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No, ANT does not support ad-hoc joining of a network. This functionality can be implemented at the application level; one example of this is the auto-shared channel reference design. Please refer to the components section.
Yes both acknowledged and burst message data types are supported in continuous scanning mode. Even though the continuous scanning mode makes full use of the radio, receiving 100% of the time; if a scanning node is configured for bidirectional communication, it is still possible to transmit data in response to a message from a master.
Background scanning channel is a special channel type that operates similar to a low priority search mode; however, instead of acquiring a master, ANT will pass the data to the host and continue searching, allowing the ANT node to continue finding other ANT masters without interrupting any other open channels. This is different from an ANT node in continuous scanning mode, where the node foregoes all synchronous channelization and begins to operate asynchronously, allowing it to receive all data from multiple nodes operating on the same network and RF frequency.
Proximity search aids in device pairing by providing a means to acquire a master based on its relative distance to a slave. Standard search mechanisms search for any master with a matching channel ID within range of the slave device. Proximity search can limit the number of possible matches by searching for a master with a matching channel ID that is within a set range or threshold. If used correctly, proximity search can acquire the master that is closest to the slave. Please refer to the AN12 Proximity Search application note for more details.
ANT is optimized for multiple network topologies such as star, tree and point-to-point. Mesh networking is not implemented in the ANT protocol natively but can be implemented at the application level.
There are two extended message formats supported by ANT, flagged and legacy, depending on the ANT device type. Later generation devices support the flagged extended messages format, AP1 does not support extended messages, and AT3 supports the legacy format. The extended messaging format and Message ID are different for flagged and legacy extended messaging formats.
In most instances, there will be no visible difference in acquisition time between a low and high priority search. The difference lies in whether the search channel or other channels take priority in the event of a collision. Whether high, low, or both types of search are used depends on the application.
A device’s range is heavily dependent on RF environment and system design (antenna design & orientation, device packaging, etc). Because of this dependency, there are no set correlations between proximity bin number and distance between devices or relative distance between bins. The specific use case should be thoroughly tested in order to determine an appropriate threshold for successful acquisition.
ANT achieves its low power consumption by intermittently transmitting data such that the radio is only on for a short period of time. 1MHz is the over-the-air bit rate whilst transmitting/receiving, therefore the overall bit rate is reduced when considering time off vs time on. Also, the bit rate accounts for the maximum bit transfer rate only. It does not account for overhead bits or timing delays. Each message packet consists of data bits and overhead bits from header and checksum fields.
In a low priority search, the activity of other channels will take priority over the search, so any timeslots in use by other channels will not be interfered with. This is contrasted by a high priority search where the channel running a search will take priority over any other active channels, thus causing some interference with those channels.
Yes, some ANT products do support RSSI, please refer to the advanced features page for more details.
ANT has an adaptive isochronous mechanism that effectively eliminates the vast majority of inter channel interference issues. ANT will only transmit in clear timeslots and ‘listens’ for drifting/interfering transmissions and can alter its own transmission slot by retiming transmissions.
The maximum theoretical network size is 2^32 addressable nodes. For a single shared channel, up to 65,535 slave nodes can be addressed.
Yes, either low or high priority search can be disabled.
ANT supports an 8-byte network key and 128-bit AES encryption for ANT master and slave channels. If further security is required, authentication and encryption can be implemented through the application level. However, the ANT-FS specification supports authentication and encryption, and ANT-FS is implemented natively by some ANT products, please refer to the advanced features page for more details.
Certain ANT chipsets have built-in frequency agility, allowing the channel to automatically hop to a different frequency if the channel performance degrades too far. It can also be implemented at the application level if required, please refer to the components section found here for a demo and source code.
Single frequency systems save on power and latency. In multi-frequency systems when searching for devices you need to search in both the time and frequency domains. Using a single frequency system reduces the duration of the search as the device only needs to search in the time domain. As searching is typically the most power-intensive operation, reducing search time also reduces power consumption. Using a simple frequency system also reduces the implementation’s complexity. From a practical perspective, single frequency systems have been shown to perform very well on Personal Area Networks.
Yes, any individual ANT channel on any ANT node can be configured as a master or a slave.
ANT has sophisticated mechanisms for avoiding inter channel interference and has been tested to work with up to 300 1 Hz independent channels in the same RF frequency in close proximity to each other.
ANT can support all forms of practical wireless sensor network topologies including peer-to-peer, star, tree, and mesh networks. This includes but is not limited to multiple synchronized peer-to-peer channels on a single ANT node, many masters communicating asynchronously with a single ANT node running in continuous scanning mode, or many ANT slaves sharing a channel managed by a single master.
ANT in new devices such as the nRF52 now offers the ability to transmit precise timing data over bi-directional channels using the Time Sync feature, enabling multiple devices to synchronize timing to any given source. For more information on Time Sync, the application note can be found here.