High RSSI Troubleshooting
Case 1 – High RSSI on one branch
This case is valid when RSSI values on one branch are very high, but the other branch is not at all affected.
Values before issue:
- Branch 1: -101.13 dBm
- Branch 2: -100.72 dBm
- Imbalance: 0.41 dBm
Values during issue:
- Branch 1: -100.55 dBm
- Branch 2: -72.37 dBm
- Imbalance: 28.18 dBm
Values after locking 2nd branch:
- Branch 1: -100.43
Case 2 – High RSSI on both branches, imbalance >= 6dBm
This case is valid when RSSI values on one branch are very high, and the other branch is also affected, but it
can be clearly seen that there is at least 6 dBm difference between the RSSI values of those two. That branch
is most likely affected by the issue of the faulty one. If that is the case, the branch with lower RSSI should
normalize when the faulty one is locked.
Values before issue:
- Branch 1: -101.65 dBm
- Branch 2: -101.51 dBm
- Imbalance: 0.14 dBm
Values during issue:
- Branch 1: -73.57 dBm
- Branch 2: -86.74 dBm
- Imbalance: 13.17 dBm
Values after locking 1st branch:
-
Branch 2: -102.36
Case 3 – High RSSI on both branches, imbalance <= 6dBm
This case is valid when RSSI values on both branches are high, and the imbalance between them is less than 6
dBm. This as a high probability to be caused by external interference.
Values during issue:
- Branch 1: -82.79 dBm
- Branch 2: -78.27 dBm
- Imbalance: 4.53 dBm
Values after locking 2nd branch:
- Branch 1: -82.62 dBm
Case 4 – Intermittent high RSSI spikes
This case is valid when RSSI values on either one or both branches have intermittent high RSSI. The spikes can
occur randomly or on a regular basis (around same time of day). Random spikes could show hardware
problem, whereas spikes that happen during the same time of day could be a sign of external interference,
where a device sends data on a regular basis and interferes with Net1 frequency.
Troubleshooting procedures*
Procedures are divided according to RSSI issue case type (1-4) and eNB installation type
(RRH on ground or top of the mast).
A.
B.
C.
D.
Troubleshooting cases 1, 2, 3 – RRH at ground level
Troubleshooting cases 1, 2, 3 – RRH on top of the mast (straight and cross-connect)
Troubleshooting case 4 – RRH at ground level
Troubleshooting case 4 – RRH on top of the mast (straight <D.I.> and cross-connect<D.II.>)
Important!
- RSSI readings are done in RRH port, no matter in which antenna port it is connected
- Before on-site intervention, remember to unlock and measure RSSI
- Before any tech intervention, remember to lock the RRH
- After each step in the guide below, RSSI values are measured
- All RSSI values after each step are recorded to easier understand the issue
* All scenarios will be presented with high RSSI issue present on Sector A, branch 2
Installation types
RRH at ground level
RRH on top – straight, split
RRH on top – cross-connect
Legend
Scenario A - Troubleshooting cases 1, 2, 3 - RRH at ground level
1. Reset RRH
There have been cases when resetting RRH restored RSSI to normal values
- Select eNB from list -> Right click -> Properties
- Go to Equipment view (1) -> Right click on RRH (2) -> Actions -> Reset
- Check box (3) -> Click Yes (4)
Did the issue clear?
- Yes: RRH fault solved by RRH reset
- No: continue troubleshooting
This is service affecting
for the sector for ~2 minutes
2. Lock branch with highest RSSI value
Locking worst branch often improves values on the
other branch of the sector, or even RSSI values on the
other sectors
-
Select eNB from list -> Right click -> Properties
Go to Components view (1) -> Select AntennaPort (2)
Uncheck “rxUsed” and “txUsed” boxes (3)
Click Apply (4) -> Yes (5)
This is service affecting for all sectors for ~2 minutes
CpriRadioEquipment (for non-cross-connect eNB):
0 – sector A
1 – sector B
2 – sector C
3. Dispatch technician on site
Technicians should take the following tools/spares with them:
- 2 x 3 meter jumper cables (this is for RRH on ground level case)
- 2 x 1/2”-7/8” connectors
- 2 x 1/2“-1 1/4” connectors
- Dummy loads (40 W / 46 dBm)
- RRH
4. Check bottom connections
- Check faulty branch connections if too loose / tight / corroded
- Tighten / loosen / replace accordingly
- Check the other branch's connections if too loose / tight / corroded
- Tighten / loosen / replace accordingly
5. Swap bottom jumpers at RRH-jumper level
- Disconnect jumper from RRH port 1
- Disconnect jumper from RRH port 2
- Connect jumper from port 1 to port 2
- Connect jumper from port 2 to port 1
Did the high RSSI values stay on same branch as last step?
- Yes: bad RRH – replace RRH
- No: continue troubleshooting
! Observation: If troubleshooting continues, the swapped
jumpers will remain as they are for the next step
6. Swap bottom jumper at jumper-feeder level
From the setup at step 5 (swapped jumpers at RRH-jumper level),
now swap the jumpers at jumper-feeder level.
Observe that the jumpers are fully swapped (branch 1 jumper on
branch 2 and vice versa)
- Disconnect jumper from feeder port 1
- Disconnect jumper from feeder port 2
- Connect jumper from port 1 to port 2
- Connect jumper from port 2 to port 1
Did the high RSSI values stay on same branch as last step?
- Yes: bad jumper – replace jumper
- No: continue troubleshooting
7. Swap back jumpers in initial position (step 4)
Or label jumpers accordingly
Before / after jumpers’ swap
8. Check top connections
- Check faulty branch connections if too loose / tight / corroded
- Tighten / loosen / replace accordingly
- Check the other branch's connections if too loose / tight / corroded
- Tighten / loosen / replace accordingly
9. Swap top jumper at feeder-jumper level
- Disconnect jumper from feeder port 1
- Disconnect jumper from feeder port 2
- Connect jumper from port 1 to port 2
- Connect jumper from port 2 to port 1
Did the high RSSI values stay on same branch as last step?
- Yes: bad feeder – escalate to Net1
- No: continue troubleshooting
! Observation: If troubleshooting continues, the swapped
jumpers will remain as they are for the next step
10. Swap top jumper at jumper-antenna level
From the setup at step 9 (swapped jumpers at feeder-jumper
level), now swap the jumpers at jumper-antenna level.
Observe that the jumpers are fully swapped (branch 1 jumper
on branch 2 and vice versa)
- Disconnect jumper from feeder port 1
- Disconnect jumper from feeder port 2
- Connect jumper from port 1 to port 2
- Connect jumper from port 2 to port 1
Did the high RSSI values stay on same branch as last step?
- Yes: bad jumper – replace jumper
- No: continue troubleshooting
11. Swap back jumpers in initial position (step 8)
Or label jumpers accordingly
Before / after jumpers swap
12. Install dummy load on bad branch
Dummy load installation should give a value of ~-104 dBm,
considering there is no loss / hardware imperfections
RSSI values should read OK at this point, as all parts up to
dummy load were checked.
Possible issues:
- Faulty antenna
- External interference
Escalate to Net1 for further troubleshooting
Scenario B - Troubleshooting cases 1, 2, 3 - RRH on top of the mast
a. Straight connection
1. Reset RRH
Same procedure as in scenario A
2. Lock branch with highest RSSI value
Same procedure as in scenario A
3. Dispatch technician on site
Technicians should take the following tools/spares with them:
- Dummy loads (40 W / 46 dBm)
- RRH
- 20 meters jumper (if available)
4. Check jumper connection in RRH
- Check faulty branch connections if too loose / tight / corroded
- Tighten / loosen / replace accordingly
- Check the other branch's connections if too loose / tight / corroded
- Tighten / loosen / replace accordingly
5. Swap jumpers at RRH-jumper level
Same jumper swap procedure as in scenario A
Did the high RSSI values stay on same branch
as last step?
- Yes: bad RRH – replace RRH
- No: continue troubleshooting
! Observation: If troubleshooting continues,
the swapped jumpers will remain as they are
for the next step
6. Swap jumper at jumper-antenna level
From the setup at step 5 (swapped jumpers at RRH-jumper level),
now swap the jumpers at jumper-antenna level.
Observe that the jumpers are fully swapped (branch 1 jumper on
branch 2 and vice versa)
- Disconnect jumper from feeder port 1
- Disconnect jumper from feeder port 2
- Connect jumper from port 1 to port 2
- Connect jumper from port 2 to port 1
Did the high RSSI values stay on same branch as last step?
- Yes: bad jumper – replace jumper
- No: continue troubleshooting
7. Swap back jumpers in initial position (step 4)
Or label jumpers accordingly
Before / after jumpers swap
8. Install dummy load on bad branch
RSSI values should read OK at this point, as all parts
up to dummy load were checked.
Possible issues:
- Faulty antenna
- External interference
Escalate to Net1 for further troubleshooting
Scenario B - Troubleshooting cases 1, 2, 3 - RRH on top of the mast
b. Cross-connected jumpers
0. Cross-connections
RRH1 port1 –> Antenna 1 port 1
RRH1 port2 –> Antenna 2 port 2
Cross-connect solution is used in difficult to
access sites for redundancy reasons.
One RRH can be lost without losing coverage
for one full sector.
RRH2 port1 –> Antenna 2 port 1
RRH2 port2 –> Antenna 3 port 2
Example of cross-connect redundancy
RRH3 port1 –> Antenna 3 port 1
RRH3 port2 –> Antenna 1 port 2
- RRH1 is lost (fiber to RRH / RRH issue)
- Antenna 1 still up and running due to
connection with RRH3 port 2
- Antenna 2 loses DL capacity due to
connection with faulty RRH1 port 2
Cross-connect redundancy trades
capacity for two sectors for the gain of
full coverage in case of RRH fault
Sites with cross-connect
(all high-masts, RRH on top)
DK_BHO3006
SE_DAL2054
SE_DAL2073
SE_GOT1067
SE_JAM2109
SE_KAL4680
SE_KRO4007
SE_NOR2290
SE_NOR2305
SE_NOR2315
SE_NOR4677
SE_OST4003
SE_VAB2237
SE_VAG1007
SE_VAL2077
If high RSSI on –> Reset
Cell A port 1 –> RRH 1
Cell A port 2 –> RRH 3
Cell B port 1 –> RRH 2
Cell B port 2 –> RRH 1
Cell C port 1 –> RRH 3
Cell C port 2 –> RRH 2
1. Reset RRH
Same procedure as in scenario A
When resetting RRH, keep in mind the following
2. Lock branch with highest RSSI value
Same procedure as in scenario A
When locking branch, keep in mind the following
If high RSSI on -> Lock
Cell A port 1 –> CPRI 0 AntPort 1
Cell A port 2 –> CPRI 2 AntPort 2
Cell B port 1 –> CPRI 1 AntPort 1
Cell B port 2 –> CPRI 0 AntPort 2
Cell C port 1 –> CPRI 2 AntPort 1
Cell C port 2 –> CPRI 1 AntPort 2
3. Dispatch technician on site
Technicians should take the following tools/spares with them:
- Dummy loads (40 W / 46 dBm)
- RRH
- 20 meters jumper (if available)
4. Check jumper connection in RRH
- Check faulty branch connections if too loose / tight / corroded
- Tighten / loosen / replace accordingly
- Check the other branch's connections if too loose / tight / corroded
- Tighten / loosen / replace accordingly
5. Swap jumpers at RRH-jumper level
Same jumper swap procedure as in scenario A
Did the high RSSI values stay on same branch
as last step?
- Yes: bad RRH – replace RRH
- No: continue troubleshooting
! Observation: If troubleshooting continues,
put back the jumpers as they were initially
If high RSSI on –> Swap jumpers in
Sector A port 1 –> RRH 1
Sector A port 2 –> RRH 3
Sector B port 1 –> RRH 2
Sector B port 2 –> RRH 1
Sector C port 1 –> RRH 3
Sector C port 2 –> RRH 2
6. Swap jumper at jumper-antenna level
From the setup at step 5 (swapped jumpers at RRH-jumper level),
now swap the jumpers at jumper-antenna level.
Observe that the jumpers are fully swapped (branch 1 jumper on
branch 2 and vice versa)
- Disconnect jumper from feeder port 1
- Disconnect jumper from feeder port 2
- Connect jumper from port 1 to port 2
- Connect jumper from port 2 to port 1
Did the high RSSI values stay on same branch as last step?
- Yes: bad jumper – replace jumper
- No: continue troubleshooting
! Observation: If troubleshooting continues, put back the
jumpers as they were initially
! Important for cross-connected sites !
When swapping at RRH-jumper level
Issue moves from –> To
Sector A port 1 –> Sector B port 2
Sector A port 2 –> Sector C port 1
When swapping at jumper-antenna level
Issue moves from –> To
Sector A port 1 –> Sector A port 2
Sector A port 2 –> Sector A port 1
Sector B port 1 –> Sector C port 2
Sector B port 2 –> Sector A port 1
Sector B port 1 –> Sector B port 2
Sector B port 2 –> Sector B port 1
Sector C port 1 –> Sector A port 2
Sector C port 2 –> Sector B port 1
Sector C port 1 –> Sector C port 2
Sector C port 2 –> Sector C port 1
7. Swap back jumpers in initial position (step 4)
8. Install dummy load on bad branch
RSSI values should read OK at this point, as all parts
up to dummy load were checked.
Possible issues:
- Faulty antenna
- External interference
Escalate to Net1 for further troubleshooting
Scenario C - Troubleshooting case 4 - RRH at ground level
Due to the intermittent nature of the issue, these cases require at least 2 dispatches in order to find the fault.
Most of the time the issue will not be present, so there is a high chance it will not be when the techs are on site.
In some cases, the high RSSI spikes come at regular time intervals (usually same time of day). This indicates that
it’s a possible external interference, but it is also easier to predict next spike, which helps troubleshooting
decisions.
Example of predictable RSSI spikes:
Example of unpredictable RSSI spikes:
1. Identify faulty branch and reset RRH
Same procedure as in scenario A, B for RRH reset.
To identify the faulty branch, simply
2. Monitor RSSI for the next pre-determined interval, OR until next RSSI spike
The interval is calculated based on the longest time interval between 2 spikes, as in the example below.
If the interval 3 days, the issue should be monitored 3 x highest interval (9 days in this case).
For lower intervals, the monitor period is calculated in the same way, for at least 7 days.
Is any high RSSI values are observed during the monitor period?
No: case solved by RRH reset or issue source not present any more
Yes: continue troubleshooting
3. Dispatch technician on site
Technicians should take the following tools/spares with them:
- 2 x 3 meter jumper cables
- 2 x 1/2”-7/8” connectors
- 2 x 1/2“-1 1/4” connectors
4. Replace bottom jumper + jumper-feeder connector
This is done to eliminate the issue in jumper and jumper-feeder connector
5. Swap RRH running the faulty branch with another RRH on site
In the example case, RRH swap is done between current RRH 1 and current RRH 2.
The RRHs will not be moved from the position in the rack mounting.
The swap is done by swapping the following:
Step a – Fibers in d2U (eCCM) between port 1 and port 2. By doing that RRH 1
becomes RRH2 and vice versa (on the logical level, RRH will identify its number
according to the eCCM port it is connected to)
After Step a
Step b – Swap both jumpers between RRHs at RRH –jumper level
Jumper in RRH/port –> Goes to
RRH 1, port 1 –> RRH 2, port 1
RRH 1, port 2 –> RRH 2, port 2
RRH 2, port 1 –> RRH 1, port 1
RRH 2, port 2 –> RRH 1, port 2
This finalizes the RRH swap. If after this step the high RSSI spikes are detected in
another sector (in this case it would move from A to B), the fault lies in the RRH.
If the issue stays on same sector, issue is further up, starting with feeder.
After Step b
Step 8
6. Swap jumpers between branches in RRH 1 (former RRH 2)
at jumper-feeder level
7. Replace top jumper and top feeder-jumper connector
8. Swap jumpers at jumper-antenna level
After step 8, by detecting on which branch
the RSSI spike occurs, it can be narrowed
down to feeder issue (issue moves on the
other branch) or antenna/ext. interference
(issue stays on the same branch).
Before
After
!!! Everything must be properly labeled so
it can easily be reverted at the next visit !!!
9. Monitor for RSSI spikes. When
detected, proceed to next step
10. Escalate to Net1 for decision
Step 6
Setup after tech visit
“Untangled” RRH1 and RRH2
for better overview
“Untangled” RRH1 and RRH2
for better overview
Scenario D.I. - Troubleshooting case 4 - RRH on top of the mast (straight)
1. Identify faulty branch and reset RRH
Same procedure as in scenario A, B for RRH reset.
To identify the faulty branch, simply
2. Monitor RSSI for the next pre-determined interval, OR until next RSSI spike
Is any high RSSI values are observed during the monitor period?
No: case solved by RRH reset or issue source not present any more
Yes: continue troubleshooting
3. Dispatch technician on site
Technicians should take the following tools/spares with them:
- 2 x 7/16 DIN connectors – these are the connectors at the
ends of the jumpers, plugging in the RRH and antenna
After
Step a
4. Swap RRH running the faulty branch with another RRH on site
In the example case, RRH swap is done between current RRH 1 and
current RRH 2.
The RRHs will not be moved from the position in the rack mounting.
Step a – Swap fibers and SFPs between RRH 1 and RRH 2.
SFP swap is required as each port uses different wavelength
Step b – Swap both jumpers between RRHs at RRH –jumper level
Jumper in RRH/port –> Goes to
RRH 1, port 1 –> RRH 2, port 1
RRH 1, port 2 –> RRH 2, port 2
RRH 2, port 1 –> RRH 1, port 1
RRH 2, port 2 –> RRH 1, port 2
After
Step b
5. Swap jumpers between branches in RRH 1 at jumper-feeder level
6. Replace connectors at the ends of the jumper
This is to avoid replacing whole jumper, as for RRH on top solution, jumpers are
usually over 20 meters long.
Start with connector at RRH end. This is where the work at RRH side is complete
and work at antenna side begins.
Replace the connector at antenna end.
7. Swap jumpers at jumper-antenna level
After step 7, by detecting on which branch the RSSI spike occurs, it can be
narrowed down to jumper issue (issue moves on the other branch) or
antenna/ext. interference (issue stays on the same branch).
!!! Everything must be properly labeled !!!
For a better overview
Setup after tech visit
“Untangled” RRH1 and RRH2
Scenario D.II. - Troubleshooting case 4 - RRH on top of the mast (cross-connect)
Thank you!