Which of the following statements is NOT true about femtocells?

The statement regarding existing WiFi or DSL routers being upgradable to a femtocell without the need for any new hardware is not true. Femtocells are specialized devices that create a small cellular coverage area, typically for enhancing cellular signal strength in homes or small businesses. They require specific hardware and software configurations that differ from standard WiFi or DSL routers.

While some femtocells may allow integration with existing broadband connections, they cannot simply upgrade existing routers into femtocells without a dedicated device. This distinction is crucial as it underscores the specialized nature of femtocells, which cannot merely use existing networking equipment to function as a cellular base station.

In contrast, the first two statements accurately reflect the operation of femtocells: mobile devices registered with a femtocell automatically switch to it when in range, and they seamlessly revert to the cellular network when exiting the femtocell's coverage area. These processes are fundamental functionalities of femtocell technology designed to ensure continuous connectivity for users.