Chang Hui-Ling, Wang Cheng-Gang, Wu Mong-Ting, Tsai Meng-Hsun, Lin Chia-Ying
Department of Computer Science and Information Engineering, National Cheng Kung University, Tainan 701, Taiwan.
Sensors (Basel). 2016 Sep 22;16(10):1560. doi: 10.3390/s16101560.
Message Queuing Telemetry Transport for Sensor Networks (MQTT-SN) and Constrained Application Protocol (CoAP) are two protocols supporting publish/subscribe models for IoT devices to publish messages to interested subscribers. Retransmission mechanisms are introduced to compensate for the lack of data reliability. If the device does not receive the acknowledgement (ACK) before retransmission timeout (RTO) expires, the device will retransmit data. Setting an appropriate RTO is important because the delay may be large or retransmission may be too frequent when the RTO is inappropriate. We propose a Gateway-assisted CoAP (GaCoAP) to dynamically compute RTO for devices. Simulation models are proposed to investigate the performance of GaCoAP compared with four other methods. The experiment results show that GaCoAP is more suitable for IoT devices.
用于传感器网络的消息队列遥测传输（MQTT-SN）和受限应用协议（CoAP）是支持物联网设备发布/订阅模型的两种协议，物联网设备可通过它们向感兴趣的订阅者发布消息。引入了重传机制来弥补数据可靠性的不足。如果设备在重传超时（RTO）到期之前未收到确认（ACK），则会重新传输数据。设置适当的RTO很重要，因为当RTO不恰当时，延迟可能会很大，或者重传可能会过于频繁。我们提出了一种网关辅助的CoAP（GaCoAP）来为设备动态计算RTO。提出了仿真模型来研究GaCoAP与其他四种方法相比的性能。实验结果表明，GaCoAP更适合物联网设备。
