A typical wireless communication system (see, for example, Japanese Patent Application Publication No. 2011-9828) will be described with reference to FIGS. 26 and 27. An application node communicates with each of a plurality of sensor nodes through a gateway device 1. Some of the sensor nodes are relayed by other sensor nodes to communicate with the application node.
The gateway device 1 sequentially sets packet transmission times in the descending order of a hop count or a child node count of each sensor node. The gateway device 1 includes information defining the hop count and the child node count of each sensor node as illustrated in FIG. 27. In general, as the hop count or the child node count increases, packet collision more frequently occurs. This gateway device, however, sets packet transmission times while placing priority to nodes with large hop counts or child node counts, and thus, packet collision is less likely to occur. Consequently, packets do not need to be sent again, and thus, the difference between an intended packet acquisition time point and an actual packet acquisition time point in an application node decreases. Accordingly, the application node can acquire data at an intended time.
The gateway device 1 sets a packet transmission time by using a network architecture table listing hop counts and child node counts (see FIG. 27). In a case where the network architecture is changed, hop counts and child node counts of sensor nodes in the entire network are calculated again, and the network architecture table is updated.