Packet Fragmentation Over Sigfox: Implementation and Performance Evaluation of SCHC ACK-on-Error

The static context header compression and fragmentation (SCHC) framework has been recently designed by the Internet engineering task force (IETF). SCHC provides adaptation layer functionality intended to efficiently support IPv6-based and other applications over low power wide area network (LPWAN) technologies. As of the writing, technology-specific profiles are being standardized in order to describe how SCHC can be tailored when used over a given underlying technology. In this article, we provide the first performance evaluation of SCHC over Sigfox, a flagship LPWAN technology. We focus on the main SCHC over Sigfox fragmentation mode, called ACK-on-Error, which offers low overhead, reliability, and reassembly functionalities. We provide a theoretical analysis and an experimental evaluation in real environments that correspond to two geographical zones with different Sigfox radio settings: 1) Barcelona (Spain) and 2) Santiago (Chile). The study focuses on modeling and evaluating packet transfer times, and the required number of uplink and downlink messages. The results show that a small change in packet sizes may significantly affect the transfer times, especially when no duty-cycle restrictions are enforced. Also, we observe that, under certain conditions, an increase in the fragment loss rate (FLR) may decrease the packet transfer time, and that the number of uplink and downlink messages is not proportional to such increase due to the fact that downlink messages are device-driven. The results provide useful insights for researchers, developers, implementers, and providers, with applicability to the application design, network planning, and resource management of Internet of Things (IoT) solutions.