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Can Wireless Sensor Network based Real-time Location Systems triumph over WLAN+RFID based RTLS? |
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Written by Chintu Parikh
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Most of the RTLS implementations today use active RFID tags and require wireless LAN coverage for the operating area. Moreover, RF fingerprinting is the most popular technique used for real-time location tracking today. WSN based real-time location systems also utilize RF Fingerprinting technique as a WLAN/RFID based system but have some unique characteristics that I think might make WSN based RTLS a much better alternative than their WLAN based counterpart. Refer to this link to understand how location tracking works with wireless sensor networks.
First, wireless sensor network motes consume much less power than their counter parts – active RFID tags and thus offer much longer life span before they require a new battery cell. That means each device that is being tracked by an active RFID tag would require three to four time more battery changes than the one with a WSN mote over its life span. Thus the cost of replacing battery for each device that is tracked can be substantial (especially if the installation is going to track hundreds or thousands of devices) for WLAN/RFID based RTLS systems compared to the WSN RTLS alternatives. Further, wireless sensor network systems are designed to conserve power during their operation which offers additional benefit over the WLAN systems.
Second, WLAN based systems requires ample wireless LAN coverage for it to operate, That normally means that each physical location within the location tracking operating area require coverage from at least three access points with a received signal strength value of at least -75dBm. Even though the access point price is always dropping, enterprise class AP is still fairly expensive ($250-$750 per unit). Moreover, the APs need to be hard wired to the Ethernet (for network connectivity and power feed) and the wiring and installation cost per AP can be equal to the cost of an AP if not higher. On other hand, wireless sensor network motes are relatively inexpensive and do not require any wiring at all. RTLS market is still nascent - a recent press release by Frost and Sullivan finds that Real-time Location Systems are implemented throughout the country with contracts that are pure pilots and consist of a few thousand dollars to larger contracts in the hundreds of thousands to even a couple in the two to four million dollar area – so WSN might be become a system of choice for real-time indoor location tracking. I would like to hear from WSNPlanet readers their opinions and comments about this article. |
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Last Updated ( Monday, 04 December 2006 )
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