LTE causing High RTWP and UL Quality degradation

[justdream]

Dears,

Have you ever faced cases for High RTWP in 3G cells and UL Quality degradation in 2G cells after activation of LTE!
I've for some cells, looking forward to hear from you about the suspected causes !

[b0r3l_1]

Hi Mate

Give us more details of your network. What freq are you using and your LTE, is it FDD or TDD?

[justdream]

Hi Mate

Give us more details of your network. What freq are you using and your LTE, is it FDD or TDD?

it's FDD, Band 3

[perimedes]

Hi,

The best way to check it if there is interference from LTE, is use a spectral analyzer in order to check the complete downlink band for power emissions. The LTE 'firm' has a clear shape of a table along the occupied bandwith (normally 10, 15 or 20 MHz). If you see frequency coincidence over GSM pilots (very common on Band 3) then you've got it. The uplink band will have got interference over the 2G uplink created from the LTE uplink UE's. The 3G high RTWP could have the same origin, though 3G over band 3 isn't so common.

The solution will be to reduce the allocated LTE bandwidth or refarm the band, to avoid interference.

Annexed is a capture of a chunk of 20 MHz from band 3, where it is easy to pin a 15 MHz LTE 'firm' out, and two interfered GSM1800 pilots on the lower LTE band.

Regards

[justdream]

Hi,

If you see frequency coincidence over GSM pilots (very common on Band 3) then you've got it.
The uplink band will have got interference over the 2G uplink created from the LTE uplink UE's.

Annexed is a capture of a chunk of 20 MHz from band 3, where it is easy to pin a 15 MHz LTE 'firm' out, and two interfered GSM1800 pilots on the lower LTE band.

Regards

Dear Friend,
Please Which Freq. could be coincidence over GSM and LTE Band 3
and I didn't get your annexed capture (did you attach)

[perimedes]

Sorry, something was wrong. Here it is the capture.

[justdream]

Experts,

Any Idea! from your practical experience.

Could RTWP increase shown in 3G after LTE activation be because of wrong installations/ Antenna - hardware configurations, etc
as it observed in high number of 3G sites

[linhhy]

Experts,

Any Idea! from your practical experience.

Could RTWP increase shown in 3G after LTE activation be because of wrong installations/ Antenna - hardware configurations, etc
as it observed in high number of 3G sites

What frequency are you using for 2G and 3G? What 3G'frequency is interference ?

[justdream]

Dears,

Any update
any previous experience about UMTS degradation (all carriers) after LTE Integration !

[sak2e]

Hi,

Do you used one feeder for LTE & 3G or LTE & 2G ? maybe this high RTWP coming from wrong feeder installation, so 2 tech with same freq in one feeder caused high interference.

BR


Dears,

Any update
any previous experience about UMTS degradation (all carriers) after LTE Integration !

[DENIOL]

Give us more details of your network. What freq are you using and your LTE, is it FDD or TDD?

[javierinfante]

Hello:
I had the same problem as you are facing now and in fact the interference was there.
I tell you what I have done:
1st: Check that the configuratin was correct, when the LTE was impletmented also TMA was installed, due to the use of the same antenna we needed to use external combiners and to avoid the attenuation we install TMA. In many cases the field engineers forgotten to set the RXBRANCH attenuation after the TMA addition.
2snd: To confirm that there is external interference activate the NBIS in the affected Ucell, if there is external interference you will see that the RTWP immediately decrease.
3rd: If the RTWP is still hight after activation of the NBIS then the interference is internal, the fastest way to check is just block/deactivate all GSM, Ucell, LTE cells in the site but the one you are investigating, and then you will see that the RTWP improve, after that just go step by step unblocking/activating cell by cell till you see the RTWP increase again and you have found the interference cell/freq.

[justdream]

Hello:
I had the same problem as you are facing now and in fact the interference was there.

1. what's the value you have used for RXBRANCH
2. sorry what's NBIS, how could I activate

[javierinfante]

Hello:
The attenuation in the RXBRANCH depends of the TMA used, 12db TMA or 24db TMA, if you have confirm that the TMA is present using the SCN ALD, then just set the att acording to that.
what I use to do is to set the RXBRANCH attenuation to 18 in the case of 12db gain TMA or 41 in the case of 24 gain TMA, just asume a 3db loss due to cables, connecotrs,,etc, later i use to set the most precise value. Remenber the att in the RXBRANCH command comes in 0.5 db unit.
The NBIS stand for narrow band interference supression, you can find this command in the MOD ULOCELL, ON or OFF, BEFORE TO SET IT TO TRUE YOU HAVE TO ACTIVATE THE LICENSE.
If your interference is very high this command will improve your throughput, but you have to solve the interference problem because this feature has an impact in the customer side, dont keep it active and forget about the interference. The NBIS is just a temporal solution while you are investigating the problem.