RTLS Technology
There are many different types of RTLS technologies and RTLS companies offer different types of RTLS solutions.
Passive RFID
Passive RFID RTLS receivers (gateways) send out radio signals. These readers are used to do two tasks. The first task is power all passive tags via electromagnetic energy within a fifteen feet range. The second task is listen for response radio signals from RFID tags.
The major benefit of RFID systems is low cost. RFID tags are very inexpensive and priced in cents, not dollars. They can last forever since there is no battery. Next, RFID tags are very small in size and generate little to no RF noise.
The maximum range from which receivers can get the signal from a tag is 15 feet. RFID readers are fairly expensive and can create technical complexity when two readers try to read the same tag. RFID readers can easily cost in $1,000+ range and require siginificant installation costs and calibration.
Ultra Wide-Band RTLS (UWB)
Ultra-wide band RTLS solutions measure the time it takes the ultra wide-band signal to travel from tag to receiver in order to calculate the distance in centimeters. This precise method gives much better ranging information for determining precise location. UWB systems can be the most accurate of all RTLS technologies, but UWB tags and receivers systems can be very expensive.
Bluetooth Low Energy (BLE)
Active RTLS BLE tags communicate with receivers (gateways) throughout a facility. Those receivers then send that information to the RTLS system hosted onsite or in the cloud. Bluetooth Low Energy (BLE) tags reduce system and operational costs and enable reliable asset tracking. These systems can also offer sensor data in addition to just positioning data.
This is often the least expensive RTLS option. BLE solutions can be complicated since Bluetooth signals can travel through walls. As a result, depending on provider selected, solutions can be complex for users looking for hyper precise location. Bluetooth receivers (gateways) can be significantly cheaper than other technologies. Reciever prices can range from $80 to $800+ dollars.
WiFi
WiFI RTLS allows active tags placed on objects to communicate with multiple “access points” via Wi-Fi signals (2.4 Ghz / 5 Ghz). Location accuracy varies across providers due access point physical location, model, and capabilities. Typical WiFi RTLS systems use general proximity to access point for location determination. Many WiFi based solution provider “claim” high accuracy using ToF (Time of Flight), which is based on the amount of time it takes for a signal to be recieved by access point from WIFi tag. These systems can leverage the existing Wi-Fi network of a business, however they can be very expensive due to high cost of RTLS capable access points, high installation costs, and complexity of support.
Infrared
Infrared RTLS systems use infrared ID signals and receivers to determone asset location. Infrared readers are typically ceiling mounted and require a clear line of sight from infrared tag to reader. Infrared systems can be very accurate and deliver precise location in environments like healthcare since infrared signals do not penetrate walls and doors.
Infrared RTLS system are very expensive to install due to quantity of receivers (gateways) required for high precision. Next, infrared tags are generally power/battery intensive. This results in shorter battery life that requires device replacemented and-or battery recharge/replacement.
GPS
GPS stands for “Global Positioning System.” GPS is a satellite based RTLS system used to determine the “outdoor” ground position of an object. The GPS system includes 24 satellites deployed in space about 12,000 miles (19,300 kilometers) above the earth’s surface. Each GPS satellite broadcasts a message that includes the satellite’s current position, orbit, and exact time. A GPS receiver combines the broadcasts from multiple satellites to calculate its exact position using a process called triangulation. Three satellites are required in order to determine a receiver’s location, though a connection to four satellites is ideal since it provides greater accuracy.
In order for a GPS device to work correctly, it must establish a connection to the required number of satellites. This process can take anywhere from a few seconds to a few minutes, depending on the strength of the receiver. For example, a car’s GPS unit will typically establish a GPS connection faster than the receiver in a watch or smartphone. Most GPS devices also use some type of location caching to speed up GPS detection
GPS receivers require a relatively unobstructed path to space and not ideal for indoor use. Therefore, smartphones, tablets, and other mobile devices often use other means to determine location, such as nearby cell towers and public Wi-Fi signals. This technology, sometimes referred to as the local positioning system (LPS), is often used to supplement GPS when a consistent satellite connection is unavailable.