ANT (network)
ANT is a proprietary wireless sensor network technology featuring a wireless communications protocol stack that enables semiconductor radios operating in the 2.4 GHz Industrial, Scientific and Medical allocation of the RF spectrum ("ISM band") to communicate by establishing standard rules for co-existence, data representation, signalling, authentication and error detection.
The ANT protocol is designed and marketed by Dynastream Innovations Inc., a Cochrane, Canada based company, which in turn is a wholly owned subsidiary of GPS equipment manufacturer Garmin.
The ANT protocol is ported to a limited set of low-power RF transceiver chips from specialist manufacturers, such as Nordic Semiconductor (since 2005)[1] and Texas Instruments (since 2010)[2]. A typical ANT protocol transceiver is a black box that comes pre-loaded with the protocol software and must be controlled by an application processor via a UART, SPI or USB interface.
ANT is characterized by a low computational overhead, and high efficiency resulting in low power consumption by the radios supporting the protocol.
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[edit] Overview
The applications for which ANT is targeted are characterized by periodic transfer of small amounts of sensor information between several, scores or hundreds of interconnected devices in point-to-point, star, tree or mesh network topologies. These applications are often constrained by strict power, footprint and cost requirements. Typical applications measure parameters that don't change rapidly (for example, temperature or humidity) so updates every few seconds are satisfactory.
Commercial wireless sensor networks must be reliable, feature low power consumption (to extend battery life and minimize maintenance), and be low cost to purchase, install and maintain.[3] In addition, transceivers in close proximity need to co-exist in harmony by being able to transmit and receive without interference from their neighbors and other wireless devices operating in the 2.4 GHz band.
ANT-powered nodes are claimed to be capable of acting as slaves or masters within a wireless sensor network. This means the nodes can act as transmitters, receivers or transceivers to route traffic to other nodes. In addition, every node is capable of determining when to transmit based on the activity of its neighbors.
[edit] Typical applications
ANT has been targeted at the sports sector, particularly fitness and cycling performance monitoring. The transceivers are embedded in equipment such as heart rate belts, watches, cycle power and cadence meters, and distance and speed monitors to form wireless Personal Area Networks (PANs) monitoring a user's performance.
Manufacturers such as Garmin,[4] Geonaute[5], Nike, Suunto, Fitbit[6] and Tacx[7] have used ANT technology in their performance monitoring products.
Recently, ANT (the company) has attempted to diversify, claiming ANT wireless sensor networking technology's low overhead, low power, interference free characteristics and operation in the 2.4 GHz ISM band suit applications the health, home automation and industrial sectors.
[edit] Technical information
The ANT protocol has an efficiency (determined by the ratio of overhead to data) of 47 percent. ANT can be configured to spend long periods in a low power “sleep” mode (consuming of the order of microamps of current), wake up briefly to communicate (when consumption rises to around 22mA (at -5dB) during reception and 13.5mA (at -5dB) during transmission)[8] and return to sleep mode.
Each ANT channel consists of one or more transmitting nodes and one or more receiving nodes depending on the network topology. Any node can transmit or receive so the channels are bi-directional.
ANT accommodates three types of messaging: broadcast, acknowledged and burst. Broadcast is a one-way communication from one node to another. The receiving node transmits no acknowledgment. This technique is suited to sensor applications and is the most economical method of operation.
Acknowledged messaging confirms receipt of data packets. The transmitter is informed of success or failure, although there are no retransmissions. This technique is suited to control applications.
ANT can also be used for burst messaging; this is a multi-message transmission technique using the full data bandwidth and running to completion. The receiving node acknowledges receipt and informs of corrupted packets that the transmitter then resends. The packets are sequence numbered for traceability. This technique is suited to data block transfer where the integrity of the data is paramount.
[edit] Comparison with Bluetooth, Bluetooth Low Energy, and ZigBee
Previous versions of the Bluetooth protocol, prior to v4.0, were designed for rapid file transfer between devices in a PAN such as a PDA, cell-phone and portable computer; focusing on applications with lower bandwidth requirements than that offered by WiFi. Previous versions of Bluetooth were not designed for large wireless sensor networks, but were capable of forming star networks of up to eight devices (one master and seven slaves).[9]
Bluetooth low energy is the new protocol released for low power wireless embedded devices that can operate on a single coin-cell battery from months to years, such as Wireless Sensor Network, watches, and sports equipment. Currently, Bluetooth low energy (BLE) only supports star-bus network topology which limits applications to a single hop communication range between 50 m to 100 m (330 ft). BLE is the hallmark feature of Bluetooth 4.0, a dual-mode core chip supporting BT v3.0 and BLE, which will give BLE a "free-ride" into the mass market of smart-phones, laptops, tablets, etc. This "free-ride" will also allow BLE to compete against other short range technologies, perhaps unfairly, such as NFC. While BLE cannot currently compete with ANT, Zigbee, or WirelessHART in applications requiring a large multi-hop coverage area, BLE can definitely compete in short-range single-hop applications. BLE is expected to debut in devices on the market late 2011. BLE silicon chips are already in mass market and provided by companies such as Nordic Semiconductor, Texas Instruments, CSR, Taiyo Yuden, Epson, and many more.
A more direct comparison can be drawn with ZigBee. ZigBee is based on the IEEE 802.15.4 standard PHY and Media Access Control (MAC) layers, and supports the ZigBee Alliance's own Network (NWK) and Application (APL) layers (refer to the OSI model). ZigBee's IEEE 802.15.4 PHY for the 2.4 GHz frequency band has a raw data rate of 250 kbit/s,[10] compared to ANT's 1 Mbit/s,[8] requiring ZigBee to stay on air longer than ANT to transmit a given volume of data.
ANT transceivers using coin cell-type batteries is claimed to operate up to three years in low use applications.[11]
[edit] Interference immunity
ANT, ZigBee, Bluetooth, Wi-Fi and some cordless phones all use the 2.4 GHz band (as well as 868- and 915 MHz for regional variants in the latter's case), along with proprietary forms of wireless Ethernet and USB.
Wi-Fi/ZigBee and Bluetooth employ Direct Sequence Spread Spectrum (DSSS) and Frequency-Hopping Spread Spectrum (FHSS) schemes respectively to maintain the integrity of the wireless link.
ANT uses an adaptive isochronous network technology to ensure co-existence. This scheme provides the ability for each transmission to occur in an interference free time slot within the defined frequency band. The radio transmits for less than 150 µs per message, allowing a single channel to be divided into hundreds of timeslots. The ANT messaging period (the time between each node transmitting its data) determines how many time slots are available.
ANT's adaptive isochronous scheme doesn't require a master clock. Transmitters start broadcasting at regular intervals but then modify the transmission timing if interference from a neighbor is detected on a particular timeslot. This flexibility allows ANT to adapt to hostile conditions but ensures there is no overhead when interference is not present.
If the radio environment is very crowded, ANT can use frequency agility to allow an application microcontroller-controlled "hop" to an alternative 1 MHz channel in the 2.4 GHz band which can then be subdivided into timeslots.
[edit] References
- ^ "Single chip ANT ultra low power wireless solutions". Nordic Semiconductor. 27 Oct. 2010. http://www.nordicsemi.com/index.cfm?obj=menu&act=displayMenu&men=82.
- ^ "ANT - Ultra-low power wireless connectivity". Texas Instruments. 27 Oct. 2010. http://ti.com/ant.
- ^ "The Economist Special Report "A world of connections"". The Economist. 26 Apr. 2007. http://www.economist.com/specialreports/displaystory.cfm?story_id=9032026. Retrieved 11 Dec. 2007.
- ^ "Garmin Forerunner 50 press release". Garmin. 16 Mar. 2007. http://www8.garmin.com/pressroom/outdoor/100407.html. Retrieved 11 Dec. 2007.
- ^ "Geonaute, Experience Improved". Geonaute. 17 Dec. 2011. http://www.geonaute.com.
- ^ "Fitbit Product Specifications". Fitbit. 27 Jan. 2012. http://www.fitbit.com/product/specs.
- ^ "How does wireless Bushido work". Tacx. 10 Oct. 2009. http://www.tacxbushido.com/en_extrainfo_werking.html.
- ^ a b "Nordic Semiconductor figures for nRF24AP1". Nordic Semiconductor. http://www.nordicsemi.com/index.cfm?obj=product&act=display&pro=88. Retrieved 11 Dec. 2007.
- ^ "How Bluetooth Technology Works". bluetooth.com. http://www.bluetooth.com/Bluetooth/Technology/Works/. Retrieved 8 Feb. 2008.
- ^ "Ember figures for e250". Ember. http://www.ember.com/products_zigbee_chips_e250.html. Retrieved 11 Dec. 2007.
- ^ "ANT figures". ANT. http://www.thisisant.com/index.php?section=24. Retrieved 11 Dec. 2007.
[edit] External links
- ANT
- Dynastream Innovations
- Nordic Semiconductor
- Texas Instruments - ANT connectivity solutions
- IEEE
- Bluetooth SIG
- Zigbee Alliance
- Wi-Fi Alliance
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