Radio-Frequency Identification (RFID)

Competitors in a Head race are conventionally identified by a plastic number attached to a holder in the bows of the boat, and by a paper number attached to the back of the person at bow and the back of the cox. These numbers can sometimes be difficult to read. They can fall off.

Identifying a single competitor without a number is not too difficult. The crew can be identified by their racing colours. But matching a competitor to the right time when boats are close together can be extremely difficult. Ideally for a Head race we would want something that communicates the identity of the boat electronically, but only when crossing the line.

Radio-Frequency Identification (RFID) is used for many other types of sports, so the question arises whether it could be adapted to Head racing. Other types of electronic identification exist besides RFID, so perhaps these could be considered too.

This page has an overview of RFID technology and its potential for Head race timing.

RFID Technology

RFID is a family of technologies for short range identification of objects, used primarily in manufacturing and distribution. In this respect it is similar to the barcode. Whereas the barcode recognition is visual, the tag or chip identification is by radio. RFID is a loose collection of technologies, some defined by standards and some not. Because it is a collection of technologies that can be applied to different problems, it is not easy to define the technical characteristics.

The essence of RFID is a microchip encoded with a unique identity number. The microchip is activated by the radio waves of a transmitter. It sends data back to a receiver.

The concept of RFID has developed technologically in two main areas:

the radio frequency used to communicate between the chip and the reader
whether the chip is energised solely by the radio waves, or has its own power supply.

There are now four main frequency bands. The actual frequencies are those allocated by individual countries to Industrial, Scientific and Medical (ISM) applications, and to Short Range Devices (SRD):

Low
High
Ultra-high
Microwave (the same frequencies as WiFi)

The use of these frequencies is controlled by government regulations. For example in the US the ISM frequencies are limited by the FCC to a maximum Effective Isotropic Radiated Power (EIRP) - the transmitter power plus the amplification effect of the antenna - of 4 Watts.

There are four broad types of communication between chip and reader:

Capacitive coupling, using contact between tag and reader. This is very short range, and usually high frequency. It is typically used for smartcards.
Inductive coupling, using the magnetic field between tag and reader. The magnetic field of the reader provides energy to the tag, which modulates the energy to send data. This is short range, and usually low frequency. It is typically used for animal microchips.
Backscatter coupling, using the energy of the radio waves from a transmitter. The radio waves provide energy to activate the tag, which modulates the reflected energy to communicate data. This type has a longer range based on the power of the transmitters and the sensitivity of the receivers. It uses the UHF or microwave frequencies. It is typically used for labels.
Beacon, where there is no coupling. The tag transmits periodically, to be picked up by any receiver within range.

There are three main power types for the tags:

Passive, where the power is supplied only by the energy of the radio waves from the antenna of the reader
Battery-assisted passive (BAP), where a battery is activated by a passive receiver to power the chip, and so can conserve power until activated
Active, where a battery provides permanent power to a receiver and a transmitter.

The battery can, of course, be more or less powerful to give greater sensitivity to a receiver or more power to a transmitter.

Within these frequencies and power sources there is a very wide range of implementations. Some follow industry standards, to ensure they can inter-operate between different suppliers and users. Some are proprietary to meet specific requirements. This makes it extremely hard to generalise about the capabilities of RFID.

Tags and readers following industry standard have reasonably defined characteristics, but these are not necessarily limitations of the technologies. ISO/IEC 18000-6:2010, for example, defines the standards for passive and BAP UHF tags used in manufacturing and distribution.

The combination of frequency, regulations, power type and standards leads to a matrix of characteristics covering:

the amount of data that can be transmitted
the number of chips that can be read in a given time
the effect of surroundings, especially water, metal, and electromagnetic interference
the range over which the chip can be read
the cost of the chips and the readers.

One view of the matrix of characteristics is shown here: Atmel.

Range is only one aspect of RFID, although it is of interest in Head racing. Maximum range is limited by the choice of frequency, the surroundings, sensitivity of the receivers, and power of the transmitters. The maximum range of UHF passive tags seems to be about 10 or 15 meters in the right conditions. The maximum range of UHF BAP tags seems to be up to about 100 meters, e.g. Intelleflex. The maximum range of active tags will be similar to WiFi, potentially several kilometers. Maximum range is discussed in this Blackhat paper 2010.

Maximum range on its own may not be useful, since it gives only an area within which the tag is present. A directional antenna would be needed to provide direction and, for example, a phased-array antenna (similar to radar) for distance. At this point it might be simpler to use GPS for location tracking.

Chip Timing

RFID has been adopted for race timing because the short range of the chip can be used to approximate the time. When a passive chip comes within range of a transmitter it is energised and sends out data about its identity. The range is very short, and so the time when a moving object is within range is moderately accurate.

RFID race timing systems have been developed with a set of parameters none of which are particularly relevant to Head races:

Low frequency passive tags are moderately low cost and impervious to water. They have a short range (perhaps 10 or 20 centimeters). They are used for racing by attaching the tag to an ankle and passing over a mat.
Ultra-high frequency tags are very low cost and can be embedded in plastic or paper, although they are susceptible to interference from water or metal (such as in the body or in clothing). They have a slightly longer practical range (perhaps 1 to 2 meters). They are used for racing by incorporating the tag in a bib and passing an antenna above, to the side or below. These tags may be battery-assisted to provide greater effective range and readability.
Active tags, either with a battery or external power source, are used for higher speeds such as motor racing because otherwise the chip would not be read within the range of the antenna. They are higher cost, and therefore come in different ownership formats: either owned by one person, or vehicle; or owned by the race track; or owned by the race organisers.

Chip timing systems can use a mix of frequencies: for example a low frequency to energise the tag, and a high frequency to transmit the data. Ultra-high frequency passive tags are relatively new (2008 onwards), and at first suffered from poor readability although this has improved with BAP tags. In 2012 there is still a wide mix of technologies in use for different forms of racing, reflecting the slightly different characteristics of each technology.

In most road and track racing RFID provides an approximate time that is good, or good enough, for most competitors. In high level competition the intermediate times may be taken by RFID but the actual result will usually be taken from photo finish or photocell. International Cycling Union and International Ski Federation rules do not allow the use of RFID for timing. However this level of accuracy is probably not a consideration for Head racing.

Examples

Chronelec active tag used for Tour de France 2012 time trials. The tag is mounted on the chainstay. The time is read when the cycle passes over an induction loop taped to the road. The maximum height of the tag is about 1.2 meters. The maximum width of the induction loop is 25 meters.

Chronelec active tag

IPICO hybrid low and high frequency passive tag used for London Marathon 2012. The time is read when the shoe passes over a mat containing the antennae. The maximum distance from the tag to the mat is about 0.3 meters. The maximum width of an antenna is about 6 meters.

IPICO shoe tag

Alien Technology Squiggle Inlay used to manufacture RFID UHF passive labels. The time is read when the label passes within range of an antenna. The maximum effective distance is about 2 meters.

Alien Technology UHF Tag Inlay

RFID for Head racing

In road and track races the competitors pass close by an antenna that triggers the tag to send its identity. The distance from the antenna is typically less than two meters. This short range enables the tag to be used for timing as well as identification, since the identity is obtained only over a short distance and space of time. On the water it is difficult to see how these systems could work.

Where a start or finish is at a bridge it may be possible to suspend the antennae. In this case it might be possible to use a standard UHF race timing system. Over open water, would it be possible to adapt commercial longer range RFID for race timing?

Powered tags (battery-assisted or active) have a potential range of 100 meters or more. For racing we don't care about battery conservation, since we can carry a bigger tag, and recharge or replace a battery.

Intelleflex tag

In its standard form the BAP tag could work to provide identification, for example by identifying crews with a missing boat number, or providing a rough sequence of crews when in the vicinity of a finish line. The tags would have a material cost. Ownership options would be similar to current active tags: personal; boat; club; sporting body; timing providers etc. A club, for example, might own a number of tags to be allocated out to racing crews. Or a sporting body might own a number of tags to be lent out to Head races.

The BAP tag would respond to an interrogator over a radius of about 100 meters. To be useful for timing as well as identification the interrogator would require highly directional antennae, or a phased array or similar. The standard type of UHF patch antenna has a horizontal coverage of about 70 degrees, which would be very imprecise for timing. Some form of technology might be applied to calculate an estimated position within the area of coverage, for example: triangulation; beam steering; or phase shift.

Other forms of radio identification

RFID is intended mainly for short range, high volume and low cost. For longer range, and where low cost and low power requirement is not such a concern, other forms of radio identification might be more suitable, for example:

GPS Tracking
Radar
WiFi
Zigbee.