Latency Aware IPv6 Packet Delivery Scheme over IEEE 802.15.4 Based Battery-Free Wireless Sensor Networks

Battery-Free Wireless Sensor Networks (BF-WSNs) have become increasingly useful for many applications and how to ensure timely information exchange between nodes in IP networks and those in BF-WSNs is indispensable. The 6LoWPAN protocol is usually used to deliver IPv6 packets over IEEE 802.15.4 based WSNs, and has resolved the size mismatching problembetween IPv6 packets and 802.15.4 Medium Access Control (MAC) frames by using packet fragmentation scheme to break an IPv6 packet into multiple small pieces with each fitted into a single 802.15.4 MAC frame. Unfortunately, IPv6 packets in BF-WSNs may suffer from intolerable delay for timely reassembling back to IPv6 packets. In this paper, we present a Latency Aware IPv6 Packet Delivery (LAID) scheme to reduce such IPv6 packet latency while maintaining high packet delivery ratio. Our LAID considers charging time, data rate, and the MaximumNumber of Transmission Trials (MNTT) used in the IEEE 802.15.4 MAC layer so that the minimum latency can be achieved by optimizing the pairing of data rate and MNTT. In addition, we apply network coding to improve packet delivery reliability. Our analysis shows that the proposed LAID significantly outperforms existing schemes with fixed data rates in terms of IPv6 packet latency.