As aerospace platforms increasingly adopt connected architectures for avionics, telemetry, and predictive diagnostics, lightweight messaging protocols have become foundational. MQTT (Message Queuing Telemetry Transport), due to its simplicity and minimal network overhead, is widely used in both ground and onboard aerospace systems. With the release of MQTT 5.0, the protocol introduces a suite of new capabilities designed to enhance scalability, reliability, and diagnostics. However, these benefits come with trade-offs in complexity and potential overhead, particularly in real-time and resource-constrained environments typical in aerospace.
This paper presents a comparative evaluation of MQTT 3.1 and MQTT 5.0, exploring their theoretical differences — such as reason codes, session expiry, user properties, topic aliasing, shared subscriptions, and enhanced error feedback — and their impact on system-level performance. We analyze these aspects using practical throughput benchmarks implemented via popular open-source tools like Eclipse Mosquitto Clients. Realistic aerospace communication scenarios are modeled for inter-module messaging, under varying QoS (Quality of Service) levels and payload conditions.
We examine throughput in terms of message rate, round-trip latency, broker CPU (Central Processing Unit) /memory usage, and protocol overhead under constrained and unconstrained network environments. The results show where MQTT 5.0 excels — especially in complex, multi-tenant systems — and where MQTT 3.1 remains sufficient or even preferable due to lower overhead.
Recommendations for protocol selection, migration strategy, and optimal broker-client configurations are also proposed.