Problem of voice quality in NSN 3G network

[josef]

Dear friends,

I need your experience to resolve one pb in our network.

The situation is:

2G/3G network (GSM/DCS/U9/U21)
constructor: NSN for RAN & Core

We have bad voice quality for 3G call (I don't know in which band) reported by customers in capital city and we can feel also when we are blocking mobiles on 3G. (The pb appears since 3 days)

Please:

1- What to check (param, counters, KPI) to know what & where the problem is ?
2- What can be the source of this problems
3- What I have to Re-tune in order to solve this pb ?

Thank you by advance.

Jo

[fangruan2201]

Dear friends,

I need your experience to resolve one pb in our network.

The situation is:

2G/3G network (GSM/DCS/U9/U21)
constructor: NSN for RAN & Core

We have bad voice quality for 3G call (I don't know in which band) reported by customers in capital city and we can feel also when we are blocking mobiles on 3G. (The pb appears since 3 days)

Please:

1- What to check (param, counters, KPI) to know what & where the problem is ?
2- What can be the source of this problems
3- What I have to Re-tune in order to solve this pb ?

Thank you by advance.

Jo

Hello,

1) Check the transmission links btw RNC and MSC. I don't know much about NSN products, but for some other vendors you can force the subscriber to each trunk link and observe the voice quality of the call on that link.
2) If it is not the case you also can check the voice processing hardware part in RNC or MSC by many ways.
3) I don't think the KPI checking can find the problems.

Cheers!

[josef]

Hello,

1) Check the transmission links btw RNC and MSC. I don't know much about NSN products, but for some other vendors you can force the subscriber to each trunk link and observe the voice quality of the call on that link.
2) If it is not the case you also can check the voice processing hardware part in RNC or MSC by many ways.
3) I don't think the KPI checking can find the problems.

Cheers!

Bro,

1st, thank u for yr answer.

How to check the voice processing hardware part in RNC or MSC ?

[rayhan]

Hi,

Could you please provide below information :

1. Does your network support TRFO operation or have you recently enabled it in your network? As there are few handsets which have problem with TRFO operation, hence not a network issue.
2. "Customer" means X no of users or only one?, check if this problem is seen only in one specific area then you can check network KPI. Poor voice quality could be due to pilot pollution at some places where all cells <serving and neighbor> have almost same signal strength.
3. What is active window size set in your network?
4. No of neighbors should not be more than 10.
5. Check if HO relationship is bi-directional.

Other than this I don't feel this could be RNC issue etc ..as if this is the case this should impact whole network.

Apart from this if you are taking regular backups for you network <RNC etc> at extreme cases you can restore it to "Golden Restore" point....
:)

[rayhan]

Some more information needed ..you have mentioned that your network comprises of UMTS 900 and UMTS 2100 bands.
Which one is HPLMN and EPLMN ?
Is Inter Band HO enabled in your network?

[zee86]

Bro,

1st, thank u for yr answer.

How to check the voice processing hardware part in RNC or MSC ?

For HW part just check alarms in RNC and MSC. If HW part have any problem it comes in alarm list

[gprastomo]

Hello First of all i will focus on Radio point of view, lets ignore the other ( i mean the other entity is good health).

THe bad voice quality is identified by bad MOS (below MOS 3), you have to make drivetes on all network, then get the mos value and filter the location which has moS <3. then find the cell and area.
The bad mos value most pobrably due to bad coverage (RSCP or ecno). I can explain by this way -> during amr call, the node b send the target EbNO and BLER which should be maintained to keep the voice qos in good condition. If the ebno and bler is below the target value so power control should take necessary action to achieve this ebno value, not too high and not to small, either it is TCP 1 or TCP 0. Then achieving this one is related to SIR to be achieved by cells.

If in some case that the power already in max power, SIR already max (cut off) so cell cant maintain the EbNo/BLER -> QoS is disturbed, it means speech quality degraded.

Usually this condition appear in high radio load UL/DL, can be due to pilot pollution or external interference.
to solve this one so remove those kind of interference.

br



Dear friends,

I need your experience to resolve one pb in our network.

The situation is:

2G/3G network (GSM/DCS/U9/U21)
constructor: NSN for RAN & Core

We have bad voice quality for 3G call (I don't know in which band) reported by customers in capital city and we can feel also when we are blocking mobiles on 3G. (The pb appears since 3 days)

Please:

1- What to check (param, counters, KPI) to know what & where the problem is ?
2- What can be the source of this problems
3- What I have to Re-tune in order to solve this pb ?

Thank you by advance.

Jo

[zee86]

Hello First of all i will focus on Radio point of view, lets ignore the other ( i mean the other entity is good health).

THe bad voice quality is identified by bad MOS (below MOS 3), you have to make drivetes on all network, then get the mos value and filter the location which has moS <3. then find the cell and area.
The bad mos value most pobrably due to bad coverage (RSCP or ecno). I can explain by this way -> during amr call, the node b send the target EbNO and BLER which should be maintained to keep the voice qos in good condition. If the ebno and bler is below the target value so power control should take necessary action to achieve this ebno value, not too high and not to small, either it is TCP 1 or TCP 0. Then achieving this one is related to SIR to be achieved by cells.

If in some case that the power already in max power, SIR already max (cut off) so cell cant maintain the EbNo/BLER -> QoS is disturbed, it means speech quality degraded.

Usually this condition appear in high radio load UL/DL, can be due to pilot pollution or external interference.
to solve this one so remove those kind of interference.

br

bro if it is because high load then network upgrade is needed

[gprastomo]

bro if it is because high load then network upgrade is needed

Hello,

If there is no pilot pollution and you have high load, yes you need upgrade or you can do the traffic balance.

But if you have pilot polution and high load, you need to reduce this one no need to upgrade. But upgrading this, i think will not clean up the bad voice because the interference still there.

[zee86]

Hello,

If there is no pilot pollution and you have high load, yes you need upgrade or you can do the traffic balance.

But if you have pilot polution and high load, you need to reduce this one no need to upgrade. But upgrading this, i think will not clean up the bad voice because the interference still there.

Yes definitely interference is a big factor