High RTWP vs. External interference
1
- RTWP: Receiving Total Bandwidth Power of the cell.
-Counters: VS.MeanRTWP = average value.
(Also VS.MaxRTWP, VS.MinRTWP = peak values).
- “Uplink (UL) interference might cause an increase in the Received Total Wideband Power (RPWP) of NodeBs.
Some interference comes from internal factors, such as equipment fault or improper installation. More
interference, however, comes from external factors.
Actually, the background noise at the antenna port of the NodeB ranges from -106 dBm to -103 dBm.
If the cell load increases, the RTWP also increases. When the load reaches 50% of the capacity, the
background noise increases 3 dB. When the load reaches 87.5% of the capacity, the background noise
increases 9 dB”.
SUMMARY:
Normal values of average RTWP should be between -100dBm and -110dBm.
If values are > -100dBm (ex: -90, -80, -70dBm) a problem exists and can be due to:
external interference or internal factors such as Hardware problems, boards, connectors,
antenna, cable, setting gain and Rx attenuation…or also traffic increasing.
2
In the current 3G network, there is a problem of drop calls when the
interference in the Uplink interference is raised due to internal UE or external
interference.
-Finding the problem:
-M2000 counters: VS.MeanRTWP between -100dBm and -110dBm is correct
but > is a problem.
Drop call increases?, traffic increasing at same time?
- M2000 alarm: Rx Branch RTWP Difference too High,
Average RTWP value of main(Unit: 0.1dBm), Average RTWP value of diversity(Unit: 0.1dBm)
Possible Causes: External interference occurs to the main antenna and diversity
antenna.
-Knowing the region: possible jammers? Mosque, military area, government
buildings… Satellite dishes, Operators… Also interference in 2G (different band
but same aim to interfere communications)?
- Others:
Nodeb LMT trace. Starting Nodeb LMT trace, the real time RTWP (main, diversity) can be
observed. But there are some limitation of the number of cells that can be traced
simultaneously.
Use RRU as a spectrum analyzer to scan a wide range frequency. But to do this, the
service of this cell will be interrupt.
3
- RTWP network checking:
Study for RTWP (uplink Received Total Wideband Power) for the days 25th (friday) and 29th (tuesday) the whole days
and period reporting 30min from M2000.
About the result, cells with RTWP worst than -100dBm, but then filtered for cells worst than -95dBm because there
were lots of them and wasn't high interference, and also checked the number of times with this value over -95dBm
(number of times related to 30 minutes reporting period).
We have 59 cells with >= 3 hours in total two days with RTWP>-95dBm.
And we have 2384 reporting periods (1192 hours) in two days with cells RTWP>-95dBm.
O bject N am e
S tart T im e
P eriod O bject N am e
29/09/2009 14:30:00
29/09/2009 15:30:00
29/09/2009 15:00:00
29/09/2009 14:00:00
29/09/2009 16:00:00
29/09/2009 04:00
29/09/2009 07:30:00
29/09/2009
29/09/2009
29/09/2009
29/09/2009
29/09/2009
00:30:00
01:00:00
00:00:00
05:00:00
03:30:00
29/09/2009 07:00:00
29/09/2009 20:30:00
29/09/2009 21:00:00
29/09/2009 08:00:00
29/09/2009 20:00:00
29/09/2009 01:30:00
29/09/2009 19:00:00
29/09/2009 21:30:00
29/09/2009 19:30:00
29/09/2009 02:00:00
29/09/2009 03:00:00
29/09/2009 06:30:00
29/09/2009 23:00:00
29/09/2009 22:30:00
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
30
V S .M eanR T W P
RIKTH02/Cell:Label=ESNNHT34011T-135171, CellID=35171
RIKTH02/Cell:Label=ESNNHT34011T-135171, CellID=35171
RIKTH02/Cell:Label=ESNNHT34011T-135171, CellID=35171
RIKTH02/Cell:Label=ESNNHT34011T-135171, CellID=35171
RIKTH02/Cell:Label=ESNNHT34011T-135171, CellID=35171
R P S K H 02/C ell:Label=ILK M Y D 55621T -261202, C ellID =61202
RPSKH02/Cell:Label=ILKMYD55621T-261202, CellID=61202
R P S K H 02/C ell:Label=ILK M
R P S K H 02/C ell:Label=ILK M
R P S K H 02/C ell:Label=ILK M
R P S K H 02/C ell:Label=ILK M
R P S K H 02/C ell:Label=ILK M
Y D 55621T -261202, C ellID =61202
Y D 55621T -261202, C ellID =61202
Y D 55621T -261202, C ellID =61202
Y D 55621T -261202, C ellID =61202
Y D 55621T -261202, C ellID =61202
RPSKH02/Cell:Label=ILKMYD55621T-261202, CellID=61202
RPSKH02/Cell:Label=ILKMYD55621T-261202, CellID=61202
RPSKH02/Cell:Label=ILKMYD55621T-261202, CellID=61202
RPSKH02/Cell:Label=ILKMYD55621T-261202, CellID=61202
RPSKH02/Cell:Label=ILKMYD55621T-261202, CellID=61202
R P S K H 02/C ell:Label=ILK M Y D 55621T -261202, C ellID =61202
RPSKH02/Cell:Label=ILKMYD55621T-261202, CellID=61202
RPSKH02/Cell:Label=ILKMYD55621T-261202, CellID=61202
RPSKH02/Cell:Label=ILKMYD55621T-261202, CellID=61202
R P S K H 02/C ell:Label=ILK M Y D 55621T -261202, C ellID =61202
R P S K H 02/C ell:Label=ILK M Y D 55621T -261202, C ellID =61202
RPSKH02/Cell:Label=ILKMYD55621T-261202, CellID=61202
RPSKH02/Cell:Label=ILKMYD55621T-261202, CellID=61202
RPSKH02/Cell:Label=ILKMYD55621T-261202, CellID=61202
-66,598
-66,657
-66,702
-67,253
-68,878
-70,054
-70,53
-70,535
-70,552
-70,608
-70,608
-70,686
-70,704
-70,719
-70,744
-70,815
-70,875
-70,969
-70,975
-70,989
-71,011
-71,064
-71,101
-71,152
-71,155
-71,159
RKRPH01/Cell:Label=HAYDAR34921T-132122, CellID=32122
RPSKH01/Cell:Label=OGULTU06111T-244971, CellID=44971
R P S K H 02/C ell:Label=ILK M Y D 55621T -261202, C ellID =61202
R P S K H 02/C ell:Label=ILK M Y D 55931T -261203, C ellID =61203
R P S K H 02/C ell:Label=M E C D Y E 55511T -260061, C ellID =60061
R P S K H 02/C ell:Label=M E C D Y E 55721T -260062, C ellID =60062
RPSKH02/Cell:Label=TURKAL60011T-261031, CellID=61031
RPSKH02/Cell:Label=ILKMYD55311T-261201, CellID=61201
R M D P H 01/C ell:Label=H A S S E V 68211T -4621, C ellID =621
RPSKH01/Cell:Label=ESATBA06111T-244441, CellID=44441
RPSKH02/Cell:Label=TURKAL60831T-261033, CellID=61033
RPSKH02/Cell:Label=KIRAZD05821T-260412, CellID=60412
RPSKH02/Cell:Label=SIVASC60221T-261002, CellID=61002
RPSKH02/Cell:Label=SIVASC60531T-261003, CellID=61003
R G A Z H 01/C ell:Label=A LY B C R 35011T -314901, C ellID =14901
RPSKH02/Cell:Label=PATNOS04931T-248053, CellID=48053
R M D P H 02/C ell:Label=C P IN A R 63311T -453331, C ellID =53331
R P S K H 02/C ell:Label=S IV A S C 60011T -261001, C ellID =61001
RKRPH02/Cell:Label=BSANAT16B31T-149753, CellID=49753
R M D P H 01/C ell:Label=B R JLS E 01011T -456791, C ellID =56791
R M D P H 01/C ell:Label=B R JLS E 01221T -456792, C ellID =56792
R P S K H 02/C ell:Label=V E Z IR T 55311T -260171, C ellID =60171
RPSKH02/Cell:Label=BOYBAT57111T-260941, CellID=60941
RANTH01/Cell:Label=ORUCIS03831T-313023, CellID=13023
R M D P H 01/C ell:Label=V A LILK 02111T -457391, C ellID =57391
RPSKH02/Cell:Label=AMASDP05621T-260442, CellID=60442
RPSKH02/Cell:Label=CARSMT55011T-260021, CellID=60021
4
Number of 30min times >95dBm in 2 days
max possible 96
96
96
96
96
96
96
96
91
90
90
86
74
67
67
58
58
54
51
48
48
48
48
41
38
31
31
31
Example 1:
One of the cells in Antalya (CI 10662) seems to have this problem. RTWP value is over -95
dBm all the time, and sometimes alarm “RF Module Rx Branch RTWP Difference Too High”
appears. Traffic is not high.
5
Example 2:
In Aegean region, 4 suspicious cells:
-1490-AlaybeyCarsi. cell: 14903 Suspicious behaviour is known, after SSV a probable ext.
interferer was reported by Huawei and each hw equipment were examined several times.
Max and Mean RTWP are usually quite high without correlating to traffic. Further
investigation is ongoing we need a test with spectrum analyser.
-1720-BahcelievlerTT. cell 17203, 1562-SirinyerMerkez. Cell 15621 and 1454ManisaAlaybey Cell 14543.
"RF module RX Branch RTWP difference Too High" alarms are present on each sites
frequently. Also mean. min and max RTWP values are too high frequently without
significant correlating to traffic. We are indicating this sites to local Huawei team for HW
checking and further examination!
Always from 10am to 1am
6
Example 3:
Ankara region:
- CI 44971 decreases a bit at 12.30h and 15.30h but always high and constant.
Sector 2 always peaks at 12.30h, 16h and 18.30h. Sector 3 ok. No alarms.
- CI 44441 always constant at -90dBm:
7
Example 4:
Karadeniz region:
- CI 61201,2&3: always very high at -80 and -70dBm but from 8h to 18.30h (working hours) decreases
S1&2. (RET alarms and other several, but not seem conncected).
- CI 60061&2: allways high at -85 and -90dBm.
8
- How to mitigate the CDR problem while finding
source?
-Accelerate cell level HHO3G2G (calls go quickly to 2G and avoid drop
call from interference).
Example (but could be an intermediate set not so aggressive):
INTERRATCSTHD2DECN0 -4
INTERRATCSTHD2FECN0 -2
INTERRATCSTHD2FECN0 -70
INTERRATCSTHD2FRSCP -50
-Decrease PCPICHPOWER (coverage area is smaller and now
interference doesn’t affect the cell, but some customers without
coverage).
-Increase Downtilt (coverage area is smaller and now interference
doesn’t affect the cell , but some customers without coverage).
9