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I've read that most dual-SIM phones can only use the other SIM for 2G voice service.

Is OnePlus 2 DUAL SIM 4G any different?

  • OnePlus 2 is fully capable of LTE and 4G data on both of its SIM card slots. At least I can attest to this fact for the international model of the phone. I don't know about the American ones. – ADTC May 13 '17 at 17:03
  • @ADTC, your comment is very misleading; you appear to claim that either SIM slot can be used for 4G, which is technically true; but in reality, there is only one 4G radio, so, if you have no 2G GSM networks to access, then you can only go online with one slot at a time. E.g., the marketing is being very misleading by assuming that folks have access to GSM networks, which many operators have never had, and many others are in the process of shutting down. – cnst May 14 '17 at 19:13
  • indeed, what you said appears to be true. Although the phone can connect to 4G network on any of the two available SIM slots (which is what I meant in my comment), it only has one 4G radio, so the other SIM slot seems to connect using the 2G radio. (I have confirmed with an app called "Network Cell Info Lite".) Now my question is, is the 4G radio also used for 3G connections? Or is there a separate 3G radio? In which case, wouldn't it be possible to connect 4G on one slot, and 3G on the other? – ADTC May 16 '17 at 5:26
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No, OnePlus 2 is not any different.

In fact, users on the forum report that the dual SIM functionality apparently requires the presence of a 2G GSM network.

https://forums.oneplus.net/threads/dual-lte.328953/page-2

I have the OnePlus 2 (A2005) and am using it in Canada. SIM 1 on Telus (4G/LTE) and SIM 2 on Wind. When I want to use data on Wind, it switches SIM1 down to 2G. Except neither Telus nor Wind has 2G. So when I choose either one for data, it shuts down the other one completely due to lack of 2G. It doesn't just step it down to 3G. This makes the phone pointless for me. Due to their advertising I was hoping that both would be 4G simultaneously, not 4G on one and 2G on the other.

To summarise:

  • You can connect to any network from any SIM (e.g., can make either SIM a primary one)

  • The non-primary SIM can only connect to a 2G GSM network

  • If your non-primary operator lacks a 2G GSM network (which are being shutdown worldwide, and some GSMA operators never had any to start with), the non-primary SIM cannot connect to UMTS or LTE, and will thus be getting no signal at all

  • What? I've had OnePlus 2 for a few years now and I can access 4G data without any problem in both SIM cards. Unless your "second SIM is 2G only" is a purely American restriction that doesn't apply to the international version of the phone that I have, your answer will not match... – ADTC May 13 '17 at 16:59
  • @ADTC, please provide the source for your claim. Pretty much everyone else agrees as to the content of this answer; if you have different experience, and lack any sort of supporting documents, I think it's pretty clear that you must be the one that's confused. (Note that the claim is that there is physically only one 4G radio that can be active at any given time; sounds like you may be disputing a different claim that wasn't made above.) – cnst May 14 '17 at 19:06
  • as explained above, my comment only meant that any of the two SIM slots can be used for a 4G connection. I didn't mean that both SIM slots access 4G network at the same time. You're right in your answer, that when one slot is on 4G, the other is on 2G. But why can't the other be on 3G? Is the same radio used for both 4G and 3G? – ADTC May 16 '17 at 5:37
  • do you have any comment for the questions I had asked? – ADTC May 18 '17 at 7:59
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    @ADTC please discuss this in a chat, both of you have the required rep. Your comments are getting into the rude section, which is why they will be removed now. cnst: not that rude, but same procedure, please ;) – Izzy May 20 '17 at 12:20
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Off topic but not by much ... I have a Galaxy S7 Duos. My SIM 1 is T-Mobile set to "Auto" band (LTE/W-CDMA/GSM), and my SIM 2 is a foreign SIM that roams on the AT&T network here in the US - set to (GSM Only).

As OP said, their phone (and most dual-SIM phones that I'm aware of) only allow 3G/4G to run on ONE SIM, and the other SIM has to use GSM.

That's how it was on my S7 Duos for most of 2016. Then after updating the firmware recently (Marshmallow CPK5 if anyone's interested), My SIM 2 was now magically capable of doing "Auto" band (3G/GSM), and my SIM 1 was STILL capable of doing "Auto" band (LTE/W-CDMA/GSM)! Of course, from what I can tell, SIM 2 is just using UMTS bare-bones 3G - nothing fancy. But it's good enough.

I think phone manufacturers are wise to AT&T shutting down their GSM network by 2017. My update came in November 2016. So maybe other phones will get similar updates before 2017? Check around, contact your manufacturers. Good luck!

  • This would be good news if substantiated with confirmations from major phone manufacturers about updating their phones to do this. If the 2G radio can be repurposed for 3G (even just barebones, for receiving calls and SMS text), dual SIM phones wouldn't become useless after 2G networks are shut down and made obsolete. – ADTC May 16 '17 at 5:43

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