Patent ID: 7541913

Claim:
A method for tracking a plurality of containers loaded onto a cargo vessel using a pre-configured low-rate wireless personal area network (WPAN), whereby each container is joined to an electronic tracking device provided with routing capabilities and a WPAN-enabled radio receiver/transmitter, and whereby each electronic tracking device is configured to attempt to connect to the WPAN upon being activated, the method comprising: activating the radio receiver/transmitter of each electronic tracking device joined to a container of the plurality of containers as the container is being loaded onto the cargo vessel; receiving an indication from each electronic tracking device that fails to connect to the WPAN upon being activated; intermittently performing a network scan to locate each electronic tracking device that is connected to the WPAN; intermittently configuring the WPAN to include each electronic tracking device that is connected to the WPAN in a hybrid tree-mesh network topology; intermittently configuring routing information stored on each electronic tracking device that is connected to the WPAN to maintain mutual communication with each electronic tracking device that is connected to the WPAN and enable mutual communication between each electronic tracking device that is connected to the WPAN using the routing capabilities of the electronic tracking devices; receiving GPS-recorded position data, environmental parameter data, and sensory reading data from each electronic tracking device that is connected to the WPAN; transmitting the GPS-recorded position data, environmental parameter data, and sensory reading data to a control station of the cargo vessel through a local area network on the cargo vessel; broadcasting a request to the WPAN to be routed between the electronic tracking devices connected to the WPAN in a depth-first traversal of the network topology, the request directing each electronic tracking device that is connected to the WPAN to enter a low-power mode when the depth-first traversal backtracks from the electronic tracking device; and receiving an acknowledgment of the request communicated from each electronic tracking device that is connected to the WPAN when the electronic tracking device enters the low-power mode.