A Survey of Limitations and Enhancements of the IPv6 Routing Protocol for Low-power and Lossy Networks: A Focus on Core Operations <s> 3) IEEE 802.15.4e TSCH and IETF 6TiSCH (Layer 2) <s> As exposed in a recent report by General Electric, an industrial Internet of Things (IoT) is emerging as a commercially viable embodiment of the IoT where physical sensors gather data readings from the field and deliver the traffic to the Internet. The collected real-time big data, in turn, allow the optimizing of entire industry verticals with enormous return of investments. Although opportunities are ample, it comes along with serious engineering design challenges as industrial applications have stringent requirements on delay, lifetime and standards-compliance. To this end, we advocate the use of an IEEE/IETF standardized IoT architecture along with a recently introduced data-centric scheduling algorithm known as traffic aware scheduling algorithm (TASA). Applying graph theoretical tools to the multi-channel, time-synchronized, and duty-cycled nature of TASA, we rigorously derive optimality and bounds on the minimum number of needed active slots (impacting end-to-end delays) and the network duty-cycle (impacting lifetime). We demonstrate the enormous superiority of TASA over traditional IEEE802.15.4/ZigBee approaches in terms of energy efficiency. The outcome of this paper is currently to lay foundations of the recently formed IETF standardization group 6TSCH with the aim to significantly improve IoT data flows over IEEE802.15.4e TSCH and IETF 6LoWPAN/ROLL enabled technologies. <s> BIB001 </s> A Survey of Limitations and Enhancements of the IPv6 Routing Protocol for Low-power and Lossy Networks: A Focus on Core Operations <s> 3) IEEE 802.15.4e TSCH and IETF 6TiSCH (Layer 2) <s> In order to cope with large multi-hop resource-constrained and IPv6-compliant Low-power and Lossy Networks (LLNs), based on IEEE802.15.4 radios, novel protocols have been standardized within the IETF. More recently, the IEEE802.15.4e Timeslotted Channel Hopping (TSCH) MAC amendment has been designed to meet the requirements of industrial applications, by reducing idle-listening and improving reliability in the presence of narrow-band interference and multi-path fading. To integrate this new powerful MAC within the framework of IPv6-based LLN protocols, a new IETF working group has been defined, namely “IPv6 over the TSCH mode of IEEE 802.15.4e” (6TiSCH). In a timely way, this paper presents our contribution to the early standardization efforts required to define (i) an optimal distributed scheduling technique able to allocate resources between any couple of neighbors, while seconding the minimal bandwidth requirements and avoiding collisions, and (ii) a scalable framework supporting setting-up and maintenance of secured domains. Supported by the scientific interest to this reasearch topic, we strongly believe that the 6TiSCH stack will be a viable solution for a wide gamut of optimal and secured IoT applications in industrial environments. <s> BIB002 </s> A Survey of Limitations and Enhancements of the IPv6 Routing Protocol for Low-power and Lossy Networks: A Focus on Core Operations <s> 3) IEEE 802.15.4e TSCH and IETF 6TiSCH (Layer 2) <s> Ubiquitous object networking has sparked the concept of the Internet of Things (IoT), which defines a new era in the world of networking. Realization of this concept needs to be addressed by standardization efforts that will shape the infrastructure of the networks. This has been achieved through the IEEE 802.15.4e, 6LoWPAN, and IPv6 standards. In addition, the IEEE 802.15.4e standard, which can be considered as the backbone of the IoT structure, has presented timeslotted channel hopping (TSCH). Although these standards provide a coherent and diffused system, several implications challenge these standards to achieve optimal performance and reliability. Node mobility can be considered as the delimited factor for realizing a fully connected network, especially with the inclusion of TSCH mode that will complicate the association process of the mobile nodes, as a result of the frequency hopping mechanism. In this paper, we investigate the impact of mobility over the TSCH sensor network, and a Markov chain model is presented to determine the parameters that affect mobile node association process. Second, we provide a proposed mobility-aware Mobile Timeslotted Channel Hopping (MTSCH) protocol that will facilitate the mobile nodes association and minimize the latency incurred by leaving the nodes dissociated from the network. TSCH and the proposed MTSCH techniques have been implemented and evaluated through Contiki OS. The proposed MTSCH manages to reduce the radio duty cycle of the mobile nodes by an average of 30% while increasing the connectivity of the nodes by 25%. Moreover, cluster heads managed to save energy by a ratio of 14%. <s> BIB003
Due to the single-channel related unpredictability of the IEEE 802.15.4 CSMA/CA in multi-hop networks, and to cope with the resource-constrained nature of LLNs, the IEEE introduced the Time-slotted Channel Hopping (TSCH) mode as an amendment to the MAC part of the IEEE802.15.4 standard in 2012 BIB002 . This new mode combines the TDMA (Time Division Multiple Access) with the channel hopping with the goal to improve both the energy efficiency and reliability BIB002 BIB003 . While the TDMA scheduling minimizes the contention, and thus providing more efficient energy consumption, the channel hopping enhances the network reliability and mitigates the effect of channel fading BIB001  . In order to integrate the TSCH MAC protocol with IPv6 LLNs especially for industrial applications, the IETF chartered the "IPv6 over the TSCH mode of IEEE 802.15.4e" (6TiSCH) working group to enable IPv6 on the top of TSCH mode  . The 6TiSCH defines the 6TiSCH Operation Sublayer (6top) that specifies how nodes can communicate to add or delete cells and when such an addition and deletion can occur. The 6TiSCH also defines a set of distributed scheduling protocols that manage the allocation of resources. At the time of writing, the 6TiSCH is still active with two RFCs and five Internet-Drafts. These IEEE and the IETF joint standardization efforts have given birth to a modified 6LoWPAN stack named the 6TiSCH stack shown in Figure 2b . 