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Indoor Positioning: The Key to Bringing Location-Based Services Indoors

“Ladies and Gentlemen, this is a general announcement: the mall will be closing in 20 minutes”

One of the worst times to hear this message, as I found out, is when scrambling to buy a gift. In my case, I was desperately hunting for a Toys’R’Us to grab a gift for a 1-year-old’s birthday party. My trusty smartphone had gotten me safely to the mall, but the Toys’R’us store was just a marker in the featureless blob that represented the mall in my maps application. After covering most of the mall, I ultimately found the store, but my search could have been much simpler if my maps application provided navigation inside the mall.

Wouldn’t it be nice to have a truly seamless level of service – with all your favorite location apps performing the same whether indoors or outdoors?  Remember those Verizon commercials with the “Can you hear me now?” pitch – unfortunately, we are temporarily stuck in the “Can I use this app here?” phase.

LBS primarily use GPS for location, yielding highly accurate positioning, but indoor situations inconveniently block out a clear view of the sky. Indoor navigation is one of the many use cases that power the growth of LBS. Others include check-ins apps, location sensitive advertising, coupon delivery, and finding your wandering kids.

So what if you don’t have a clear view of the sky?

A variety of other positioning techniques exist, which provide varying degrees of accuracy. Some examples:

  • Cellular network based: This consists of using one or more cell towers to estimate position – either by the handset measuring downlink cell signals or the network measuring uplink transmissions. Either the cell information, signal time of arrival, or overall RF pattern can be used for location.
  • WiFi-based Positioning: The signal strengths, SSIDs, and other Access Point information can be reported back to the network. RF fingerprinting techniques are then applied to the collected information to determine the position.
  • Sensors: Typical smartphones are equipped with accelerometers, gyroscopes, magnetometers and other sensors to detect how the phone moves – allowing you to use fun apps (such as one that simulates a mug of beer!). This sensor functionality can be extended for location purposes.
  • RFID tags, beacons, etc: An indoor environment such as the mall itself can have beacons embedded at specific known locations, which work with technology integrated into the phone to find its location (e.g. NFC tags and readers)

These techniques can potentially be used simultaneously – even incorporating GPS if there’s any sky visibility – in a “hybrid” approach. How good the actual performance is depends on factors such as

  • How accurately and quickly the RF environment can be measured
  • How much the accuracy of sensor measurements degrades over time
  • The ability of the device to juggle the demands of positioning with other, concurrent services

Measuring GPS positioning performance is relatively straightforward – the technology was extensively studied even before implementation on mobile phones. However, many non-GPS techniques (such as WiFi positioning) are not standardized and are proprietary. Measuring device performance when such techniques are used is likely to be much more challenging – likely involving plenty of field testing. Field testing is essential to achieving good indoor performance, but does have the side effects of being expensive and time consuming.

Indoor LBS has the potential to make a lot of people’s lives very easy, but the key factor is ensuring accurate performance. The techniques mentioned in this post (apart from GPS) provide accuracy ranging from 10-200m. The level of desired accuracy depends on what the app needs – indoor navigation, for example, needs very high accuracy. This begs the question – what is likely to be the most popular use of indoor LBS?

 
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