A network system includes Internet of Things (IoT) devices, computation server, and gateways. At least one of the computation servers is configured to: tag, according to a signal quality of a signal of the IoT devices, the IoT devices as first devices and second devices; compute a device number of the first devices connecting with the gateways, and while the gateways are connected to the second devices, compute a gateway number the second devices capable of connecting to; compute a load index associated with the device number and the gateway number of the gateways; compute a transmission energy consumption index of a first link between the gateways and the computation servers; select, according to the load index and the transmission energy consumption index of the gateways; and obtain a communication network, wherein the communication network comprises the first devices, the second devices, and the gateways selected.