What does the mobile wireless network infrastructure currently look like?

From 1: "The mobile wireless network infrastructure may be organized into a cell hierarchy as shown in the following figure, based on technology either already deployed or still under development. Starting from the home cell with coverage in private buildings such as a house or office to public hotspot locations such as airport, train station, conference center, service may be provided through an access point. In a hierarchical multi-layered cell environments, extra intelligence is required so that the network can find a specific terminal or the terminal can determine the boundaries between wireless networks and switch to the most appropriate one.

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