Interference in the 800 Mhz LTE, 20 Mhz bandwith

[javierinfante]

Hello:
In my network I have several cells with external interference in LTE 800.
the interference is narrowband, looking at the cell performance I can see that it affect only one RB, but after a while the interference move to the left and affect a different RB, the interference can stay active for many days always in the same position and with the same energy or suddenly disappear.
Does anyone have any idea what can be the interference source, and any idea how to mitigate it?
Just look to the print screen images attached.

[Muhammad]

Can you share the exact frequencies of the UL bandwidth in your region.

[javierinfante]

hello Muhammad:
here it is:


Network Type
LTE (FDD)


E/U/ARFCN
6350


Band Name
EU Digital Dividend


Uplink Frequency
(phone to base station)
852 MHz


Downlink Frequency
(base station to phone)
811 MHz


Band Number
20





Network Type
LTE (FDD)


E/U/ARFCN
6350


Band Name
EU Digital Dividend


Uplink Frequency
(phone to base station)
852 MHz


Downlink Frequency
(base station to phone)
811 MHz


Band Number
20

[krobelux]

how much RSSI detected at eNodeB? if it happen at only 1 RB i dont think its an interference, all your subs is mobile users or there are any CPE equipment at your network?

[Jose1975]

Hello:
In my network I have several cells with external interference in LTE 800.
the interference is narrowband, looking at the cell performance I can see that it affect only one RB, but after a while the interference move to the left and affect a different RB, the interference can stay active for many days always in the same position and with the same energy or suddenly disappear.
Does anyone have any idea what can be the interference source, and any idea how to mitigate it?
Just look to the print screen images attached.

I was having the same issue like you javier and we had to buy a spectrum analyzer, with this device i was able to find out where the external interference was coming from, inmedeately I got in touch with the other operator that was making noise into our band wich by the way is 2.5 ghz LTE and problem solved all the interference dissapeared in all the 5 EnodB that were beign affected I Think you will have to go out and make test with the spectrum analyzer I tried everything possible since my office nothing worked out I have to go out to the field and make test by myself is the best choice. if you do not have a spectrum analyzer you can hire a company that offers that service believe me for me it was the only way. check the other operator frequency , is there any other operator working in the same band as you are???

[tpkj]

I was having the same issue like you javier and we had to buy a spectrum analyzer, with this device i was able to find out where the external interference was coming from, inmedeately I got in touch with the other operator that was making noise into our band wich by the way is 2.5 ghz LTE and problem solved all the interference dissapeared in all the 5 EnodB that were beign affected I Think you will have to go out and make test with the spectrum analyzer I tried everything possible since my office nothing worked out I have to go out to the field and make test by myself is the best choice. if you do not have a spectrum analyzer you can hire a company that offers that service believe me for me it was the only way. check the other operator frequency , is there any other operator working in the same band as you are???

Could I have a questions?
Your site was like sitesharing with other operators (church, ...)? Looks like PIM, or not?.
The noise what you mentioned, was narrowband or wideband?
Was that noise coming from combination of 2G-2G of other operator, or from combination of 2G-4G of other operator?

[Jose1975]

Could I have a questions?
Your site was like sitesharing with other operators (church, ...)? Looks like PIM, or not?.
The noise what you mentioned, was narrowband or wideband?
Was that noise coming from combination of 2G-2G of other operator, or from combination of 2G-4G of other operator?

the noise was wimax vs LTE and in my case my company works with LTE BAND 2.5 GHZ and 2.6 GHZ and the other operator was working in wimax in the band 2.5 ghz and 2.6 ghz the frequencies used by the other operator were very close to our frequencies so in order to solve this issue I decided to use noise filters in our radios and antennas to get rid of the interference in the other hand the other operator was fined because they were using a frecuency of our band.

[Muhammad]

hello Muhammad:
here it is:


Network Type
LTE (FDD)


E/U/ARFCN
6350


Band Name
EU Digital Dividend


Uplink Frequency
(phone to base station)
852 MHz


Downlink Frequency
(base station to phone)
811 MHz


Band Number
20





Network Type
LTE (FDD)


E/U/ARFCN
6350


Band Name
EU Digital Dividend


Uplink Frequency
(phone to base station)
852 MHz


Downlink Frequency
(base station to phone)
811 MHz


Band Number
20



The most frequent sources in 800 MHz band are due to the PIM or CATV leakage (In case you have Cable TV networks in your country). The Audio component of the TV signal spans over 200 ~ 400 Khz. check for the spectrum scanning option and look for the above mentioned possibilities. You can consult the PIM calculators which are also available online.


BR
Jamil

[javierinfante]

it was an interference, very clear in the FFT scan and also in the PRB interference check. now the interference has gone by itself.

[javierinfante]

We have a service from the telecom department that check for interference when we report any, the problem is that many times the interference disappear before they to go onsite.
And the strange situation is the fact that is a narrowband interference very strong and permanent, it can be active for several days all the time or suddenly disappear.

[javierinfante]

Hi TPKJ, in my network we have all technologies, GSM 900/1800, UMTS900/2100, LTE 800/2600/1800, but in this case I can ensure 100% that there wasnt any kinnd of intermodulation.
The intermodulation problems can be found very easy, the power in the another technology (interference) is increased and then the efect can be seen in the LTE (cell under interference). but here all was OK, in the FFT there was a big spike that was there for several days and suddenly it has gone.
the site was almost isolated, just covering a small village.
Many times we have interference form repeaters, but I can identify that signal, I have seen it many times, but this one was totally different, just a spike without any variations in the power.
We also have interference problems when the site is close to the train track but again we know the cause.

[dannthemann]

Hello,

Which counters can I use to check the interference in LTE?

Thanks

[tpkj]

Hello,

Which counters can I use to check the interference in LTE?

Thanks

RSSI on each antenna port before procesing
and Noise Interference (NI) of each RB in the cell 20MHz spectrum is 100 of NI of RB after processing.

[javierinfante]

Hi, it is solved now, when we have or suspect external interference we send a request to the government telecom department and they make a survey.
this time they found that the source was a radio equipment installed in a truck, after the radio was switched off the interference disappear.