Choosing An RFID or Bluetooth Tracking System
Updated: Jun 1, 2020
Types of personnel or asset tracking are often defined by the technologies that they use, such as RFID tracking or BLE beacon tracking. This approach requires a lot of technological understanding and can be confusing, even to many who have been in the tracking industry for a long time! In this document, we will discuss different types of tracking from a business perspective, then refer to technologies that can be used. Using the common who, what, when and where (and hopefully producing the why and how through reporting and analytics), we can better understand cost and value tradeoffs. The who and what, of course, refer to people and things. But, we’re not actually tracking something unless we also know the where and when. The question of “where” is the hardest one to answer. “Where’s my stuff?” is the often-heard refrain of the frustrated manager or customer. Another common question is “How long?” That question brings “when” into the conversation.
To answer these questions, we need to look at tracking from a range (proximity), granularity (precision), frequency (continuous vs.
intermittent), then a technology basis. For the purpose of this document, there is no difference between personnel and object tracking. Furthermore, our interest lies in tracking for business purposes, not in the invasive tracking of individuals outside of a business location (e.g. mass surveillance) where the conversation immediately goes to privacy and “big brother” questions. The tracking that we are discussing revolves around safety, reducing waste, and improving profitability. While privacy concerns remain in personnel tracking, our goal is to focus on the benefits of such tracking.
When designing or considering which Tracking System to implement, several variables need to be considered.
Data Collection Range - near or far proximity
Location Granularity - coarse or precise, distance and direction
Data Frequency - how often data is reported
Communication Range - near or far
We will discuss each of these in turn.
Tracking System Variables
Data Collection Range - Near or Far Proximity
The distance that data can be collected varies according to the technology being employed. Passive technologies, such as barcode and RFID, can be read from inches to several yards. Passive technologies still require an electronic device to read them, but the tags themselves are not powered. The readers are sometimes called receivers or interrogators.
Active technologies, those which are battery-powered, can read from inches to miles, depending on the amount of signal power they are permitted to use. Both passive and active technologies operate within a specific frequency range, and that operation is regulated by government agencies.
To determine which technology to use, consider your use case. For example, if workers are passing through a turnstile and you would like them to present a badge, RFID or barcode may be a good option. If you want to capture the presence of the worker in the general vicinity of a gate, use an active technology, such as BLE beacons.
Location Granularity - precision, distance and direction
In addition to the range or proximity that the technology can read a tag, technologies vary on how accurate the location information is. The location can be coarse or precise in its accuracy, and the distance and direction from the read point can also be known or unknown.
Location data can be coarse or quite precise, as in the case of GPS. You’re likely a frequent user of GPS on your phone and the accuracy is typically 2-5m, though it can be 1m or less. The downside is that GPS only works outdoors in view of satellites. Some indoor systems, such as using multiple WiFi or BLE access points or readers, can be pretty accurate, but they can suffer from obstacles, especially reflection from metal objects. Other technologies, such as Ultra-wideband (UWB), work well in metal-filled environments, but are generally more expensive than other systems. RFID systems that provide detailed location information are called RTLS, real time location systems.
For coarse precision, one can report only the proximity of the object being tracked, such as a radius around a reader. You will know generally where the asset is. For precise location, distance and direction, you need multiple read points (antennas, receivers or transmitters). Obtaining direction is like going from 2D to 3D: it requires multiple “receive points,” just like you need 2 eyes to see depth. For example, with UHF RFID, one could use 2 antennas, along with arrival, departure and signal strength to determine direction. Without getting too technical, the multiple read points are used to calculate time differentials, which can be used to calculate angles. The angles, time and signal strength can be used to calculate the location.
The distance metric here differs from the data collection range in that the distance being measured is not the distance of the technology capabilities, but rather the distance from the read point. For example, with BLE beacons, one can tell whether the beacon is close, intermediate or far. In all three cases, it is within the range of the reader, but we can tell relative distance from the reader based on signal strength. The same is true of RFID, based on the read signal strength indicator (RSSI), you can gain some information about the distance of the tag from the reader, somewhat like a geiger counter.
Data Frequency - how often data is reported
The frequency at which the data is reported has a big impact on various aspects of the overall system: communication network, location tracking, etc. As one would expect, the more frequently the data is reported, the higher the overall cost and required bandwidth, but high frequency yields more accurate data (realtime data). Frequent reporting causes increases in the network and cloud usage, and where batteries are required (e.g. BLE beacons), reduces the overall battery life. Thus, it’s important to determine the overall value provided by the frequency of reporting.
The frequency of reporting needed can sometimes be determined by the speed or velocity of the object being tracked. For example, consider a BLE beacon. It can be programmed to report every second or once every minute or longer. If the application is human walking speed, then reporting every few seconds is probably sufficient. RFID readers, on the other hand, can read hundreds of tags per second. This makes RFID work well in conveyor or similar systems, when a reader and antenna(s) can be placed in close proximity to the tagged, moving items.
Communication Range - near or far
Once the data has been collected by a local reader, it must be communicated to the cloud, a server, or an edge device. Common communication technologies used for this purpose include both wired and wireless: Ethernet, WiFi, or Cellular. Newer options for communication include LoRa-TDM or LoRaWAN (long-range wireless), NB-IoT (narrowband IoT), LTE-M, or others.
Many factors go into determining the type of communication that you will need to use. These include bandwidth, distance and cost. For example, cellular has both good distance and a relatively high bandwidth capacity, but can cost $10 per device per month or much more. LoRaWAN has a low bandwidth capacity, but can also reach up to miles away at no or little monthly cost.
The type of communication that you should use will depend on the other variables listed above. For example, if you need to report data frequently, you will need a technology that has a higher bandwidth capacity.
Types of Tracking
Availability in TallyFlow (our tracking system): Now
One form of tracking based on general proximity is Chokepoint Tracking, which may also be referred to as gate tracking, or entry-exit tracking. This type of tracking occurs at irregular intervals (intermittent) and must be in the proximity of the reader or receiver. The receiver is receiving data continuously, as tags or beacons are in the proximity of the reader, but the movement of the person or item (asset) makes the recording intermittent.
The data obtained from the receiver can be directional, when using multiple read points, or non-directional. Since the reader is fixed, and the assets are moving, technologies that are typically used in this scenario are barcodes, RFID tags and beacons, such as Bluetooth Low Energy (BLE) beacons. In the table below, you will see a comparison between UHF RFID and BLE beacons.
UHF RFID and BLE Beacon comparison
A careful analysis of this table will show that the costs of the system can vary widely based on the number of read points required, or the number of tags or beacons to be used in the system. For example, for a large number of tags, such as tracking medical supplies, RFID is much more cost-effective. For a small number of people, BLE beacons typically represent a better value.
Examples of Chokepoint Tracking are as follows:
Personnel tracking as the individuals enter or exit through a gate or doorway
Package tracking through a receiving door
Work-in-process (WIP) tracking as items are assembled
Vicinity or Proximity Tracking
Availability in TallyFlow: now
Vicinity tracking does not imply a direction, but tracking in the vicinity of a receiver. This tracking is similar to Chokepoint tracking with the exception of the use case. You can think of Chokepoint Tracking as passing from one zone to another, where Proximity Tracking is a general radius around a read point, or in a cone shape from a read point. This tracking can be implemented using a Bluetooth receiver reading BLE beacons. (Bluetooth 5.1 is expected to bring direction finding and precise distance to BLE beacon tracking in the 2021 timeframe using multiple antennas in a device.) Examples of this type of tracking include the following:
Muster point - e.g. which workers are near (and consequently, not near) a muster point
Golf cart tracking - e.g. measuring pace of play with a reader at each tee box
Building location tracking - e.g. who is near the elevator on the 3rd floor
Availability in TallyFlow: Partial
With the Covid-19 Pandemic in 2020, Contact Tracing became a hot technology topic. The primary way of doing this type of tracking is using Bluetooth. As mentioned above, one can tell whether the BLE beacon is close, intermediate or far away. Having both a reader and beacon on the same device, whether a phone, or a custom device, allows you to both receive and send the beacons. Using the signal strength, you can measure social distancing. Please contact us if you need to learn more about Contact Tracing.
Choosing a tracking system can be challenging and complex. The goals of the tracking system are key to selecting the right system. While there is overlap in the capabilities of different tracking systems, a cost-benefit analysis can narrow the selection. When in doubt, you can talk with one of our TallyFlow consultants to help you decide on the tracking system that is best suited to your needs and budget.