Mobile Fundamentals · Cellular Networks · Lesson 5 of 5

Challenge: Reporting Abroad

Guide a reporter's phone through roaming, fake towers and call records.

Landing abroad

Your friend Lena is a reporter. She lives in the UK and is flying abroad to cover a large protest in another country's capital. She has asked you to help her understand what her phone will be doing on the trip, so she can keep herself and her sources safe.

Her phone is a recent Android model with a SIM from her UK carrier. She hasn't bought a local SIM.

When she lands and switches the phone on, the status bar soon shows a local network's name instead of her UK carrier. A text arrives welcoming her and listing roaming prices.

Lena is curious. This network has never seen her phone before, yet it worked out which carrier to check with before letting her on.

Down to 2G

On the day of the protest, Lena works near the main square. At her hotel that morning her phone showed a strong 4G signal. Now, in the middle of the crowd, it suddenly shows 2G, even though the area is full of modern towers.

A colleague from a digital rights group warns that this can be a sign of a fake tower nearby. Such a device pulls in phones with a strong signal and then pushes them down a generation. Lena wants to make sure her phone can't be pushed down like that again.

Going quiet

Later, Lena meets a nervous source in the back room of a cafe. While they talk, she doesn't want her phone connecting to any tower at all, real or fake.

She still needs to send a few messages to her editor, though, and the cafe's Wi-Fi is all she needs for that. She opens the quick settings panel and looks at the switches.

The drive to the airport

On her last day, Lena drives to the airport while on a long phone call with her editor. She's still roaming on the local network. The call lasts the whole drive, about forty minutes along a busy highway.

Back home, a lawyer for her newspaper asks what records that call might have left with the carriers, and how precisely those records could place her along the route.