I'm playing with various bits of the TETRA V+D (Voice+Data) digital radio standard, with maybe the end-goal of producing some working open-source tooling/implementations around it.
As I learn and build stuff, I'll be posting updates here.
The first post I make after this will probably be a "what have I done so far?" type update since I've been playing with this stuff for the better part of a year now.
Who?
I'm a software/firmware/electronics guy with an interest in digital amateur radio and communications technology.
What?
What is TETRA? Well, there are lots of descriptions of that online, but I'll say what I think it is here. It's a trunking digital radio standard in use by medium-to-large organisations for real time, critical communication. It's in the same space as DMR, P25, NXDN and the like. It's the convenience and speed of walkie-talkies meeting the scalability of cellular telephony. Users include emergency services, oil & gas, large events & hospitality. There were/are even public TETRA networks akin to public 3GPP mobile networks.
Why?
I've always found TETRA interesting. It's one of those paradoxically-open ecosystems where technically anyone can and could build an implementation, but (almost1) nobody tries. While the specifications are public, much of the real gritty detail is still veiled behind commercial implementation specifics. The specifications can be very difficult to read, and "actual engineer, not spec-writer" translations have not yet been written, or are incorrect, outdated or both.
High equipment cost is (was?) one reason for this. Terminals have gotten cheaper as the standard has been around for a long while now. There are also rumblings of major users migrating to LTE & 5G based systems in the near future which will likely flood the market with cheaper equipment. Base stations and infrastructure remain expensive, however. Software remains tricky to obtain. Cables remain undocumented and sometimes unobtainable.
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There are a few projects that have made some inroads. Some of them have been extremely helpful already. osmo-tetra is a notable example.