AirTight: A Resilient Wireless Communication Protocol for Mixed-Criticality Systems

Abstract

This paper describes the motivation, design, analysis and implementation of a new protocol for critical wireless communication called AirTight. Wireless communication has become a crucial part of the infrastructure of many cyber-physical applications. Many of these applications are real-time and also mixed-criticality, in that they have components/subsystems with different consequences of failure. Wireless communication is inevitably subject to levels of external interference. In this paper we represent this interference using a criticality-aware fault model; for each level of interference in the fault model we guarantee the timing behaviour of the protocol (i.e. we guarantee that packet deadlines are satisfied for certainly levels of criticality). Although a new protocol, AirTight is built upon existing standards such as IEEE 802.15.4. A prototype implementation and protocol-accurate simulator, which are also built upon existing technologies, demonstrate the effectiveness and functionality of the protocol.

The AirTight Protocol for Mixed Criticality Wireless CPS

“…We assume that clock drift is insigni cant when compare to the slot duration. (In our prototype implementation [8] a slot length of 10ms has been achieved. This is the slot length in most WirelessHART implementations [17]).…”

“…9 ILLUSTRATIVE EXAMPLE 9.1 An Avionics Use-case A good example of the potential deployment of a wireless communication media is within an aircraft engine for the purposes of active health monitoring [43]. Figure 2 shows the communication graph for a 25-node wireless network inspired by a possible engine monitoring system [8]; it is clear that the topology of this example is a 5-node subsystem repeated 5 times. In total this network has 55 packet ows mapped to the 25 nodes; 25 of these ows are de ned to be of HI-criticality and 30 of LO-criticality.…”

“…The 5-node subsystem was also used in a prototype implementation of the protocol. This implementation 2 is described in detail in a conference paper [8] and therefore is not covered here. In addition to the implementation, a protocol-accurate simulator for AirTight has been produced and validated against the prototype.…”

“…Many Cyber-Physical Systems (CPS) require some form of wireless communication and contain components/subsystems of di erent levels of criticality. AirTight [8] is a wireless protocol that is designed to meet the challenge of supporting mixed-criticality real-time tra c between computational nodes. In this paper we signi cantly expand the initial de nition of AirTight [8] and consider how a complete system can be speci ed via heuristics and the application of genetic algorithms.…”

“…The rst contribution of this paper is to present new analytical techniques for wireless Cyber-Physical Systems. Firstly, the analysis in our previous AirTight paper [8] is extended to support multi-hop ows by considering the summation of individual hop response times along the route. This improved analysis is referred to in this work as Single Channel Analysis (SCA).…”