Periodic PLCA: Deterministic and Bandwidth Efficient Medium Access for Ethernet Multidrop Networks

Abstract

Recent in-vehicle networks (IVN) have witnessed growing adoption of automotive Ethernet, driven by increasing bandwidth demands and the transition to zonal architectures. In particular, the use of 10BASE-T1S is expanding to extend Ethernet beyond backbone networks to edge devices, enabling the realization of an “All-Ethernet vehicle.” 10BASE-T1S employs an Ethernet multidrop topology that preserves a bus structure similar to conventional CAN and prevents collisions in the multidrop environment through Physical Layer Collision Avoidance (PLCA). However, the dynamic variation of the PLCA BEACON interval leads to fluctuating jitter, posing a critical safety risk for real-time vehicle control systems. To address this problem, this paper proposes Periodic PLCA (P-PLCA). Unlike prior approaches that combine standard PLCA with upper-layer time-aware scheduling or optimize access within its variable-period cycle, P-PLCA enforces periodicity directly at BEACON generation in the PLCA Reconciliation Sublayer. This distinct implementation strategy also improves channel utilization through a residual-time reuse mechanism. Numerical analysis demonstrates that whereas standard PLCA exhibits delay variations depending on the transmit opportunity (TO) at the time of message generation, P-PLCA establishes a deterministic jitter bound through BEACON synchronization. Under the restricted condition in which periodic traffic is synchronized with the BEACON period and the occupancy of all preceding TOs remains invariant across cycles, this jitter bound is reduced to zero. Furthermore, we implemented simulation models using a network simulator and compared four protocols under various load conditions. The results demonstrate that, under the synchronized single-rate scenario evaluated in this study, the proposed P-PLCA maintains zero jitter for periodic traffic across all tested background-load conditions and sustains aperiodic traffic throughput even under 80% load.