Section: New Results

Solutions for Safety-Critical Communications in IVNs

Participant : Gérard Le Lann.

In 2016, we have followed a divide-and-conquer approach. Rather than considering medium-range omnidirectional communications, we have split the problem space in two sub-domains, longitudinal short-range SC communications and lateral short-range communications. Our research has been directed at MAC protocols, string-wide message dissemination based on longitudinal communications, and distributed agreement algorithms based on longitudinal and lateral communications. New results are:

• A rigorous characterization of what is meant by SC communications in IVNs: the space-time bounds acceptability (STBA) requirements, as follows:

  • $STB{A}_1$: a MAC protocol is acceptable if and only if the distance traveled in $\lambda$ time units by any vehicle involved in a SC scenario is an order of magnitude smaller than average vehicle size.

  • $STB{A}_2$: a string-wide message dissemination algorithm, or a string-wide distributed agreement algorithm, is acceptable if and only if the distance traveled in $\Delta$ time units by any vehicle involved in a SC scenario is smaller than average vehicle size.

• Specification of SWIFT (Synchronous Wireless Interference-Free Transmissions), a collision-free MAC protocol that solves the BCAD and the TBMA problems introduced in [48] (no solutions given in this publication), and that also achieves fast string-wide acknowledged message dissemination,

• Analytical formulae of worst-case upper bounds $\lambda$ and $\Delta$ achieved with SWIFT [36],

• Specification of Fast Distributed Agreement (FastDA), a problem that arises in IVNs in the presence of conflicting concurrent SC events (e.g., lane changes and brutal braking), under two instances, single-lane (longitudinal) agreement and multilane (lateral and longitudinal) agreement [37],

• Specifications of solutions to FastDA: the Eligo algorithm for the single-lane string-wide agreement (SLA), and the LHandshake protocol for the multilane agreement (MLA),

• Analytical formulae of worst-case upper bounds ${\Delta }_{SLA}$ and ${\Delta }_{MLA}$ achieved with Eligo and LHandshake, respectively [37],

• Verification that SWIFT, Eligo and LHandshake meet the STBA requirements.

It turns out that SWIFT, Eligo, and LHandshake outperform existing stochastic solutions.