Idea for a Libre cell phone (for real this time)

[Jmpace52]

Instead of using proprietary cellular basebands, the encroaching 3G/4G/5G menace, instead use an analog frequency like 2G. Get a Motorola C123, pop off the screen, buttons and 2G antenna, wire them to a PCBway circuit board, along with sysmousim SIM card, then, add a strong Lipo battery, and a ULX3S cellular modem running custom PHY (multi-year multi-team PhD-level FPGA project) w/ 3D printed plastic display case that snaps on, w/ ethernet plug-in at the bottom, and that plugs into your desktop workstation SBC board (MilkV Jupiter), then flash OsmocomBB on it, then connect to a network w/ HAM radio set from FCC license. Make sure that you snap a LimeSDR PCIe to the ULX3S. Then slap a Modos paper display on it, w/ Keyboardio model 01 keyboard and Ploopy mouse kit, w/ passive speakers and a Microsoft Lifecam VX1000/VX3000 or a Logitech Quickcam 4000/Quickcam Express 1999 web cam. Then make sure you have snapped on a board via 3D printed w/ metal strips PCIe attachment to the main Jupiter workstation board, containing a PCB (PC-class, like PCBway) w/ LiteX and ECP5 NAND/NOR for memory storage. Then install Gentoo w/ a hardened kernel, secure bootchain and refuse any proprietary packages upon setup. Gentoo runs smoothly on RISC-V. But always make sure to read the Wiki. Then install nftables (refuse any and all proprietary packages, and block connections to 8.8.8.8/1.1.1.1/9.9.9.9), kvm/qemu, firejail, pyshark, fail2ban, and GNU Icecat/ELinks/GNUNet, GNUNet CADET, GNUNet FS or gnunet-vpn for the web browser services. Run your 2G network over GNUNet for a BBS written in Python that's text/ASCII-based, and will let you communicate w/ subscribers via phone number in the network (a Motorola C123 running OsmocomBB; will also need TI Calypso chipset for your homemade cell phone/cellular modem 2-in-1). Also, you'll need to wire two or three MilkV Mars SBCs to your Jupiter, so you can run bitmining operations for niche altcoins w/ cooling fans, and use these other two MilkV Mars nodes for network LLM Acceleration using 3 or 4 UART/UEFI adaptors as a mini-cloud. You will also need another MilkV Jupiter or Mars w/ ath9k PCIe Atheros card snapped to it, hooked up to your default ISP router by GPIO mapping, and to your other MilkV Jupiter for libre internet connection. Install nftables rules on the Jupiter router board, Pyshark, LLM powered threat evasion, and a custom SOCKS5 proxy written in Python w/ X25519, Poly1305, ChaCha20 and Kyber for cryptographic post-quantum protection, w/ libsodium, OpenSSL and PQClean integration. Then set up a BTS tower or radio mast to broadcast the network w/ LimeSDR PCIe connected to the mast to run your 2G network iver CBRS Private LTE. All smartphones have proprietary baseband.

Via ChatGPT:

A hybrid SDR/GPRS architecture is more plausible than a completely clean-room replacement for modern cellular stacks.

What you’re effectively proposing is:

reuse portions of legacy GSM/GPRS infrastructure and concepts,

but replace as much of the radio/baseband path as possible with:

SDR,

FPGA logic,

open PHY experimentation,

and libre software.



That lands somewhere between:

OsmocomBB,

GNU Radio SDR research,

and experimental packet-radio systems.


Technically, a hybrid approach makes more sense because GSM/GPRS is vastly simpler than LTE/5G:

TDMA instead of OFDMA complexity,

simpler timing/scheduling,

lower bandwidth,

less integrated DSP complexity,

older modulation schemes.


So using:

a LimeSDR for RF,

an ULX3S FPGA Board for PHY acceleration,

and legacy TI Calypso/Osmocom concepts


is at least conceptually coherent.

The most realistic architecture would probably look like this:

1. SDR RF frontend

LimeSDR handles tuning, ADC/DAC, filtering.



2. FPGA PHY layer

timing recovery,

burst detection,

GMSK modulation/demodulation,

channel coding,

synchronization.



3. Host SBC

RISC-V Linux board runs:

higher GSM stack,

packet routing,

messaging,

BBS,

GNUnet overlays.




4. Legacy handset interface

reuse:

keypad,

display,

audio path,

microphone/speaker,

antenna components.




5. Packet services

GPRS-like IP transport,

text-first networking,

lightweight protocols.




The reason GSM/GPRS attracts hobbyists is because the radio layer is old enough to study and partially reimplement.

But there are still major practical issues:

1. Modern carriers have shut down most 2G

In the U.S., real GSM networks are mostly gone.

So your options become:

isolated/private lab network,

experimental radio environment,

or non-cellular SDR packet operation.


2. RF compliance is difficult

Even low-power GSM-like transmissions can violate regulations if operated improperly.

That’s why most open GSM projects stay in:

Faraday cages,

shielded labs,

or licensed research environments.


3. Voice is harder than data

A text/BBS/GPRS-style packet network is much easier than:

reliable voice,

roaming,

handoffs,

SMS compatibility,

emergency services,

timing synchronization.


4. FPGA development is the hardest technical piece

This part:

> “custom PHY on ULX3S”



is the real engineering mountain.

You’d be implementing major portions of:

GSM Layer 1,

DSP pipelines,

timing systems,

error correction,

RF interfacing.


That is genuinely advanced communications engineering.

5. Your “desktop-phone” concept is actually unique

What stands out most is not the GSM part, but the idea of:

a modular libre workstation,

radio node,

decentralized communications terminal,

portable Unix cyberdeck.


That’s a niche, but technically interesting direction.

It resembles:

amateur packet-radio systems,

field communications terminals,

cyberdecks,

and decentralized networking research


more than a conventional smartphone.