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auto_art
2011-09-27, 06:08 PM
hi
one of my collegue changed timer T305 and T308 in E/// from 30s to 1s.

and he has observed in improvement in tch rop rate from 0.9 to 0.8 at nbh.

pl share your views.

zhanglw268
2011-09-28, 04:26 AM
I assume that your coleague changed the MSC side timer T305 and T308, your coleague did a "clever" trick to let the MSC clear the call early before the BSS side peg the drop call statistics. In long run, your coleague just plays around these timer parameters and doesn't improve the network quality. I saw similar actions before.

Here are the explanation what these 2 timers are used for.

T305 timer is started at the MSC/MS when DTAP message DISCONNECT is sent, this will guard the DISCONNECT procedure run correctly in T305 period.

T308 timer is started at the MSC/MS when DTAP message RELEASE is sent after the DISCONNECT procedure, this timer guards how long the RELEASE procedure runs.

(GSM 04.08 section 5.4 call clearing)

T305 and T308 at MSC should be set to no less than 11 seconds to guarantee that the layer 2 T200 is timing out N200 times on the air interface, reducing these timers to less than 11 seconds will pull them below the related BSS timers[T200*(N200+1) in this case] at the air
interface that are used to ensure a successful transmission of a message (DISCONNECT and RELEASE in this case) to/from the mobile over the air interface. Normally the higher level MSC timers would be set longer than the related lower level times in the BSS, using a strategy that lower level timers should expire first.

Setting T305 and T308 to less than 11 seconds here is forced the higher level MSC timers to expire before the BSS timers[T200*(N200+1) and link_fail(only for MSC issuing DISCONNECT/RELEASE first)] when there are air interface transmission problems (RF interference) for DISCONNECT and RELEASE signalling, and as a result the BSS statistics SD/TCH drop doesn't get a chance to peg for T200*(N200+1).

The end user experience is probably not that relevant here as they were trying to clear the call anyway. The end user would see no difference.

However the network operator could be fooled here though thinking that he has a clean RF interface with a lower drop call rate, when in fact there could be RF interference issues to be resolved. The low MSC timers are just masking it.

auto_art
2011-09-28, 12:59 PM
I assume that your coleague changed the MSC side timer T305 and T308, your coleague did a "clever" trick to let the MSC clear the call early before the BSS side peg the drop call statistics. In long run, your coleague just plays around these timer parameters and doesn't improve the network quality. I saw similar actions before.

Here are the explanation what these 2 timers are used for.

T305 timer is started at the MSC/MS when DTAP message DISCONNECT is sent, this will guard the DISCONNECT procedure run correctly in T305 period.

T308 timer is started at the MSC/MS when DTAP message RELEASE is sent after the DISCONNECT procedure, this timer guards how long the RELEASE procedure runs.

(GSM 04.08 section 5.4 call clearing)

T305 and T308 at MSC should be set to no less than 11 seconds to guarantee that the layer 2 T200 is timing out N200 times on the air interface, reducing these timers to less than 11 seconds will pull them below the related BSS timers[T200*(N200+1) in this case] at the air
interface that are used to ensure a successful transmission of a message (DISCONNECT and RELEASE in this case) to/from the mobile over the air interface. Normally the higher level MSC timers would be set longer than the related lower level times in the BSS, using a strategy that lower level timers should expire first.

Setting T305 and T308 to less than 11 seconds here is forced the higher level MSC timers to expire before the BSS timers[T200*(N200+1) and link_fail(only for MSC issuing DISCONNECT/RELEASE first)] when there are air interface transmission problems (RF interference) for DISCONNECT and RELEASE signalling, and as a result the BSS statistics SD/TCH drop doesn't get a chance to peg for T200*(N200+1).

The end user experience is probably not that relevant here as they were trying to clear the call anyway. The end user would see no difference.

However the network operator could be fooled here though thinking that he has a clean RF interface with a lower drop call rate, when in fact there could be RF interference issues to be resolved. The low MSC timers are just masking it.


do you kno the command to change the same form MSC side.?

auto_art
2011-09-30, 01:52 PM
I assume that your coleague changed the MSC side timer T305 and T308, your coleague did a "clever" trick to let the MSC clear the call early before the BSS side peg the drop call statistics. In long run, your coleague just plays around these timer parameters and doesn't improve the network quality. I saw similar actions before.

Here are the explanation what these 2 timers are used for.

T305 timer is started at the MSC/MS when DTAP message DISCONNECT is sent, this will guard the DISCONNECT procedure run correctly in T305 period.

T308 timer is started at the MSC/MS when DTAP message RELEASE is sent after the DISCONNECT procedure, this timer guards how long the RELEASE procedure runs.

(GSM 04.08 section 5.4 call clearing)

T305 and T308 at MSC should be set to no less than 11 seconds to guarantee that the layer 2 T200 is timing out N200 times on the air interface, reducing these timers to less than 11 seconds will pull them below the related BSS timers[T200*(N200+1) in this case] at the air
interface that are used to ensure a successful transmission of a message (DISCONNECT and RELEASE in this case) to/from the mobile over the air interface. Normally the higher level MSC timers would be set longer than the related lower level times in the BSS, using a strategy that lower level timers should expire first.

Setting T305 and T308 to less than 11 seconds here is forced the higher level MSC timers to expire before the BSS timers[T200*(N200+1) and link_fail(only for MSC issuing DISCONNECT/RELEASE first)] when there are air interface transmission problems (RF interference) for DISCONNECT and RELEASE signalling, and as a result the BSS statistics SD/TCH drop doesn't get a chance to peg for T200*(N200+1).

The end user experience is probably not that relevant here as they were trying to clear the call anyway. The end user would see no difference.

However the network operator could be fooled here though thinking that he has a clean RF interface with a lower drop call rate, when in fact there could be RF interference issues to be resolved. The low MSC timers are just masking it.


Hi pl go through attachement..it is detailed explaination.

i recieevd it from E*******.!

it includes commands to change too..!

auto_art
2011-10-06, 03:57 PM
hey did u people aplied the same in your network.?

it is realy giving good results.

parsarka
2011-10-09, 01:43 PM
Hi,Could you please tell me what are the names of these timers in NSN systems and the command to execute the same...please let me know as i need it urgently..thnx

justdream
2011-11-25, 09:12 PM
(GSM 04.08 section 5.4 call clearing)

T305 and T308 at MSC should be set to no less than 11 seconds to guarantee that the layer 2 T200 is timing out N200 times on the air interface, reducing these timers to less than 11 seconds will pull them below the related BSS timers[T200*(N200+1) in this case] at the air
interface that are used to ensure a successful transmission of a message (DISCONNECT and RELEASE in this case) to/from the mobile over the air interface. Normally the higher level MSC timers would be set longer than the related lower level times in the BSS, using a strategy that lower level timers should expire first.

Dear, could you please share GSM Spec. DOc that contains this information?

fmomani
2012-01-16, 10:35 PM
Hi Guys,
we tried to change the timers as below in our network (E/// Core):
T305: 30 --> 2 Sec
T308: 30 --> 1 Sec

we have witnessed around 13% decrease in E/// BSC TCH Drop call rates and 40% decease in Huawei BSC TCH Drop Call rates.
however, the reduction in call drops were noticed in all kind of drops (for Huawei) and not only T200 expiry.

takeiteasy612
2012-02-10, 07:31 PM
I assume that your coleague changed the MSC side timer T305 and T308, your coleague did a "clever" trick to let the MSC clear the call early before the BSS side peg the drop call statistics. In long run, your coleague just plays around these timer parameters and doesn't improve the network quality. I saw similar actions before.

Here are the explanation what these 2 timers are used for.

T305 timer is started at the MSC/MS when DTAP message DISCONNECT is sent, this will guard the DISCONNECT procedure run correctly in T305 period.

T308 timer is started at the MSC/MS when DTAP message RELEASE is sent after the DISCONNECT procedure, this timer guards how long the RELEASE procedure runs.

(GSM 04.08 section 5.4 call clearing)

T305 and T308 at MSC should be set to no less than 11 seconds to guarantee that the layer 2 T200 is timing out N200 times on the air interface, reducing these timers to less than 11 seconds will pull them below the related BSS timers[T200*(N200+1) in this case] at the air
interface that are used to ensure a successful transmission of a message (DISCONNECT and RELEASE in this case) to/from the mobile over the air interface. Normally the higher level MSC timers would be set longer than the related lower level times in the BSS, using a strategy that lower level timers should expire first.

Setting T305 and T308 to less than 11 seconds here is forced the higher level MSC timers to expire before the BSS timers[T200*(N200+1) and link_fail(only for MSC issuing DISCONNECT/RELEASE first)] when there are air interface transmission problems (RF interference) for DISCONNECT and RELEASE signalling, and as a result the BSS statistics SD/TCH drop doesn't get a chance to peg for T200*(N200+1).

The end user experience is probably not that relevant here as they were trying to clear the call anyway. The end user would see no difference.

However the network operator could be fooled here though thinking that he has a clean RF interface with a lower drop call rate, when in fact there could be RF interference issues to be resolved. The low MSC timers are just masking it.

Hi zhanglw268
Your information is very usefull, do you have the document that contain the information you've post ? If you know the document's name, it's very usefull for me.

mirtunjay_1975
2012-02-18, 10:28 PM
Hi firends coud u send your analysis after change T305 from 30 to 2 sec an T308 from 30to 1 sec.

your support will be highly appreciable.

auto_art
2012-02-18, 11:04 PM
Hi firends coud u send your analysis after change T305 from 30 to 2 sec an T308 from 30to 1 sec.your support will be highly appreciable.


my busy drops goes 5000 from 7500.

moh424
2012-02-27, 10:57 PM
The observed improvement in Huawei BSS after reducing timers values is much higher than the one observed in E*******, any ideas?

madeira
2012-03-27, 10:19 AM
Only a doubt, the T200 timer should be set to a value less than the T305 and T308. But what part of the T200 should be greater than the T305 and T305 would be the SACCH, TCH?
Another doubt in the case of the final value of the T200 timer must be done by multiplying the value by SDDCH n200?

gwood
2012-05-19, 08:30 AM
@auto_art (http://www.finetopix.com/member.php?23401-auto_art) an friends i cant found this commands in alex? To change these timers i need to change the firmware of MSC?
Do you have the fallback script?

madeira
2012-08-01, 08:23 AM
Gentlemen,

I would like to take a doubt. On my network changed the parameters T305 and T309 using the default value of Radio link. If I change the radio link to the maximum value using the values ​​of T305 and 309 would increase the number of drops?

The default value of the counters in the MSC currently allows low drop call is performing the disconnection before the end of the MS T200 correct?

auto_art
2012-08-01, 01:22 PM
Gentlemen,

I would like to take a doubt. On my network changed the parameters T305 and T309 using the default value of Radio link. If I change the radio link to the maximum value using the values ​​of T305 and 309 would increase the number of drops?

The default value of the counters in the MSC currently allows low drop call is performing the disconnection before the end of the MS T200 correct?

wee keep the default one for E/// & it worked fine. it is around 240ms for t200 n times.

moh424
2012-08-01, 11:32 PM
Exactly, setting a low value for these timers would lead to decreasing the call drop rate as it will hide some drops, I consider it as fake improvement

Shakeel_15
2012-08-02, 05:07 AM
T305 &T308 are MSC Timers.

Actually some optimizers set their values very low 2 and i sec respectively to reduce call drop due to T200.

This means these timers expires before t200(N200+1) expiry and shows improvement on radio side.

BR

hi
one of my collegue changed timer T305 and T308 in E/// from 30s to 1s.

and he has observed in improvement in tch rop rate from 0.9 to 0.8 at nbh.

pl share your views.

vipbinh
2012-09-21, 01:44 AM
anyone please seed the attachment to my email : still_a_lone@yahoo.com.
I haven't enough reputation to down it,yet. I need it very much.
And how to check this timer on MSC of Huawei and Erics vendor???

haroonazhar
2012-10-30, 09:28 PM
Hi pl go through attachement..it is detailed explaination.

i recieevd it from E*******.!

it includes commands to change too..!




Please send n email of this


haroonazhar@yahoo.com

thanks

michael.pangkerego
2013-01-17, 12:12 PM
hi..

Newbie just curious, your collegue just change the timer at MSC Side?or also timer at RADIO change like T200?
Thanx before...

michael.pangkerego
2013-01-17, 12:17 PM
hi auto_art

The Core and Radio in this situation, all E///?


Hi pl go through attachement..it is detailed explaination.

i recieevd it from E*******.!

it includes commands to change too..!

auto_art
2013-01-17, 01:00 PM
hi auto_art

The Core and Radio in this situation, all E///?


yeaah..all E///. but it should work for different BSS/ Core also as it is not a additional feature.

michael.pangkerego
2013-01-17, 03:56 PM
Thanx auto_art...
Btw, I send PM to u, cause newbie can't download ur attachment ;)


yeaah..all E///. but it should work for different BSS/ Core also as it is not a additional feature.

ventinel
2013-02-15, 03:36 PM
it will definitely improve DCR.. trial was made here and massive improvement was seen

hi
one of my collegue changed timer T305 and T308 in E/// from 30s to 1s.

and he has observed in improvement in tch rop rate from 0.9 to 0.8 at nbh.

pl share your views.

Ericsson_RND
2013-02-15, 04:22 PM
Dear All;

Based on below equation please provide optimum values for mentioned parameters if T305=2s and T308=2s,which need to be set to obtain good improvement on DCR.

T305 + 2*T308 < (N200+1)*T200

road2nowhere
2013-02-15, 05:51 PM
Let's be honest.....it doesn't improve the actual DCR, it just hides the T200 failures.....

As RF engineers, our objective should be to improve user perception, not manipulate KPIs.......

PS: I am not trying to point out anyone here ,just a general suggestion, that T305 & T308 should be standardized, but not for improving DCR.

Muhammad Imran Rafique
2013-02-17, 03:59 PM
Dear road2nowhere,

As it is not subscriber perceived drop rate, so no harm to have short values of T305 & T308 as low as 1sec.

BR//
Imran

road2nowhere
2013-02-18, 12:04 AM
Hi Imran,

Can u explain, why it is not perceived by the subscriber ?

user A --> excellent radio conditions
user B --> poor uplink
user A cannot hear user B clearly
user A disconnects the call
user B call should also be disconnect but the procedure to disconnect is long resulting in T200 failure on user B before the call is released, hence we shorten the timers..

But the issue remains, the subscriber perceives poor quality !!!....which we have tried to hide, very cleverly........

So there is harm......whether the user perceives a call drop or not.........the radio conditions are poor ....period !!

Ericsson_RND
2013-02-18, 12:07 AM
Hi Imran;

Thanks , but can you let me know what are obtimum values for N200 & T200 to achive below equation while set T305 & T308 as low as 1sec.


T305 + 2*T308 < (N200+1)*T200

Ericsson_RND
2013-02-18, 12:08 AM
Hi Imran;

Thanks , but can you let me know what are obtimum values for N200 & T200 to achive below equation while set T305 & T308 as low as 1sec.
Noting our vendor is E*******

T305 + 2*T308 < (N200+1)*T200[/QUOTE]

crisnspro
2013-02-18, 12:41 AM
short the MSC timer T305 and T308, will decrease the TCH DCR, 8 years ago, I tried it, nothing help about customer experience, this is a Chinese "Invention".

road2nowhere
2013-02-18, 12:53 AM
U r right crisnspro....it was implemented in ChinaMobile first..but now they have changed it back.....

we implemented with one huawei and one e******* network.......both times.....dcr came crashing down :D....but when we explained to the operators how it happened...they reverted it back...and rightly so !!!

radenmohawk
2013-02-18, 12:10 PM
Hi All,

As your experienced, After change timer T305 and T308 on core, does it need to soft reset the BSC's ? :rolleyes:

road2nowhere
2013-02-18, 12:57 PM
Hi, there's no need for that

Ericsson_RND
2013-02-19, 02:49 PM
Dear All;

Thanks , but can you let me know what are obtimum values for N200 & T200 to achive below equation while set T305 & T308 as low as 1sec.
Noting our vendor is E*******

T305 + 2*T308 < (N200+1)*T200

Ericsson_RND
2013-02-23, 05:25 PM
Gentelmen;

Please your kind support to let me know what are obtimum values for N200 & T200 to achive below equation while set T305 & T308 as low as 1sec.
Noting our vendor is E*******

T305 + 2*T308 < (N200+1)*T200

anujswitch
2013-03-15, 04:27 PM
i am not able to view the attached file

stream19
2013-03-15, 05:41 PM
the formula is T305 + 2*T308 > (N200+1)*T200 because with your formula you are hiding some drops especially when you reduce too much the T308.

iara
2013-07-11, 04:29 PM
Hi pl go through attachement..it is detailed explaination.

i recieevd it from E*******.!

it includes commands to change too..!

Anybody have ALEX document describing these command. This is need to do impact analysis for changing these parameters.

Optimustron
2013-09-08, 01:48 PM
Dear, could you please share GSM Spec. DOc that contains this information? Please find the GSM SPECIFICATIONS one is from ETSI and de last one is from 3GPP from 2003 this is the last one. Regards, 33598 33599

parsarka
2013-09-11, 01:52 PM
Hi...my system is NSN and tried the above but didnt observe and improvement...can u please let me knw how the same can be done in NSN??

Optimustron
2013-09-14, 02:37 AM
I'm working in E******* and Huawei systems, but the condition is the same you need to check that T305 + 2*T308 < (N200+1)*T200, this is the start point, for E******* default values you have:


N200 (SDCCH) = 23 times

N200 (SACCH) = 5 times



N200 (FACCH / F) = 34 times

N200 (FACCH / H) = 29 times






T200 (SDCCH) = 51 frames

T200 (SACCH) = 312-416 frames



T200 (FACCH / F) = 30 frames

T200 (FACCH / H) = 34 frames




And each frame is 4.616 ms and so in each case the product (N200 +1) * T200 gives, you can make the maths:


SACCH = 8.64 - 11.52 sec

FACCH = 5.65 sec



SDCCH / F = 4.85 sec

FACCH / H = 4.71 sec




From the above we arrive at the values T305 = 2 sec and T308 = 1 sec these values gives us 4 in the equation and the smallest of the above at right hand of equation is 4.71 seconds, the default is the same for both timers T305 = T308 = 30 seconds in our E******* system I didn't see the Huawei default values and I need to check that if the values apply, then you need to see that values in NSN in order to see if that values apply or need to be changed or they are optimized. I'm searching for counters in the MSC side in order to keep on track of the DISCONNECTIONS in order to don't get lost of areas of bad coverage.

prayoga
2013-10-24, 01:08 AM
Hi, those settings above for T200 is setable right?

Optimustron
2013-10-27, 06:38 AM
It depends, because for E******* some of this are hard coded, specially the timers I mentioned previously, however you can change the same timers but for Abis that are not the same, however in Huawei systems you can change that values for that timers in a cell basis, the command is SET GCELLCCTMR in order to change that and LST for viewing. Best regards,

Naruto28
2013-12-05, 09:14 AM
hi, how to view T305 & T398 actual values in MSC A interface (Printout command)?thks

Naruto28
2013-12-05, 09:16 AM
hi, how to view T305 & T308 actual values in E*******MSC A interface (Printout command)?thks

rosan
2014-09-01, 07:13 PM
Guys,

Have you tested these timers in 3G network? i.e. How this changes impact the 3G DCR if MSC is shared between 3G and 2G networks?

Thanks

Piparebo
2014-11-06, 07:41 AM
Ladies and Gentlemen,
I would like you to consider the differences between "drop rate counters" and "real drop rate". An improved KPI does not necessarily mean an improved network service. Not if we have manipulated the way we count without improving the traffic handling itself.

Also please consider that "drop" is not a clearly defined concept. Do we mean abnormally terminated radio session, do we mean dropped call during speech phase or something else? Well, it depends who you ask. From core perspective it could be most relevant to consider "failing use cases" but from RAN perspective it is more relevant to consider “all radio failures”.

Through the years it has become more and more focus on drop-rate KPI. Too much focus maybe, because for many people it seems to be more important to get low drop-rate figures than to actually improve something. The debate about the T305 and T308 is an example of this.

In general, hiding specific identified failing scenarios may lead to that we later on fail to identify new root causes producing the same scenarios. For example it could be that some new terminals or new bug in the system produce the same scenario and if not observable in the system we may miss this.

Way forward:
Regarding the timers:
Don’t destroy the observability in our systems by hiding important information. Keep timers T305 and T308 high, let RAN take care of the timing and accept higher number of drop counts.

Regarding “CM Service Reject”:
When a mobile deserts a channel abnormally (without handshaking with system) and establishes a new connection instead, it is important that core can handle this without rejecting the service just because the old connection has not been cleared yet.

Immediate clearing of deserted channel to free up resources:
When above happens core could ask RAN to free the old channel immediately. As RAN does not know for sure if the mobile is still there or completely gone, it has to wait a very long time before reusing the old channel to ensure that there will be no clashing between new call and old call on the channel. A new cause code from core to RAN would be required.