Hi there, dear Community members!
This post features the BBU3900 & BBU3910 configuration slots for UBBP. Please see more details as you scroll further down the topic.

BACKGROUND INFORMATION
No matter whether it is in a BBU3900 or BBU3910, a UBBP board can be configured in any of the slots 0 to 5, as shown in the following figure:

When configured in a BBU3900, UBBP boards in different slots provide different capabilities:
in UMTS mode, only the UBBP board in slot 2 or 3 can provide CPRI ports;
in GSM mode, the UBBP board in any of slots 0 to 3 can provide CPRI ports;
in LTE mode, the UBBP board in any of slots 0 to 5 can provide CPRI ports.
When configured in a BBU3910, UBBP boards in different slots provide the same capabilities, that is, the UBBP board in any slot can provide CPRI ports.