# ANT (network)

ANT (originates from Adaptive Network Topology) is a proprietary (but open access) multicast wireless sensor network technology designed and marketed by ANT Wireless (a division of Garmin Canada). It provides personal area networks (PANs), primarily for activity trackers. ANT was introduced by Dynastream Innovations in 2003, followed by the low-power standard ANT+ in 2004, before Dynastream was bought by Garmin in 2006.
ANT defines a wireless communications protocol stack that enables hardware operating in the 2.4 GHz ISM band to communicate by establishing standard rules for co-existence, data representation, signalling, authentication, and error detection. It is conceptually similar to Bluetooth low energy, but is oriented towards use with sensors.
As of November 2020, the ANT website lists almost 200 brands using ANT technology. Samsung and, to a lesser part, Fujitsu, HTC, Kyocera, Nokia and Sharp added native support (without the use of a USB adapter) to their smartphones, with Samsung starting support with the Galaxy S4 and ending support with the Galaxy S20 line.

## Overview

ANT-powered nodes are capable of acting as sources or sinks within a wireless sensor network concurrently. 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.

## Technical information

ANT can be configured to spend long periods in a low-power sleep mode (consuming current on the order of microamperes), wake up briefly to communicate (when consumption rises to a peak of 22 milliamperes (at −5 dB) during reception and 13.5 milliamperes (at −5 dB) during transmission) and return to sleep mode. Average current consumption for low message rates is less than 60 microamperes on some devices.
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 (or many). The receiving node(s) transmit no acknowledgment, but the receiving node may still send messages back to the transmitting node. 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 re-sends. The packets are sequence numbered for traceability. This technique is suited to data block transfer where the integrity of the data is paramount.

## Comparison to other protocols

ANT was designed for low-bit-rate and low-power sensor networks, in a manner conceptually similar to (but not compatible with) Bluetooth Low Energy. This is in contrast with normal Bluetooth, which was designed for relatively high-bit-rate applications such as streaming sound for low-power headsets.
ANT uses adaptive isochronous transmission to allow many ANT devices to communicate concurrently without interference from one another, unlike Bluetooth LE, which supports an unlimited number of nodes through scatternets and broadcasting between devices.
| | ANT | Z-Wave | Bluetooth | Bluetooth LE | Zigbee |
| Standardisation | Proprietary | Proprietary | Standard | Standard | Standard |
| Topologies | Point-to-point, star, tree, mesh | Mesh | Point-to-point, scatternet | Point-to-point, star, mesh | Mesh |
| Band | 2.4 GHz | 2.4 GHz and 900 MHz (varies slightly per country) | 2.4 GHz | 2.4 GHz | 2.4 GHz (+ sub-GHz for Zigbee PRO) |
| Range | 30 metres at 0 dBm | 10–100 metres | 1–100 metres | 10–600 metres in air (Bluetooth 5) | 10–100 metres |
| Max data rate | Broadcast/Ack – 200 Hz × 8 bytes × 8 bits = 12.8 kbit/s Burst – 20 kbit/s Advanced Burst – 60 kbit/s | 100 kbit/s | 1–3 Mbit/s | 125 kbit/s, 250 kbit/s, 500 kbit/s, 1 Mbit/s, 2 Mbit/s (Bluetooth 5 PHY speeds) | 250 kbit/s (at 2.4 GHz) |
| Application throughput | 0.5 Hz to 200 Hz (8 bytes data) | | 0.7–2.1 Mbit/s | 305 kbit/s (Bluetooth 4.0) | |
| Max nodes in piconet | 65533 per shared channel (8 shared channels) | 232 devices per network | 1 sink and 7 active sensors, >200 inactive | 1 sink and 7 sensors (but scatternet unlimited), mesh – 32767 | star – 65536 |
| Security | AES-128 and 64-bit key | AES-128 | 56–128-bit key | AES-128 | AES-128 |
| Modulation | GFSK | FSK | GFSK | GFSK | OQPSK |

## Interference immunity

Bluetooth, Wi-Fi, and Zigbee 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 coexistence with other ANT devices. 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 time slots. The ANT messaging period (the time between each node transmitting its data) determines how many time slots are available.

## ANT+

ANT+, introduced in 2004 as "the first ultra low power wireless standard", is an interoperability function that can be added to the base ANT protocol. This standardization allows the networking of nearby ANT+ devices to facilitate the open collection and interpretation of sensor data. For example, ANT+ enabled fitness monitoring devices such as heart-rate monitors, pedometers, speed monitors, and weight scales can all work together to assemble and track performance metrics.
ANT+ is designed and maintained by the ANT+ Alliance, which is managed by ANT Wireless, a division of Dynastream Innovations, owned by Garmin. ANT+ is used in Garmin's line of fitness monitoring equipment. It is also used by Garmin's Chirp, a geocaching device, for logging and alerting nearby participants.
ANT+ devices require certification from the ANT+ Alliance to ensure compliance with standard device profiles. Each device profile has an icon which may be used to visually match interoperable devices sharing the same device profiles.
The ANT+ specification is publicly available. At DEF CON 2019, hacker Brad Dixon demonstrated a tool to modify ANT+ data transmitted through USB for cheating in virtual cycling.