differences between co-BCCH & co-BSIC interference

[kahnoie]

what are the differences between co-BCCH & co-BSIC interferences?

[zlobster]

what are the differences between co-BCCH & co-BSIC interferences?

You have co-BCCH interference is you have two or more co-BCCH ARFCNs with common serving area (sometimes this area is not that obvious). You can easily check this with a drive test. Set the scanner to decode BSICs at -100dBm or so.

Co-BSIC interference? Hmm, maybe you mean co-BCCH cells having the same BSIC? Which if true, is the worst case scenario. The BSICs are used to differentiate two cells with the same BCCH ARFCN, so the UE would know for sure to which cell it has camped on.

If you have two or more cells with not co- or adjacent BCCH ARFCNs then it's perfectly fine to have the same BSICs. Which I think should be avoided too, since you have many options for different BSCIs (64 if memory serves me right).

BTW, do you share a common RF spectrum with another operator or sub-network?

Hope I was clear.:p

[kahnoie]

If I understand correctly co-BISC interference should also be co-channel or adj-channel while co-BCCH interference can be from same BCCH corresponding to different BSIC, rite?
I did not understand "Set the scanner to decode BSICs at -100dBm or so."
Why at -100 dBm?

I have another question related to interference:
http://www.finetopix.com/drive-test/19518-actix-interference-analysis.html

[leteo]

Co BCCH, different BSIC : Maybe OK, just poor quality => SD drop, call drop,... => poor KPI.
Different BCCH, co BSIC : OK.
Co BCCH and Co BSIC : Not OK because UE can not distinguish which cell it belongs to :lol :handshake :victory:

[zlobster]

As for the term 'co-BSIC' interference, I don't think it's an interference at all. Yes, it can thrash your network performance, but it's not interference at all, like it's with RF interference.

Basically, same BSICs should be avoided on co- AND adjacent BCCH ARFCNs (but only on cells having the same serving area), otherwise will cause you a heap of trouble. It's perfectly fine to have co-BSIC co-BCCH cells which are 100km away (assuming the propagation loss is enough).

As for the scanner, if your RF scanner is calibrated well, -100dBm as a BSIC decoding threshold should show you where you may have RF conflict. The value itself is derived from my practice. I know that the specs and calculations would produce another value, but believe me, many cases I've seen co-BCCH at -100dBm is enough to deteriorate the RX quality severely.

OMG, it's hard even for me to understand what I just wrote. :eek:

Anyway, let me know if you can't get something.

[zlobster]

Co BCCH, different BSIC : Maybe OK, just poor quality => SD drop, call drop,... => poor KPI.
Different BCCH, co BSIC : OK.
Co BCCH and Co BSIC : Not OK because UE can not distinguish which cell it belongs to :lol :handshake :victory:

I would also advice to avoid adj-BCCH, co-BSIC. See the spectral mask of the burst as per spec for more clarification.

[kahnoie]

I got it now. You mean to say that -100 dBm is the minimum level to start taking interference into consideration, ie. if the interferer is at -100 dBm it is sufficient to cause interference.rite?
I would agree with this for co-channel interference.

But for adjacent channel interference, If the difference between the signal levels of the victim and interferer is > 6 dB then you can ignore it and the interference will not be significant. Is this true?

[zlobster]

I got it now. You mean to say that -100 dBm is the minimum level to start taking interference into consideration, ie. if the interferer is at -100 dBm it is sufficient to cause interference.rite?
I would agree with this for co-channel interference.

But for adjacent channel interference, If the difference between the signal levels of the victim and interferer is > 6 dB then you can ignore it and the interference will not be significant. Is this true?

As for the first statement - yes, you got me right.

As for the second - I'd rather disagree, this value of 6dB is quite optimistic. I've seen interferer being 13dB less than the 'victim' but still causing bad quality. I was able to decode the interferer's BSIC (adj. BCCH) at 13dB less than the 'victim' and after a RF retune the things got just excellent. But once again, that's just from my experience. :rolleyes: