Pilot Pollution

[Areej]

Hi there,

I have a problem in understanding the Pilot Pollution problem in UMTS Analysis

I know that in case I find more than 3 pilots having RSCP with close difference and the difference between the strongest and the weakest pilot is appro. 5dB , this is a pilot pollution problem.

now I want to know is it a condition that the Pilot is an AS ??or we look at all the pilots whether they are AS or MN ??


it would be great if some one shows me a snap shot of a pilot pollution problem analysis using TEMS.


Thanks in Advance,

[firstmaxim]

Pilot pollution should be considered only for those cells not in the active set. Remember ...either you are with us or against us!

[Areej]

You mean that even if I find 3 Active Sets with close RSCP that will not affect the quality (Ec/No) of each other? and this case is not considered a pilot pollution?

[agenov]

Hi there,

I have a problem in understanding the Pilot Pollution problem in UMTS Analysis

I know that in case I find more than 3 pilots having RSCP with close difference and the difference between the strongest and the weakest pilot is appro. 5dB , this is a pilot pollution problem.

now I want to know is it a condition that the Pilot is an AS ??or we look at all the pilots whether they are AS or MN ??


it would be great if some one shows me a snap shot of a pilot pollution problem analysis using TEMS.


Thanks in Advance,

Why you use UE instead of scanner device?

[Areej]

Why you use UE instead of scanner device?

I don't get what you mean

[agenov]

I don't get what you mean

I meant that you don't care about detected, monitored set and etc. The evaluation is done based on scanner device. Whenever you have more than 3 pilots whithin app. 5dB then you get pollution and following actions should be done in order to avoid it.

[zeezzoo]

yes agenov is right you should use a scanner and take into the consideration all the detected cells by the scanner . then you can use pilot pollution criteria . i've been rreading today about this pilot pollution issue i found about 4 criterias used but i'm gonna list two of them :

1) Huawei :
* 4 Pilots are detected by the scanner (or more than 4) & each one of them fulfils : RSCP > -100 dBm .
* RSCP(for 1st Pilot == Storngest one) - RSCP(4th Pilot == weakest one) < 5 dB .

2) Actix :
* after sorting the detected pilots in descending order (in terms of Ec/No) , you should check if the 4th one (poorest one == lowest Ec/No) has its Ec/No > -15 dB ==> the that means you have pilot pollution .

I hope this will be useful .

PS : for Actix criteria .... it's already built in actix where you can plot the pilot pollution marker on the map .
but for huawei .. it's not and i spent the whole day trying to build a query in actix but i'm failed because actix queries interface has no enough functions to do that .if i succeeded I will share it .

[agenov]

yes agenov is right you should use a scanner and take into the consideration all the detected cells by the scanner . then you can use pilot pollution criteria . i've been rreading today about this pilot pollution issue i found about 4 criterias used but i'm gonna list two of them :

1) Huawei :
* 4 Pilots are detected by the scanner (or more than 4) & each one of them fulfils : RSCP > -100 dBm .
* RSCP(for 1st Pilot == Storngest one) - RSCP(4th Pilot == weakest one) < 5 dB .

2) Actix :
* after sorting the detected pilots in descending order (in terms of Ec/No) , you should check if the 4th one (poorest one == lowest Ec/No) has its Ec/No > -15 dB ==> the that means you have pilot pollution .

I hope this will be useful .

PS : for Actix criteria .... it's already built in actix where you can plot the pilot pollution marker on the map .
but for huawei .. it's not and i spent the whole day trying to build a query in actix but i'm failed because actix queries interface has no enough functions to do that .if i succeeded I will share it .

My friend,

Believe me Actix is one of the most powerfull post processing tool and posses all necesserarily options to do amazing things, pilot pollution plot (even of Huawei estimation) is just one simple example. Search the forum and you will find the answer.

BR
Alex

[zeezzoo]

My friend,

Believe me Actix is one of the most powerfull post processing tool and posses all necesserarily options to do amazing things, pilot pollution plot (even of Huawei estimation) is just one simple example. Search the forum and you will find the answer.

BR
Alex

yes I'm searching the forum . for the queries actix is good for the simple ones but it's not that good when you have a complicated query (in this case i'm using excel)

thx so much Alex

[Areej]

yes agenov is right you should use a scanner and take into the consideration all the detected cells by the scanner . then you can use pilot pollution criteria . i've been rreading today about this pilot pollution issue i found about 4 criterias used but i'm gonna list two of them :

1) Huawei :
* 4 Pilots are detected by the scanner (or more than 4) & each one of them fulfils : RSCP > -100 dBm .
* RSCP(for 1st Pilot == Storngest one) - RSCP(4th Pilot == weakest one) < 5 dB .

2) Actix :
* after sorting the detected pilots in descending order (in terms of Ec/No) , you should check if the 4th one (poorest one == lowest Ec/No) has its Ec/No > -15 dB ==> the that means you have pilot pollution .

I hope this will be useful .

PS : for Actix criteria .... it's already built in actix where you can plot the pilot pollution marker on the map .
but for huawei .. it's not and i spent the whole day trying to build a query in actix but i'm failed because actix queries interface has no enough functions to do that .if i succeeded I will share it .

Just a tiny Q : when you say Ec/No > -15 dB you mean that Ec/No is -14 & -13 ....etc ??? , if so then the Ec/No is getting better not worst..how can I consider it pilot pollution?

or you mean Ec/No > -15 dB i.e. -17 & -18 ...etc?




BUT REALLY you post is very useful to me THAAAAAAAANKS

[zeezzoo]

Just a tiny Q : when you say Ec/No > -15 dB you mean that Ec/No is -14 & -13 ....etc ??? , if so then the Ec/No is getting better not worst..how can I consider it pilot pollution?

or you mean Ec/No > -15 dB i.e. -17 & -18 ...etc?




BUT REALLY you post is very useful to me THAAAAAAAANKS

yes dear Ec/No > -15 dB means better than -15 dB . ==> all of the four detected cells have acceptable Ec/No . where in Huawei :

* Good : Ec/No >= -8 dB
* Fair : -8 dB < Ec/No <= -14 dB
* Poor : Ec/No < -14 dB

so in othe words there's no dominant cell for the UE to camp on (you will see a lot of Handovers & cell Reselections ) .

This is from E******* : " In idle or cell_FACH mode, phenomenon of the pilot pollution is that a UE cannot firmly camp on a cell at one location because of receiving many pilot channels with similar quality (or signal strength), i.e., Ec/No (or RSCP).
The condition to determine the area has pilot pollution in idle or cell_FACH mode is that third pilot appears in the cell re-selection region.
In cell_DCH mode, phenomenon of the pilot pollution is that a UE at one location frequently changes its active set cells (active set update rate is very high) because of receiving many pilot channels with similar quality (or signal strength), i.e., Ec/No (or RSCP). It causes high signaling load in RRC and Iub interfaces and the capacity of RNC is consequently reduced. "

only one thing to be added that for the pilot polluted areas there will be wasted resources because i think the UE will be mostly in soft handover mode (maybe the pilot polluted area is not nearby the cell edge) ==> that's resource wasting .

hope it will be useful
Br,

[agenov]

Gentelmen,

Seems to me like we have an issue here. The question obviously is how everyone of you as radio optimization engineers defined pilot pollution in your analyses, based on what, please for your standpoint/definition?

[Areej]

yes dear Ec/No > -15 dB means better than -15 dB . ==> all of the four detected cells have acceptable Ec/No . where in Huawei :

* Good : Ec/No >= -8 dB
* Fair : -8 dB < Ec/No <= -14 dB
* Poor : Ec/No < -14 dB

so in othe words there's no dominant cell for the UE to camp on (you will see a lot of Handovers & cell Reselections ) .

This is from E******* : " In idle or cell_FACH mode, phenomenon of the pilot pollution is that a UE cannot firmly camp on a cell at one location because of receiving many pilot channels with similar quality (or signal strength), i.e., Ec/No (or RSCP).
The condition to determine the area has pilot pollution in idle or cell_FACH mode is that third pilot appears in the cell re-selection region.
In cell_DCH mode, phenomenon of the pilot pollution is that a UE at one location frequently changes its active set cells (active set update rate is very high) because of receiving many pilot channels with similar quality (or signal strength), i.e., Ec/No (or RSCP). It causes high signaling load in RRC and Iub interfaces and the capacity of RNC is consequently reduced. "

only one thing to be added that for the pilot polluted areas there will be wasted resources because i think the UE will be mostly in soft handover mode (maybe the pilot polluted area is not nearby the cell edge) ==> that's resource wasting .

hope it will be useful
Br,

mmm Thanks zeezzo

I thought that pilot pollution is equivalent to interference in 2G where is the interferer affects on the serving cell QUALITY and make it BAD, so as a comparison in 3G the Ec/No must be affected.

I believe that in pilot pollution case pilots has very close RSCP and so as you said there will not be a dominant cell .

But, I didn't know that even if the Ec/No is good (but close) this can be called pilot pollution !!

anyway thanks :)

your explanation made things very clear to me .. many many thanks

[zeezzoo]

Gentelmen,

Seems to me like we have an issue here. The question obviously is how everyone of you as radio optimization engineers defined pilot pollution in your analyses, based on what, please for your standpoint/definition?

dear i think that the different criterion for pilot pollution practically lead into the same result (with a small differences) .
but for me i prefer to use huawei criteria . i think it makes more sense .
i can use some help dears can you tell me what criteria you are using ??

[zeezzoo]

mmm Thanks zeezzo

I thought that pilot pollution is equivalent to interference in 2G where is the interferer affects on the serving cell QUALITY and make it BAD, so as a comparison in 3G the Ec/No must be affected.

I believe that in pilot pollution case pilots has very close RSCP and so as you said there will not be a dominant cell .

But, I didn't know that even if the Ec/No is good (but close) this can be called pilot pollution !!

anyway thanks :)

your explanation made things very clear to me .. many many thanks

Yes of course pilot pollution affects Ec/No for the cell that is supposed to be the dominant one for a given area . ==> you will not have a good Ec/No for all of the detected cells in the pilot polluted area . your Ec/No will be in the fair range . but when you solve the pilot pollution problem , you will have a good Ec/No for the dominant cell .

for the second question : " But, I didn't know that even if the Ec/No is good (but close) this can be called pilot pollution !! "

in case of pilot pollution you will never ever have a good Ec/No (Good : Ec/No>= -8 dB) but you may have a fair Ec/No or a bad one ( depending on " RSSI " & " RSCP for each pilot " )

[Areej]

Yes of course pilot pollution affects Ec/No for the cell that is supposed to be the dominant one for a given area . ==> you will not have a good Ec/No for all of the detected cells in the pilot polluted area . your Ec/No will be in the fair range . but when you solve the pilot pollution problem , you will have a good Ec/No for the dominant cell .

for the second question : " But, I didn't know that even if the Ec/No is good (but close) this can be called pilot pollution !! "

in case of pilot pollution you will never ever have a good Ec/No (Good : Ec/No>= -8 dB) but you may have a fair Ec/No or a bad one ( depending on " RSSI " & " RSCP for each pilot " )


Thaaaaaaaaaaaaaaaaaaaaaaaanks :)
I know that Iam asking too many questions ...sorry

Now , as a conclusion
a pilot pollution problem happens when:
having 4 or more pilots with RSCP > -100 and the Ec/No of them is in the fair or in the bad range.


but, just a note :)

when you said :
for Actix : after sorting the detected pilots in descending order (in terms of Ec/No) , you should check if the 4th one (poorest one == lowest Ec/No) has its Ec/No > -15 dB ==> the that means you have pilot pollution .)


that means that Ec/No > -15 dB is worst than Ec/No = -15, NOT as you said in the #11 post (yes dear Ec/No > -15 dB means better than -15 dB)
, and hence Ec/No > -15 means -16 , -17 , -18 which can't happen mathematically ..

ORRRR
If we consider Ec/No > -15 means -14 , -13 , -12 .. etc which mean better as you said
But, in this case : why he is putting a condition making the Ec/No be in the better ranges although we said Ec/No must be in the bad or fair range ???

Also in this case the condition of the fair region must be edited from (Fair : -8 dB < Ec/No <= -14 dB) to ( Fair : -8 dB > Ec/No >= -14 dB) to serve this mathematical definition.



thanks for help zeezzoo

[Areej]

I edited the last post.

[stilloboy]

yes agenov is right you should use a scanner and take into the consideration all the detected cells by the scanner . then you can use pilot pollution criteria . i've been rreading today about this pilot pollution issue i found about 4 criterias used but i'm gonna list two of them :

1) Huawei :
* 4 Pilots are detected by the scanner (or more than 4) & each one of them fulfils : RSCP > -100 dBm .
* RSCP(for 1st Pilot == Storngest one) - RSCP(4th Pilot == weakest one) < 5 dB .

2) Actix :
* after sorting the detected pilots in descending order (in terms of Ec/No) , you should check if the 4th one (poorest one == lowest Ec/No) has its Ec/No > -15 dB ==> the that means you have pilot pollution .

I hope this will be useful .

PS : for Actix criteria .... it's already built in actix where you can plot the pilot pollution marker on the map .
but for huawei .. it's not and i spent the whole day trying to build a query in actix but i'm failed because actix queries interface has no enough functions to do that .if i succeeded I will share it .

Hmmm..., I think the second point you listed as criteria actually derives from the default values Actix uses. In other words, you can provide your own set of threshold values as input to Actix. Even, the criteria that Huawei uses can be applied as input to Actix. It is important we remember here that ACTIX IS A TOOL and so cannot peg the thresholds to a set of values. It only uses the default values when the user does not provide their own set of thresholds.

KR,
Stilloboy

[agenov]

dear i think that the different criterion for pilot pollution practically lead into the same result (with a small differences) .
but for me i prefer to use huawei criteria . i think it makes more sense .
i can use some help dears can you tell me what criteria you are using ??


Why you think it makes more sense than the others?
BR
Alex

[zeezzoo]

Hmmm..., I think the second point you listed as criteria actually derives from the default values Actix uses. In other words, you can provide your own set of threshold values as input to Actix. Even, the criteria that Huawei uses can be applied as input to Actix. It is important we remember here that ACTIX IS A TOOL and so cannot peg the thresholds to a set of values. It only uses the default values when the user does not provide their own set of thresholds.

KR,
Stilloboy

yes that's right dear you can set the thresholds in actix . also for each threshold actix has its recommended , min & max value . for pilot pollution in actix -15 dB Ec/No is the recommended value but as you mentioned you can change the threshold according to what you think is better .

[zeezzoo]

Why you think it makes more sense than the others?
BR
Alex

i think it's easier to deal with RSCP than dealing with Ec/No ( Ec/No = RSCP/RSSI) . but of course this is not a holy book every one can use the criteria he/she thinks it's the best one .

Dear Alex can you tell me what the criteria you are using . and if you have some actix or excel queries could you please share .

[zeezzoo]

Now , as a conclusion
a pilot pollution problem happens when:
having 4 or more pilots with RSCP > -100 and the Ec/No of them is in the fair or in the bad range.


Dear Areej

you keep mixing things .
in huawei criteria there is no Ec/No at all :

* (4 Pilots) > -100 dBm ( -99 , -98 ......)
* (1st Pilot RSCP) - (4th Pilot RSCP) < 5dB



that means that Ec/No > -15 dB is worst than Ec/No = -15, NOT as you said in the #11 post (yes dear Ec/No > -15 dB means better than -15 dB)
, and hence Ec/No > -15 means -16 , -17 , -18 which can't happen mathematically ..


for the Ec/No Values i see that you have some confusion .
(Ec/No > -15 dB) == (Ec/No is better than -15 dB) == (-14 , -13 ..... dB)

also a small not : in actix you don't have to do any ype of sorting or anything . just drag & drop the pilot pollution event to the map . when i talked about the sorting for Ec/No , i was explaining the algorithm .



ORRRR
If we consider Ec/No > -15 means -14 , -13 , -12 .. etc which mean better as you said
But, in this case : why he is putting a condition making the Ec/No be in the better ranges although we said Ec/No must be in the bad or fair range ???


i think i missed typing the fair ranges of Ec/No accidentally . i'm sorry for that mistake :
Good : Ec/No >= -8 dB .
Fair : -14 dB =< Ec/No < -8 dB .
bad : Ec/No < -14 dB .

I think every thing is clear now .
I'm sharing some docs from Huawei about pilot pollution definition & a practical case taken from a real live network (with RSCP & Ec/No Values) .
I hope it will be useful . No Password
Br

[Areej]

Dear Areej

you keep mixing things .
in huawei criteria there is no Ec/No at all :

* (4 Pilots) > -100 dBm ( -99 , -98 ......)
* (1st Pilot RSCP) - (4th Pilot RSCP) < 5dB



for the Ec/No Values i see that you have some confusion .
(Ec/No > -15 dB) == (Ec/No is better than -15 dB) == (-14 , -13 ..... dB)

also a small not : in actix you don't have to do any ype of sorting or anything . just drag & drop the pilot pollution event to the map . when i talked about the sorting for Ec/No , i was explaining the algorithm .



i think i missed typing the fair ranges of Ec/No accidentally . i'm sorry for that mistake :
Good : Ec/No >= -8 dB .
Fair : -14 dB =< Ec/No < -8 dB .
bad : Ec/No < -14 dB .

I think every thing is clear now .
I'm sharing some docs from Huawei about pilot pollution definition & a practical case taken from a real live network (with RSCP & Ec/No Values) .
I hope it will be useful . No Password
Br

Yes , Thanks zeezzoo for all this help.