RuBee (IEEE standard 1902.1) is a two way, active wireless protocol designed for harsh environment, high security asset visibility applications. RuBee utilizes Long Wave (LW) magnetic signals to send and receive short (128 byte) data packets in a local regional network. The protocol is similar to the IEEE 802 protocols in that RuBee is networked by using on-demand, peer-to-peer, active radiating transceivers. RuBee is different in that it uses a low frequency (131 kHz) carrier. One result is that RuBee is slow (1,200 baud) compared to other packet based network data standards (WiFi). 131 kHz as an operating frequency provides RuBee with the advantages of ultra low power consumption (battery life measured in many years), and normal operation near steel and/or water. These features make it easy to deploy sensors, controls, or even actuators and indicators. Because RuBee uses long wavelengths and works in the near field (under 50 feet) it is possible to simultaneously transmit and receive from many adjacent antennas, without interference providing the signals are synchronized. That makes it possible to enhance bandwidth and remove any angle sensitivity normally seen with other RF systems.
RuBee has no reflections and is not blocked by steel or liquids and therefore is volumetric (not line-of-sight). That makes RuBee robust in harsh environment visibility and security applications. It also means RuBee has no TEMPEST target or eavesdropping risks in secure facilities. RuBee is the only wireless technology to ever be approved for use in secure facilities by the U.S. Department of Energy (DoE). RuBee has also been approved by DoE and HERO tests by the DoD for use in high explosive areas with a Safe Separation Distance (SSD) of zero. RuBee is also only wireless technology to ever be approved by DoE with an intrinsic safety zero SSD. RuBee tags may be detected with high sensitivity through doors, even if the asset is hidden in steel brief case, as well as in vehicles though gates using antennas buried in a road.
RuBee is often confused with Radio Frequency Identification (RFID). It does not work like passive or active RFID, and has a protocol more in common with WiFi and Zigbee. All passive and active RFID protocols use what is known as backscattered transmission mode. Passive and active RFID tags act like a mirror, and work as reflective transponders. In contrast RuBee, similar to WiFi and Zigbee in that it is peer-to-peer, is a networked transceiver that actually transmits a data signal on demand, but is much slower (6-8 two way packets per second). The main difference between RuBee and WiFi or Zigbee is that RuBee works in the long wavelength band using the magnetic field, whereas WiFi, Bluetooth, Delta7, and Zigbee work in the VHF, UHF or SHF bands and with the electric field. The 1902.1 standard has been approved by the IEEE. RuBee received the Technology of the year award from Frost & Sullivan in 2007.
The IEEE 1902.1 protocol details
1902.1 is the "physical layer" workgroup with 17 corporate members. The Workgroup was formed in late 2006. The final specification was issued as an IEEE standard in March 2009. The standard includes such things as packet encoding and addressing specifications. The protocol has already been in commercial use by several companies, in asset visibility systems and networks (see www.rubee.com). However, IEEE 1902.1 will be used in many sensor network applications, requiring this physical layer standard in order to establish interoperability between manufacturers. A second standard has been drafted 1902.2 for higher level data functions required in Visibility networks. Visibility networks provide the real-time status, pedigree and location of people, livestock, medical supplies or other high-value assets within a local network. The second standard will address the data-link layers based on existing uses of the RuBee protocol. This standard, which will be essential for the widespread use of RuBee in visibility application's, will support interoperability of RuBee tags, RuBee chips, RuBee network routers and other RuBee equipment at the data-link layer.
RuBee tag details
RuBee is bidirectional, on-demand, and peer-to-peer. It can operate at other frequencies (e.g. 450 kHz) but 131 kHz is optimal. RuBee tags can have sensors (temperature, humidity, jog), optional displays and may have a full 4 bit microprocessor with static memory. The RuBee protocol uses an IP Address (Internet Protocol Address). A tag may hold data in its own memory (instead or in addition to having data stored on a server). Some tags have as much as 5 kB of memory. RuBee functions successfully in harsh environments, with networks of many thousands of tags, and has a range of 1 to 30 m (3 to 100 ft) depending on the antenna configuration. By 'harsh environment' we mean situations in which one or both ends of the communication is near steel or water. RuBee radio tags function in environments where other radio tags and RFID may have problems. RuBee networks are in use in many visibility applications, including: exit entry detection in high security government facilities, weapons and small arms in high security armories, mission critical specialized tools, smart shelves and racks for high-value assets; smart entry/exit portals.
How RuBee works
IEEE 1902.1 RuBee uses magnetic waves also often called inductive communication. James Clerk Maxwell presented his now famous set of equations (Maxwell's Equations) to the Royal Society in 1864. These equations describe what happens when an electron travels along a conductive wire. Two fields are created, the Electric Field, labeled E, and the Magnetic Field, labeled H. These electric and magnetic fields travel through the aether, (i.e. outer space or the far field), at the speed of light with an assumed impedance of 377 Ω. E, the electric field, may be given in newtons per coulomb or volts per meter, and H, the magnetic field, may be given in gauss or amperes per meter. The two fields are tied together with the aether to form simple electric circuit capable of transferring power. However, when these two fields are measured in what is called the near field (much less than the wavelength of the signal) very strange things happen. (Also see Capps “Near Field or Far Field"). E and H are no longer connected in a simple predictable manner. The value of c (speed of light) and the resistance of the aether are altered and it is possible to produce large H values with low E values. It is as if the aether impedance has been reduced to only a few ohms.
Virtually all of the energy radiated by a RuBee base station or a RuBee radio tag is contained in the magnetic field (H), not the electric (E) field. This stems from the fact that the RuBee antennas are short relative to the wavelength (about a mile and half or 2½ km at 131 kHz), and RuBee operates in the near field. A typical emitted E from a RuBee base station is about 40-50 nanowatts, and H is about 900 milligauss (90 µT). Finally, RuBee is a packet based protocol in which only one end of the communication at a time generates fields, that is, a RuBee tag is a radiating transceiver.
RF is based on physics, and can be reliably modeled with prediction tools and tuned models (see RF Microwaves, and Migraines, Electro Magnetics Explained). RF is not always predictable because the active environment (people, steel shelves, floors, cabinets, doors) are all part of the same tuned circuit, and change with time. For example, a cell phone call to a phone in a building is modified by steel in the building. Reception may be improved by moving the phone near a window, or pointing the antenna in a particular direction. Radio waves are affected by just about everything around us. Many environmental factors influence performance. The more significant ones include steel and water, but people and electrical noise sources are also high on the list.
Magnetic waves can pass through almost anything, even rock. That same rock blocks RF after only a few feet. An RF signal falls off as 1/r, whereas the strength of a magnetic wave falls off far faster at the rate of 1/r³. This means that the magnetic signal will not travel nearly as far as the RF signal.
At first glance this difference in fall-off rate may appear as a negative for the range of a tag using magnetic signaling, but, as explained below, it turns out to be quite a plus in a local visibility network. Secondly, an unexpected advantage is that the noise RuBee sees is also magnetic, so it too falls off 1/r³. Noise and interference sources must be much more local to have significant strength, and tend to be easy to locate and minimize in an IEEE 1902.1 network.
RuBee is 99.99% magnetic waves it therefore is not affected at all by people or animals, mud or water. Steel can alter performance, but steel can actually enhance a magnetic signal. A high frequency (over 1 MHz) RF antenna on or near a steel shelf has three problems: 1. The steel detunes the antenna; 2. RF nulls will appear on the shelf with no signal at all (Swiss cheese field) this is because steel blocks radio waves; and 3. Steel also reflects the radio waves (E in Maxwell's equations) contributing to communication errors and shelf nulls.
In contrast Long Wavelength magnetic transmissions (below 1 MHz) is not blocked or reflected by steel so nulls do not occur. The loop antennas may be detuned by the steel, just like higher frequencies. But, unlike higher frequencies, magnetic loop antennas may be re-tuned with external capacitors, and, in many cases, circuits can be created that dynamically pick the optimal external capacitor for the antenna. Thus the de-tuning issue can vanish in a RuBee network. But the tuning has to be set to the right frequency by adjusting the capacitor to match the tuning curve with steel in place.
Parasitic inductance and capacitance (see Self-resonant frequency) of the antenna wire and the shelf steel limit the range of tuned frequency of any antenna circuit. A simple loop of speaker wire about 100 ft (30 m) in diameter maybe tuned to resonate at 131 kHz with a simple external capacitor. A loop of only a 1 inch (25 mm) may be also tuned to resonate at 131 kHz. At 30 MHz, however, you might be able to tune the 1 inch (25 mm) antenna, but not the 100 ft (30 m) antenna, and not the shelf.At 30 MHz the largest tunable loop is about 1-foot (30 cm). RuBee's frequency is low on purpose so that it can nearly always re-tune to compensate for the parasitic inductance and capacitance despite use in harsh environments like steel shelves (see Roche et al. 2007). Back to the shelf example—the RuBee installation actually tunes the steel in the shelf, and the shelf itself becomes the antenna - the shelf becomes part of the resonate circuit and the H signal gets stronger near the shelf. For frequencies over 1 MHz it's not possible to incorporate most things you find in a warehouse, office building or factory as part of the antenna.
RuBee works well in harsh environments because most steel items resonate well at the RuBee frequency of 131 kHz. As the frequency goes up over 1 MHz fewer steel items resonate. At a frequency of 10 MHz for example, nothing large made of steel can be tuned to resonance.
How big can a RuBee loop antenna be? As the antennas get larger and larger noise becomes the gate keeper. A 100 ft (30 m) diameter loop can detect lighting storms hundreds of miles away. The biggest source of noise is deep space kilometric noise. While it is possible build a second antenna and do differential subtraction, a 10,000 sq ft (1,000 m2) limit of a RuBee network is adequate for most practical visibility applications. RuBee antennas may also use ferrite rods with wire coils and get same range but without large loops.
RuBee disadvantages and advantages
The major disadvantage RuBee has over other protocols is speed and packet size. The RuBee protocol is limited to 1,200 baud in existing applications. The IEEE 1902.1 specifies 1,200 baud. The protocol could go to 9,600 baud with some loss of range. However, most visibility applications work well at 1,200 baud. Packet size is limited tens to hundreds of bytes. RuBee's design forgoes high bandwidth, high speed communication because most visibility applications do not require them.
The use of LW magnetic energy brings about a number of advantages:
- Long battery life – Because of the use of low frequencies and data rates the chips and detectors can run at low speed. Using (lowest cost) 4 micrometre CMOS chip technology, this leads to extremely low power consumption. LW magnetic wave tag systems can and have achieved 15 year lives using low-cost lithium batteries. This is also the expected battery shelf life.
- Tag data travels with the asset – Because data is stored in the tag, IT (Information Technology) costs are reduced. This means that with a low-cost handheld reader one can simply read a RuBee tag and learn about the asset — manufacturing data, expiry date, lot number, etc. — without having to go to an IT system to look it up. In addition, the distance between the reader and the asset is not critical. RuBee can also write to a tag at the same range as it can read it. RFID, on the other hand, uses EEPROM memory, and writing to the tag is awkward. (In the case of RFID, range is limited, more power is required and write times are long.)
- Human Safe – A RuBee base station produces only nanowatts of radio energy. RuBee's LW magnetic waves are not absorbed by biological tissues and are not even regulated by OSHA. In fact, RuBee produces less power and lower field strengths than the metal detectors in airports and the anti-theft detectors in retail stores operating at similar frequencies — by a factor of about 10 to 100. Recently published studies show that RuBee has no effect on pacemakers or other implantable devices (Hayes et al., 2007).
- Intrinsically Safe – A RuBee base station and tag produces a low level of magnetic energy simply not capable of heating explosives or creating a spark. In independent studies carried out by the Department of Energy RuBee was given a Safe Separation Distance (SSD) of zero, and is the only wireless technology to have that rating. That means tags and base stations can be placed directly on high explosives with no risk of accidental ignition or any heating.
- High security and privacy RuBee tags have many unique advantages in high security applications. The Eavesdropping range (the range at which a person with unlimited funds can listen to tag conversations) is the same as tag range. That means if someone is listening, they must be close enough for you to be able to see them. This is not true for RFID or 802 protocols (see Wall Street Journal May 4, 2007 Credit Card Data). That means no one can secretly listen to tag/base station conversations. In addition, since RuBee tags have a battery, a crystal and sRAM memory, they can use strong encryption with nearly uncrackable one time keys, or totally uncrackable one time pads. RuBee is in use today in many high security applications for these reasons. RuBee is the only wireless technology approved for use in secure US government sites.
- Controlled volumetric range – RuBee has a maximum volumetric range of approximately 10,000 square feet (900 m²), using volumetric loop antennas — From even a small volumetric antenna of 1 sq ft (900 cm²), RuBee can read a tag within an egg-shaped (ellipsoid) volume of about 10 x 10 x 15 ft (3 x 3 x 5 m). A special feature of IEEE P1902.1 known as Clip makes it possible to place many adjacent loop antennas in an antenna farm, and read from tens to hundreds of base-stations simultaneously.
- Cost effective - With RuBee, relatively simple base stations and routers can be employed, which means receivers and card readers can be reasonably priced as compared to higher frequency transceivers. In addition, the tags often include a single chip, a battery, a crystal and an antenna, and can be priced competitively with respect to active RFID tags (those including a battery).
- Less noise – Because ambient noise in a region falls off as 1/r³, RuBee exhibits reduced susceptibility to extraneous noise. The major limit to antenna size is deep space noise.
Unique RuBee application example: mission critical asset availability and security
Because RuBee is secure and magnetic it can provide real-time automated visibility, and the highest possible security of Mission Critical Assets—Mission Critical Assets (MCA) are assets that simply can not be lost or stolen, worth far more on the street or in hands of terrorists than the cost to replace. Visible Assets, Inc., Dasco Date, Inc., SMi Ltd, and Laser Device Inc. provide RuBee based automated MCA visibility and security using three important security layers:
- Security Layer 1: Real-Time, Storage Physical Inventory. Assets in storage in a warehouse on racks, shelves or weapons in armory racks or other secure facility have RuBee wireless tags embedded or attached. RuBee enabled smart racks and smart shelves turn the steel in these racks into an antenna, and Visible software applications do daily or hourly audit trails of each item and report inventory and asset status.
- Security Layer 2: Issuance Check Out/In. When an asset is removed from inventory, we know it has been removed from shelf, but ownership has to be transferred from a “storekeeper” to a new owner, a soldier or guard or asset guardian. This is done using ruggedized Apple iPads known as gRaps® that have a RuBee embedded reader. Tags are read as the asset is passed across the check out counter.
- Security Layer 3: Exit/Entry Detection. When the asset leaves the facility RuBee portal platforms provide identification detection and alarms using DoorGuard® and GateGuard®. Both detect RuBee enabled assets and IDs as a person passes though a door or gate, on foot or in a vehicle. These systems have passed many objective User Acceptance Tests (UAT) with 100% detection of assets even if hidden inside a steel case or vehicle.
Security becomes far more reliant on human trust with loss of any layer. RuBee reduces that human trust reliance with full “process free” automation in all three layers. For example, if something is removed from inventory off the racks, but does not get checked out an alarm is issued. If an asset exits facility but is not checked out, an alarm is issued etc. RFID and barcode systems are blocked by steel and the human body. As a result, security is based on new human processes focused only on Layer 2. Both become human assisted asset tracking systems, not real-time automated security systems. Visible has repeatedly proven that RuBee is the wireless technology that can provide fully integrated, visibility with three security layer automation.
RFID and barcode systems are blocked by steel and the human body. As a result, security is based on new human processes focused only on Security Layer 2. Both become human assisted asset tracking systems, not real-time automated security systems. Many in-use secure sites provide, process-free, fully automated, RuBee visibility with three-layer security.
Compare to NFC and Qi Inductive Power Transfer
This protocol is similar at the physical level to NFC (13.56 MHz carrier, basically an air-core transformer pair) and also Qi's inductive energy transfer (100 kHz-300 kHz carrier). Both modulate the receiver's coil load to communicate to the sender. Some NFC tags can support simple processors and a handful of storage like this protocol. NFC also shares the physical security properties of "magnetic" communications like RuBee.
- "RuBee protocol overcomes RFID shortcomings". Retrieved 2007-09-02.
- "2007 North American Supply Chain Visibility Solutions Technology Innovation of the Year Award" (PDF). Frost & Sullivan. Retrieved 2007-09-02.
- Prithvi Raj, 2007 North American Supply Chain Visibility Solutions Technology Innovation of the Year Award, Frost&Sullivan Frost & Sullivan
- "IEEE Begins Wireless, Long-Wave Standard for Healthcare, Retail and Livestock Visibility Networks; IEEE P1902.1 Standard to Offer Local Network Protocol for Thousands of Low-Cost Radio Tags Having a Long Battery Life," Business Wire, June 8, 2006
- "Visible Assets Promotes RuBee Tags for Tough-to-Track Goods," by Mary Catherine O'Connor, RF Journal, June 19, *2006, http://www.rfidjournal.com/article/articleprint/2436/-1/1/
- Charles Capps, “Near Field or Far Field,” EDN, August 16, 2001, pp. 95–102. This excellent article is available online at: Near Far Field RF - New link (correct?)
- Hayes DL, Eisinger G, Hyberger L, Stevens JK. Electromagnetic interference (EMI) and electromagnetic compatibility (EMC) of an active kHz radio tag (Rubee [TM], IEEE P1901.1) with pacemakers (PM) and ICDs. Heart Rhythm 2007;4:S398 (Supplement - Abs). Mayo Clinic Study
- Martin Roche MD, Cindy Waters RN, Eileen Walsh RN, Visibility Systems in Delivery of Orthopedic Care Enable Unprecedented Savings and Efficiencies. U.S. Orthopedic Product News, May/June 2007 Orthopedic Visibility