A method for tracking a plurality of containers each joined to an
electronic tracking device having routing capabilities and a WPAN-enabled
radio receiver/transmitter configured to attempt to connect to a
pre-configured WPAN upon being activated comprises activating the radio
receiver/transmitter of each tracking device joined to a container being
loaded onto a cargo vessel; receiving an indication from each tracking
device that fails to connect to the WPAN; intermittently performing a
network scan to locate each WPAN-connected tracking device;
intermittently configuring the WPAN to include each WPAN-connected
tracking device in a hybrid tree-mesh network topology; intermittently
configuring routing information stored on each WPAN-connected tracking
device to maintain mutual communication with each WPAN-connected tracking
device and enable mutual communication between each WPAN-connected
tracking device; receiving transport-related data from each
WPAN-connected tracking device; transmitting the transport-related data
to a control station through a LAN on the vessel; broadcasting a request
to be routed between the WPAN-connected tracking devices in a depth-first
traversal of the network topology that directs each WPAN-connected
tracking device to enter a low-power mode when the depth-first traversal
backtracks from the tracking device; and receiving an acknowledgment of
the request communicated from each WPAN-connected tracking device when
the tracking device enters the low-power mode.