Network/Connectivity Losing 4G data when receiving and during a call (Dual SIM)

  1. StealthEye95
    Eclair Jul 29, 2019

    StealthEye95 , Jul 29, 2019 :
    I'm making this thread due to the lack of answers for the 6T.

    Can someone (who actually knows for a fact) please explain why on my OnePlus 6T, I lose my 4G data connection on SIM 1 when receiving a phone call on SIM 2?

    As far as I've been able to find out, the 6T with having the SD 845, supports Dual Active 4G connections i.e. simultaneous 4G connections. But is this limited to only 4G i.e. if your network routes calls on any other connection e.g. 2G/3G, then it means all other 4G connections are disabled until the call has ended? Is it perhaps a network support thing where I need to receive a 4G call in order to maintain my 4G data connection? Why does my 4G data connection not switch down to 3G when receiving a phone call?

    For the record, both networks (in South Africa) I'm on (Vodacom & MTN) support VoLTE as well as 4G and yes I do have the "Dual 4G" setting turned on in my Network Settings on my 6T.

  2. C1564458934183
    Cupcake Jul 30, 2019

    C1564458934183 , Jul 30, 2019 :
    I'm having this exact issue - only just got a second SIM last week. Both SIMs are on the same provider (Telstra in Australia).

  3. StealthEye95
    Eclair Jul 30, 2019

    StealthEye95 , Jul 30, 2019 :
    Yeah I'd love some clarification around the "Dual 4G" and what is required for it to work as well as in what scenarios it drops 4G. I simply cannot find any information regarding the 6T.

  4. C1564458934183
    Cupcake Jul 30, 2019

  5. StealthEye95
    Eclair Jul 30, 2019

    StealthEye95 , Jul 30, 2019 :

  6. gkarkala
    Cupcake Aug 20, 2019

    gkarkala , Aug 20, 2019 :
    Unfortunately 6t is ONLY DUAL SIM DUAL STANDBY (DSDS). You need phones with DUAL SIM DUAL ACTIVE (DSDA) to use BOTH SIMs at the SAME TIME. This is a hardware based and cannot be changed with different ROMs.

    There are multiple threads on this issue. I also logged a ticket (and a discussion thread) when I got 6t back in Nov 2018.
    Unfortunately there are no flagship phones with DSDA feature that I know of.

  7. StealthEye95
    Eclair Aug 21, 2019

    StealthEye95 , Aug 21, 2019 :
    Hey thanks for the reply and and info. I completely understand what you're saying. However as in my original post, the 6T using the SD845 has the hardware in terms of the X20 modem to support Dual Active connections and it even states in the settings, "Dual 4G". So I guess one explanation could be that if both networks are 4G only and as such do calls and data purely on 4G and nothing else, then that might then allow for a data connection to remain active during a call on the other sim. But like I said, I'm not sure and there is almost no actual hard facts and nothing from OnePlus themselves properly explaining this anywhere which as a user is extremely infuriating.

    On a side note, please could you link these discussions that you speak of of having when you bought the 6T last year November.

  8. LegolasX
    Jelly Bean Aug 21, 2019

    LegolasX , Aug 21, 2019 :
    your device uses a single modem and is dual sim dual standby thus only one sim will receive calls at one time.
    if you have VoLTE active on any sim, have data enabled on it and get the call on same sim then your data connection will remain active.
    dual 4G simply means you will have 4G signals on both sim cards at same time on standby.

    StealthEye95 likes this.
  9. StealthEye95
    Eclair Aug 21, 2019

  10. StealthEye95
    Eclair Aug 21, 2019

  11. StealthEye95
    Eclair Aug 21, 2019

    StealthEye95 , Aug 21, 2019 :
    Ok that makes sense thanks for explaining. So to summarize if I understand what you're saying, the X20 modem in the SD845 in the 6T supports Dual VoLTE connections meaning HD calls on both SIMs negating the need to preference one SIM over the other for voice call quality. However, it still only supports 4G data on one SIM at a time meaning when a call comes in it has to deactivate the 4G data connection on whichever SIM is used for data and enable the VoLTE for the particular SIM that is receiving the call?