Z5 Dual unable to connect 2nd sim on ATT network in USA

[TZMike]

Just today I received a new Z5 Dual to replace a Z3+ Dual which started acting up. I like the dual sim with dual sim standby capability as a way to eliminate carrying around a 2nd cell phone. The problem with the Z3+ was that on Wed 01-04-2017 it stopped establishing a USA ATT network connection on the 2nd sim. Swapping the sim positions didn't help. And data transfer also stopped working altogether. Rather than try to figure out the problem buying a new phone seemed a quicker solution.

I chose the Z5 Dual and am happy with the quality of the case and the sleek look. I installed both sims and restored all the contacts, texts, etc backed up from the Z3+ Dual. I was able to get both sims working, but not at the same time.

So here is the issue: In settings/more/mobile networks if the preferred network type of one sim is set for LTE/WCDMA/GSM the other one automatically defaults to GSM. Unfortunately the sim set for GSM does not connect to a mobile network. I went to the local ATT office for help but they had no answers. I looked around on-line and found this:

https://www.att.com/esupport/article.html#!/wireless/KM1084805   AT&T 2G GSM 850/1900MHz network shutdown

It seems that ATT has recently shut down the 2G GSM network to provide more bandwidth for the 4G LTE network.

I tried switching to 3G WCDMA network but the phone always defaults the other sim to GSM.

So now it seems I have a dual sim cell without the dual standby feature.

Has anyone else seen this?

Is Sony aware of this network change which has eliminated the desirable dual standby feature?

Hopefully there is a solution?

Thanks in advance for any help...

Regards,

Mike

[MarlonUk1]

the Z5 Dual supports the following bands:

2G bands	GSM 850 / 900 / 1800 / 1900 - SIM 1 & SIM 2
3G bands	HSDPA 850 / 900 / 1700(AWS) / 1900 / 2100 - E6633, E6683
4G bands	LTE band 1(2100), 2(1900), 3(1800), 4(1700/2100), 5(850), 7(2600), 8(900), 12(700), 17(700), 20(800) - E6633
	LTE band 1(2100), 2(1900), 3(1800), 4(1700/2100), 5(850), 7(2600), 8(900), 12(700), 17(700), 20(800), 38(2600), 39(1900), 40(2300), 41(2500) - E6683

and the at&T shut down of 2g bands happened after a year the device was released. so sony wouldn't any control regarding this situation, as far as I know most dual sim phones work the same as Z5 did.

http://support.sonymobile.com/global-en/xperiaz5dual/userguide/Selecting-mobile-networks/

Your device supports the use of two different networks at the same time. You can select from the following network mode combinations when two SIM cards are inserted in your device:

• One LTE network and one GSM network
• One WCDMA network and one GSM network
• Two GSM networks

[TZMike]

Thanks for the list of supported networks.

I'm not suggesting Sony had any control over the shutting down of an ATT network. I'm wondering if anyone else has had this problem in the USA, and if there may be any solutions available, and/or if anyone is even working on a solution.

Looking at available dual sim phones from Sony and others it seems this will be more of an issue in the future as other carriers drop 2G networks in favor of 3G and 4G..

I am curious why it is not possible to use LTE for both sims. Would the phone need a 2nd set of circuitry for the 2nd LTE?

Thanks,

Mike

[Uliwooly]

@TZMike

I'll escalate this 

[MarlonUk1]

@TZMike.. there are lots more to learn about dual sim tech. https://www.quora.com/Why-cant-we-use-3G-4G-on-two-Sim-cards-together-in-the-same-mobile

in most part it is due to hardware configuration that limits this capability.

[TZMike]

Thanks. I'd be interested in how this news is received up the ladder...

[TZMike]

good info in that link. thanks.

So with the elimination of the G2 network the Z5 Dual (and almost all DSDS dual sim phones) has become a DSSS phone, at least on the ATT network in the USA.

Mike

[pressefr]

Dual SIM issue. After some trouble shooting and calling I found the reason why.

I found out that AT&T in the US has turned off all their 2G networks the begining of the year for 2017. That is why my 2nd SIM card on my Sony Xperia Z5 Premium Dual recently stop working. From my understanding one SIM is 4G LTE for Data Text Calling and the other ran on 2G via calls and text.

Now Sony will have to make Dual SIMs differently internally as two SIMs cannot both be on LTE technically to have both on a signal 4G LTE. Maybe you have to have put in two independent antennae for their next gen of Dual SIM phones.

Endless there is a solution to configure my 2nd sim to read 3G via APN manual setting. Or a software update to manage two 4G LTE SIMs simultaneously.

I read that Europe may close their 3G before their 2G, and plan to shut down 2G in 2020. So perhaps it maybe still useful when I travel outside the country.

With 5G recently shown at CES 2017. How will Sony produce their Dual SIM phones now?

[MarlonUk1]

Xperia XZ dual has this following configurations:

Your device supports the use of two different networks at the same time. You can select from the following network mode combinations when two SIM cards are inserted in your device:

• One LTE network and one WCDMA network
• One LTE network and one GSM network
• Two WCDMA networks
• One WCDMA network and one GSM network
• Two GSM networks

http://support.sonymobile.com/global-en/xperiaxzdualsim/userguide/Selecting-mobile-networks/

[TZMike]

Thanks for that ZX Dual info. Sounds like that's the way to go for ATT network in the US.

I tried using the WCDMA 3G network on my Z5 Dual and found that it did work with either sim. Unfortunately the other sim always defaults to GSM 2G.

I wonder if a firmware update could allow the Z5 Dual to access the WCDMA 3G network by default instead of the now defunct ATT GSM 2G network- in other words can the Z5 Dual be made to work like the ZX Dual?

Now that would be serious Sony support!

It has been very frustrating to constantly switch back and forth between the two sims just to see if I have missed any text messages. And there is not way to tell if I have missed any calls on the inactive sim unless the caller leaves a voicemail.

It looks like I will need to start carrying around a 2nd phone again.

Mike

anyone interested in a Z5 Dual for cheap? Only used for about 1 week