-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
1/54
Huawei Confidential. All Rights Reserved
OMF000403
GSM Interferene Anal!sis
ISS"# $.0
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
2/54
2 Internal Use
To introduce affection brought by
interference to the GSM system, fault
location method and troubleshooting
method, this course hereby lists out
the possible interference sources, and
offers description of cases to facilitate
fault location and troubleshooting.
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
3/54
3 Internal Use
O%&etivesO%&etives
Upon completion this course, you will be
able to
Understand the cause of interference andmaster the method of locating the
interference source!
Master the method of o"ercoming
interference.
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
4/54
# Internal Use
Chapter 1Ch
apter 1 OverviewOverview
Chapter 2 Location and Clearance of Interference
Chapter 3 Case Analysis
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
5/54
$ Internal Use
Affetion of InterfereneAffetion of Interferene
%hen there is interference in the networ&, the subscribers usually encounter the
following phenomenon The subscriber cannot hear the "oice , and the bac&ground noise is too loud.
%hen fi'ed telephone subscriber calls MS subscriber, or MS subscriber calls fi'ed
telephone subscriber, call drop occurs after (du, du , du) is heard.
The con"ersation cannot be carried on smoothly, and call drop often happens.
%hen interference e'ists in the networ&, from the result of traffic statistic, there are
some characteristic as following.
There are *e"el #+*e"el $ interference band in T- measurement function , and
the measurement "alue is more than .
ongestion rate is comparati"ely high.
The call drop rate is higher than other cells.
The hando"er success rate is low.
Through /ri"e Test, it is found that
It is difficult to hando"er .
The 0' le"el is high, but the 1uality is bad.
Through tracing the bis interface signaling with signaling analyer
4M56725$8, it is found that the bit error rate is higher than other cells.
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
6/54
9 Internal Use
Classifiation of Interferene SouresClassifiation of Interferene Soures
'atural 'oise
tmosphere noise
Gala'y noise
Solar noise 41uiet period8
Man()ade 'oise
Interference of ignition systems of "ehicles or other engines
Interference of electronic communication system
Interference of power line
Interference of scientific research, medical and household appliances
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
7/54: Internal Use
Main Interferene Soures Affeting Mo%ile Co))uniationMain Interferene Soures Affeting Mo%ile Co))uniation
Internal interference
T0; fault if the performance of T0; is reduced due to manufacture
cause or application, which will cause self
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
8/54? Internal Use
Main Interferene Soures Affeting Mo%ile Co))uniationMain Interferene Soures Affeting Mo%ile Co))uniation
0epeater interference
s the installation of repeater is non standard, causing insufficient
isolation between the donor antenna and the subscriber antenna, so
self
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
9/54A Internal Use
Main Interferene Soures Affeting Mo%ile Co))uniationMain Interferene Soures Affeting Mo%ile Co))uniation
B'ternal interference
Interference of other communication e1uipment with high power
0adar station @rom :5s+?5s of the 25th century, the fre1uency used by
the decimeter wa"e radar was similar to that of GSM, and its transmitting
power was "ery high, which generally reached tens and hundreds of
&ilowatts, so the out
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
10/545 Internal Use
Chapter 1 Overview
Chapter 2Chapter 2 Location and Clearance of InterferenceLocation and Clearance of Interference
Chapter 3 Case Analysis
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
11/54 Internal Use
*isovering Interferene via OMC +raffi Measure)ent*isovering Interferene via OMC +raffi Measure)ent
*isovering ,otential interferene via traffi statistis result
hec& the ("erage T- busy time 4second8) in T- measurement
function of each cell, the reason is that this inde' can show the T-
mean occupied time 4s)8, which is usually called (T- mean holding
time) in the =S of other manufacturer), within the measurement period.
If it is found that the "erage T- busy time 4second8 of certain cell is
comparati"ely short 4such as less than 5s8, then maybe there is strong
interference in the cell, causing that hando"er6call drop happens due to
bad 1uality after T- channel occupied to MS.
ertainly, if hardware fault occurs in certain T0; 4non
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
12/542 Internal Use
*isovering interferene via handover data*isovering interferene via handover data
%hen certain cell initiates hando"er, if the a"erage recei"ing 1uality 4uplin&8
is # 4this is true when there is no fre1uency hopping, if there is, it shouldbe $8, and the mean recei"ing le"el is 2$4
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
13/543 Internal Use
*isovering ,otential interferene via all dro, inde-*isovering ,otential interferene via all dro, inde-
If the call drop times of certain cell is rather higher the the other with same
traffic load, and the main cause of call drop is owning to connection fault,then it is possibly caused by interference.
If the a"erage recei"ing le"el during call drop is comparati"ely high 42$8,
while the a"erage recei"ing 1uality le"el is 9, then the cell should be listed
into the interference source.
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
14/54# Internal Use
*isovering ,otential interferene via interferene %and*isovering ,otential interferene via interferene %and
=TS will utilie an idle TS in a frame to scan the uplin& fre1uencies of the
fre1uencies used by T0;, and then ma&e measurement to the le"el $interference band. The default setting of interference bands in =S of
-uawei is as follows 5, 5$, A?, A5, ?: and ?$ 4unit
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
15/54$ Internal Use
OMC Alar) and Su%sri%er Co),laintOMC Alar) and Su%sri%er Co),laint
Subscriber complaint is also important clew for finding the potential
interference. Information which should be collected from user complaintincludes MS number, MS model, called number and fault phenomenon of
calling side and fault phenomenon of called side and particular fault location,
etc. If the alarm information is more detailed, it will be more easily to find out
the networ& problems.
%hen there is interference in the networ&, the direct feelings of the
subscriber may be hea"y noise, both parties or either party cannot hear
each other clearly, call drops and call cannot be put through, etc. Thus, when
many subscribers within the same area complain the same problem, then
wor& should be done to chec& whether there is interference in the area.
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
16/549 Internal Use
*isovering Interferene via *rive +est*isovering Interferene via *rive +est
there are two /ri"e Test methods a"ailable idle mode test and dedicated
mode test. Under the idle mode, the test e1uipment can measure the signal le"el of
both ser"ing cell and ad>acent cell. In addition, the e1uipment can also
perform fre1uency scanning test to the specified fre1uency or fre1uency
band.
Under dedicated mode test, the test e1uipment can measure the signalle"els, recei"ing 1ualities, power control registrations and time ad"ance, etc.
of both the ser"ing cell and ad>acent cells. %hen high le"el 4358 and low
1uality 40'EFual98 remain in certain section, it can be concluded that
interference e'ists in the section. @urther, part test e1uipment can directly
display the frame elimination rate 4@B08. Generally when the @B0 2$D,
subscribers can feel the discontinuous "oice, that is to say, interferencee'ists in this section of highway.
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
17/54: Internal Use
Reo))ended roedures for /oation andReo))ended roedures for /oation and
Clearane of InterfereneClearane of Interferene
/etermine Interference ell according to 7ey erformance Inde' 47I8
hec& larm of HM
@re1uency lanning hec&
hec& arameter Setting of ell
/ri"e Test
Interference learance
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
18/54? Internal Use
rief introdution to S,etru) Anal!1errief introdution to S,etru) Anal!1er
Spectrum nalyer is a broadband signal recei"er with high performance
which can display the spectrum of the recei"ing signals. The recei"ing signal resolution bandwidth 40=%8 namely the minimum
signal bandwidth the Spectrum nalyer can recognie. The smaller theparameter is, the higher the recei"ing sensiti"ity of instrument.
Input fre1uency the fre1uency range the Spectrum nalyer can recei"e. Sensiti"ity generally the minimum recei"ing le"el with - signal bandwidth
is defined as recei"ing sensiti"ity of the Spectrum nalyer. The recei"ingsensiti"ity of -?$ series Spectrum nalyer can be below
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
19/54A Internal Use
*iretional Antenna*iretional Antenna
/irectional antenna is used for searching interference sources. The stronger
the directionality of antenna is, the higher the antenna gain is. nd the abilityto search will become better. So the logarithm
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
20/5425 Internal Use
+he wa! to +est Internal Interferene+he wa! to +est Internal Interferene
Set the Spectrum nalyer to proper state
@or A55M =TS f5KA52M-,SJK35M-,TTK5,0=%K35&-,=%K35&-!
@or ?55M =TS f5K:$M-,SJK5M-,TTK5,0=%K35&-,=%K35&-. Screw out the connector of output port of /U di"ider, then connect the output signal
of the di"ider to the Spectrum nalyer to carry out a test. If the fractional fre1uency
spectrum le"el is less than L?5d=m, it shows that there is no internal interference! if
more than L?5d=m, it shows that /U or T0; inside =ase Station are under
interference or self
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
21/542 Internal Use
+he wa! to +est #-ternal Interferene+he wa! to +est #-ternal Interferene
%hen we are sure that interference is caused by the e'ternal cause, first we
should confirm the location of interference source and the spectrum
distribution state. @irst, set the Spectrum nalyer to proper state.
hoose output port of di"ider of cell under interference.
Screw out the selected connector, then use oa'ial able to import the
output signal of di"ider to the Spectrum nalyer!
iew the spectrum distribution state of the Spectrum nalyer, and findout the abnormal interference signal. The way to calculate the le"el of
interference signal is as follows
ntenna port interference le"el K interference le"el tested by the
Spectrum nalyer L $d= Tower Top mplifier Gain 3d= cable
loss L :d= di"ider gain.
The ma'imum interference le"el at antenna port without influence on
system K
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
22/5422 Internal Use
+he wa! to Searh #-ternal Interferene Soures+he wa! to Searh #-ternal Interferene Soures
In the cell under interference, select a test point without building obstruction.
Set the Spectrum nalyer, and connect the directional antenna.
If there is rotatable platform, the antenna can be placed on it, and ma&e the
wa"e beam of the antenna point to the front, and the antenna with "ertical
polariation should be placed "ertically! if there is no interferent signal, one
can raise the antenna o"er head with hands. 0otate the antenna slowly, and
at the same time "iew the change of signal of the Spectrum nalyer. Hncethere e'ists abnormal signal, fi' the orientation of the antenna immediately
and change uptilt of the antenna to ma&e the recei"ing signal to the
strongest.
nalye the signal spectrum distribution carefully, and confirm that it is
interference signal, record the signal strength and record the aimuth and
downtilt of antenna wa"e beam. @ind new test point along with the direction of antenna wa"e beam, then
return to step 2 to carry out a test till interference source is found.
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
23/5423 Internal Use
Chapter 1 Overview
Chapter 2 Location and Clearance of Interference
Chapter 3 Case AnalysisChapter 3 Case Analysis
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
24/542# Internal Use
Antenna erfor)ane *egradationAntenna erfor)ane *egradation
Fault desri,tion2 There are $ =TSs for a certain networ& in a county
configured as S#6#6# and 96969, the =TS type includes =TS25 and =TS35.The interference band $ in T- measurement function of some cells is o"er
$, and there is no alarm information in HM
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
25/542$ Internal Use
Antenna erfor)ane *egradationAntenna erfor)ane *egradation
Fault loation ,roess
0egister the statistics tas& of interference band of 2# hours for the cellwith problems, it is found that interference band $ mainly occurs in
daylight, and in the small hours near middle night, the interference band
"alue is almost 5.
fter opening the idle =U0ST of all =TSs and transmitting it in the early
morning, it is found that the interference band occurs. It disappears aftertransmitting is stopped. It can be >udged from this phenomenon that the
interference comes from internal networ& and has nothing to do with
other e1uipment.
Jo fre1uency in the networ& and data are modified before the
interference occurs, accordingly, the interference is irrele"ant with the
fre1uency planning. It can be seen from the abo"e second and third points that the problem
is rele"ant with the =TS e1uipment.
Hbser"e the 0;M test interface of /U with the spectrum analyer in
pea& hour in the daylight, it can be seen that unstable strong broadband
interference and rise of bac& noise occur.
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
26/5429 Internal Use
Antenna erfor)ane *egradationAntenna erfor)ane *egradation
Fault loation ,roess
@irst replace all boards 4T0;, /U, @U, -, and power board8 of this
=TS 4=TS25, with Tower Top mplifier8 one by one, at the same timeobser"e the spectrum signal of 0;M test interface, it can be seen that
interference e'ists all the time. This indicates that the interference is
rele"ant with the antenna feeder 4including di"ider, combiner, feeder,
antenna, lightning arrester, Tower Top mplifier, >umper and connector8
instead of the board.
Since the abo"e =TS under test has the Tower Mount mplifier, the
antenna and feeder chec& is incon"enient, replace another
=TS354S#6#6#8 4dualumper at the top of the cabinet8 of the cells which
are with and without interference in the =TS in the e"ening. Then send
idle =U0ST, it is found that the interference follows the antenna and
feeder. This step helps further locate the fault which should e'ist in
antenna and feeder system.
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
27/542: Internal Use
Antenna erfor)ane *egradationAntenna erfor)ane *egradation
Fault loation ,roess
The situation remains the same e"en after replacing lightning arrester of
antenna feeder and chec&ing all >umper connectors. Then it can be surethat fault e'ists in the feeder or antenna.
0eplace the >umper 4i.e., antenna8 at the top of the tower, it is found that
the interference follows the antenna, so the feeder fault can be e'cluded
while the antenna fault is 1uite possible. 4It should be noted that the
e'ternal interference at this step cannot be e'cluded because the actual
installation place of the antenna does not change, but the e'ternal
interference has already been e'cluded in the abo"e step. 8
@inally chec& the antenna. The strong interference disappears
immediately after the antenna is replaced on the tower by using the
dual
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
28/54
2? Internal Use
Antenna Conneted Inversel!Antenna Conneted Inversel!
Fault desri,tion2 the interference bands # and $ often occur in the traffic
measurement after certain =TS is on ser"ice, the inter
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
29/54
2A Internal Use
Antenna Conneted Inversel!Antenna Conneted Inversel!
Fault loation ,roess
Since the interference bands # and $ occur along with low hando"ersuccess rate and congestion, it is doubted that the interference causes
the abo"e phenomena.
hec& the fre1uency planning first, no problem is found. The e'ternal
interference becomes the chief consideration after the fre1uency
planning problem is e'cluded. hange the original used fre1uency A intothe far
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
30/54
35 Internal Use
Antenna Conneted Inversel!Antenna Conneted Inversel!
Fault loation ,roess
The congestion analysis indicates that T- assignment failure is usuallycaused by uplin&. fter registering the traffic measurement of
uplin&6downlin& balance, it is found that the measurement item of
uplin&6downlin& balance for cell and cell 3 focus on le"el and . This
indicates that se"ere imbalance occurs between uplin& and downlin&.
The imbalance between uplin& and downlin&, in combination with muchhando"er failure in cell and 3 turn the doubt to the antenna and feeder
which may be connected in"ersely.
Hn
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
31/54
3 Internal Use
Co(hannel InterfereneCo(hannel Interferene
Fault ,heno)enon2 The co
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
32/54
32 Internal Use
Co(hannel InterfereneCo(hannel Interferene
Fault loation ,roess
The fre1uencies assigned for the =TS are 9#, and A2 49# is of =-fre1uency8.
In the optimiing test, the recei"ing 1uality 41uality le"el is less than 38 is
continuously good as the downlin& signal le"el is
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
33/54
33 Internal Use
Co(hannel InterfereneCo(hannel Interferene
Fault loation ,roess
arry out continuous con"ersation test with one test MS and scan testfor 9#N fre1uency with another MS. The test carried out again in the
section from /u ity to -uanggang re"eals that the signal strength of
9#N fre1uency is already less than
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
34/54
3# Internal Use
Co(hannel InterfereneCo(hannel Interferene
Fault loation ,roess
arry out continuous con"ersation test with one test MS and scan test
for 9#N fre1uency with another MS. The test carried out again in the
section from /u ity to -uanggang re"eals that the signal strength of
9#N fre1uency is already less than
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
35/54
3$ Internal Use
Co(hannel InterfereneCo(hannel Interferene
Fault loation ,roess
The interference disappears after the application is made to the
customer to modify the fre1uency. t the same time, the customer
should ad>ust the ad>acent cell relation of peer e1uipment.
arry out test again at the place where the original co
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
36/54
39 Internal Use
Ad&aent(hannel InterfereneAd&aent(hannel Interferene
Fault ,heno)enon2The call drop ratio is uni"ersally high and e"en up to
about $D in busy hour after se"eral =TSs are cut o"er. nd it is difficult forthe call to be set up during on
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
37/54
3: Internal Use
Ad&aent(hannel InterfereneAd&aent(hannel Interferene
Fault loation ,roess
ll =TSs are connected to the same =S, and call drop occurs aftercuto"er of new =TSs.
The transmission 1uality is good, and T0; test is carried out for the
abo"e =TS with call drop and this indicates that each T0; is all right. Jo
fault is found by chec&ing the data and carrying out the test for 32=IB
port corresponding to the =TSs. @rom the abo"e analysis, the T0; fault,
=S hardware fault, interface circuit fault and transmission fault can
be e'cluded.
nalysis of traffic measurement result re"eals that serious interference
occurs in each cell of the abo"e se"eral =TS. Most cells ha"e
measurement "alues in interference band # and $, and the number of
channels falling into interference band $ in se"eral cells is up to :. So itis sure that the interference in the abo"e se"eral cells is 1uite serious.
Ad& t h l I t fAd& t h l I t f
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
38/54
3? Internal Use
Ad&aent(hannel InterfereneAd&aent(hannel Interferene
Fault loation ,roess
It is found that there are many ad>acent channels and the fre1uencyplanning is irrational after chec&ing the fre1uency configuration of abo"e
=TSs and the ad>acent cells. Bspecially, the area where the abo"e =TSs
are located, is newly added, and interference e'ists among them. nd
they also ha"e interference in between them and the surrounding
running =TSs.
all drop disappears after ad>usting and loading the fre1uency
configuration of this area.
I t f C d % OI t f C d % O
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
39/54
3A Internal Use
Interferene Caused %! Over(overageInterferene Caused %! Over(overage
Fault ,heno)enon2The hand o"er success rate of a certain GSM networ&
is low, the call drop rate is high and con"ersation 1uality is poor. The hando"er success rate is less than ?5D, and the call drop rate is more than 2D.
It is found that there are many times of downlin&6uplin& strength hand o"ers
through "iew and analysis of traffic measurement data. while there are many
times of bad downlin& 1uality, and uplin& strength among the times of
unsuccessful hando"er. The analysis of cause of call drop indicates that the
times of bad downlin& 1uality are more than those of bad uplin& 1uality .There is no alarm message in HM system
I t f C d % OI t f C d % O
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
40/54
#5 Internal Use
Interferene Caused %! Over(overageInterferene Caused %! Over(overage
Fault loation ,roess
@rom the result of traffic measurement, it can be >udged that downlin&
interference may e'ist in the system or the co"erage is not "ery good. The actual result of /ri"e Test shows that the strength of outdoor signal
can be up to
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
41/54
# Internal Use
Interferene Caused %! Over(overageInterferene Caused %! Over(overage
Fault loation ,roess
The cause for bad networ& indices lies in o"erusting the networ&
parameter. The following operations can be adopted lower the power
le"el of cell = and add the ad>acent cell of cell =, at the same time
increase the le"el threshold of candidate cell from 5 to $. The networ&
indices e'hibit ob"ious impro"ement after the abo"e chec& andmodification are performed for all cells in the downtown area, moreo"er,
the hand o"er success ratio rises up to ?$D, while call drop ratio drops
to .3D.
R t I t fRe,eater Interferene
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
42/54
#2 Internal Use
Re,eater InterfereneRe,eater Interferene
Fault ,heno)enon2 subscribers of a certain networ& complain that they
cannot occupy channel in some area for con"ersation since some day, ornoise is hea"y after occupancy of channel though the signal of MS is strong
at this time. There are two directional =TSs in this area and both of them are
=TS35 with the "ersion 5$.5$2A. The aimuth of the first cell directs at north.
The =TS in this area wor&s normally and the networ& indices conform to
re1uirement before the complaint. =oth =S and MS are de"ices of
-uawei and two =TSs are connected in star mode. The traffic measurementindices show that traffic of both =TSs decreases ob"iously after occurrence
of this problem, especially in the first and third cells. lthough the signal of
channel is "ery strong, the 1uality of "oice is poor. Then it can be seen from
traffic measurement that the interference band of these four cells is in class
three, four, and fi"e, and A$D of channels are under interference. In
addition, interference of different classes also e'ists in other cells. Sosubscribers complained strongly. nd there is no alarm message in HM
system
R t I t fRe,eater Interferene
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
43/54
#3 Internal Use
Re,eater InterfereneRe,eater Interferene
Fault loation ,roess
The feedbac& of subscribers shows the possible causes as follows .roblem occurs in transmission and leads to error code! 2. roblem
occurs in antenna feeder! 3. @ault e'ists in TMU! #. Internal or e'ternal
interference may e'ist.
The traffic measurement console shows the possible reasons as follows
. There may e'ist strong uplin& interference signal in the north lean to
west in this area. This leads to interference of different le"els in the first,
second and third cells, especially in the first and third cells!
It is found that it is difficult to put through the call in the first and third
cells through onudged from this point that interference only e'ists in uplin&.8
Re,eater InterfereneRe,eater Interferene
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
44/54
## Internal Use
Re,eater InterfereneRe,eater Interferene
Fault loation ,roess
arry out test on site with antenna feeder analyer. Jo problem of =TS
itself is found, and the situation remains the same after TMU is replaced.Therefore, we as& customers whether there are such newly constructed
e1uipment as microwa"e station, repeater, etc. surrounding the =TS.
They told that they didnCt set up them.
It is said that hina Mobile sets up a repeater in the area, which is
located about two &ilometers away in the north lean to the west of both
=TSs of -uawei, and when it is acti"ated, the problem will occur in-uawei =TS. Then customers negotiated with hina Mobile se"eral
times. @inally hina Mobile carried out on
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
45/54
#$ Internal Use
Mirowave InterfereneMirowave Interferene
@ault phenomenon it is found that call drop rate in the second and third cell
of a certain =TS 4S262628 in traffic measurement increases abruptly. alldrop rate is up to about 25D at some time.
Mirowave InterfereneMirowave Interferene
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
46/54
#9 Internal Use
Mirowave InterfereneMirowave Interferene
Fault loation ,roess
iew of =S traffic measurement shows that idle T- number ininterference band in this =TS begins to increase in interference band 3udged from the abo"e phenomenon
that interference e'ists.
Since this =TS operates well before, the problem of fre1uency planning
can be e'cluded.
erform power
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
47/54
#: Internal Use
Mirowave InterfereneMirowave Interferene
Fault loation ,roess
iew of all =S traffic measurement data shows that interference ofdifferent le"els e'ists in the cells of all =TSs nearby, which is facing the
same direction as the second and third cells in this =TS. nd
sometimes S/- channels in the cells with serious interference are
all occupied at the same time, while the occupancy ratio of S/- at
the same time is "ery little according to the amount of subscriber. So it
can be sure that e'ternal interference e'ists in uplin&, but theinterference may be rele"ant with direction instead of fre1uency.
To further locate, >umpers of the first and third cell are interchanged on
the rac& top. s a result, it is found that interference occurs in the first
cell, but interference disappears in the third cell, so this has pro"ed the
abo"e >udgement.
Since interference is not rele"ant with fre1uency, =TS interference may
be caused by high
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
48/54
#? Internal Use
Mirowave InterfereneMirowave Interferene
Fault loation ,roess
Measurement on =TS di"ider output port with spectrum analyer showsthat high
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
49/54
#A Internal Use
False InterfereneFalse Interferene
Fault ,heno)enon2 the reconstruction of some office found that the
interference band of an S96969 =TS25 in a county is "ery high.Theinterference band of two cells in it changed from $ to :.
False InterfereneFalse Interferene
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
50/54
$5 Internal Use
False InterfereneFalse Interferene
Fault loation ,roess
/uring the past interference test ofthis office, some cells with highinterference band were located. This is because antenna
intermodulation resulted in the interference of normal signal in case of
large traffic and it made the interference band "ery high. So change the
antenna, but the interference band did not fall down ob"iously after that.
/uring the prior period, the fre1uency planning has been chec&ed
se"eral times, and the ad
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
51/54
$ Internal Use
False InterfereneFalse Interferene
Fault loation ,roess
Trace the state of interference band of each channel "ia Maintenanceonsole and find that high interference band mainly focuses on the four
T0;s of the cell.
@irst set the fre1uency with less interference to the T0; with more
interference, and find that the interference band does not change. It
shows there is no relation to the fre1uency. %hether there is something
wrong with T0; board or not is un&nown. -owe"er, the situation is
unchanged after the T0;s were interchanged.
Then confirm the T0; numbers, and find that the four carriers come
from the same di"ider. @rom the abo"e process, the problem may be
the di"ider. =ut it is found that the interference band becomes high
when the =TS is e'panded from S#6#6# to S96969. %hile thecombiner6di"ider used to be normal. Maybe the de"ices brea& down
after some time. So we decided to change the combiber6di"ider to ha"e
a try.
False InterfereneFalse Interferene
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
52/54
$2 Internal Use
False InterfereneFalse Interferene
Fault loation ,roess
The idea that four carriers with high interference band are connected tothe same second le"el di"ider before the di"ider is changed. The :
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
53/54
$3 Internal Use
Su))ar!Su))ar!
H"er"iew
*ocation and learance of Interference ase nalysis
Su))ar!Su))ar!
-
7/23/2019 OMF000403 GSM Interference Analysis ISSUE1[1].0
54/54
-uawei onfidential. ll 0ights 0eser"ed