Domenico De Guglielmo

IEEE 802.15.4e: A survey

Abstract 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 Multi-channel 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.

From IEEE 802.15.4 to IEEE 802.15.4e: A Step Towards the Internet of Things

Wireless Sensor and Actuator Networks (WSANs) are expected to have a key role in the realization of the future Internet of Things that will connect to the Internet any kind of devices, living beings, and things. A number of standards have been released over the last years to support their development and encourage inter-operability. In addition IETF has defined a set of protocols to allow the integration of sensor and actuator devices into the Internet. In this chapter we focus on the 802.15.4e, released by IEEE in 2012 to enhance and add functionality to the previous 802.15.4 standard, so as to address the emerging needs of embedded industrial applications. We describe how the limitations of the 802.15.4 standard have been overcome by the new standard, and we also show some simulation results to better highlight this point.

A performance analysis of the network formation process in IEEE 802.15.4e TSCH wireless sensor/actuator networks

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.

SAD-SJ: A self-adaptive decentralized solution against Selective Jamming attack in Wireless Sensor Networks

Wireless Sensor Networks (WSNs) are currently used in many application scenarios, including industrial applications and factory automation. In such scenarios, Time Division Multiple Access (TDMA) is typically used for data communication among sensor nodes. However, TDMA-based WSNs are particularly prone to Selective Jamming attack, a specific form of Denial of Service attack aimed at severely thwarting network reliability. In this paper, we present SAD-SJ, a self-adaptive and decentralized MAC-layer solution against selective jamming in TDMA-based WSNs. SAD-SJ does not need a central entity, requires sensor nodes to rely only on local information, and allows them to join and leave the network without hindering other nodes activity. We show that SAD-SJ introduces a limited overhead, in terms of computation, communication and energy consumption.

A Model-based Beacon Scheduling algorithm for IEEE 802.15.4e TSCH networks

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.

Accurate and Efficient Modeling of 802.15.4 Unslotted CSMA/CA through Event Chains Computation

Many analytical models have been proposed for evaluating the performance of event-driven 802.15.4 Wireless Sensor Networks (WSNs), in Non-Beacon Enabled (NBE) mode. However, existing models do not provide accurate analysis of large-scale WSNs, due to tractability issues and/or simplifying assumptions. In this paper, we propose a new approach called Event Chains Computation (ECC) to model the unslotted CSMA/CA algorithm used for channel access in NBE mode. ECC relies on the idea that outcomes of the CSMA/CA algorithm can be represented as chains of events that subsequently occur in the network. Although ECC can generate all the possible outcomes, it only considers chains with a probability to occur greater than a pre-defined threshold to reduce complexity. Furthermore, ECC parallelizes the computation by managing different chains through different threads. Our results show that, by an appropriate threshold selection, the time to derive performance metrics can be drastically reduced, with negligible impact on accuracy. We also show that the computation time decreases almost linearly with the number of employed threads. We validate our model through simulations and testbed experiments, and use it to investigate the impact of different parameters on the WSN performance, in terms of delivery ratio, latency, and energy consumption.

Analysis and Experimental Evaluation of IEEE 802.15.4e TSCH CSMA-CA Algorithm

Time-slotted channel hopping (TSCH) is one of the medium access control (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 is special slots assigned to more than one transmitter, whose concurrent access is regulated by a carrier-sense multiple access with collision avoidance (CSMA-CA) 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 for deriving a number of metrics, such as delivery probability, packet latency, and energy consumption of nodes. Moreover, it considers the capture effect (CE) 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. Furthermore, we found that the CE plays a fundamental role as it can significantly improve the performance experienced by nodes.

Strategies for optimal MAC parameter setting in IEEE 802.15.4 wireless sensor networks: A performance comparison

Recent studies have shown that the IEEE 802.15.4 MAC protocol may suffer from severe limitations in terms of reliability and energy efficiency if a non appropriate parameter setting is used. Hence, a number of solutions have been proposed to select the optimal parameter setting to provide reliability with minimum energy consumption. In this paper we compare, by simulation, three different algorithms that take different approaches to the problem, namely offline computation, model-based adaptation, and measurement-based adaptation. We show that adaptive algorithms perform well, however the model-based adaptive approach has some limitations that make it unsuitable in practical scenarios, where operating conditions may vary over time and transmission errors cannot be neglected. Instead, the measurement-based adaptive approach is flexible and effective.

Just-in-Time Adaptive Algorithm for Optimal Parameter Setting in 802.15.4 WSNs

Recent studies have shown that the IEEE 802.15.4 MAC protocol suffers from severe limitations, in terms of reliability and energy efficiency, when the CSMA/CA parameter setting is not appropriate. However, selecting the optimal setting that guarantees the application reliability requirements, with minimum energy consumption, is not a trivial task in wireless sensor networks, especially when the operating conditions change over time. In this paper we propose a Just-in-Time LEarning-based Adaptive Parameter tuning (JIT-LEAP) algorithm that adapts the CSMA/CA parameter setting to the time-varying operating conditions by also exploiting the past history to find the most appropriate setting for the current conditions. Following the approach of active adaptive algorithms, the adaptation mechanism of JIT-LEAP is triggered by a change detection test only when needed (i.e., in response to a change in the operating conditions). Simulation results show that the proposed algorithm outperforms other similar algorithms, both in stationary and dynamic scenarios.

A localized slot allocation algorithm for wireless sensor networks

While energy efficiency is typically considered the major concern in wireless sensor networks (WSNs), many real-life applications also require reliability, timeliness, and scalability. In such scenarios, Time Division Multiple Access (TDMA) is typically used for data communication, as it avoids collisions and provides predictable latency and minimum energy consumption. TDMA requires a slot scheduling algorithm to allocate transmission slots to sensor nodes. In this paper, we propose a decentralized slot allocation algorithm which is localized and self adaptive, i.e., each node selects its slot(s) and adapts its behavior only basing on locally-available information. We derive analytically the time taken by the algorithm and the average energy consumed by the network to achieve a complete schedule. We also show that our solution performs significantly better than another previous similar algorithm.