11 May 2020

Tags are not Beacons

This article discusses the main differences between two devices, Beacons and Tags, commonly used for Bluetooth®-based location systems. The aim is to highlight that even though Tags use similar hardware to their predecessors, Beacons, they are in fact very different as devices. The firmware, operational logic and usage differ significantly between the two different types of devices. Beacons are typically stationary, while Tags are in motion. This in turn affects the design principles behind the devices.

Tags and Beacons are both commonly used terms for Bluetooth devices used in location systems. Although different devices, with Tags derived from the original Beacons, the terms are often confused, leading to misunderstandings about what Bluetooth can offer. The aim of this article is to clarify some of the common misconceptions by comparing the two technologies.

Let’s start by defining Beacons, which were introduced to the market around 2010 and are often thought of as the enabler technology for Bluetooth-based location solutions for mobile devices (e.g. phones, tablets and computers). Beacons are relatively simple Bluetooth devices that typically work as fixed nodes, sort of like a lighthouse, installed at a fixed and known location to periodically broadcast signals (typically following the Eddystone and/or iBeacon profiles) over the three Bluetooth advertising channels (37,38 and 39). Mobile devices receiving these signals can then compute their own relative position using Received Signal Strength Indicator (RSSI) measurements. In some cases, the Beacons also offer connection-oriented services for remote telemetry and configuration.

Since the introduction of Beacons, the Bluetooth Special Interest Group’s (Bluetooth SIG) member companies have continued to push forwards, taking the principle of Beacons and developing it into a new state of the art technology. Today, technologies based on Bluetooth Direction Finding can provide some of the most advanced Real-Time Locating Systems (RTLS) and Indoor Positioning System (IPS) available on the market. High-accuracy, low-latency and robust are just some of the signature features that systems based on Bluetooth Direction Finding can achieve. What’s more, they are cost effective and scalable.

Over the years, the market has introduced various devices that have carried the name “tag”, but the introduction of Bluetooth Direction Finding formalised the specification for smarter Tag devices, such as the Quuppa Tags. On a hardware-level, these Tags are very similar to their predecessors, Beacons. However, their operational logic and firmware are very different. Rather than just statically broadcasting signals, tags are dynamic devices that can move around and change their operating behaviour (i.e. profile) depending on their location, state of motion (static or moving) and other configured factors (e.g. remote commanding). The ability to effectively track items that are in motion using the newer Bluetooth Direction Finding methodologies have changed the game for the asset tracking business.

The key differences between Beacons and Tags can be summarised as follows.

  1. Profile Logic

    While Beacons are typically installed to fixed locations and transmit signals according to a defined profile, Tags move around and dynamically change (using a finite-state-machine logic) their transmit power and rate according to their state of motion, location, or commands from the centralised system. This ability to transfer between states, by dynamically adjusting their transmit rate and power based on profile settings, significantly extends battery lifetime and reduces the radio congestion in the area improving system capacity and performance.
    Example:

    • A Tag can be attached to an industrial tool and configured to transmit at 2-3 Hz while in motion (for smooth and continuous tracking) at 0.1 Hz when stationary (e.g. left on a shelf). In some advanced cases, artificial intelligence (AI) logic could also be integrated into the Tags so they can automatically detect pre-defined events (e.g. man down situations where a person has fallen over).
  2. Density of Deployment

    While Beacons are typically uniformly distributed throughout the environment, Tags are attached to items in motion and can be found in high concentrations in certain areas. For example, when tracking goods or tools in an industrial facility. With the ability to switch between states as needed, Tags make it possible to have thousands of devices transmitting Bluetooth signals in the same space without overloading the air interface.
    Example:

    • It is not uncommon to be in an industrial environment where 30,000 units (e.g. boxes, pallets, tools, machinery, barcode scanners, printers) need to be tracking in real time (e.g. a warehouse facility). If all of these devices are active simultaneously and broadcast at 1 Hz, the air interface would become very congested. However, it is much more common that only some of these items are in motion at the same time and so, by controlling the transmit rate based on motion (moving 2-3 Hz, static at 0.1 Hz) we can dynamically allocate air interface resource to those tags that are in motion and need to be tracked more actively by the system. Similarly, tags attached to items that are in storage can be set to transmit infrequently to reduce air interface load.
  3. Form Factor

    As Beacons are typically installed in fixed locations, their size or shape is not strictly dictated by the use case (although a larger device does enable larger battery capacity to be added). However, as Tags are dynamic devices that move around the environment, the form factors (e.g. shape, size, weight and ergonomics) become essential design parameters.
    Example:

    • Wearable Tags such as those integrated into ID badges must be small, light and unobtrusive. These requirements differ significantly from those of a robust industrial tag what will be attached to equipment.
  4. Colour Selection

    The differences in use between Tags and Beacons also affects the colour choices in the design phase. Beacons are effectively infrastructure devices that are designed to blend into the background while Tags are used for tracking items that are moving around and need to be spotted easily whenever needed (e.g. if they need to be removed). For this reason, Tags often have bright, even fluorescent, colours so that they stand out.
    Example:

    • Tags used to track items on manufacturing lines are typically attached to objects at the beginning of the production line and moved once the item is ready for shipping. This means that they need to be easy to find and remove when the right time comes.Additionally, the aviation industry has foreign object damage (FOD) policies that require foreign objects (e.g. Tags) to be easily identifiable against the surrounding environment.
  5. Mechanical Mounting

    The mounting requirements of Tags and Beacons vary significantly. For Beacons, the attachment is designed for static use (i.e. once fixed, the Beacon will not be moved). Tags, on the other hand, have much more versatile attachment requirements. They need to be mountable to a large variety of mobile objects (e.g. people, equipment, machinery, pallets, boxed). They need to be firmly secured, possibly even configured to send an alarm if removed unintentionally, but also easily removable when needed. It is even quite common to see various temporary mounting options such as zip ties, glue, tape, Velcro, magnets, bolts or screws used for fastening Tags.
    Example:

    • Tags used to track items in warehouses are typically attached when the item arrives at the facility and removed as the item is shipped out. The Tag needs to be securely fastened to the item and remain in place through the duration in the warehouse but be easily removable when the item is ready to be shipped.
  6. On-Board Sensors

    Unlike Beacons, Tags can carry a variety of sensors making them optimal devices to be used for a combination of tracking and remote sensing. Sensors to track parameters like acceleration, temperature, light, humidity and pressure are commonly added to devices. Additionally, sensors can report the states of motion for the objects that they are attached to, for example if they are static, moving or vibrating. All of this data can be sent, via the Locator (also operating as an IoT gateway) to the software application layers. Wearable Tags can even be used to give real-time feedback to people wearing them or to expose the person vital sign information.
    Example:

    • Wearable tags can be used for collision avoidance use cases by sending a real-time notification (e.g. buzzing sound, vibration or light signal) to the person carrying them if the system identifies potential danger ahead, e.g. a forklift that may collide with the person.
  7. Radio Characteristics

    The design characteristics of Tags and Beacons also differ. Beacons are designed for wireless data transfer whereby the transmission of the data is more important than how the data moves between the Beacon and the phone (this is similar to how Wi-Fi for internet connectivity works). However, Tags are designed for positioning and the positioning system uses the radio signal propagation characteristics to estimate the signal source. This means that it is important to minimise phenomena such as rich scattering, shadowing and multipath propagations, which are otherwise typically considered useful for wireless data transfer. To ensure best results, the Tag’s antenna needs to be carefully designed to maximise the visibility of the Tag.
    Example:

    • Tag antenna designs should be optimised according to the radiation patterns. For this, the antenna should be as omnidirectional as possible so that deep nulls are minimised. Due to this requirement, it is also recommended to use PCB printed antennas instead of ceramic dipoles. In some cases it may also be useful to design tags to have dual-antennas so that transmitted packets are sent alternately to add spatial and polarisation diversity.
  8. Manufacturing Properties

    Compared to Beacons, Tags are subjected to significantly more mechanical stress over the course of their lifetimes. To withstand the wear and tear, everything needs to be designed to be robust. The soldering to the battery attachment, all of the components and the PCB need to be built to last.
    Example:

    • Tags are mounted on mobile objects that are subject to high use and in some cases, high acceleration and even collision (e.g. forklifts and ice-hockey pucks). In manufacturing, the same Tags are used time and again across the manufacturing line, meaning they need to last extended use in industrial conditions.

The table below summarises the above comparison between Tags and Beacons.

 

DeploymentBehavioural LogicBattery ConsumptionOn-Site DensityRadio Characteristic
BeaconsDevice or node, typically fixed mounting on walls or or other static structures.Simple behaviour, continuously transmitting a periodic signal.Predictable over time as its operation behaviours stay constant 24/7.Low, at most one device on a grid of 2-3 m distance.Typically optimised for wireless data communication. Directive antennae may be used to optimise.
TagsTypically attached to objects that are constantly moving. Can even be a wearable device that is carried by a person.Advanced dynamic behaviour, running a final-state-machine logic.Depends on the duty-cycle between active and inactive states, as well as its configuration parameters.Can be very high, with tens of thousands of Tags per facility. Optimised antenna  radiation pattern for radio visibility. The wireless communication is typically not limited by range.

In summary, it is important to note that although both are devices used for Bluetooth-based location solutions and applications, Tags and Beacons differ significantly and should not be confused. Beacons are essentially simple radio devices designed to be mounted in a fixed location and typically operate statically throughout their lifetime. Tags, on the other hand, are designed to be attached to moving objects, requiring a higher level of robustness, customisation to the use case and extra firmware logic to enable dynamic behaviour. These differences allow Tags to provide far better tracking results for RTLS solutions.

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