Uplink Interference Complain: What information should be reported

[makeev]

Dear Experts

We have a complaint from border where another country operator is complaining of interference from our side affecting thier 1900 UMTS uplink. They have provided us with all scans and noise floor level is high. Reportedly, from the report they are claiming that they are receiving interference via sea. Distance between our border and their is approximately 500 Km.

My question is since they have only given Lat,Long of interference location which points to middle of sea, what information should i request from them to identify if interference is coming from our end. e.g. System identification, Cell ID and any other information that can be asked from their side to help me identify and validate their complain.

Regards

[Philippe]

Hello,

Which system are you using in their UMTS 1900 uplink band? UMTS, CDMA, GSM?

[makeev]

UMTS, they are complaining that their 1900 uplink has high interference originating from our side, a sea border of about 500 KM from their location.

[Philippe]

So your UMTS Uplink interfering their UMTS uplink? I would rather believe interference produced by another downlink system using their uplink band.

[makeev]

No, the complaint is that in their 1900 band they are receiving interference and it seems to come from our side. They have not mentioned any further details so i need to ask them to provide us exact details such as triangulation of location, cell id they are seeing, i want to ask experts here what other information/details should be asked so we can do a trace, as interference is faced on their side so i dont have a way of checking via spectrum analyzer or drive test.

[Optimustron]

Makeev, first one, 500 km is very long away in order to produce interference but you can thing about ducting because of presence of sea, although it is a rare phenomenon it may occur, I recommend you do the following:

1. For coordinates you need ask what projection they are using and what map datum, because you can be using WGS84 and they can be using a local projection for their system or conversely, that can explain why the coordinates points in the middle of the sea, then they or you need to convert from one system to another and plot again.
2. Ask him wich band of 1900 Mhz in order to see if that band is above or below your band, by the way wich is your band you don't specify that because it can explain the interference and if you have a very powerful sector with high gain antennas at very high altitude at your side.
3. Ask him too for at least one site coordinates, if the area of interference is large ask for 3 sites, a far left site, a middle site and a far right site, this is in order to check what of your sites are facing directly to that zone, you can ask to for the severity of the interference of this three sites in order to have a very good picture.
4. With the data of the two items above you can make a better analysis and shut down your sector or sectors in order to see if they are causing that interference but you need to ask him at that moment if the interference goes away, if not maybe is another system.
5. If you are using the same band then is very strage because in the uplink then your mobiles are transmiting at very high power, 5, 10, 20 watts and that doesn't exist, right?, of course maybe someone in a boat can have a repeater a very powerful repeater but they need to be all the time in the sea and that almost doesn't happen, but they can have a routine to go sea and then the interference appears in the side of the operator.

Excuse me for all the items but is only to check what can you do, maybe you do that before, however I hope this can help you,

[makeev]

Thankyou so much, your response has been extremely helpful, the complain is of interference in 1.97 to 1.98 GHz band.

[dekili]

Hi,

if you are talking about 500km in distance it is impossible to create interference. Pure LoS loss is 153dB. So, based on the noise floor, you can evaluate roughly what is the radiated power at your side. You are all using UMTS in accordance with ITU regulations so it would be that your uplink is causing interference to their uplink? Obviously, they might gave you wrong coordinates or it is caused by some other system. Even UMTS repeaters would transmit in downlink a per ITU recommendations and would not cause interference. Regulator from your country an that country should already coordinated frequencies and powers that are used close to borders. That would eliminate interference for such long distances for sure. Can they identify cells that are causing interference? How they had eliminated option a this might be some higher harmonic from signal from some vessel or other maritime system?Such systems operate with higher powers in order to compensate loss and to provide long range. Also, it might be a radar on the boat (ship). I would be a pulse signal, short duration, wide spectrum, high average power. Ask them how they had eliminated all these else options and came directly o UMTS.

[webkasperl]

Hi,
They should be able to provide some screenshots form a spectrum analyzer where they can show that the interferenc is really a 5 MHz downlink WCDMA carrier you are using. But I cannot imagine that you interfere theme at a distance of 500 km as some more experienced people than I stated already before.
Regards