| Summary: | 碩士 === 國立成功大學 === 資訊工程學系 === 104 === Internet of Things (IoT) devices are usually wireless connected with high data loss rate and unstable latency. The devices installed with sensors and actuators are usually battery-operated and resource-limited. Current protocols for IoT application generally operate on top of UDP for lightweight purpose. To ensure reliability, these protocols need to provide retransmission mechanism, where a message is retransmitted when a retransmission timeout (RTO) timer expires. The RTO value can be configured as fixed or dynamic. Fixed RTO is simple, but may cause terrible message delivery ratio (MDR) and latency. Dynamic RTO improves MDR and latency, but consumes more energy in computation. In this thesis, we propose a method which calculates dynamic RTO values in gateway instead of calculating in devices. Simulation experiment results show that the average latency increases slightly, but the number of retransmission and the MDR improves significantly when the number of IoT devices is greater than 30. Our results also show that our method can decrease the number of retransmissions as long as the number of IoT devices is greater than 6. Furthermore, the power consumption can be effectively reduced as the number of retransmissions decreases. In other words, our proposal provides energy-efficient RTO values for resource-constrained IoT devices.
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