Unlike later technologies, GSM can provide full service to device without full authentication. This can be useful in some private networks, allowing a device to bring its own SIM without needing a roaming agreement.
Cell broadcast (CB) is a way to deliver a text message to large numbers of handsets over the cellular network. Its main use today is the delivery of Public Warning System (PWS) messages, also called CMAS, ETWS, or other names in different parts of the world. The Legba Lab Kit is an easy and inexpensive way to generate PWS test messages on your bench.
Many 4G networks cannot carry plain old telephone calls, so many mobile operators support voice calls by transferring the handset to a 2G or 3G network for the duration of the call. The procedure for doing this is called “Circuit-Switched Fallback”, or CSFB. CSFB is an interesting procedure from a network operation perspective and from a security perspective. With a pair of Legba Lab Kits, one in 2G mode and one in 4G mode, you can reproduce and modify the CSFB procedure on a test bench.