>>4177972I was thinking about building a developer cell network.
Step 1: buy an old Thinkpad W500, libre it w/ Coreboot, then install Trisquel GNU/Linux w/ openrc and Sway/XFCE. Then turn it into a makeshift Linux server by taking 5 raspberry pi 5's, stacking them via PCIexpress lane, then plug them into your laptop via USB adaptor.
Step 2: buy an Ovrdrive USB flash drive and flash the LUKS2 decryption key to unlock the desktop, after using LUKS2 for FDE (Full Disk Encryption).
Step 3: buy a LimeSDR mini w/ LMS7002M SDR transceiver and antennas for RF frontend. Plug it into your laptop. This'll serve as your cellular modem.
Step 4: buy a sysmousim developer SIM card, pop it into a USB SIM reader, and plug it into your laptop to program it for your custom network.
Step 5: then you'll need to run OsmoBTS - BTS implementation, OsmoBSC - BSC functionality, OsmoMSC - mobile switching, OsmoHLR - subscriber database, OsmoMGW - media gateway and Asterisk - optional SIP/VoIP integration. All over Linux.
Step 6: pop your sysmousim into a Nokia 6310i (RH-17; can be patched up to support band 850) or a Nokia 6230 (RH-28; comes w/ GSM850 out the box) running OsmocomBB flashed onto it via laptop and USB cord and self-activate onto the network.
Step 7: make a BTS tower out of a 60-80 ft tall pole, some scavenged 800W-1kW solar panels, a solar charge controller, maybe an inverter if your PAs don't use DC, 2x 12V 100Ah LiFePO4 batteries in series (24V system) or a 48V system, and high-gain directional antennas if you're doing a point-to-point, or sector antennas if you're doing omnidirectional but with massive gain. Will also need Power Amplifier (PA) (A DIY LDMOS amplifier (like those based on the MRF6S211 or L3Harris parts) or a commercial 2W-10W PA with good linearity), Low-Noise Amplifier (LNA), and proper duplexers/bandpass filters (need filtering to prevent the PA's harmonics from frying the LNA and to prevent interference). Let's take my state (South Carolina) for example. If I needed enough coverage for someone in Pelion to call someone in Columbia, I'd need 3x or 4x omnidirectional sector antennas all pointed 120deg of each other to cover different regions so that way a good portion of the midlands and coastal areas would be covered and you would need to place it in Clarendon County (like Turbeville or Manning) because it's the highest elevated region in the area. And again, broadcast on band 850 because it has better range and reception than, say, band 1900. Nodes in the network will still need a 2G Yagi antenna to place outside their house on the front porch for better reception. May need to setup multiple BTS towers throughout the state for better range.
Step 8: now you can run the GPRS connection to self-host a custom BBS written in Python scripted as a GNUNet overlay w/ installation instructions as provided on your Tor website (hosted over Wifi). Now you can use GNUNet BBS for sending SMS/notifications to subscribers to your free network that are within range, and create messageboards or even attach files to sites (say, audio files, like OPUS or AMR-NB - native to GSM voice codecs) over GNUNet FS and SIP routing through GNUNet CADET.
Now you just created a hacker network that doesn't keep logs, is encrypted w/ PGP, not stored on any cloud servers, is non-digital (circuit switched 2G over SDR), and is completely open source and free. And you now pissed off the FCC. Hope you can keep this as an offgrid option.
Note: You'll need osmo2mo or a custom Linux-USB-GSM stack. The LimeSDR is primarily a software-defined radio (SDR) for research, not a dedicated cellular modem. You'll be writing or adapting drivers to talk to the GSM stack. It's possible, but expect significant CPU overhead and latency.
Do you want to contribute to my project and perhaps start building nodes w/ licensing in Denmark?
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