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Thread: A question about CA

  1. #16
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    Quote Originally Posted by zivan56 View Post
    That data from the other menu most likely comes from SIB4. It basically indicates all the potentially available bands that are on the network, not bands that are usable necessarily.
    Telus SIB4 would indicate B17 (EARFCN 5815) , but I've found Telus' rrcConnectionReconfiguration messages actually send you the B12 equivilent (EARFCN 5145) for CA, instead of B17, for some reason. So that would explain the discrepancy, which I also see here in Vancouver on a few devices (never seen any CA combo with B17, but all with B12).
    I am guessing since B12 is a superset of B17, they've decided to have more CA combos having B12 as a band rather than B17. But the reasoning is probably buried somewhere in the 3GPP standards documents or something.
    Ok, I guess that makes senses. I always look at the American side of the forums and the newer Samsungs at least, show band 12 now a days. True, that is more how ATT probably configures their networks but it would makes some sense for Canada to follow in that direction.
    I feel like a noob when it comes to understanding how all this works, even with reading up on things. I'm just glad others like yourself and sheytoon can help fill in the gaps.

  2. #17
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    Banter has been deleted. Please keep on topic. A ban has also been issued, and I'm happy to give out more. Let the moderators do the moderating. See an offending post? Report it and walk away! Responding in kind will get you some time away from the forums.

    Thank you for your cooperation

  3. #18
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    In Calgary on Bell I see them using band 12 as well for CA instead of band 17.

    Sent from my FRD-L04 using HoFo mobile app

  4. #19
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    Let's say my phone support B2-B4 CA, does it also support B4-B2? I have an honor 8.
    Specs for CA:
    Interband CA B2-B17,B5-B4,B5-B2,B2-B12,B2-B4
    Intraband Continuous CA: B2

    Sent from my FRD-L04 using HoFo mobile app

  5. #20
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    No, not necessarily.
    Want to learn more about how LTE works?
    https://productioncommunity.publicmo...ls/td-p/130581

  6. #21
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    That explains why I rarely get over 70 Mbps downloads. Probably I'm almost never on CA.

    Sent from my FRD-L04 using HoFo mobile app

  7. #22
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    That's a bit tricky to answer, because it varies from device to device and manufacturer to manufacturer. There may be hardware or other limitations on both the phone and network that would not allow some combinations of PCC/SCC (primary/secondary cells).
    Just limiting this discussion to the phone (UE) side of the equation (completely ignoring the network side factors):

    Your phone, once connected to LTE, will be asked by the network to provide its "capabilities" (UE-EUTRA-Capability) to the network. This is essentially a giant list of all the features/bands your phone supports.

    One of these capabilities is the "supportedBandCombination" list (Here is one entry for B4-B12 CA from an Axon 7):
    Code:
                               SupportedBandCombination-r10[18]
                                      BandCombinationParameters-r10[0]
                                        bandEUTRA-r10 : 12
                                        bandParametersDL-r10
                                          BandParametersDL-r10[0]
                                            ca-BandwidthClassDL-r10 : a
                                            supportedMIMO-CapabilityDL-r10 : twoLayers
                                      BandCombinationParameters-r10[1]
                                        bandEUTRA-r10 : 4
                                        bandParametersUL-r10
                                          BandParametersUL-r10[0]
                                            ca-BandwidthClassUL-r10 : a
                                        bandParametersDL-r10
                                          BandParametersDL-r10[0]
                                            ca-BandwidthClassDL-r10 : a
                                            supportedMIMO-CapabilityDL-r10 : twoLayers

    It essentially tells the network every single CA combination (among other things) your phone supports. This list includes both intra and inter band CA combinations and whether each band in the combination can be used for both upload and download. Keep in mind, in this list, order is not important. So B2-B4 CA can be listed with B2 or B4 first or second, it does not matter. I've observed some phones send this combination as advertised (i.e B2-B4), while others send it reversed (B4-B2).

    Diving deeper, there are rules in place, set by the 3GPP, on all the possible supported CA combinations and their restrictions (bandwidth, downlink only, etc).
    Some of these rules specify clearly which band is downlink only. So that, for example, any combination using B29 (downlink only) will always have B29 as an SCC (you need to be able to transmit on a band for it to be a PCC). Only a small amount of bands have this restriction. From my example, the Axon 7 can upload/download on B4, and B12 is for downlink only.

    So, basically, there is no clear answers unless you are able to get the UE-EUTRA-Capability message from your phone. If your phone is Qualcomm based, you can potentially root it and install Network Signal Guru and capture this message. It will basically list all of the above and you can determine support based off the message.

    EDIT: Just to clarify, that was only 1 supported band combination listed above. There could also be another message (have not verified) where the Axon 7 can have PCC B12 and SCC B4. Also, there is uplink CA, which I haven't covered in the basic overview above.
    Last edited by zivan56; 02-05-2017 at 06:34 PM.

  8. #23
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    Quote Originally Posted by zivan56 View Post
    That's a bit tricky to answer, because it varies from device to device and manufacturer to manufacturer. There may be hardware or other limitations on both the phone and network that would not allow some combinations of PCC/SCC (primary/secondary cells).
    Just limiting this discussion to the phone (UE) side of the equation (completely ignoring the network side factors):

    Your phone, once connected to LTE, will be asked by the network to provide its "capabilities" (UE-EUTRA-Capability) to the network. This is essentially a giant list of all the features/bands your phone supports.

    One of these capabilities is the "supportedBandCombination" list (Here is one entry for B4-B12 CA from an Axon 7):
    Code:
                               SupportedBandCombination-r10[18]
                                      BandCombinationParameters-r10[0]
                                        bandEUTRA-r10 : 12
                                        bandParametersDL-r10
                                          BandParametersDL-r10[0]
                                            ca-BandwidthClassDL-r10 : a
                                            supportedMIMO-CapabilityDL-r10 : twoLayers
                                      BandCombinationParameters-r10[1]
                                        bandEUTRA-r10 : 4
                                        bandParametersUL-r10
                                          BandParametersUL-r10[0]
                                            ca-BandwidthClassUL-r10 : a
                                        bandParametersDL-r10
                                          BandParametersDL-r10[0]
                                            ca-BandwidthClassDL-r10 : a
                                            supportedMIMO-CapabilityDL-r10 : twoLayers

    It essentially tells the network every single CA combination (among other things) your phone supports. This list includes both intra and inter band CA combinations and whether each band in the combination can be used for both upload and download. Keep in mind, in this list, order is not important. So B2-B4 CA can be listed with B2 or B4 first or second, it does not matter. I've observed some phones send this combination as advertised (i.e B2-B4), while others send it reversed (B4-B2).

    Diving deeper, there are rules in place, set by the 3GPP, on all the possible supported CA combinations and their restrictions (bandwidth, downlink only, etc).
    Some of these rules specify clearly which band is downlink only. So that, for example, any combination using B29 (downlink only) will always have B29 as an SCC (you need to be able to transmit on a band for it to be a PCC). Only a small amount of bands have this restriction. From my example, the Axon 7 can upload/download on B4, and B12 is for downlink only.

    So, basically, there is no clear answers unless you are able to get the UE-EUTRA-Capability message from your phone. If your phone is Qualcomm based, you can potentially root it and install Network Signal Guru and capture this message. It will basically list all of the above and you can determine support based off the message.

    EDIT: Just to clarify, that was only 1 supported band combination listed above. There could also be another message (have not verified) where the Axon 7 can have PCC B12 and SCC B4. Also, there is uplink CA, which I haven't covered in the basic overview above.
    Amazing explanation. Thanks for enlighten my sunday!

    Sent from my FRD-L04 using HoFo mobile app

  9. #24
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    Quote Originally Posted by zivan56 View Post
    So, basically, there is no clear answers unless you are able to get the UE-EUTRA-Capability message from your phone. If your phone is Qualcomm based, you can potentially root it and install Network Signal Guru and capture this message. It will basically list all of the above and you can determine support based off the message.
    What is the exact name of the message in Network Signal Guru that gives the list of supported bands?
    Is it actually called "rrcConnectionReconfiguration" as stated above?

  10. #25
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    It should be UE Capability Information. You may need to go to airplane mode and come back to re-attach to the network.

  11. #26
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    I think they've named it EUTRA Capability Information in the app or similar. It's a message sent to the network, so it will be orange.

  12. #27
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    I've finally found it for the first time in version 1.3.1 as "UE EUTRA Capability" with an orange UP arrow next to it.
    There are other messages that look similar, but they don't contain the CA information like this specific message.

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