T-Mobile Personal 4G LTE CellSpot is a mini cell tower for your home or small office. It creates a 3G/4G and 4G LTE signal to create better indoor coverage, more dependable voice calls, and consistent data speeds. Voice & data usage is billed to your account the same as your usage of the larger T-Mobile cellular network. You don't need any Wi-Fi or home Internet for it to work. It catches signal from outside when placed near a window or other spot with best reception. Then it amplifies that signal and broadcasts it throughout the house up to 13,000 sq. ft.