Why do we need an Indoor Positioning System?
Global Positioning Systems don’t work indoors,since they only work in two dimensions, and with more and more business needing a context-aware solution,IPS are becoming more popular. With the giant leap to the Internet of Things(IoT), precise indoor positioning opens countless possibilities for new generation mobile applications.For instance, image you are inside a mall and having trouble with finding the right product; or you would like to have a peek at personalized product promotions nearby; or you lost in a skyscraper; or you want to find the precise location of assets and people.No matter if the aim is customer engagement, risk mitigation or improved productivity, an indoor positioning system will help you to achieve all of these goals.
This is the first in a series of blog posts that introduce three main technologies used to implement IPS: beacons, WiFi, and magnetic position. Starting in Part 1 which focuses on Bluetooth LE Beacons we will compare the pros and cons from the perspective of mechanism, accuracy, and cost.
Part 1 (Bluetooth LE Beacon)
What is the beacon? How does the beacon work?
Not the bacon, but the beacon, “What is it?” You may ask.Well, a beacon is actually a small wireless device that broadcasts Bluetooth low energy signals.Through these signals each beacon itself forms a geo-fence(a virtual perimeter for a real word geographic area).When the user holding a bluetooth enabled phone with an appropriate application installed goes inside the perimeter, the phone will trigger related actions which can include addressing the user’s position via the known location of the beacon and signal strength.According to different signal strength (RSSI) from each beacon, when the signal strength crosses a fixed threshold the app will do the corresponding calculation using complex data science and algorithm processing sensor data to achieve the positioning.
To be specific,the algorithm mainly used is trilateration, we can get the information about proximity based on the RSSI reading from each beacon.By assessing the signal strength from at least three beacons as fixed reference points, and theoretically, knowing the distance between device and each beacon, the app can position user’s exact location.While this works well in theory, signal strength is impacted by various factors such as beacon transmit power, the environment, radio wave physics,interference, etc, which have a huge impact on positioning accuracy. We will talk about accuracy in the next section.
Accuracy
Our technical consulting team did a series of tests to assess the accuracy of beacons.In general, the best resolution an IPS based on beacon technology can reach is 1 to 3 meters most of the time, and under certain conditions consistently around 1 meter.We believe for an IPS, the more accurate the better, so we will focus on several main factors for achieving 1 meter accuracy.We divide the constraints mainly into 3 parts: venue constraints, beacon constraints, and user device constraints.
About the venue constraints: 1) Venue size matters.The smaller venue and the more beacons we place inside the venue, the better accuracy. For a small room around 20 square meters with 6 beacons, 1 meter accuracy is achievable. 2) Venue shape matters.A regular shape such as a rectangle results in better accuracy than irregular shapes. 3) Venue openness matters.Since the Bluetooth signal needs to be readily registered by the sensing device,like a mobile phone, for example, people density in the venue must be low.People and other obstacles have a huge impact on Bluetooth signal.Generally speaking the more open the area the better.
Beacon constraints: 1) Beacon density and position in the venue matters.Within reason, the higher the beacon density, the better accuracy. We suggest not placing the beacons in the corner it will cut the beacon’s radius of operation to a quarter.Best positioning is place the beacon on the wall vertically about chest height, distributed around the venue on open parameter surfaces with one beacon every 4 meters. 2)Beacon configuration matters.Beacon internal configuration is very important. We should change the beacon transmit power corresponding to the venue size.The advertising interval should also be set to transmit as frequently as possible. If we’re using a battery powered beacon this will have a significant impact to beacon battery life, but also has a significant impact to application performance, providing a more near-time update of positioning.
User device constraints: 1) The way a user holds the device matters.For best accuracy, the user needs to hold the device normally in front of their chest while walking around the venue.The greatest accuracy is achieved when the device’s antenna is positioned facing a beacon and the device is given some time to settle. This doesn’t seem very practical for many real-world scenarios, so achieving optimal, 1 meter accuracy, is challenge in many situations.2) Distance between the device antenna and beacons matters.The closer the device’s antenna is relative to a beacon, the better the accuracy.
Cost
Beacon market price varies from brand to brand.Generally speaking beacon accuracy and beacon price parallel one another: the higher the accuracy, the higher the price.Overall,however, beacons are comparatively cheap, so the cost for deploying them as an IPS is acceptable.
Verdict
Summarizing the factors above, the beacon is a relatively good option for indoor positioning. It provides a location context for mobile apps and devices, which enables a whole lot of possibilities and benefits for both business and customer. We believe beacon related solutions will be continue to emerge as a trendy thing in this Internet of Things era.
