Several studies have highlighted that the IEEE 802.15.4 standard presents a number of limitations such as low reliability, unbounded packet delays and no protection against interference/fading, that prevent its adoption in applications with stringent requirements in terms of reliability and latency. Recently, the IEEE has released the 802.15.4e amendment that introduces a number of enhancements/modifications to the MAC layer of the original standard in order to overcome such limitations. In this paper we provide a clear and structured overview of all the new 802.15.4e mechanisms. After a general introduction to the 802.15.4e standard, we describe the details of the main 802.15.4e MAC behavior modes, namely Time Slotted Channel Hopping (TSCH), Deterministic and Synchronous Multichannel Extension (DSME), and Low Latency Deterministic Network (LLDN). For each of them, we provide a detailed description and highlight the main features and possible application domains. Also, we survey the current literature and summarize open research issues.

Time Slotted Channel Hopping (TSCH) is one of the MAC behavior modes defined in the IEEE 802.15.4e standard. It combines time slotted access and channel hopping, thus providing predictable latency, energy efficiency, communication reliability, and high network capacity. TSCH provides both dedicated and shared links. The latter are special slots assigned to more than one transmitter, whose concurrent access is regulated by a CSMACA algorithm. In this paper we develop an analytical model of the TSCH CSMA-CA algorithm to predict the performance experienced by nodes when using shared links. The model allows to derive a number of metrics such as delivery probability, packet latency and energy consumption of nodes. Also, it considers the capture effect that typically occurs in real wireless networks. We validate the model through simulation experiments and measurements in a real testbed. Our results show that the model is very accurate. Also, we found that the capture effect plays a fundamental role as it can significantly improve the performance experienced by nodes

-Time Slotted Channel Hopping (TSCH) is one of the access behavior modes defined in the IEEE 802.15.4e standard. It combines time slotted access with multi-channel and channel hopping capabilities, providing predictable latency, energy efficiency, high network capacity, and high communication reliability. In this paper we focus on the formation process of TSCH networks, which relies on the regular advertisement of Enhanced Beacons (EBs). We consider a simple random-based advertisement algorithm, and evaluate its performance, through analysis and simulation, in terms of joining time (i.e., total time taken by a new node to join the network). We found that the joining time depends on a number of factors and, mainly, on the number of channels used for EB advertisement.

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Time Slotted Channel Hopping (TSCH) is an emerging MAC protocol defined in the IEEE 802.15.4e standard. By combining time slotted access with multi-channel and channel hopping capabilities, it is particularly suitable for critical applications that require high reliability and deterministic latency.In this paper we focus on the formation process of TSCH networks. This relies on periodic advertisement of Enhanced Beacons (EBs), however, the standard does not specify any advertising strategy. By taking a theoretical approach, we first derive a general model of the network formation process and provide an analytical formulation of the average joining time (i.e., the time taken by a node to join the network). Then, we derive an optimal strategy for scheduling EB transmissions that minimizes the average joining time. Finally, we propose a new Model-based Beacon Scheduling (MBS) algorithm that approximates the optimal strategy in real networks. We evaluate the performance of MBS by simulation. Our results show that the proposed algorithm outperforms previous solutions present in the literature.