Hello Experts,
I have a weird situation…
My phone is displaying 5G icon, but there’s no 5G coverage…
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It’s perfectly possbile.
In NSA mode (suppose your case), the 5G icon simply means that the ULI (Upper Layer lndication) received via SIB2 in LTE is set to “True.”
That makes possible some UEs to display 5G icon even if there is no 5G coverage. Due to (UpperLayerIndication in SIB 2).
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In Huawei, the transmission of upperLayerIndication-r15 in SIB 2 is controlled by a parameter called “Upper Layer Indication Switch”.
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From a technical standpoint, if upper Layer Indication set to True, it means that the network supports ENDC capability.
In other words, it indicates to the upper layers of the protocol stack that there is 5G NR Cell colocated to the LTE Cell.
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You can find more details here:
http://www.5g-bullets.com/5G%20in%20Bullets%20-%20LTE_Idle_Mode_Sample.pdf
There 4 types of phones config A, B,C and D as in the table from the link above.
There is another group of Operators who shows 4G for HSPA+ and 5G while using LTE 4CA.
I.e. they display the logo they need without following the above table.
Mostly it will be TAC based classification.
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Do you know about Motorola Edge and Huawei P40?
Seems most of manufacturers option D.
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This parameter is part of sib2 having misleading information sometime that is without 5g cell addition device show 5g icon.
Option D is best practice
Actually 5G Icon appears in your phone due to LTE SIB2 that include UpperLayerIndication-r15 IE flag that supposed to be “1” . So this scenario is likely occurring because of 5G icon shows it is just configuration issue.
The GSM Association (GSMA) has agreed upon a set of 4 candidate UE configurations which determine when a UE should display the 5G icon. These 4 configurations are presented in Table (this config is depends on UE manufacture vendor).
configuration ‘A’ is the most conservative because it limits the UE to displaying the 5G icon when the UE is already connected to both LTE and NR cells.
In contrast, Configuration ‘D’ is the most aggressive because it allows the UE to display the 5G icon when using only an LTE cell belonging to an NSA Base Station, without having to verify NR coverage.
Configurations ‘B’ and ‘C’ rely upon the UE verifying that NR coverage exists
Solution: some vendor have setting for UpperLayerIndicationSwitch that may configure so let LTE SIB2 broadcast upperlayerindication-r15 only if E-UTRAN cell is configured with at least one neighboring NRCell.
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