First off, a few config notes:
- Battery: I'm currently using a ZeroLemon extended battery with the included TPU case. I know it typically does cause a MINOR signal performance drop, but nowhere near what I'm seeing now.
- ROM: This seems to occur with most ROMs. At a minimum, I've seen this on: CM 10.2.1 final, CM 11 Snapshot M3, Gummy 4.4 nightlies, Mastamoon's CM11 nightlies and the KitKang series.
- Modem: Currently on VRBMF1
- Network Extender: I have the 3G Model, SCS-2U01
- Settings: It doesn't seem to matter if location and bluetooth are enabled or not. NFC is disabled.
- Apps: I currently check signal via SignalCheck Lite.
When I'm about 3 feet from the network extender, I end up with very poor LTE signal - typically between 100 and 110 dB. When I switch down to CDMA/EVDO only, I get better signal - often 2-3 bars, and IIRC 70-80 dB - but still end up dropping calls way too often.
An example test point from 1am (so should be very low traffic and interference):
LTE -109dBM (LTE/CDMA mode, shows as 'one bar')
CDMA -56dBM (CDMA/EVDO only mode, shows as 'three bars')
1xRTT -85dBM (Connected during both CDMA and CDMA/LTE)
I suspect that I'm running into two issues:
I may be having issues with my network extender - inferference from a nearby PC (wifi is set up in a nearby room, so it's likely not the issue), too close to extender, etc. I know that two other Verizon Samsung Galaxy devices in the apartment work just fine.
The phone can't decide properly between a 'OK' network extender CDMA signal and a 'BAD' LTE signal, and when it prefers an LTE tower, the voice signal suffers for it (I know it's not VoLTE, so I'm not 100% sure what the situation here is.)
My ideal solutions would be, in order:
- Everything just works - I don't have to switch LTE on/off, etc. - and I have no dropped calls, ideally talking to the network extender
- Some way to swap it automatically - none of the CM hooks seem to exist right now in those builds, so instead of Tasker, etc., right now I have to do it manually. I know of at least one app (Advanced Signal Status) that can manually swap it, so there is an API of some sort...
- A fairly easy way to set up wifi-based calling that works with my cell phone number - I've got a Linux server running, so I'm willing to experiment there.
I'd really like to stay on a 4.4 build if possible.
I'll update this main post with more info as I gather it.