Evaluation of Receiver-Feedback Techniques for Fragmentation Over LPWANs

Abstract

The Internet Engineering Task Force (IETF) has standardized a new framework for IPv6 support over Low Power Wide Area Networks (LPWANs), called Static Context Header Compression and Fragmentation (SCHC). SCHC includes acknowledgment (ACK)-based mechanisms for reliable fragmented packet transmission. For the latter, SCHC defines a Receiver-Feedback Technique (RFT), called Compressed Bitmap (CB), by which a receiver reports to the sender whether the fragments carrying a packet have been received or not. Such information is carried as ACK payload. Considering the extraordinary frame size and message rate constraints of LPWANs, ACK payload size becomes crucial. In this paper, we compare the performance of CB with that of several alternative RFTs, namely List of Lost Fragments (LLF), List of Deltas (LoD), and Uncompressed Bitmap (UB), where the latter is used as a benchmark. We evaluate the considered RFTs in terms of ACK size, number of Layer 2 (L2) frames needed to carry an ACK, and ACK Time on Air. Our analysis shows that the use of RFTs different from CB offers significant performance improvement in many scenarios. Furthermore, we provide guidance on which RFT should be used for different packet sizes, error rates and error patterns.

Energy Consumption Model of SCHC Packet Fragmentation over Sigfox LPWAN

“…Simulation No [2] Header compression, number of fragments, number of ACKs Theoretical No [10] Channel occupancy, goodput, total delay Simulation No [11] ACK message overhead, ACK bit overhead with and without L2 headers Theoretical No [12] Error rates and patterns Simulation No [13] Packet delivery ratio, goodput per ToA Experimental No [14] Network delay, SNR, power consumption Experimental No [15] Transfer time, number of uplink and downlink messages Theoretical, Experimental No [16] Channel occupancy efficiency…”

“…Optimal configuration values for SCHC F/R over LoRaWAN and Sigfox were provided in [ 11 ]. SCHC Receiver-Feedback Techniques (RFTs) and alternative RFTs were presented and evaluated in [ 12 ] over LoRaWAN, as part of a reliable fragmentation method. Results show that alternative RFTs may be optimal depending on the error rate and pattern, providing greater efficiency.…”

“…Considering the energy constraints of IoT devices (many of which are not mains-powered), it is fundamental to evaluate the energy performance of SCHC fragmented packet transmission. However, to the best of our knowledge, there is no previous work in the literature on this topic [ 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ].…”

Contributions to IPv6 support over low rate low power wireless networks

“…The two-byte SCHC Fragment header may be used to comply with the IPv6 MTU of 1280 bytes, and may also be useful for applications that require long packet sizes, such as smart meters (e.g., gas, water, etc. ), waveform captures, data logs, and large data packets using rich data types [97,[105][106][107].…”

“…Optimal configuration values for SCHC F/R over LoRaWAN and Sigfox were provided in [59]. SCHC RFTs and alternative RFTs were presented and evaluated in [105] over LoRaWAN, as part of a reliable fragmentation method. Results show that alternative RFTs may be optimal depending on the error rate and pattern, providing greater efficiency.…”