Simple ARQ Protocol for Reliable Transport in LowPANs

Due to the surge in IoT devices, numerous protocols have been proposed to meet their needs. UDP is commonly used for IoT because of its simplicity, low latency, minimal overhead, and low energy consumption. In contrast, TCP is less suitable for IoT due to its higher resource demands, complexity, and greater energy consumption, which are challenging for small devices with limited resources. Therefore, often, reliability is provided by upper-layer protocols, mainly by the applications themselves. In fact, classical IoT applications such as sensing, identification and actuating generate multiple copies of data due to the hardware redundancy and periodic updates. Examples of such applications include, agricultural, environmental, traffic, and healthcare monitoring. UDP and TCP protocols may be inadequate for IoT applications requiring reliable, real-time communication. In critical situations like battlefields or disasters, sensors might only send a few messages before being destroyed. Therefore, the network itself must ensure reliability in these scenarios. Moreover, smart textiles are more and more integrating sensory devices and require reliable transmissions. In fact, with the very stringent resource constraints on one hand, and the requirements to respect the Specific Absorption Rate (SAR) of human bodies, on the other hand, re-transmissions and power must be kept at their lowest levels. In this paper, we propose a simple Automatic Request (SARQ) transport protocol that uses acknowledgments and a retransmission mechanism. Through a realistic simulation setup using Contiki motes in cooja simulator, we show that our protocol exhibits slightly higher energy consumption and resource requirements than UDP, but far less than TCP. Conversely, we show that our protocol exhibits 99% Packet Delivery Ratio (PDR), while UDP and TCP exhibit 74% and 99% PDR, respectively.