LTE connectivity & KitKat

[pyod0004]

I am a USA AT&T mobile customer with the Xperia T2 Ultra (D5306). My issue is with 4G LTE. My phone will stop using the LTE. I am going to outline my experience below.

1. Purchase phone and activate it to AT&T network. It is running Jellybean (19.0.1.A.0.223) and works on AT&T LTE. This is US Sony android version.
2. Unlock bootloader, install KitKat (19.1.1.A.0.165). Phone restarts and works on AT&T LTE.
3. LTE works for about 1 week to 1 month, then LTE disconnects. Usually happens after phone is in area with bad mobile, no LTE coverage.
4. LTE doesn't work. WCDMA will connect.
5. Reflash phone, continue at step 3.

I know the phone works on the AT&T bands but only for a limited time and then it disconnects. The only way I can fix it is by using WCDMA or reflashing. This problem does not happen on the Jellybean build, it only happens with I use the KitKat build 19.1.1.A.0.165.

Any thoughts? I really like this phone but I want to use KitKat for the SD storage. I took it to AT&T but they do not sell Sony phones so they have no idea what they were doing. Any mobile users with similar issues?

[Thommo]

Is the firmware you flash official USA firmware

[pyod0004]

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@Thommo wrote:

Is the firmware you flash official USA firmware

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No, it is not. I've tried a number of firmwares, usually Mexico. The only USA firmware is still Jellybean.

LTE works after flashing a Mexico firmware but then it quits within a month.

[Uliwooly · Accepted solution]

Just wait for lollipop to be released somewhere here in the Americas, either Canada or USA and then flash it, or check the XDA forum, perhaps there's something you could flash. I know while on 4.4.4 you can flash other firmwares and exclude the baseband and LTE still work with AT&T. 

[pyod0004]

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@uliwooly wrote:

I know while on 4.4.4 you can flash other firmwares and exclude the baseband and LTE still work with AT&T. 

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Am I correct saying that the baseband is the firmware which controls the antenna? This could be directly related to the problem because when I switch to LTE (preferred) in 'Network Mode', the mobile connection shuts off completely, including voice and tex. When I switch to WCDMA (preferred) or GSM the mobile connection works fine.

[Uliwooly]

There you go, I've experienced this myself, when I flash different firmwares and forget to exclude the baseband. 

[pyod0004]

Update on the LTE issue.

A week ago I flashed the original, US Jellybean Android. I then flashed back to Lollipop 4.4.3 and excluded the baseband.

This has worked effectively for a week.

I don't know if this has solved the LTE issue but things that triggered the phone losing LTE connection (such as losing service in building) are not causing it to lose connection now.

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@pyod0004 wrote:

I am a USA AT&T mobile customer with the Xperia T2 Ultra (D5306). My issue is with 4G LTE. My phone will stop using the LTE. I am going to outline my experience below.

1. Purchase phone and activate it to AT&T network. It is running Jellybean (19.0.1.A.0.223) and works on AT&T LTE. This is US Sony android version.
2. Unlock bootloader, install KitKat (19.1.1.A.0.165). Phone restarts and works on AT&T LTE.
3. LTE works for about 1 week to 1 month, then LTE disconnects. Usually happens after phone is in area with bad mobile, no LTE coverage.
4. LTE doesn't work. WCDMA will connect.
5. Reflash phone, continue at step 3.

I know the phone works on the AT&T bands but only for a limited time and then it disconnects. The only way I can fix it is by using WCDMA or reflashing. This problem does not happen on the Jellybean build, it only happens with I use the KitKat build 19.1.1.A.0.165.

Any thoughts? I really like this phone but I want to use KitKat for the SD storage. I took it to AT&T but they do not sell Sony phones so they have no idea what they were doing. Any mobile users with similar issues?

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[Uliwooly]

were you able to solve it?

[pyod0004]

Yes, this seems to resolving losing US AT&T LTE connectivity when flashing from jellybean to kitkat.

[Uliwooly]

Excellent