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RF/Microwave??

On the quest to find the right indoor location tech

Posted: 22 Dec 2014 ?? ?Print Version ?Bookmark and Share

Keywords:indoor location? GPS? cellphone? 911? Qualcomm?

Polaris Wireless technology is quite unique and innovative. Just as every human has unique fingerprints for identification, Polaris Wireless has a database of locations tagged against RF imprint, based on signal strength and interference patterns. During a call, your cellphone transmits the necessary RF parameters as measured on location to a server that runs it against the tagged locations for a match. It would be interesting to see what kind of location accuracy one can obtain using this technology, since it is directly related to how extensive, granular, and recent the RF signature scan is.

On the face of it, NextNav's technology, which is based on a terrestrial network and signal arrival time, looks very similar to AFLT, but there are some significant differences. Cellular tower placement/position is decided with the goal of increasing coverage and addressing cell traffic, but rarely for location. So NextNav's secret sauce is in the optimal or strategic placement of terrestrial towers to aid in the trilateration process. The result? Better accuracy. NextNav's other differentiator is in detecting height from barometric readings taken at the tower and receiver. This is an ingenious innovation, since air pressure is a localised phenomenon. So the pros are very little modification to cellphones and greater location accuracy with regard to vertical coordinates. The main con is the installation of new towers.

Horizontal location accuracy in metres

Horizontal location accuracy in metres. (Image: CSRIC WG3 report)

So how do these companies and technologies fare among themselves? I expected NextNav and Qualcomm AFLT technology to perform similarly, due to their terrestrial beacon and arrival time-based technology. But results for dense urban and urban area show that NextNav performed better than AFLT. Does this mean that strategic beacon placement coupled with a different signal structure (unlike CDMA) holds the key for better location fix?

It is too early to declare winners at this time. This round of evaluation showed that current participants have come close but are still shy of the FCC search rings. There is an expectation that forthcoming evaluations may have new players such as Boeing (using Iridium satellites), while current participants will improve and showcase their next-generation technologies to hit the mark.

I feel horizontal location and accuracy improvements are relatively easy compared to fixing vertical location and accuracy. It will be interesting to see what future evaluations show us. Those that meet the requirements will not find instant gold; market dynamics with cellular network operators will determine who gets the backing. Remember that some of these technologies have upfront costs, take time to deploy, and may involve handset modification.

I feel an overriding and important aspect will be how scalable the technology is, so that gradual improvements increase accuracy over time without the need to rip things out over and over again.

- Srivatsan Raghavan
??EE Times


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