 access slots (one radio frame) and the 20 ms spans 15 access slots (two
radio frames).
If you need to have an individual PRACH (UE) repeat multiple times within the 80 ms time period, you
may want to use the 10 ms setting. Since you are limited to 60 access slots (80 ms), the 20 ms setting will
decrease the number of times a UE’s PRACH can be retransmitted within the 80 ms time period.
3. Enter the number of access slots from the preamble to the message part (Tp-m).
The number of access slots starts from the beginning of the preamble and ends at the beginning of the
message part. Figure 16-28 shows a PRACH with a Tp-m of 3 access slots.
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