3G to 2G cell reselection in idle mode

[foufou007]

Dear experts,
I am experiencing a very weird behavior on our network. I have an iphone 4s and a Huawei android, I am in a very good 3G coverage area very close to the site. The iphone 4s keep going to 2G in idle mode every once in a while, the android does i but not that often. If I wanna quantify it, I would say the iphone 4s goes to edge 50% of the time but the android about 5%.
Any explanation?
Thanks

[ak_rf]

Hi,
We are also having similar problems with various phones in the Network. Did you manage to get any solution ?
Thanks

[a19997104]

what network do you have? huawei ?

[aluruwaichi@yahoo.com]

-->this problem seems to be specific to smart phones? or even other normal 3g phones? check if the iphone is transmitting with very high power to the RBS.It is very possible to miss it out.

[chronix_ray]

This is maybe due to parameter issue within what venndor.

[evertonESF]

Hi,

The some case, parameters for Selection and Reselection, the triggers are too near, for eg.: Qqualmin, IdleSintrasearch, SsearchRat.

[Handover24]

Issue solved Guys PLEASE ADD REPUTATION :-) Huawei has maden a mistake...check those parameters :
THRUTRANHIGH
THRUTRANLOW
default value is 20 on Hedex...but this is not OK because it means that if the LTE UE ( only UE read this SI2 quater message ) reselect UTRAN from Geran only if UTRAN RSCP is at 60 dBm...too high...puttong this value to 5 this issue has been solved :D



If the measured RSCP value of one or more neighboring UTRAN cells is higher than the value of this parameter, the MS is allowed to reselect a neighboring cell in UTRAN whose priority is higher than the GERAN priority. The values of this parameter correspond to the following decibel values: 0: 0 dB, 1: 2 dB, 2: 4 dB, 3: 6 dB, ..., 30: 60 dB, 31: 62 dB.





If the receive levels of the serving cell and all neighboring GSM cells are lower than "Low GSM Threshold Based on Priority", and if the measured RSCP value of one or more neighboring UTRAN cells is higher than the value of this parameter, the MS is allowed to reselect a neighboring cell in UTRAN whose priority is lower than the GERAN priority. The values of this parameter correspond to the following decibel values: 0: 0 dB, 1: 2 dB, 2: 4 dB, 3: 6 dB, ..., 30: 60 dB, 31: 62 dB.




Release 8

19

15

64-QAM

MIMO

.82

35.3



Release 8

20

15

64-QAM

MIMO

.98

42.2



Release 8

21

15

16-QAM

Dual-Cell (http://www.finetopix.com/wiki/High-Speed_Downlink_Packet_Access#Dual-Cell)

.81

23.4



Release 8

22

15

16-QAM

Dual-Cell

.97

28.0



Release 8

23

15

64-QAM

Dual-Cell

.82

35.3



Release 8

24

15

64-QAM

Dual-Cell

.98

42.2



Release 9

25

15

16-QAM

Dual-Cell + MIMO

.81

46.7



Release 9

26

15

16-QAM

Dual-Cell + MIMO

.97

55.9



Release 9

27

15

64-QAM

Dual-Cell + MIMO

.82

70.6



Release 9

28

15

64-QAM

Dual-Cell + MIMO

.98

84.4



Release 10

29

15

64-QAM

Triple-Cell

.98

63.3



Release 10

30

15

64-QAM

Triple-Cell + MIMO

.98

126.6



Release 10

31

15

64-QAM

Quad-Cell

.98

84.4



Release 10

32

15

64-QAM

Quad-Cell + MIMO

.98

168.8



Release 11

33

15

64-QAM

Hexa-Cell

.98

126.6



Release 11

34

15

64-QAM

Hexa-Cell + MIMO

.98

253.2



Release 11

35

15

64-QAM

Octa-Cell

.98

168.8



Release 11

36

15

64-QAM

Octa-Cell + MIMO

.98

337.5








if then your net is ok....add me reputation :-) UEs which could be affected are :

[giegala]

Reputation added. It is exactly the problem. We had to switch off 2G- LTE reselection support .

[fahmi]

Dear Hnadover24,

Could you please explain "the LTE UE ( only UE read this SI2 quater message ) reselect UTRAN from Geran only if UTRAN RSCP is at 60 dBm" because the default value 20 correspond to 40 db !!
Also does putting these parameters to 5 push the CS traffic from 2G to 3G ??

BR,
Fahmi

[Handover24]

Fahmi I think there is a great mistake on Huawei Documents. Putting 5 it means -110-2*5 so reselection on UTRAN will be done on -100.
We were having a lot on complaints....solved changed this parameters....we found them on SI2quater message.
If you put that to 20...reselection will be done at 60=110-2*20.
Best regards.

[Handover24]

pay attention also to the condition UTRANPRI must to be > GERANPRI :D

[giegala]

Well, when we were debugging the issue, i had different assumption.

IRAT reselection for the phone supporting LTE is quite different. In this case each network layer (including carrier layer) is assigned a priority. The phone will camp on the highest priority layer if signal level for the layer is above threshold of particular layer.

So my assumption was, that Huawei assigns higher priority to 2G, than the priority is assigned to 3G, therefore the phone will be driven to 2G. Actually, we had cases of phone going from 3G to 2G at a very good signal level of 3G (RSCP >-60).

Too bad i had no time to verify the case.

[Muhammad Imran Rafique]

Hi All,

I would like to highlight E// (2G-->3G/LTE) reselection default values, which too are somehow has created a problem in reselections.

GSM (G10B) onwards selection priority concept is added and its compulsory if you want direct reselection to LTE from GSM.

Based on RxLev, RSCP, RSRP, selection proiroty is calculated and then further particular cell is selected within that technology.

We experienced same case in one of E// NW where default parameter settings are applied and many Ue stuck in 2G, reason is as.

Default Settings allows reselection as

LTE (RSCP > QRXLEVMINE(-140) + HPRIOTHR(44))
RSRP: -96 dBm for LTE
_______________________________________________________


UTRAN (RSCP > QRXLEVMINU(-119) + HPRIOTHR(18))
RSCP: -101 dBm for 3G

on top of it FDDQMIN is always applicable -12dB
________________________________________________________

Default settings are too aggressive and we recommend here to revise HPRIOTHR as

UTRAN (2) ~ 4dB

LTE (10) ~ 20dB

BR//
Imran

Note: Plz add reputation, if it is really helpful for you.