The HTC One Max is a Sprint Spark (therefore tri-band) device that doesn't do simulaneous 1x/LTE... it's therefore a device that uses eCSFB, right?
If I'm right, then the problem belongs here... otherwise, please let me know where I should post it... thanks!
My One Max has really strange behavior when connected to LTE which leads me to believe that it's having ECSFB problems. The reason I'm saying this is because I have non-triband devices to test with which I can ensure are connected to the same tower under the same conditions.
In my room, I get LTE 1900 (UCF/DCF 1912.5/1992.5 says Signalcheck) at around ~-95dBm. The signal fluctuates if I move around the room, but the lowest I can get it to go is -105dBm (which is in my closet). Even then, I don't experience losing signal and the phone disconnecting from LTE.
However, when using this, I have several issues:
SMS and MMS never come in and are never sent
Ping fluctuates up to 6000ms
Download speed slows to ~800kbps (very consistent) and once it drops, it doesn't improve until airplane mode is toggled (probably an unrelated issue?)
Occasionally, downloads and uploads both stop. However, the phone still says it's connected to LTE, but I get a notification that says "Could not connect to mobile data connection." (or something similar.) During this time, I cannot receive calls, I cannot sent or receive messages, and cannot use data whatsoever. After 10-15 seconds, everything suddenly starts working again.
The reason I'm suspecting it's eCSFB is because a regular HTC One (M7) and a Galaxy S3 work flawlessly for hours without a single hiccup.
Thoughts?