User's Manual

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User Guide for WhereTag IV Module D1587 Rev 01
©2010 Zebra Enterprise Solutions. WhereTag IV and all product names and numbers are Zebra Enterprise Solutions trademarks. All other trademarks are the property of their respective owners.
1 INTRODUCTION
1.1 System overview
The ZES Real Time Locating System (RTLS) is designed to permit users to determine the position
of tagged assets in both indoor and outdoor facilities such as factories and freight yards. The system
locates tagged assets by a process involving redundant triangulation. Each tag autonomously emits
a 2.4 GHz direct sequence spread spectrum (DSSS) radio signal at predetermined blink rate. Each
tag’s blink rate is randomized around its predetermined value to minimize the number of collisions
between transmissions made by different tags. The signal emitted by the tag is received by a
minimum of four Location Antennas. A typical transmission contains a preamble which is used to
synchronize the receiver, the tag’s serial number which identifies the tag, a status word which
monitors various tag functions, data stored in the tag’s memory and finally a CRC used to assure
that the tag’s message is correct as received.
The principal components of ZES’s RTLS are shown in Figure 1.
1.2 WhereTag IV Module
The WhereTag IV Module is a compact battery powered radio frequency device which is used in
WhereTag IV, WhereCall III+ and WhereCall IV tag products. These tag products are key
components of the ZES Real Time Locating System (RTLS). The tags can be attached to assets of
many kinds, such as forklifts, containers, ULDs, hospital and test equipment as well as trailers and
container chassis's. It is used to manage those assets by allowing them to be identified and located
by the system.
The WhereTag IV Module "blinks" an RF transmission at pre-programmed rates ranging from 1
second to 5 days between blinks. The ZES RTLS infrastructure receives these blinks and use
sophisticated Differential Time of Arrival, (DTOA), algorithms to determine the location of the tag.
Accuracy of this determined location can be as low as 2 meters and is nominally within 3 meters in
most installations. The WhereTag IV Module complies with the ISO 24730-2 RTLS standard. It