Proteus uses a number of technologies in order to locate and track items. The most common of these is Radio Frequency Identification (RFID). In recent years, RFID systems have developed rapidly. Advances in digital electronics and RF has led to making the systems smaller and less expensive because of the increased integration capacity of chips. Performance and ability to overcome the wired architectures have been the main driving forces behind this rapid growth.
A RFID system uses tags, or labels attached to the objects to be identified. Two-way radio transmitter-receivers called interrogators or readers send a signal to the tag and read its response.
RFID tags can be either passive, active or battery-assisted passive. An active tag has an on-board battery and periodically transmits its ID signal. A battery-assisted passive (BAP) has a small battery on board and is activated when in the presence of an RFID reader. A passive tag is cheaper and smaller because it has no battery; instead, the tag uses the radio energy transmitted by the reader. However, to operate a passive tag, it must be illuminated with a power level roughly a thousand times stronger than for signal transmission. That makes a difference in interference and in exposure to radiation.
Tags may either be read-only, having a factory-assigned serial number that is used as a key into a database, or may be read/write, where object-specific data can be written into the tag by the system user. Field programmable tags may be write-once, read-multiple; “blank” tags may be written with an electronic product code by the user.
An RFID reader transmits an encoded radio signal to interrogate the tag. The RFID tag receives the message and then responds with its identification and other information. This may be only a unique tag serial number, or may be product-related information such as a stock number, lot or batch number, production date, or other specific information. Since tags have individual serial numbers, the RFID system design can discriminate among several tags that might be within the range of the RFID reader and read them simultaneously. This data is then combined with our Application software sends control commands to connectivity devices and receives tag data, giving businesses access to all the information collected. This software enables businesses to integrate real-time, accurate RFID data across multiple business applications and may manage reader health, perform remote firmware updates, and configure reader infrastructure.
RFID Radio waves behave differently at the various frequencies, so it is imperative to select the right frequency for your application. For example, low-frequency tags have a long wave-length and are better able to penetrate thin metallic substances. Additionally, LF RFID systems are ideal for reading objects with high-water content, such as fruit or beverages, but the read range is limited to centimetres or inches. Typical LF RFID applications include access control and animal tagging.
High-frequency tags work fairly well on objects made of metal and can work around goods with medium to high water content. Typically, HF RFID systems work in ranges of centimeters, but they can have a maximum read range of about 1 meter. Typical HF RFID applications include tracking library books, patient flow tracking, and transit tickets.
UHF frequencies typically offer much better read range (centimeters to 20m+. depending on the RFID system setup) and can transfer data faster (i.e. read many more tags per second) than low- and high-frequencies. However, because UHF radio waves have a shorter wavelength, their signal is more likely to be attenuated (or weakened) and they cannot pass through metal or water. Due to their high data transfer rate, UHF RFID tags are well suited when many items need to be read at once, such as boxes of goods as they pass through a dock door into a warehouse or racers as they cross a finish line. Also, due to the longer read range, other common UHF RFID applications include electronic toll collection and parking access control.
In Wi-Fi based RTLS, the tag actually has a Wi-Fi radio in it that transfers data out to multiple access points or beacons throughout a building or area. The beacons then use time difference of arrival (TDOA) and differences in signal strength to ‘triangulate the tag ‘compute location and send it to the cloud.
One of the benefits of using Wi-Fi -based RTLS is that you may be able to use existing Wi-Fi structure with some firmware updates. However, wireless networks are typically designed to carry voice or data using an access point. To locate a device by triangulation, it must remain in contact with at least three access points at all times. To convert an existing wireless infrastructure so that it can be used as a RTLS network, your wireless network needs to be fundamentally changed and a large number of wired access points should be added, multiplying infrastructure cost by 3 or 4 times.
With Proteus’ RTLS system, Proteus’ location beacons connect to your existing Ethernet and Wi-Fi infrastructure. All tag/badge receiver communications occur at a separate network infrastructure layer. So your Wi-Fi network maintains its integrity and stability. No need to invest to quadruple the number of existing access points. As PDAs, Wi-Fi phones, PCs and other telemetry devices in your infrastructure, few Proteus location receivers are seen as mere network equipment thus preserving the capacity of your current network for your applications.
Wi-Fi is also significantly more accurate in determining position as it uses time-of-flight (TOF) measurements with a wider bandwidth. There is a correlation between bandwidth and indoor accuracy—so if you’re doing 80 GHz of 5-GHz Wi-Fi, you can get accurate location positioning within a few meters.
GSM/GPS based devices are great for locating devices in a wide area by using GPS and cell tower triangulation. GPS connects to satellites orbiting the Earth, and figures out where the device is compared to the satellites. Cell tower triangulation connects to nearby cell towers, and performs a similar calculation. Accuracy is usually between 2.5 – 10 meters give or take in good conditions, and in less than optimal conditions (like bad weather and winds) it can deviate by about 50-100 meters. The disadvantage with GPS is that you need good reception and direct contact with GPS-satellites in order for it to work properly. This means that without additional antennas it does not work well indoors. It can be combined with Wi-Fi in order to provide pinpoint accuracy even indoors.