For RTLS to function, the location of tagged items must be determined either by a central processor or by an embedded mobile computing facility. Locating is generally accomplished in one of the following ways:
Examples one (1) and three (3) have much of the same characteristics. They typically require that a node be assigned at a time to a single reader/signpost. Separation from overlapping readers/signposts is roughly provided by RSSI or Physical Space Division (walls/floors/ceilings). Readers/signposts are often associated with highly stable location boundaries (i.e. a room or room division). In these examples, locations are listed as "Current Location" or "Last Known Location."
Example two (2) requires that distances between nodes in the sensory network be determined in order to precisely locate a node. In this instance, the determination of the location is called Localization. The location is calculated through Trilateration or Multilateration from the determined distance between the nodes or through Triangulation from the determined angles between nodes. The determination of distances is called Ranging.
Methodologies used in Real Time Locating Systems include:
US Patent Issued to Alcatel on Sept. 21 for "Amplification for Optical Fibre Ultrawide Band Transmission Systems" (French Inventor)
Sep 22, 2010; ALEXANDRIA, Va., Sept. 28 -- United States Patent no. 7,801,444, issued on Sept. 21, was assigned to Alcatel (Paris)....