How to improve PSR at 3G and 2G when UE Cell Reselection from 3G to 2G and contrary

[Interface]

Hi all Experts,
In our network, 3G and 2G sites are cosite. Because the 3G coverage is smaller than 2G so that UEs usually have to reselect from 3G to 2G and contrary. When UEs are making this procedure, if have an paging message sent to them, it will be fail and PSR is very bad.
How to solve this problems ? Please help me.

[electron]

Hi all Experts,
In our network, 3G and 2G sites are cosite. Because the 3G coverage is smaller than 2G so that UEs usually have to reselect from 3G to 2G and contrary. When UEs are making this procedure, if have an paging message sent to them, it will be fail and PSR is very bad.
How to solve this problems ? Please help me.

This case usually happening in beginig of 3G network lunch.Try to have coverage optimization to avoid unstability in idle mode and then define some IRAT relation for your 3G cells use GWNCS in E******* for example.

[Interface]

Hi expert,
Our problems is paging during UE make cell reselection from 2G to 3G or contracy. So that have any resolution for this problem.
In my opinion, we can set 3G and 2G sites at same LAC of same MSC where they are cosite.

[twenty8]

Hi, if you set the same LAC for 2G and 3G then there will be high volume of paging and may cause interference and congest the PCH. Better to optimise the reselection parameters to make it more dominant on either RAT, and reduce the amount of reselections.

[gprastomo]

Hi,

I have the same config, but the PSR still around 95% and there is no problem.
Better to check your cell reselection parameter, im afraid that your network parameter has ping pong 2G<->3G reselection, usually i put an offset of 3-4 dB.
Just check below parameters :
in 2G :
1. FDDQOFFSET = always
2. FDDRSCPMIN = should be greater than IRAT threshold due to RSCP (let say -102 dBm)
3. FDDQMIN = should be greater than IRAT threshold due to EcNo (FDDQMIN = let say -12 dB) and Qqualmin+s_search_rat (-18+4 = -14dB).
4. QSearch_I = always

in 3G :
1. Qqualmin + s_search_rat (-18+4 =- 14 dB)
2. IRATthreshold due to RSCP = let say -105 dBm
3. IRAT threshold due to EcNo = let say -15 dB

By those threhold, it may prevent ping pong 2G 3G reselection which may avoid bad PSR due to LAC update frequently.

But if you set (let say), the FDDQMIN (in 2G) to -18 dB, then the Ue will reselect from 2G to 3G then it will directly reselect to 2G, in this case, your case will happen.

Just check your cell reselection parameters.

Then If it is ok, i guess there is another problem. I have investigate this kind of problem, since there was a problem in 3G which make the ue unreachable, then i tried to increase the PRACH parameter, then the PSR increase & the complaint was reducing.

br

[Interface]

Thanks Pgrastomo,
We are setting these parameters as below:
2G:
1. FDDQOFFSET = 0
2. FDDRSCPMIN = -100dBm
3. FDDQMIN = -10dB
4. QSearch_I = always
3G:
1. Qqualmin + s_search_rat (-18+4 =- 14 dB)
2. IRATthreshold due to RSCP = let say -103 dBm
3. IRAT threshold due to EcNo = let say -13 dB
So I think that hasn't got any problem at parameters.:(
I will check value of the PRACH parameter. Thanks you again.
But have any way to view the Cell reselection times from 3G to 2G ? I only able to view the cell reselection times from 2G to 3G.

[gprastomo]

Hi Interface,

What is the PSR value for those problematic LAC ?
Have you check for the PCH load, is there any Paging deletion from the Node B due to PCH overload ? How many paging delivered on the air interface ?

For the 3G to 2G reselection time, im not sure you can get it. May be you can get it on 2G counters, SDCCH att due to registration or interrat resel (if any) or other ?

br

[Interface]

Hi Expert,
Our PSR value is ~ 90%. I checked the Paging load but hasn't got any paging discard. So i think that it's not the reason of this problems.:(

[jimjim]

Hi Expert,
Our PSR value is ~ 90%. I checked the Paging load but hasn't got any paging discard. So i think that it's not the reason of this problems.:(

Hello there,


Paging Access Failure Troubleshooting-(VII)



• there can be several places where paging could get congested: Iu interface, IuB
interface, RNC boards, or PCH interface . PICH channel is the only channel that
is never congested!

• Check with CN how many paging repetitions have, how do they page: by IMSI or
by TMSI. If first paging fails how many repetitions? Last paging is network wide or
LAC wide only?

• --- is currently facing PCH channel load: all smart phones are in cell PCH state. In
this state can only receive paging but can not transmit any data. Any paging for a
UE it is sent specifically to that cell. How RNC knows where is such an UE? By
cell update!. Every time UE changes the cell in cell PCH there is a cell
update+cellupdate confirm, utran mobility information confirm. That means that
the RNC is aware about new location of the UE.

• How much is the paging success now in --- network?

• What solutions we have to offload the PCH channel?:

• LAC split.

• Page by TMSI

• Reduce ping-pongs (and reselections)
• Improve best server area and reduce overlapping

[jimjim]

Hello there,

Here is another more detailed document about paging.

Overview .................................................................................................................................................. 7
2 Paging Problem Analysis Process .............................................................................................................. 9
2.1 Problem Analysis Flow ......................................................................................................................... 9
2.2 Network Information Collection ......................................................................................................... 10
2.2.1 Traffic Statistics ............................................................................................................................ 10
2.2.2 Alarm .......................................................................................................................................... 13
2.2.3 Subscriber Complaints .................................................................................................................. 13
2.2.4 History Record of Network Planning Optimization ..................................................................... 14
2.2.5 Radio Parameter Configuration .................................................................................................... 14
2.3 Determining Optimization Goal .......................................................................................................... 15
2.4 Locating Paging Problems .................................................................................................................. 15
2.4.1 Determining Basic Location Direction ......................................................................................... 15
2.4.2 Direct Causes of Paging Loss ....................................................................................................... 16
2.4.3 Further Analysis on Paging Loss Cause ....................................................................................... 17
2.4.4 Other Cause Analysis.................................................................................................................... 17
2.5 Paging Problems Optimization ............................................................................................................ 17
2.6 Optimization Verification ................................................................................................................... 17
3 Typical Paging Problem Analysis ............................................................................................................ 18
3.1 Too Large Paging Area Planned ......................................................................................................... 18
3.1.1 Problem Analysis .......................................................................................................................... 18
3.1.2 Optimization Measures ................................................................................................................. 19
3.2 Improper Setting of CN Paging retransmission Times and Interval ................................................... 19
3.2.1 Problem Analysis .......................................................................................................................... 19
3.2.2 Optimization Measures ................................................................................................................. 20
3.3 Improper Setting of UTRAN Paging Retransmission Times and Interval .......................................... 21
3.3.1 Problem Analysis .......................................................................................................................... 21
3.3.2 Optimization Measures ................................................................................................................. 21
3.4 CN Adopts Whole-Network Paging .................................................................................................... 21
3.4.1 Problem Analysis .......................................................................................................................... 21
3.4.2 Optimization Measures ................................................................................................................. 21
3.5 Improper Setting of DRX Paging Cycle Coefficient ........................................................................... 22
3.5.1 Problem Analysis .......................................................................................................................... 22
3.5.2 Optimization Measures ................................................................................................................. 23
3.6 Improper setting of Np value ............................................................................................................... 23
3.6.1 Problem Analysis .......................................................................................................................... 23
3.6.2 Optimization Measures ................................................................................................................. 24
3.7 UE Identifier Utilized by CN Paging .................................................................................................. 24
3.7.1 Problem Analysis .......................................................................................................................... 24
3.7.2 Optimization Measures ................................................................................................................. 25
3.8 UTRAN Should Activate IMSI ATTACH and DETACH Functions ................................................. 25
3.8.1 Problem Analysis .......................................................................................................................... 25
3.8.2 Optimization Measures ................................................................................................................. 26
3.9 Too Low Power allocation of Paging Channels .................................................................................. 26
3.9.1 Problem Analysis .......................................................................................................................... 26
3.9.2 Optimization Measures ................................................................................................................. 26
3.10 Existence of Coverage Dead Zones .............................................................................................. 27
3.10.1 Problem Analysis ................................................................................................................... 27
3.10.2 Optimization Measures ........................................................................................................... 27
3.11 UE Performance Problems ............................................................................................................ 27
3.11.1 Problem Analysis ................................................................................................................... 27
3.11.2 Optimization Measures ........................................................................................................... 27
4 Outstanding Problems .............................................................................................................................. 27

[gprastomo]

Hi Expert,
Our PSR value is ~ 90%. I checked the Paging load but hasn't got any paging discard. So i think that it's not the reason of this problems.:(

If there is no problem on the air interface, just check you PRACH parameter (have you check it? Ill compare with my network) and dont forget to check the TPAG (MSC timer to supervise the paging response) may be the TPAG is soo quick.

And also check the MSS counter, whether you have alot of repaging/ second paging, if your tpag is so fast maybe you ll have alot of repaging which is unnecesary.

Dont forget one thing, if you have high signalling rejection (RRC rejection due to congest, or whatever) just clean it, since the paging response will be sent after the RRC is setup successfully.

[Interface]

Hi Expert,
The PRACH we are using is: constantValueCprach -19.
We don't change this parameter before. But our PSR stated decrease 2 months ago.
How can to check the congestion at some interface of network?

[gprastomo]

Hi Expert,
The PRACH we are using is: constantValueCprach -19.
We don't change this parameter before. But our PSR stated decrease 2 months ago.
How can to check the congestion at some interface of network?

Hi,

-19 is enough. You may have another problem.
Could you breakdown on which LAC, the PSR had degradation ?

may be it degraded on specific LAC.

br

[jackkarpar]

If there is no problem on the air interface, just check you PRACH parameter (have you check it? Ill compare with my network) and dont forget to check the TPAG (MSC timer to supervise the paging response) may be the TPAG is soo quick.

And also check the MSS counter, whether you have alot of repaging/ second paging, if your tpag is so fast maybe you ll have alot of repaging which is unnecesary.

Dont forget one thing, if you have high signalling rejection (RRC rejection due to congest, or whatever) just clean it, since the paging response will be sent after the RRC is setup successfully.

Would the low bchPower setting cause the PSR drop?

[komitko]

How did you find out the problem is at the bordering area?
Do you have many blackberry UEs in your network?

fddqmin and and rscpmin are optional, aren't they?