# Autonomous Controller-Aware Scheduling of Intra-Platoon V2V Communications
## 8 Conclusions  
This work investigated the aspects of the efficient use of radio resources in an autonomous platooning employing wireless communications. We considered a quasi-periodic exchange of information, where the interval between subsequent transmissions by a platoon vehicle is selected dynamically in an event-dependent way. An optimization problem focusing on the minimization of the number of wireless intra-platoon transmissions was introduced, with a simultaneous safety-based constraint on the expected number of violations of the minimum inter-vehicle distance applied. We derived a recursive formula representing the changes of distance error between the first pair of vehicles in a platoon over time, aiming at a reformulation of the constraint. As the optimal solution for the stated problem cannot be directly found, we proposed a heuristic algorithm employingthe prediction of the inter-vehicle distance error evolution over a finite time window, performing an exhaustive search over the transmission intervals set to select the one securing the longest time until the predicted activation of emergency braking when the minimum distance threshold is violated. The proposed approach and the heuristic solution were then evaluated using numerical simulations, with the results showing the advantages of the adaptive transmission scheduling over fixed-interval communications. Based on the presented results, a conclusion can be drawn where it is possible to reduce the use of radio resources with the proposed adaptive approach while maintaining safe platoon operation. However, a more detailed analysis of platoon behavior is required, particularly focusing on the string stability of the platoon using adaptive transmission intervals. Furthermore, the work can be extended by considering an imperfect communication model and accounting for random drops of data packets, as well as constraints on the resource allocation mechanisms applied in V2X communications. Conceptualization, All; methodology, All; software, P.S. ; validation, A.K., E.S., and T.S. ; formal analysis, All; investigation, All; writing--original draft preparation, review, and editing, P.S. ; visualization, P.S. ; supervision, A.K., E.S., and T.S. ; project administration, A.K. ; funding acquisition, A.K. All authors have read and agreed to the published version of the manuscript. The work has been realized within the NCN project 2018/29/B/ST7/01241 at the Institute of Radiocommunications, PUT. Not applicable. No new data were created or analyzed in this study. Data sharing is not applicable to this article. The authors declare no conflict of interest. The following abbreviations are used in this manuscript: \begin{tabular}{l l} ABS & Anti-lock Braking Systems \\ ACC & Adaptive Cruise Control \\ ASR & Anti-Slip Regulation \\ CACC & Cooperative Adaptive Cruise Control \\ CAM & Cooperative Awareness Message \\ C-V2X & Cellular Vehicle-to-Everything \\ DCC & Dynamic Congestion Control \\ DSRC & Dedicated Short-Range Communications \\ ESP & Electronic Stability Program \\ V2V & Vehicle-to-Vehicle \\ V2X & Vehicle-to-Everything \\ \end{tabular}   
List of Symbols  
The following symbols are used in this manuscript: \begin{tabular}{l l}
**Symbol** & **Description** \\ \(N\) & number of vehicles in platoon \\ \(t\) & time \\ \(k\) & time sample \\ \(\Delta t\) & discrete system model time step (\(t=k\Delta t\)) \\
**A** & state transition matrix \\ \(\mathbf{s}(k)\) & system state vector at time instant \(k\Delta t\) \\ \end{tabular}