Inter System HO from 3G to 2G ; NSN versus Huawei

**kyokuman** · 2011-07-13, 05:22 PM

Hi Experts,

Regarding HO from 3G to 2G :

- Huawei uses 2D/2F

- NSN uses 1F/2F

As I am about to swap from NSN to Huawei, do you know how it can affect the behavior/performances?

Thanks for your help !

**Finetopix** · 2011-07-13 05:22 PM

**wolverine** · 2011-07-14, 04:03 AM

There isn't much difference in my opinion (assuming you set the threshold the same). If anything event 2D implementation is slightly better as the UE only sends this once to trigger the HO while for event 1F the UE needs to send this for ever RL in the AS.

**kyokuman** · 2011-07-14, 03:58 PM

Thanks.

That's the thing! After swapping few sites to Huawei, ISHO attempts increased by 4 times. Thresholds were mapped with NSN (-112dBm)

Huawei advised to increase 2D threshold to -110dBm, in order to decrease ISHO attempts.

When using 2D, conditions must be fullfilled on AS basis.
Why with NSN, it is more restrictive, all cells must fullfilled criterias.

**kyokuman** · 2011-07-14, 09:04 PM

What I wrote below doesnt explain the difference in terms of ISHO attempts I guess.

But I just noticed that Huawei uses an hysteresis (Hystfor2d) :
Qused < 2D_threshold - Hystfor2d/2

NSN, as far as I know, doesnt use any hysteresis. Condition to be fullfilled is Ecno_Threshold (FMCS)

You guys have probably some comments!? Thanks a lot ! I will add Rep for any answer

**agenov** · 2011-07-14, 09:18 PM

Originally Posted by kyokuman

What I wrote below doesnt explain the difference in terms of ISHO attempts I guess.

But I just noticed that Huawei uses an hysteresis (Hystfor2d) :
Qused < 2D_threshold - Hystfor2d/2

NSN, as far as I know, doesnt use any hysteresis. Condition to be fullfilled is Ecno_Threshold (FMCS)

You guys have probably some comments!? Thanks a lot ! I will add Rep for any answer

As far as i remember this is 3GPP so all the vendors must obey. Check 25.331 (if i am not wrong)

BR

**boring** · 2011-07-14, 11:01 PM

hi,

NSN triggers compressed mode when all cells in AS has triggered an event 1f which is completely equivelant with Huwaei (and E*******) behaviour of event 2d.

any difference in the amount of ISHO attempts is merely due to different RSCP thresholds. for a large UE population 1 or 2 dBs can make big difference!

you should remember also that NSN is using other triggers for CM apart from RSCP (e.g. EcNo, UE Tx power and some internal triggers). perhaps the others are causing this amount of ISHO attempts.

br

**kyokuman** · 2011-07-15, 07:31 PM

Hi guys,

I have only ISHO due to RSCP activated.

Huawei explained the difference of number of HO by saying that NSN uses 1F while Huawei uses 2D.

For me, the reason is more likely the hysteresis that is not used by NSN.
So the final threshold is simply different.

I just increased 2D_RSCP threshold by 2dB and number of HO attempts are same now, compare with before swap.
so now, I have :
-110dBm, while with NSN it was -112dBm.
Number of HO is same now.

More comments are of course welcome

**tilangminh** · 2011-07-15, 10:40 PM

anything else ??

**boring** · 2011-07-17, 09:20 PM

Originally Posted by kyokuman

Hi guys,

I have only ISHO due to RSCP activated.

Huawei explained the difference of number of HO by saying that NSN uses 1F while Huawei uses 2D.

For me, the reason is more likely the hysteresis that is not used by NSN.
So the final threshold is simply different.

I just increased 2D_RSCP threshold by 2dB and number of HO attempts are same now, compare with before swap.
so now, I have :
-110dBm, while with NSN it was -112dBm.
Number of HO is same now.

More comments are of course welcome

I think you are spot on now. essentially both approaches behave similarly and it is good to know that there is this difference between the two vendors because of the hysteresis

br

**twenty8** · 2011-07-27, 02:30 AM

Hi,

In NSN system, my understanding is that there is a time hysteresis which is normally set to about 100ms. So e1f is only send when the HHORscpThreshold (eg. -115 dbm) is meet for a period of 100ms (the hysteresis).

In Huawei system, as you mentioned the e2d is send when TUsed2d-H2d/2 , my understanding is that H2d has a default of 6 which makes it 3db , so if we set the trigger condition as same for NSN and HW , ie HHORscpThreshold = -115 dbm as well as TUsed2d = -115 dbm , we would actually get an earlier trigger in Huawei system, as the e2d is send when -115 - 3 = -112 dbm.

I believe this is the reason for the difference.