[999900000999]

I was trying to build an LTE solar powered phone of last resort.

After looking into it, LTE makes this nearly impossible to do economically.( Plus there's like 4 different types of LTE depending on county.)

I really want energy coms devices!

[siliconwitch]

It’s a massive rabbit hole! Thankfully LTE Cat-M1 that we use is much simpler than full blown LTE, but even still, the most iteration we’ve had to do is around the antenna system. Huge number of frequencies and bandwidths to support and much of the information is quite difficult to track down. Thankfully with the help of the SoC maker, antenna maker and SIM provider, we’ve just about managed to figure it all out

[dogma1138]

How is it better than having any phone + a backpack solar charger?

If you are looking for a doomsday scenario then LTE isn’t the way to go, handheld radios is the way to go.

In virtually any large scale disaster scenario cell networks are one of the first things to go, they get overwhelmed and if there is a power loss then cell towers go down.

[999900000999]

It's more like if I get lost in my main phone battery dies or something or gets broken, I want a way to call for help.

[siliconwitch]

The SoC we use will also be gaining support for non-terrestrial networks soon. It’s the same feature that new iPhones have for Satellite based SOS when you’re outside of cell range. We’re not sure when it’ll be ready yet, or what the power consumption will be, but perhaps that could be something useful for this sort of use case. As far as I know it’ll support regular data traffic too, not just for emergencies.

[999900000999]

Anyway to make a solid voice call?

I know you probably have better things to do, but I have mockups and some rough designs if you’d like to talk

[siliconwitch]

Voice is possible over LTE-M but it’s sort of the wrong technology for it. It’s designed for low power so the data rate is quite slow and the latency won’t work for two people trying to talk to each other.

It’s a similar speed to Bluetooth LE (not Bluetooth audio which headphones use). Sub 100kBps

NTN will be even slower. Few kBps. Really intended for sensor data or machine related actions

[999900000999]

Hmm.

As long as it can signal emergency services it'll be fine for what I'm thinking of. Texting emergency services a preset message like "Paramedic requested, at GPS cords..."