A Bulky Way of Getting Voice Service Through Multiple Cell Carriers

Hardware Librem 5
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This solution might be over the top for most people, but I enjoy thought experiments like this.

I use my phone in multiple areas, and in some areas, only Verizon has good coverage. In another, only T-Mobile has good coverage. If poor coverage is limited to a building with Internet service that you can connect to, then a microcell can be used to fix this. AT&T discontinued their microcell because Wi-Fi Calling makes this device unnecessary for most people. If the signal is weak, a signal booster might work. For me, AT&T covers both areas, but very poorly with dead spots. A portable signal booster might work, but probably not in some spots. If I travel to rural areas exclusively covered by different carriers, a dual SIM phone will let me receive service from 2 different carriers on a single phone, but I will have a different phone number for each service.

A Wi-Fi connection-only SIP/VoIP phone connected to mobile hotspots solves this. A VoIP/SIP service with a Bring Your Own Device plan will let me send and receive calls over the Internet via Wi-Fi. To use this outside of normal Wi-Fi coverage, I would get a Alcatel LINKZONE for T-Mobile and a Verizon Ellipsis Jetpack for Verizon. I can remove the cell modem from the Librem 5. Not using the Librem 5’s cell modem will increase its battery life, but now I have a second device to charge, the mobile hotspot. I am guessing that the battery lasts for about 8 hours for their intended purpose, but for a cell phone that idles most of the time, I hope that it would last a little longer. While I would have to carry 2 devices around, only the weaker Wi-Fi radio will be next to my brain, while the cell modem will be blasting away in a pocket or on a desk. With any luck, the Wi-Fi chips will automatically turn down the transmit strength given how close the receivers are. Commercial grade Wi-Fi devices usually let you lower the transmit power, consumer devices, not so much.

Operating 2 hotspot only plans is expensive, but I can connect it to my laptop and tablet and not get charged for another device or have to pay for tethering. So I am getting 3 devices connected to cell service for this. Also, I can use it with my desktop (via a USB Wi-Fi adapter) if my wire based (fiber, cable, DSL) Internet service goes out. The starting plans do not include a lot of data, but most of what I do when I am not on Wi-Fi is simple browsing and e-mail. I tend to not watch video when I am on cell service, mostly because I do not want to be too disconnected with my surroundings when I am not in my own space.

Another down side to this is that there is no way to send or receive texts from the phone. The hotspots can receive text messages and can display them in their web administration interface, but at least one of them is limited to receiving text messages from the carrier, so it cannot be used for receiving texts from other people, in theory. Also, one of them limits the number of texts stored to a very small amount. Using the hotspots for text messaging would have the same problems as having 2 phone numbers on different carriers. An SMS gateway with an e-mail client can send messages. If you have an old iPhone or Android phone service, then you can configure it to forward texts to an e-mail account. TextPort or TextMagic lets you send and receive SMS from a web browser. SMS should be treated as an unencrypted messaging service. Avoid it if possible, but it is a least common denominator for people with cell phones.

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Purism Stated eventually they want the L5 to be a carrier free device or atleast have that capability by down the road incorporating VOIP functionality native to the device so you won’t need a carriers compatibility / permission .

This will be a truly historic device.

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Yes, https://puri.sm/posts/what-a-no-carrier-phone-could-look-like/

One concern that I just thought of is 911 calling. Basic 911 service requires verbally stating your location. This works, but in theory, an app could be developed to turn on the GPS (and display instructions to turn off the kill switch if on), and dial the appropriate local emergency center instead of the basic 911 service. Wi-Fi access points can also provide approximate location without the need of a GPS, since most are stationary. I am thinking that the user can associate a location with these instead of trusting a GeoIP service. The GeoIP service can prepopulate the location field for the user. So, there is a workaround, and a way to make it better. Since this logic runs on the phone at our request, privacy is maintained.

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See also Advanced Mobile Location when calling emergency services

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Thanks. Sending a HTTPS POST request with the location information is easy enough. In theory, this means that a more precise location can be given after the call has been placed. This is good because GPS sometimes takes a while to lock onto enough satellites, or maybe the person is moving to a better spot or simply avoiding danger.

This topic is a “do it yourself” solution, so for now, only hobbyists will be interested in this. But native VoIP functionally is on the roadmap, so there is also commercial interest.

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AML defines the maximum number of seconds that may elapse. AML will be a legal requirement in the EU as of 2022.

At the current time it would appear that only one country (Austria) supports AML via HTTPS.

For those countries that support AML now, it would seem that you could “DIY” as long as you follow the spec. That would be showing courage of your conviction in your hobbyist code. :slight_smile:

Emergency calling would seem to be a side-issue for this topic.

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I might be hyjacking the thread here, but…

Since the Purism/Librem have partnering plans with Nextcloud, and…
Nextcloud has a longer range plan for their Spreed/Talk application,
maybe were going to get it via software in the future?

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What is described in this topic needs a SIP client to work, so I would say that this is on topic. Or something else that gives you a regular telephone number for other people to call you with. I would assume that there already is one that can be installed, such as Empathy, but it might not be optimized for a phone screen and touch input.

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