Fig. 5 shows cell base stations in residential-attribute areas within the Sixth Ring Road. These areas are very dense due to
the large population of urban residents in Beijing. The three largest residential areas, Tiantongyuan (No. 1), Huilongguan (No.
2), and Wangjing (No. 3) are clearly identified by our clustering results. There are many residential-attribute cell-areas in
Beijing because of the large number of mixed-land use developments