Frequently asked questions and answers
Most frequent questions and answers
BiDaE Object Tracker is always correct about on which floor an object is. Its horizontal location accuracy depends primarily on the size of the area covered by a single locator and to a lesser extent the deployment density of locators. Generally speaking, the goal of the system is to bring the user to within the line of sight of the sought-after objects. So, the coverage area of each locator is about 3-5 meters or 5-10 meters, usually called the bed-level (or desk-level) accuracy or room-level accuracy, respectively. In hospitals and other healthcare facilities, locators are typically deployed to achieve these levels of accuracy in emergency room and patient wards.
Object tracker systems are sometimes configured to provide zone-level accuracy (i.e., 10-20+ meters) in all or part of the area covered by the system. A system thus configured enables its user to determine on which part of a floor each tracked object is. Since fewer locators are required to achieve zone-level accuracy, the cost of the system is lower. Some systems may have locators only at elevator halls and stairwells and at main entrances/exits. They can help users confirm that a tracked object is a specific floor or is in the building. When this accuracy suffices, the cost of the system is at a minimum.
BiDaE Object Tracker can respond to thousands of concurrent searches for thousands of objects within 2 seconds. When a tracked object moves, the GUI shows its new location after a 10 second delay. In real-life operating environments, many factors can cause unpredictable fluctuations in strengths of tag signals received by locators. Consequently, the GUI may show the objects attached to the tags moving sporadically or haphazardly. Such apparent changes in object locations returned by the system due to unpredictable changes in signal strengths is referred to as false movements. Users are likely to find false movements annoying. The 10 second delay is a design tradeoff introduced to reduce false movements. It can be shortened when the user prefers more timely update of object locations.
The BiDaE Positioning System (BPS) is structured as an IoT (Internet of Things) fog. It remains responsive when overloaded in the presences of thousands of tags/objects and degrades gracefully when network connection is disrupted and parts of it damaged.
Specifically, the work of locating and tracking objects is done collaboratively by two types of components: tags and locators. Both are Bluetooth low energy devices. Each tag has a universally unique ID (UID). Object trackers use tags to make objects to be located and tracked visible to the system: This is done by having a tag attached to (or worn by) every object and storing in the server an association of the tag ID with the object ID/name. BiDaE Object Tracker provides two types of tags: simple tags or sensor tags. Regardless its type, every tag broadcasts continuously advertizing packets containing its own UID and thus makes its own presence, and the presence of the object associated with it, known to Bluetooth receivers nearby. This is all simple tags do. Each sensor tag contains sensors. In addition to its ID, each sensor tag also broadcasts readings of its sensor(s) as payload of the advertizing packets.
Locators are Bluetooth low-energy (BLE) transceivers. Some of them also provide gateway function to link locators nearby to the local WLAN. Locators/gateways are pervasively installed, usually under or above ceilings in the area where objects are to be located and tracked and navigation is supported. Each locator stores and broadcasts its own 3D coordinates via a directional antenna continuously. Thus, it provides navigation apps, including Seeing-I-Go, on devices in its coverage area with position data. Each locator also scans its coverage area continuously and communicates via WiFi to the BPS server. Whenever a locator hears a tag, it sends to the server the UID of the tag, its own 3D coordinates, and the time interval during which the tag is heard. Based on the data from all locators installed in the area covered by the platform, the server determines at any time the location of every tag and the time interval in which the tag has been at the location.
Every locator also forwards to the server time stamped sensor readings from every sensor tag. In this way, locators together effectively function as a sensor data crowdsourcing system.
Locators are not only BLE transceivers. They also are embedded processors that carry out data processing at the edge of a IoT cloud: Each locator processes UID's extracted from advertizing packets of tags to eliminate duplicates, timestamps UIDs of tags to be sent to the server, generates its own health report, and so on. By doing this work, locators relieve the server from CPU intensive data processing tasks and reduce significantly the volume of data between locators and the server. This is why BPS platform is scalable.
As stated earlier, some locators function as gateways. They collect location data and health reports from locators nearby and forward the data via WiFi or Ethernet to the server. These embedded processor prioritizes the transmissions of data from locators according to the required response time, e.g., scheduling the transmission of data indicating alert conditions at the highest priority and transmissions of locator health reports at the lowest priority. As a consequence, object trackers running on the platform is able to deliver time critical alerts such as alerts from geo-fences within 1-2 seconds.
The locators are connected to AC power line or are powered by PoE (Power over Ethernet). Bluetooth tags use button batteries with 8 months to one year battery life. When the battery of a tag is too low, the user can replace the battery and continue to use tag. The object tracking system provides tools for displaying tag battery status and delivering low-battery alarms.
Some sensor tags are smart watches. They are equipped with a cable for battery charging. The system integrates the power indicator of the smart watch and its own low battery alarms, and thus notifies the person who wears the watch and/or the person's caretaker when the watch need to be charged.
BiDaE positioning system (BPS) is designed to be highly dependable. Dependability is achieved by building the BPS server and storage unit (hereafter referred to collectively as the server) on a high availability architecture on the one hand, by enabling the remainder of the system to degrade gracefully on the other hand.
Graceful degradation of BPS follows straightforwardly from the fact locators stores and broadcast their own coordinates and collect UIDs of tags in their covered areas essentially independently of one another. When a locator failures, the system can rely on locators in its vicinity to provide degraded service. For example, in an area where locators are configured to provide bed (or room) level accuracy, location accuracy may degrade to room (or zone) level when one or more locator failed. To provide added dependability, each locator automatically and continuously assess its own health during normal operation and their health reports are sent to the server periodically. Consequently, faulty and defective locators can be identified on a timely basis. Oftentimes their health can be restored remotely before failure occurs.
The battery status of each Bluetooth tag tracked by the BiDaE Positioning System platform will be continuously detected, and the object tracking system also provide tools such as battery status list and low battery warning, allowing users to timely know that any bluetooth tag has a low battery condition to prevents objects from being not found due to a dead bluetooth tag.
BPS server would be a single point of failure. For this reason, the server is built on a highly available architecture. The design goal is to achieve equal or better availability that is typically required of hospital information systems, that is, in the range of 99.95 to 99.99%. In other words , total downtime per year is shorter than 4h 22m 58s and 52m 35s, respectively.
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