PDA

View Full Version : Concentric cell issue



plannerguy
2010-01-20, 03:39 PM
Dear all


i am facing a problem with concentric cells, in my network i have both 900 an 1800 frequencies , 900 in outer cell and 1800 in inner cell.
normal configuartion is 4 trx in 900 and 2 in 1800 band . so after the 1800 TRx added the quality or 900 hopping TRx goes week.which earlier was having good quality.


experts please through your inputs over the same .

Regards
Plannerguy

RF engineer
2010-01-20, 05:13 PM
Dear all


i am facing a problem with concentric cells, in my network i have both 900 an 1800 frequencies , 900 in outer cell and 1800 in inner cell.
normal configuartion is 4 trx in 900 and 2 in 1800 band . so after the 1800 TRx added the quality or 900 hopping TRx goes week.which earlier was having good quality.


experts please through your inputs over the same .

Regards
Plannerguy
what type of Hopping you are using it and after expansion the traffic still is high in 1800 or now pushing to 900
BR
RF

punto
2010-01-20, 09:49 PM
@plannerguy :)

... :( could be vendor related problem/solution, pls state the vendor ... P:)

plannerguy
2010-01-21, 05:43 PM
i am using 1*1 hopping, calls getting pushed to 1800 ...and now issue with 1800 Trx KPIs....

i am using siemens network.....


Regards
Plannerguy

RF engineer
2010-01-22, 01:03 AM
i am using 1*1 hopping, calls getting pushed to 1800 ...and now issue with 1800 Trx KPIs....

i am using siemens network.....


Regards
Plannerguy
I really can not get it what you mean .
BR
RF

kokoeg
2010-01-22, 04:42 AM
I was having a problem like this in my network, and after investigation we found cross sectors in DCS. So the Az of GSM TRX and DCS TRX were different.

plannerguy
2010-01-22, 02:09 PM
Dear RF


900 hopping TRXs quality is bad and 1800 trx quality is good.also 900 BCCH quality is good.for eaxample

Bcch---95%
TRx1---84%
TRx2---82%
Trx3---78%
TRx4--94%(1800 band)
TRx5---97%(1800 Band)

Regards
Plannerguy

RF engineer
2010-01-22, 05:14 PM
Dear RF


900 hopping TRXs quality is bad and 1800 trx quality is good.also 900 BCCH quality is good.for eaxample

Bcch---95%
TRx1---84%
TRx2---82%
Trx3---78%
TRx4--94%(1800 band)
TRx5---97%(1800 Band)

Regards
Plannerguy
May be you have cells shooting to this cell after expansion or the power for TRXs change incidentally make drive test and see what happen.
BR
RF

plannerguy
2010-01-22, 05:33 PM
hi

checked with drive test, but nothing major changes observed, also no overshooting sectors sectors.....





Regards
Plannegruy

RF engineer
2010-01-22, 07:05 PM
[QUOTE=plannerguy;66242]hi

checked with drive test, but nothing major changes observed, also no overshooting sectors sectors.....





Regards
Plannegruy[/QUOTE
In this case you have to do test per TRX you have to lock the second and third TRX and make test see what you have in TRX1 then lock TRX1&3 to see performance for TRX2 and as for TRX3 may be one of TRX not functioning .
BR
RF

plannerguy
2010-01-22, 09:12 PM
hi

i have checked this by call testing in each TRx and quality found to be bad in all .

if i lock 1800 TRx then 900 TRx works fine ie quality increase.


Regards
Plannerguy

RF engineer
2010-01-22, 09:46 PM
hi

i have checked this by call testing in each TRx and quality found to be bad in all .

if i lock 1800 TRx then 900 TRx works fine ie quality increase.


Regards
Plannerguy
really is strange i think may be your 1800 TRXs create intermodulation interference in 900 band frequency check for any wrong connection in cell
BR
RF

plannerguy
2010-01-25, 11:34 PM
i am sorry i didnt get the point ,intermodulation interference?,

1)how can 1800 frequencies distrurb 900 band?.

Regards
Pannerguy

RF engineer
2010-01-26, 12:37 AM
i am sorry i didnt get the point ,intermodulation interference?,

1)how can 1800 frequencies distrurb 900 band?.

Regards
Pannerguy
This is just assumption i know technically is impossible but no one know this is equipment check if you idle band interference increase or not.
BR
RF

plannerguy
2010-01-27, 03:39 PM
sure ......

i shall check

but if 1800 causes interfernce in 900 then BCCH freuqency should also be interfererd no?....but this not happening and qulaity of Hopping TRx only degraded



Regards
Plannerguy

RF engineer
2010-01-27, 05:26 PM
As you know BCCH is working with full power and there is no power control but in the other there is so may be the interference power generated is not in the range of BCCH as for example BCCH power is 43 dBm but power of inter modulation interference is 40 dbm as the power of hopping TRX.
below is small description of intermodulation
BR
RF

plannerguy
2010-01-27, 09:51 PM
thanks

i shall check the same, is it possible to check the same with spectrum analyser


Regards
Plannerguy

justdream
2010-06-22, 05:05 AM
sorry experts,
can you kindly tell me what's the technical meaning of concentric cells?

banisha
2010-06-22, 06:18 AM
sorry experts,
can you kindly tell me what's the technical meaning of concentric cells?

This is a cell that has two zones (inner and outer zone) on same azimuth. Inner is usually 1800 band with smaller coverage, and outer is usually 900 band with bigger coverage.

Maybe the image explains it a little better (f1 is 1800 band, f2, f3 are 900 band).

Cheers

http://www.********.com/General/Reports/Tech_Dev/CE30196P/diag.gif

kevin_h811
2010-06-22, 01:04 PM
Hi Plannerguy,

Have u made some trial and error of your parameter setting, which is Traffic Threshold of Underlaid Subcell, may be the distribution of traffic is not balance between your 900Mhz and 1800 Mhz band...

Regards//

plannerguy
2010-06-22, 07:05 PM
Hi

have Tried over the parameter HORXLVDLI and HORXLVDLO but then also no changes..


Regards
Plannerguy

kevin_h811
2010-06-23, 02:36 PM
Hi PLANNERGUY,

May I know what is the transmission type. Is this microwave link or leased line?

Regards//

plannerguy
2010-06-23, 07:29 PM
Hi

its Microwave link



Regards
Plannerguy

justdream
2010-06-24, 05:53 PM
This is a cell that has two zones (inner and outer zone) on same azimuth. Inner is usually 1800 band with smaller coverage, and outer is usually 900 band with bigger coverage.

Maybe the image explains it a little better (f1 is 1800 band, f2, f3 are 900 band).

Cheers

http://www.********.com/General/Reports/Tech_Dev/CE30196P/diag.gif


Thanks a lot, kindly help me to understand the following:
in your picture, there's a comment F1 (Source of co-channel interference)!!! what does it mean?

Secondly, what's the difference between concentric cell and Dual band site that has one antenna transmitting GSM and DCS