A C implementation of the AirTight protocol from the Real-Time Systems group at the University of York.

AirTight is a protocol for critical wireless communication based on the IEEE 802.15.4 MAC and physical layers.

AirTight is described in the paper:

A. Burns, J. Harbin, L. Indrusiak, I. Bate, R. Davis and D. Griffin, "AirTight: A Resilient Wireless Communication Protocol for Mixed-Criticality Systems," 2018 IEEE 24th International Conference on Embedded and Real-Time Computing Systems and Applications (RTCSA), Hakodate, 2018, pp. 65-75, doi: 10.1109/RTCSA.2018.00017.

An existing implementation of AirTight, for TinyOS using NESC, is available at: https://github.com/RTSYork/airtight.

This implementation itends to be more platform independent than the existing implementation and more extensively documented. For the purposes of development, testing, and as an example, the Pi-Puck platform was used for testing, and the XBee module on the platform was targeted for the example radio port.

To build the XBee library:

cd xbee
make

If you wish to make sure you are using the latest version:

git clone https://github.com/digidotcom/xbee_ansic_library.git
cd xbee
./import_library.sh

Then build as before.

To build the docs you will need Doxygen.

With doxygen installed simply run:

make doc

The XBee library is a dependency and therefore must already be built.

From the project root simply run:

make

At it's core AirTight features a Priority Critical Queue (PCQ) which stores packets due to be sent or forwarded. To configure the PCQ use the following:

• To set the number of priority levels edit AIRTIGHT_PRIORITIES in src/airtight_types.h.
• To set the depth of each queue edit PRIORITY_CRITICAL_QUEUE_SIZE in src/airtight_priority_critical_queue.h.
• To set the criticalities of each queue edit AT_CONF_CRITICALITIES in src/airtight_mac_config.h.

The other core structure is the scheduling table used to organise transmissions and receptions on the AirTight network. To configure the schedule table use the following:

• To set the number of rows and columns in the schedule table edit AT_CONF_SLOT_TABLE_ROWS and AT_CONF_SLOT_TABLE_COLUMNS respectively in src/airtight_slots_config.h.
• To set the contents of the table edit the file src/airtight_slot_table.txt.

The full network of connections between nodes and the hops required to route packets around the network is specified in the file src/airtight_routes_config.txt with each HOP rule having a node ID to which it applied, a final packet destination, and a "hop" destination. Unspecified routes will be assumed to be direct with a single hop.

Further configuration parameters can be found in src/airtight_mac_config.h and are documented there.

The XBee module must have the 802.15.4 firmware and the following configuration must be set:

Debugging is enabled by default but can be disabled by undefining AIRTIGHT_DEBUG in src/airtight_utilities.h.

Logging is enabled and prefixed with "LOG" by default. Logging can be disabled by undefining AIRTIGHT_LOGGING in src/airtight_logging.h.

This project is licensed under the BSD 3-Clause license, see LICENSE for details.

The XBee ANSI C library is Copyright Digi International, 2013 and licensed under the Mozilla Public License, v. 2.0. See https://github.com/digidotcom/xbee_ansic_library for further details.