RFID: Finding the Right Place for RTLS

RFID: Finding the Right Place for RTLS - Tim Harrington, WhereNet

June 08, 2007

RFID Connections interviewed Mr. Tim Harrington, VP of Product Strategy for WhereNet, about the benefits of multimode real time locating system tags.

Tim’s views can be heard by clicking on the “podcast” in the article.   So if you don’t have time to read Tim’s entire interview now, download it onto your iPod/MP3 player and listen in on your way home.

Note: Written transcript has been edited from audio interview for grammar and syntax.

RFID Connections: Without making this sound like a commercial, I do have to note that WhereNet has just introduced the first multimode RFID tag for asset tracking that supports both ISO 24730 and IEEE 802.11 (WiFi)-based real-time locating system (RTLS) applications. So, aside from the obvious advantage of being able to work with both standards, what’s the benefit of having a multimode tag?

Well, one of the biggest benefits, I think, is that it allows us to match the requirements of specific applications. Very often people look to us to supply them with the right application and this allows us to now tune the solution that we bring to the requirements.

In other words, there are some applications which the precision capabilities of the ISO 24730 standard warrant a more sophisticated system that will give very, very high benefits in terms of ROI because of locate capability. And then there are other times when that same amount of accuracy is not required and therefore having an 802.11 type solution might be a better solution for that particular application. Now that we have both available in the same tag, it really does allow us to provide best of breed solutions.

From a system perspective, can you briefly explain the difference between WiFi and ISO 24730 systems?

Certainly. An ISO 24730 system uses a wideband signal which takes up most of the 2.4 to 2.483 GHz bandwidth. This very wide signal is able to filter out multipath and be able to be very precisely located using a time difference of arrival system, TDOA.   TDOA is what’s also used for things like GPS and LORAN systems, so it’s sort of the benchmark for high degrees of accuracy.

802.11 systems were systems that, from the very onset, were designed to be high speed data communications systems. So, using them as locate systems now is sort of an added feature, an added benefit that it gives. It being a narrower band signal which is not using spread spectrum in the same way, it tends to get some more reflections and such, so virtually all vendors use RSSI which is Received Signal Strength Indicator as the method to locate.

What they do is they build up a map throughout the facility at different points -- what’s the relative signal strength at multiple receive stations. And so, you get a very different type of locate, one which is on the order of about 10 meters to 15 meters accuracy whereas the TDOA of the wideband signal of ISO 24730 tends to be outdoors at about six to seven feet or one-and-a-half meters, approximately, to about three to four meters indoors, most time three meters.

Can you give some examples of the types of applications or facilities where it might be preferable to have both types of systems tracking the same asset?

Certainly. One would be last mile of the supply chain. If we envision something that is say a truck trailer that is making its way through the supply chain carrying goods out to a retail store, when it’s at the transload facility, that is where the containers are brought off the marine terminal and over to the transloaders, the transloaders then break it up and put it into trucks. Those trucks can be outfitted with tags and the transload containers can have temporary tags which allows that entire facility to run much more efficiently.

Yard management techniques can be used that, instead of making guesses as to where things are, know exactly precisely where things are located, and it allows the software to make very informed decisions and allows processes to be automated that were never automated before.

The same holds true when we get now to the distribution center, the next node in the chain, if you will, and now we start to again run that distribution center a new way, a much more efficient way. From the distribution center we now have trucks that would go out to the actual stores. Well, out in the stores, there isn’t necessarily a requirement to have any sort of precision locating or such. There’s typically one to three dock doors back there and that same requirement doesn’t exist.

However, there is a requirement to know "when did the truck arrive?", "how long did it stay there?", "when did it leave?", so that it can fit into schedules of where the trucks are going for their next stop and allows much more efficient scheduling of the truck routes. And that can be 802.11 and work perfectly well and just have the cost of a very low cost 802.11 access point there. So, that’s an example in the supply chain.

Within a facility, you can have coverage over the entire facility which, in the past with ISO 24730, might not have been the most economical because the front office typically doesn’t require that same kind of locate information. But if we were to take the example of an entire facility where the back room application such as out on the actual factory floor in the warehouse we’re using ISO 24730 high precision locates to be able to make the businesses run much more efficient, then there could be other places such as the front office, the carpeted areas, where there could still be tracking for laptops, for voice over IP phones, that’s one of the things that comes to mind.

In fact, is to be able to locate people that have their voice over IP phones, executives and such, no matter where they might be in the facility because as they went from an area of 802.11 coverage to an area of 24730. They would now do so seamlessly with no knowledge that they had, in fact, transitioned from one technology to the other. It makes the technology transparent and really moves the whole solution up a level to where it’s just the benefits and the attributes of the application that are the things that are of consequence to the user.

Source: AIM Global