Is it difficult to make a cell phone ( 4G ) ?

[NiHaoMike]

Sounds linuxy/open sourcery.
That exists ?, nice one

There's a very long list of officially supported devices and quite a few unofficial ports for other devices on XDA.
https://wiki.lineageos.org/devices/

[Jan Audio]

I can't see why you wouldn't just buy a second-hand old mobile phone with no Android/iOS/Windows Mobile. Something just 2G for instance. I have no crystal ball of course

They stop supporting 2G is the problem, i already have such a phone.

Happy to donate to the upcoming crowdfunded network satellite launches too... hit it.

No rules in space, the problem is to get it in space.

[Bicurico]

@Jan Audio:

1) What do you want to achieve, really? Why do you want to build a 4G cell phone from scratch? I ask, because maybe you don't really need/want to start from scratch and could use a different approach, i.e. as already mentioned, using a mobile phone module (SoC), using a cheap phone and rip off the required parts (for a one timer) or, like what they do with expensive luxury phones, getting a premium smartphone, redesign its case (i.e. in pure gold and covered in diamonds - for inspiration see here: http://www.goldvish.com/single-post/2016/04/22/guinness-world-records-most-expensive-phone-for-goldvish) and modifiying the firmware (see XDA Developers forum).

2) When you ask how difficult it is to make a cell phone (4G), you need to add your starting point! How difficult it would be for Nokia, based on their 3G technology or for you based on existing chips, or based on existing chip layouts, based on existing knowledge, based on existing manufacturing processes, etc. This can be taken to the extreme: imagine you are able to carry the latest Samsung Galaxy S21 Ultra plus a network cell and all required hardware to operate it and travel back to 1960. How much time would be needed to replicate the mobile phone technology of 2021? My guess is that it would basically take more or less the same time! Why? Because the world would not be able to deliver rare earth metals, battery technology, RF knowledge, xx nanometer chip design, software technology, etc.

So if you would want to start from scratch to develop a 4G cell phone, you would need to develop:
- software
- chips
- manufacturing processes
- materials engineering
- etc.

If you "cheat" and say you would start with FPGA and what not, you would still have to develop more than you could achieve in a lifetime. Think of compression algorithms, modulation algorithms, antenna design, etc.

3) Your question does not specify how many people are to be involved! Is it just you, 10 people, 100 people or 1000 people? How "smart" and "educated" are the people on your team? Do they cover all required technological aspects?

4) Your question does not specify how much money you are prepared to invest. As others mentioned, the certification and NDA's will cost you a 6 figure number alone!

If you are really committed into developing your own 4G cell phone and I have no doubt that there are people smart enough to put this off, your way to go is this:

1) Get yourself a propper SDR, like this: https://www.ettus.com/all-products/un210-kit/
2) Learn how to program it using the SDR, FPGA, etc.
3) Install GNU Radio
4) Learn how to use GNU Radio, how to develop in Python and C++ for GNU Radio
5) Build the required blocks (many are already available)
6) Build a 4G implementation using the blocks
7) Publish the results of your software defined 4G cell phone and you will be a star! I mean that seriously.

Regards,
Vitor

PS: It has already been done (partially) - https://github.com/kit-cel/gr-lte

[robca]

Good news: They don't.

Did you not know a regular used smartphone connects to 10.000 unique IP adresses within 1 hour ?
Only you dont see, how do you know then ?, how can you be sure the telephone is not connecting to anything ?

If a telephone can only call then i am sure it wont connect to anything.

You seem to be missing a pretty fundamental point: if you disable data connection on a feature phone like the ones suggested, you will get a phone that can only make audio calls and send SMS

There's no need to build your own phone if all you want is a phone that can only make phone calls, even a 4G one. Simply disable completely data connectivity, and you can be sure that none of the phone built in apps can do anything. It won't matter if the phone has Facebook built in.

[amyk]

If you are really committed into developing your own 4G cell phone and I have no doubt that there are people smart enough to put this off, your way to go is this:

1) Get yourself a propper SDR, like this: https://www.ettus.com/all-products/un210-kit/
2) Learn how to program it using the SDR, FPGA, etc.
3) Install GNU Radio
4) Learn how to use GNU Radio, how to develop in Python and C++ for GNU Radio
5) Build the required blocks (many are already available)
6) Build a 4G implementation using the blocks
7) Publish the results of your software defined 4G cell phone and you will be a star! I mean that seriously.

Regards,
Vitor

PS: It has already been done (partially) - https://github.com/kit-cel/gr-lte

Also https://bellard.org/lte/ (that guy is a real genius - has written a bunch of other amazing things, including ffmpeg, QEMU, TCC, etc.) Of course, he doesn't have to ask "is it difficult"... he just does it.

[kutte]

They stop supporting 2G is the problem, i already have such a phone.
No rules in space, the problem is to get it in space.
[/quote]
@Jan
did you realize that 4G -also called LTE - has been designed for data communications and not so much for telefone use. Many  smartphones switch back from from 4G to 3G or 2G if you want to make a phone call or use voice over LTE (VoLTE similar to  VOIP).
I do'nt think, that is  what you want.
Kutte

[Monkeh]

Voice is just data anyway. No reason to design a network to do anything but carry IP.

[james_s]

Anybody remember when they used to charge obscene amounts of money per text message? It was something like $0.25 each to send or receive. I never used them back then but I remember thinking that just a few seconds of voice must use as much data as hundreds of text messages.

[GodIsRealUnless DefinedInt]

Here is the $12 retail price Chinese street phone for the curious.

Quadband GSM, Bluetooth, 260 MHz 32-bit cpu, 2 color oled display, 8 MiB RAM USB, microSD, Sim connectors, lipo battery. This was to see what could be done in China comparison to less than a price of a pizza in the west. Over here you would never be able to pull something like this off and you might get an 8bit arduino clone with 2K RAM for that much. I'm sure they will have other radios for more money.

[Alex Eisenhut]

I'd like to see this back

https://en.wikipedia.org/wiki/Motorola_StarTAC

[NiHaoMike]

Here is the $12 retail price Chinese street phone for the curious.

Quadband GSM, Bluetooth, 260 MHz 32-bit cpu, 2 color oled display, 8 MiB RAM USB, microSD, Sim connectors, lipo battery. This was to see what could be done in China comparison to less than a price of a pizza in the west. Over here you would never be able to pull something like this off and you might get an 8bit arduino clone with 2K RAM for that much. I'm sure they will have other radios for more money.

In the US, there occasionally are deals on really cheap smartphones, sometimes as low as $5. I suspect the intent is to get kids using smartphones at an early age, but it turns out they also get great performance for the price for mining certain cryptocurrencies.

[Berni]

In the US, there occasionally are deals on really cheap smartphones, sometimes as low as $5. I suspect the intent is to get kids using smartphones at an early age, but it turns out they also get great performance for the price for mining certain cryptocurrencies.

Those are usually tied to cell carrier contracts. It is a common tactic here to sell you a phone for 1€ but you bind yourself to that carrier for 2 years or something so that they can make back the cost of the phone. It was mostly a deal to get you onto there network. Back then they ware also allowed to sim lock the phones so that the phone would only work with that carriers sim card. This later became illegal so they had to unlock your phone if you asked to.

The US carriers tended to go even deeper than that and secure exclusivity deals with phone manufacturers. So some phones became only available on one carrier, so if you wanted that phone you needed to switch to them.

[NiHaoMike]

Those are usually tied to cell carrier contracts. It is a common tactic here to sell you a phone for 1€ but you bind yourself to that carrier for 2 years or something so that they can make back the cost of the phone. It was mostly a deal to get you onto there network. Back then they ware also allowed to sim lock the phones so that the phone would only work with that carriers sim card. This later became illegal so they had to unlock your phone if you asked to.

The US carriers tended to go even deeper than that and secure exclusivity deals with phone manufacturers. So some phones became only available on one carrier, so if you wanted that phone you needed to switch to them.

The ones I'm referring to do not require signing up for service to get for that price. That's what makes them particularly good for some cryptocurrency mining - relatively cheap to build a cluster of them as some did to mine Perk back in the day.

[Gyro]

Here is the $12 retail price Chinese street phone for the curious.

Quadband GSM, Bluetooth, 260 MHz 32-bit cpu, 2 color oled display, 8 MiB RAM USB, microSD, Sim connectors, lipo battery. This was to see what could be done in China comparison to less than a price of a pizza in the west. Over here you would never be able to pull something like this off and you might get an 8bit arduino clone with 2K RAM for that much. I'm sure they will have other radios for more money.

That reminds me, although they're usually difficult to forget! ...

[gnuarm]

Here is the $12 retail price Chinese street phone for the curious.

Quadband GSM, Bluetooth, 260 MHz 32-bit cpu, 2 color oled display, 8 MiB RAM USB, microSD, Sim connectors, lipo battery. This was to see what could be done in China comparison to less than a price of a pizza in the west. Over here you would never be able to pull something like this off and you might get an 8bit arduino clone with 2K RAM for that much. I'm sure they will have other radios for more money.

That reminds me, although they're usually difficult to forget! ...

Wow!  I thought it was funny the way they changed camera angles every time she bends over to pick up another phone.  lol 

[Terry Bites]

Incestuous rather than just close!