ARS Solutions for Healthcare: Low-cost Indoor Tracking System

Background:

A significant obstacle to the adoption of most indoor asset-tracking systems – particularly in healthcare environments – is the need for an installed infrastructure. Add to this the set-up, maintenance, and management of the entire process change, which can be complex and costly, and it becomes quite clear that healthcare organizations need a thoroughly reliable, low-cost solution to their high-value asset-tracking.

Active RFID Systems, Inc. 433.92 MHz solutions are designed to allow healthcare institutions increase patient safety and throughput, optimize asset and resource management, synchronize workflows, and reduce operational costs.

ARS has developed a family of tracking systems that are not only very inexpensive but also exceptionally easy to install and setup. The low cost is achieved through the following:

  The system is operable by “plugging” readers into existing 110/220 VAC power outlets or by powering them directly from an Ethernet switch in the “Power over Ethernet” mode of operation. This requires no added permanent building infrastructure.

  The system utilizes an adaptation of Active RFID Systems, Inc.‘s low cost, dual-mode infrared/RF tags.

  All communications and data-forwarding are performed wirelessly, with no loss of data and no network set-up costs.

  The system does not require new wiring or expensive location mapping, since the location mapping is consistent with building walls and power outlets.

System Description:

The baseline system comprises two basic components:

1. Dual mode infrared/RF tags, which incorporate an infrared sensor that responds to an incoming coded signal in such a way that the tag will transmit an RF output signal when it is in the vicinity (range) of an infrastructure-mounted device. The output consists of the tag identification (ID) value and the identification of the infrared transmitting unit. Thus the RF output serves to identify both the item (or person) and the location with a single transmission.
   
2. Wall mounted readers or trigger/network transceivers (TNT), designed to be powered from wall transformers that are “plugged into” the common wall outlets for 110/220 VAC power sources, thus obviating the need for hard wiring. These devices incorporate a number of infrared signal transmitters and are continuously emitting the coded infrared signals that the tags respond to. The power of these infrared emitters is remotely controllable in the networked versions. The power of these emitters also determines the range of the system and can be adjusted from several inches to tens of feet. In this manner a near spherical volume of “engagement zone” is created. Within this “engagement zone” any tag will be triggered and the reception of this signal received by the trigger/network transceiver devices.

These trigger/network transceivers contain a 433.92 MHz receiver that records each tag's RF signal. These TNT devices output either via an Ethernet connection to a central database, or optionally, they may be equipped with an incorporated wireless 802.11.b/g radio as well.

When a tag is in the vicinity of an infrared device, it transmits the 433.92 MHz “payload” of data to the trigger/network transceiver device. The trigger/network transceivers establish RF communication with all other trigger/network transceiver devices in range and pass the tag ID and location information upstream until the data basing control computer is reached and the data stored and or displayed for operator or archiving use.

The figure below illustrates the basic operating principles of this system.

In the ARS system, the wall-mounted triggers are shown (marked as IDs 1 through 4) fixed to wall outlets in the vicinity of the items to be monitored. These readers emit a continuous encoded infrared signal that is transmitted hemi-spherically (shown in blue gradient and defined above as the “engagement zone”) from each trigger device. These signals can be adjusted for approximate range; however, it is likely that signals will occasionally “spillover” into another reader's range. The system hardware enables manual adjustments of these infrared signals.

When the tags (shown in red) receive an infrared signal they transmit a 433.92 MHz signal (illustrated in green) back to the reader. This signal may be received by a multitude of reader devices. However, since this signal packet contains both trigger signal ID as well as tag ID, only one reader recognizes the tag as being in its sphere of influence. Again, there will occasionally be overlap due to infrared signal spillover, in which case the location will be noted as within multiples of the readers' range. Continuous receipt of a reader trigger signal will cause the tag to remain silent except for periodic updates.

The data from the readers is transmitted to a central database either through the Ethernet connections or through the readers, now functioning as trigger/network transceivers, which can, in turn, re-transmit data at 2.45 GHz to each trigger/network transceiver device within range. (This is shown in the figure as the magenta-colored RF signals.) This is expected to include from 1-100 trigger/network transceiver devices.

The reader nearest to the master tag (MT), shown in the figure next to the computer and database, transmits this data to the master tag which in turn pushes the data into the database. The master tag also transmits queries downstream to all of the trigger/network transceiver devices in the network and constantly establishes the network communication paths, the correct timing of events and notes the addition or loss of readers.

The readers can be set up to form a “wall” at portals enabling the tracking of items that are entering or exiting through such a portal opening.