A method and apparatus is disclosed for position tracking and
communication within a defined locale. Low power transmitters and
receivers, called probes, are placed in key locations throughout the
locale, called ranges. The persons or objects to be tracked carry a
battery-powered device, called a tag. The battery in the tag can be used
to limit the tag's life span (useful for applications such as limited
time span, system renewal according to expected turnover rate, etc.),
thereby allowing reuse of the ID. The tag is encoded with a two-level ID
code with the common part used in communication with probe in normal
condition. The tags respond to beacon upon entering a probe's range. The
response is gathered by a probe and fed to a central computer where the
tag's current position is recorded and combined with site-specific
information and past history to determine the most likely position of
each tag. Since the tags do not need to perform any complex computation
or high-power communication, they can be constructed inexpensively and
deployed as a disposable device. The whereabouts and past information can
be queried at various reporting locations. There can also be public
announcement, such as speaker or display, placed throughout the locale.
The tag can be equipped with some alert or display capability for
communication. The present invention provides a low cost, highly usable
position tracking system. The system is able to function even with radio
signal deafening structure, and provides a site-specific meaningful
report. This type of system is especially valuable for transient
travelers in territories such as in a convention hall, amusement part,
shopping mall, cruise ship, etc. This system is also useful to track
highly transitory inventory.