The network architecture of a WPAN is illustrated in Figure 2, and is built up of clusters of devices. Each cluster has one device designated as a “cluster head,” and one of these cluster heads is the WPAN coordinator. Although the communications range between one device and another is limited to about one meter, networks of clusters can communicate over a much longer distance. Each device uses wireless communications to communicate with its neighbors, and one device can communicate with a supply chain management system using Ethernet, WiFi or WiMAX.