Hello everyone, today I will share a case that DBS3900 reports degraded unit performance. Hope it helps you！
Problem description
A new broadband cluster DBS3900 macro base station uses eRRU3232, which is a 4T4R RRU.
The connection between the RRU and the antenna is as follows: the first RRU enables 0 cells and 2T2R, the second RRU enables 1 and 2 cells and 2T2R.
After the site is deployed and the unit is activated, the unit service capability decreases, and the U2000 reports a VSWR alarm.
Alarm message
A VSWR alarm is generated on the RRU of the subrack 60.
Cell performance degradation is reported in cell 0.
Process flow
Disable unit 0 and replace the RF cable between the RRU and the antenna.
Activate the cell. The alarm persists.
Ask the construction team to take photos for the RRU connection.
The RRU used by unit 0 is the RRU with subrack number 60. The RRU uses ports 0 and 2 to connect to the antenna.
The RRU of unit 1 is in the sub-frame 61. The RRU is connected to the antenna using ports 0 and 2.
The RRU of unit 2 is in the sub-frame 61. The RRU uses ports 1 and 3 to connect to the antenna.
Change the RRU used by unit 0 to ports 0 and 1 of the RRU with subrack number 60.
Change the RRU used by unit 1 to ports 0 and 1 of RRU in subrack 61.
Pass unit 2 to ports 2 and 3 on the RRU in rack 61.
10. Reactivate the unit. The alarm has been cleared.
Root Cause
The RF ports of the RRU and the antenna are incorrectly connected.
Solution
Replace the cable between the RRU RF port and the antenna RF port.
Suggestions
The RF ports on the eRRU3232 are divided into two groups: RF ports 0 and 1, and RF ports 2 and 3. RF ports 0, 2, 4, and 6 of the eRRU3253 form a group, and RF ports 1, 3, 5, and 7 form a group.
A connection error between the RRU RF port and the antenna RF port will affect the cell service capability.
Thanks!
