I was recently asked by a potential customer if we supported Gx over Gy. I’d never heard of this before, so I gave my standard “If it’s in the spec we should support it, but I’ll check” answer, and got them to send me a PCAP, which I’ve got. This is weird. So for starers, … Continue reading Tales from the Trenches – Gx over Gy? →

This is an idea I’ve been kicking around for a little while – A single GSM TRX being broadcast across multiple cell sites. Generally in GSM land, a “TRX” is a cell or a sector – but it doesn’t need to be. Later in GSM features like antenna diversity allow the same signal to be … Continue reading GSM SuperCell →

OsmocomBB is an open-source project that replaces the stock baseband firmware on old Motorola phones (C118, C139, etc.) that use the Texas Instruments Calypso chipset. By flashing custom "layer23" firmware over serial, these cheap legacy handsets become capable of accessing raw GSM radio data at the baseband level, enabling cell scanning, burst capture, and passive […]

I do a lot of protocol testing, writing Diameter/PFCP/GTP-C etc, and spend a lot of time referencing the standards. So I built this – Inspired by a 1990s video game / TV / Playing card franchise online reference tool, but rather than identifying pocket monsters, it’s identifying AVPs and stuff You can punch in the … Continue reading Protocoldex – A quick reference guide for AVPs / IEs / Commands…

One of our customers is an MVNE and they reached out the other day with an issue. They were turning up a new PGW and they’d see Create Session Request, everything looked OK, it’d get a response, but then in the GUI of the PGW-C they’d see the session drop. The logs showed the newly … Continue reading Tales from the Trenches – PGW-C Deleting Sessions →