1. What is the difference between RFID and RTLS?
2. Why can't I just use GPS to track my assets?
3. What is the difference between RTLS and LLS?
4. Why can't my 802.11 Wireless LAN locate my assets?
Q. What is the difference between RFID and RTLS?
A. RFID (Radio Frequency Identification) tags are read as they pass fixed points in a structured process, while RTLS tags are read automatically and continuously, independent of the process that moves the tags. With RTLS, no intervention or controlled process is needed to determine asset location.
RFID systems, with their relatively limited read ranges (typically 2 meters or less), can detect the passage of assets past stationary points in a fixed process. For example, RFID readers might be installed as part of a manufacturing process, with all tags passing a particular point being read. For less structured processes, a business must rely on people to place assets within range of a reader or handheld readers within range of a tag. In either case, an RFID
system does not necessarily report an asset's current location; rather, it reports the location where the asset was last seen. For this reason, RFID's tracking capabilities are typically deployed in conjunction with highly structured business processes.
Unfortunately, the limitations of RFID make it unsuitable to track many of the world's personnel and assets. Consider some common examples:
- Pallets or containers are stored in the wrong location in a large warehouse or yard and cannot be found when needed. A shipment of perishable goods is ruined, or a just-in-time operation is halted until the item is found. Expensive tools or parts cannot be found when needed, slowing production. More are purchased to make them easier to find, and asset utilization drops as capital expenditures rise.
- Critical work-in-process cannot be found among hundreds of similar-looking items.
- High-security facilities have no knowledge of personnel movements after individuals clear security checkpoints.
- Businesses have thousands of high-value mobile assets. Pilferage and inefficiency are considered unavoidable facts of life.
- RTLS products are designed to address these kinds of everyday business challenges.
Q. Why can't I just use GPS to track my assets?
A. The Global Positioning System, or GPS, is a type of RTLS technology, very useful for tracking vehicles as they move across the globe. But GPS is not appropriate technology for tracking hundreds or thousands of tags in a fixed space, especially indoors. GPS-based tracking applications are mostly limited to vehicles that have a need for a cell phone, and are integrated with the cell phone.
Despite extraordinary advances in GPS technology, millions of square meters of indoor space are out of reach of Navstar satellites. Their signals, originating high above the earth, are not designed to penetrate most construction materials. So the greater part of the world's commerce, conducted indoors, cannot be tracked by GPS.
Even for outdoor applications, GPS does not provide the accuracy of location that is possible with Local Locating Systems. Some of these systems are capable of providing asset location accurate to a radius of 10 feet. GPS systems are not capable of providing this level of accuracy.
Additionally, GPS does not provide a cost-effective way to track thousands of assets. GPS chips are highly complex and require a substantial power source for operation. Additionally, although GPS can determine its own location, a second radio system is needed to report this location to a central computer.
Q. What is the difference between RTLS and LLS?
A. RTLS (Real Time Locating System) is any wireless technology that can be used to continuously determine and track the real-time location of assets and personnel. LLS (Local Locating System) is a particular type of RTLS, designed to track objects in a constrained indoor or outdoor area. LLS readers are installed in a facility, and those readers periodically communicate with all tags in range to confirm that the tags are still in range and estimate the tag locations.
Some LLS technologies utilize the concepts underlying GPS to locate tags. In GPS, satellites transmit a signal, and receivers on the ground estimate objects' locations by calculating the time for the radio signal to travel from the satellites. (A radio signal travels about one foot per nanosecond, or billionth of a second.) LLS inverts this process; a tag transmits a signal, and an LLS receiver estimates the tag's location by measuring the signal's time of flight.
Q. Why can't my 802.11 Wireless LAN locate my assets?
A. The IEEE 802.11 standard was developed for high-speed data communications. The architecture was designed to operate at data rates of a minimum of 1Mbps. In order to communicate at these data rates over ranges of hundreds of feet requires about 100mW. Therefore, these radios are normally installed in devices that have rechargeable batteries and have an operating period of one to two eight hour shifts. Locatable tags must operate for years in order to be maintenance free and cost effective. Consequently the data rates of these tags are much slower, trading data rate for range, while still requiring only very low power transmissions from the tags.