New 4g+ Not Working With Bands 1800+2600mhz


Odrilow

Odrilow

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Nov 9, 2017
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Hello dear miui users, I have a Big problem with the Xiaomi Mi Mix 2 with the 4G+ it cant aggregate with 1800+2600 bands in my country (France) with Freemobile (Carrier). It works correctly with 800/700+2600. And for me this is anoying. Can Someone explain me why this is not working? because my friend with a OnePlus 5 have it in the same area :/ or if there is a tool to flash the modem ? Maybe I can wait for the next Android Oreo?'

  • Xiaomi Mi Mix 2 (Chiron)
  • Beta 7.12.21
 
Last edited:
Odrilow said:
Hello dear miui users, I have a Big problem with the Xiaomi Mi Mix 2 with the 4G+ it cant aggregate with 1800+2600 bands in my country (France) with Freemobile (Carrier). It works correctly with 800/700+2600. And for me this is anoying. Can Someone explain me why this is not working? because my friend with a OnePlus 5 have it in the same area :/ or if there is a tool to flash the modem ? Maybe I can wait for the next Android Oreo?'

  • Xiaomi Mi Mix 2 (Chiron)
  • Beta 7.12.21
Click to expand...
The CA Matrix is dependent on the RF devices, and how they are configured.

4G+ is NOT dependant on Carrier Aggregation (CA), so your problem of no 4G+ is not related to the CA Matrix.

The prime determinant of 4G+ is the downlink quality (SINR). It can also be blocked by an operator for certain service classes of SIM, i.e. prepaid or low-cost plans - not that this appears to be the situation in your case, as 4G+ is working with 700 and 2600 CA, if I understand your situation correctly.

Is your friend with OP5 using the same carrier?

From what I can see the Operator has LTE700, 1800 and 2600, but no indication which bands they have available for CA.

CA needs to be configured in the network elements, (MME and eNodeB), as they advise the mobile which bands are available for CA.Then the UE reports what CA combinations it is capable of, and if the SINR is suitable BEFORE the network will decide if there is the requirement for CA to meet the downlink demand, prior to sending the UE a Radio Bearer Reconfiguration message to activate it.

My guess is that the operator has not enabled LTE 1800 & 2600 CA, due to capacity limitations or some other technical reason.
 
Last edited:
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Odrilow said:
Hello dear miui users, I have a Big problem with the Xiaomi Mi Mix 2 with the 4G+ it cant aggregate with 1800+2600 bands in my country (France) with Freemobile (Carrier). It works correctly with 800/700+2600. And for me this is anoying. Can Someone explain me why this is not working? because my friend with a OnePlus 5 have it in the same area :/ or if there is a tool to flash the modem ? Maybe I can wait for the next Android Oreo?'

  • Xiaomi Mi Mix 2 (Chiron)
  • Beta 7.12.21
Click to expand...
If your device is rooted, please install Network Signal Guru, and post screenshots of screens 6 (default), 5 (swipe left-to-right once from default) and 1, then I will have a better chance to identify the issue for you.
 
GreasyMonkey1960 said:
The CA Matrix is dependent on the RF devices, and how they are configured.

4G+ is NOT dependant on Carrier Aggregation (CA), so your problem of no 4G+ is not related to the CA Matrix.

The prime determinant of 4G+ is the downlink quality (SINR). It can also be blocked by an operator for certain service classes of SIM, i.e. prepaid or low-cost plans - not that this appears to be the situation in your case, as 4G+ is working with 700 and 2600 CA, if I understand your situation correctly.

Is your friend with OP5 using the same carrier?

From what I can see the Operator has LTE700, 1800 and 2600, but no indication which bands they have available for CA.

CA needs to be configured in the network elements, (MME and eNodeB), as they advise the mobile which bands are available for CA.Then the UE reports what CA combinations it is capable of, and if the SINR is suitable BEFORE the network will decide if there is the requirement for CA to meet the downlink demand, prior to sending the UE a Radio Bearer Reconfiguration message to activate it.

My guess is that the operator has not enabled LTE 1800 & 2600 CA, due to capacity limitations or some other technical reason.
Click to expand...

"Is your friend with OP5 using the same carrier?" Yes the same carrier (Freemobile) at the same location. and my carrier is the first for 4G+ for the moment with 1800+2600 bands.

There is a video:
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And I know the coverage is poor here where I am but when I get closer to the antenna is the same. When i'm on 2xCA, this is my second sim on carrier Orange with 800+2600 aggregation.

I have also created a thread on XDA forum and a bug repport on Official Xiaomi forum.
https://forum.xda-developers.com/mi-mix-2/help/4g-bands-1800-2600mhz-t3728419
http://en.miui.com/thread-1419511-1-1.html
 
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Odrilow said:
"Is your friend with OP5 using the same carrier?" Yes the same carrier (Freemobile) at the same location. and my carrier is the first for 4G+ for the moment with 1800+2600 bands.

There is a video:
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And I know the coverage is poor here where I am but when I get closer to the antenna is the same. When i'm on 2xCA, this is my second sim on carrier Orange with 800+2600 aggregation.

I have also created a thread on XDA forum and a bug repport on Official Xiaomi forum.
https://forum.xda-developers.com/mi-mix-2/help/4g-bands-1800-2600mhz-t3728419
http://en.miui.com/thread-1419511-1-1.html
Click to expand...
Thanks for the additional information.
Looking at the video, your RSRP is very low, at -121dBm or lower. The SINR values are at what I would expect for that level of RSRP, so the modem appears to be functioning OK. A SINR below +4 or +5dB is likely not going to be sufficient to trigger 4G+, but that is dependent on the network settings - unfortunately not something we can access OTA.

If your friend can get 4G+ and 2CA at a given point, and you cannot with your phone, have you tried swapping SIM's, to eliminate the SIM as an issue (not at all likely, but best to eliminate it)?

If L1800 is at such a low level, then L2600 would not be detectable from the same e-NodeB, assuming that intra-site CA is used, not inter-site CA (the latter is rarely deployed, due to X2 interface transport availability and latency issues).

From the information given, it looks like a faulty antenna or RF front-end in your device.

Sorry that I cannot give you a more complete diagnosis.
 
Last edited:
GreasyMonkey1960 said:
Thanks for the additional information.
Looking at the video, your RSRP is very low, at -121dBm or lower. The SINR values are at what I would expect for that level of RSRP, so the modem appears to be functioning OK. A SINR below +4 or +5dB is likely not going to be sufficient to trigger 4G+, but that is dependent on the network settings - unfortunately not something we can access OTA.

If your friend can get 4G+ and 2CA at a given point, and you cannot with your phone, have you tried swapping SIM's, to eliminate the SIM as an issue (not at all likely, but best to eliminate it)?

From the information given, it looks like a faulty antenna or RF front-end in your device.

Sorry that I cannot give you a more complete diagnosis.
Click to expand...
Yes signal is very poor I said it but when I'm going outdoor when the signal is under -100dBm is the same. The phone won't aggregate on 1800 and the OnePlus can... I've talked to some devs on XDA and is probably because the baseband / modem or whatever in relationship with LTE needs to be updated by Xiaomi.
 
There is a screenshot of my friend using the OnePlus 5.
 

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Here is an assumption: In France the band used is B3=1800 and can not aggregate with this one because it probably set the other the B9 band.
 
Odrilow said:
Yes signal is very poor I said it but when I'm going outdoor when the signal is under -100dBm is the same. The phone won't aggregate on 1800 and the OnePlus can... I've talked to some devs on XDA and is probably because the baseband / modem or whatever in relationship with LTE needs to be updated by Xiaomi.
Click to expand...
My Mi Mix 2 successfully has had B1, B3 and B5 as inter-site CA, and also B3 intra-band CA (2CA), so I can say that there is not a generic issue in the hardware or modem firmware.
 
GreasyMonkey1960 said:
My Mi Mix 2 successfully has had B1, B3 and B5 as inter-site CA, and also B3 intra-band CA (2CA), so I can say that there is not a generic issue in the hardware or modem firmware.
Click to expand...

So you have the Mi Mix 2 in Spain and B3 1800Mhz aggregates with 2600Mhz ? Do you have a screenshot of that ?
 
Odrilow said:
Here is an assumption: In France the band used is B3=1800 and can not aggregate with this one because it probably set the other the B9 band.
Click to expand...
Japan is the only market in the world that uses B9, and your phone is clearly working on B1800, so the B9 assumption is not correct.

Using the Band Lock function on Network Signal Guru, try going out to a place with strong signal, block all but B7 (2600) and see if you can get a measurement on it.

I cannot check the B3/B7 CA capability of the Mix 2 at present, but I can assure you that the Mix 2 device with B3 does aggregate correctly with other LTE bands.
If your device does not aggregate other LTE bands, then it is a individual device fault, not a systemic hardware, ROM or Modem software problem causing the problem.
 
Odrilow said:
So you have the Mi Mix 2 in Spain and B3 1800Mhz aggregates with 2600Mhz ? Do you have a screenshot of that ?
Click to expand...
I was getting B1, B3 and B5 in Manila, Philippines (Smart Communications) where I was working, and now seeing 2CA intra-band on B3 with Telia in Finland.
I will need to check back through my screenshots, see if I have one.
EDIT: yes, I have a screenshot, will try to upload it.
 
GreasyMonkey1960 said:
I cannot check the B3/B7 CA capability of the Mix 2 at present, but I can assure you that the Mix 2 device with B3 does aggregate correctly with other LTE bands.
Click to expand...
Ok, for my case I assure you when i'm in low or high RSCP the Xiaomi Mi Mix 2 B3 1800Mhz band can't be aggregated in France on Freemobile Carrier.
New video:
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GreasyMonkey1960 said:
I was working, and now seeing 2CA intra-band on B3 with Telia in Finland.
I will need to check back through my screenshots, see if I have one.
EDIT: yes, I have a screenshot, will try to upload it.
Click to expand...
Ok, fine but My carrier can only do inter-band.
 
GreasyMonkey1960 said:
I will try tomorrow when I am back in a city-centre in Finland, I expect there should be B7 (I know there is B3), shall post the results tomorrow evening.
Click to expand...

And if you see theses screenshots this looks like the phone has LTE-CA 1800Mhz but no CA in Signal Guru...
AP5BrHOwqkIIDHisWYOlp9JFWXthTM.png

nP86UUblXljCiBMwrGrMDFJbIMww9S.png
 
GreasyMonkey1960 said:
What are the tools used for these screenshots?
Click to expand...
This is RNC Mobile, An app developped by French for Freemobile Carrier to identify Antenas and evaluate the performances. the other app is Netmonster.

GreasyMonkey1960 said:
Will look for an area with B3/B7 2CA this evening.
Click to expand...
Ok, good :) Hope you can't aggregate ^^ Otherwise it would mean that it's my model that has a modem problem. (Is it possible?) ^^
 
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