- This topic has 19 replies, 1 voice, and was last updated 12 years, 7 months ago by pix.
18th July 2008 at 12:27 #53154AlexGuest
In some cases I see adjacent frequecies of BCCH frequency by TEMS pocket which is whitout any Cell ID.When I lock on these frequency,MS couldn’t find the network.Also RxLev of them are very good.
My question is :
1-Why there is such this adjacent freauency?
2-If it is because of a faulty in hardware,which part of RBS may cause it?
Thanks18th July 2008 at 18:23 #53155pixGuest
TEMS can measure the adjacent frequencies of the serving frequency. It will just measure the RXLEV, not taking care about which cell uses this frequency (as far as i know !).
When you lock on this frequency, you should be to camp on it and setup a call … if this is a BCCH frequency !
Are you sure it’s BCCH ?
If it is BCCH, then which cell is it ? maybe the cell is too far, or suffer very very bad interference in the area where you try to perform this drivetest.18th July 2008 at 19:21 #53156AlexGuest
Suppose we are near a cell with a TEMS and we know the BCCH of it,for example BCCH=25.
I mean MS not only measures this ARFCN(25)and camps on this cell but also MS measures two adjacent frequencies which are 24 and 26.
There is no any external interfernce.I found it by changing the BCCH (for example to 32) so I could see two adjacent frequencies again (which are 31 and 33).
What is your idea now?19th July 2008 at 08:41 #53157PixGuest
What you are explaining is correct. I don’t really understand your problem 🙂
What do you mean by external interfernce ?
Adjacent channels will interfer the BCCH 25 only if they are received 6 to 9dB stronger than the freq. 25.20th July 2008 at 04:32 #53158resonanceGuest
if interference is high than you r not able too decode the bsic of any particular bcch and you will not be able to make call on that bcch. is that explain your problem20th July 2008 at 17:30 #53159AlexGuest
I mean two adjacent frequencies(ARFCN-1,ARFCN+1)of BCCH frequency(ARFCN)propagate from antenna so I can visit them by TEMS but I couldn’t camp on.
I guess there would be a problem with Antenna or RBS(but I don’t know which part of RBS also).
this site is a stand-alone site and there is no any interference around it.20th July 2008 at 20:04 #53160rf fanGuest
Frist you must check your measurement equipment. May be you phones are broken …
If everything is OK and this happening only few BTS’s , may be there is a problem with BCCH TRX. (Bad RF fiter or someting else).
Do you have declared adjacent’s with ARFCN +/- chanel on this cell ? If you don’t have, but your phone measure ARFCN +/- , problem is clear 🙂22nd July 2008 at 13:20 #53161pixGuest
alex, can you give some numerical values :
if there is no other GSM cells than this cell, then there are three possibilities :
– external interferer (army radars ?)
– faulty BTS (leaky rf filter, as suggested by rf fan)
– faulty TEMS (or TEMS with undesired behaviour, to be politically correct…)23rd July 2008 at 11:00 #53162AlexGuest
Thanks rf fan and Pix,
I am sure that problem comes from faulty RBS because I changed the BCCH number but the situation was the same.
By the way,Which part of RBS may cause this peroblem?
Alex23rd July 2008 at 13:41 #53163rf fanGuest
I suspect BCCH TRE – but next step (if this doesn’t resolve problem) are to replace ANC ….23rd July 2008 at 13:51 #53164pixGuest
i’ll not answer any other question if you don’t give me the rxlev values 😀
but i’m surprised that radio frequency leaks so strongly on adjacent channels… that’s why i’m asking the values..
when you check out other BTS, the adjchannels are weaker ?23rd July 2008 at 15:32 #53165AlexGuest
Suppose I am under BTS and measuring the BCCH’s frequency,so results are as belew:
BCCH Freq.(ARFCN=25) ….RxLev=-37 dbm
Adj1 Freq.(ARFCN-1=24)…RxLev=-41 dbm
Adj2 Freq.(ARFCN+1=26)…RxLev=-40 dbm
What do you mean about “ANC” ?23rd July 2008 at 17:10 #53166rf fanGuest
Combiner + Equalizer + SomeFilters and control blocks in our vendor is in Block called “ANC”.
Wich is your vendor ?24th July 2008 at 06:07 #53167AlexGuest
Hi rf fan,
Ericsson is vendor here.24th July 2008 at 07:18 #53168PixGuest
ANC meanss Antenna Network Combiner (in alcatel-lucent).
Thx for the values… interesting problem.
Have you activated the SFH perhaps ?