Patent ID: 8130678

Claim:
An automatic fall behind warning method applicable to a group activity environment, comprising the steps of: (a) forming a network with a plurality of nodes each corresponding to a communication device carried by an individual participated in a group activity; (b) initializing an outside node table consisting of all outside nodes determined by an outside determination algorithm according to initial topology of said network; (c) obtaining a link quality index (LQI) table of said network, said LQI table having a plurality of connection entries with each connection entry specifying a connection between two nodes that are able to communicate and signal strength of the connection; (d) generating a list specifying current inside nodes and current outside nodes determined by said outside determination algorithm according to current topology of said network; (e) comparing the outside nodes in said outside node table with said current outside nodes specified in the generated list of step (d); (f) if there is an outside node in said outside table disappears from said current outside nodes of step (d), proceeding to step (g); otherwise, updating said outside node table with said current outside nodes of step (d) and returning to step (c); (g) checking whether the disappearing outside node becomes one of said current inside nodes of step (d); and (h) if the disappearing outside node is one of said current inside nodes of step (d), updating said outside node table with said current outside nodes of step (d) and returning to step (c); otherwise, declaring that the disappearing outside node is falling behind and issuing a warning; wherein said outside determination algorithm determines each node in the topology of said network as being either an inside node or an outside node with the outside node being a node located in an outskirt part of said group activity according to the topology of said network.