A method, network system, and non-transitory computer readable medium that arrange a set of wireless mobile devices into a two-level clustering structure including a cluster in a first-level and a cluster in the second-level, based on node status registered and algorithm preinstalled in a back-end server, where each of the set of wireless mobile devices is assigned either one of a slave member of a cluster in the first-level, a master of a cluster in the first-level where the master is also a member of a cluster in the second-level, or a super master of a cluster in the second-level where a master of a cluster in the first-level is assigned as the super master. The two-level clustering structure is periodically updated. Only the super-masters are configured to communicate with the back-end server via a long-range connection to WLAN, while a short-range wireless interface is used for internal communications.