Scalable Telematics Control Unit Firmware Design for Large-Scale Connected Vehicle Ecosystems

Abstract

The telematics control unit (TCU) constitutes the communication and computation nexus of connected vehicle architectures, integrating cellular connectivity, CAN-bus signal aggregation, over-the-air firmware update management, and remote diagnostic services within a single resource-constrained embedded platform. As fleet sizes scale from hundreds to hundreds of thousands of deployed vehicles, TCU firmware architectures face compounding challenges: memory-constrained real-time task scheduling, bandwidth-optimized data telemetry, deterministic OTA update execution across heterogeneous ECU networks, and secure remote diagnostic session management — all simultaneously within platforms often limited to 128KB of RAM. This paper presents a scalable TCU firmware design methodology for large-scale connected vehicle ecosystems, implementing OTA logging and OTA firmware update capabilities on a FreeRTOS-based 128KB RAM microcontroller platform. The proposed architecture introduces a memory-optimized real-time task scheduling framework that maintains deterministic execution guarantees for safety-critical vehicle communication functions under simultaneous multi-service load. A selective CAN signal acquisition framework enables configurable signal capture from downstream ECUs with cloud-portal-managed filtering, minimizing storage and bandwidth consumption while preserving diagnostic observability. UDS (ISO 14229) service implementation over CAN provides standardized diagnostic session management and memory transfer operations supporting scalable OTA deployment. Evaluation across a deployed fleet of 10,000 vehicles demonstrates cloud upload reliability of 99.3%, OTA update success rates of 96.8%, and CAN signal acquisition latency within the 50ms window required for telematics diagnostic applications. The results establish a principled firmware architecture for scalable, reliable, and memory-efficient TCU deployment in large connected vehicle fleets.