A framework for energy based performability models for wireless sensor networks

A novel idea of alternating node operations between Active and Sleep modes in Wireless Sensor Network (WSN) has successfully been used to save node power consumption. The idea which started off as a simple implementation of a timer in most protocols has been improved over the years to dynamically change with traffic conditions and the nature of application area. Recently, use of a second low power radio transceiver to triggered Active/Sleep modes has also been made. Active/Sleep operation modes have also been used to separately model and evaluate performance and availability of WSNs. The advancement in technology and continuous improvements of the existing protocols and application implementation demands continue to pose great challenges to the existing performance and availability models. In this study the need for integrating performance and availability studies of WSNs in the presence of both channel and node failures and repairs is investigated. A framework that outlines and characterizes key models required for integration of performance and availability of WSN is in turn outlined. Possible solution techniques for such models are also highlighted. Finally it is shown that the resulting models may be used to comparatively evaluate energy consumption of the existing motes and WSNs as well as deriving required performance measures

MAC protocols with wake-up radio for wireless sensor networks: A review

The use of a low-power wake-up radio in wireless sensor networks is considered in this paper, where relevant medium access control solutions are studied. A variety of asynchronous wake-up MAC protocols have been proposed in the literature, which take advantage of integrating a second radio to the main one for waking it up. However, a complete and a comprehensive survey particularly on these protocols is missing in the literature. This paper aims at filling this gap, proposing a relevant taxonomy, and providing deep analysis and discussions. From both perspectives of energy efficiency and latency reduction, as well as their operation principles, state-of-the-art wake-up MAC protocols are grouped into three main categories: (1) duty cycled wake-up MAC protocols; (2) non-cycled wake-up protocols; and (3) path reservation wake-up protocols. The first category includes two subcategories: (1) static wake-up protocols versus (2) traffic adaptive wake-up protocols. Non-cycled wake-up MAC protocols are again divided into two classes: (1) always-on wake-up protocol and (2) radio-triggered wake-up protocols. The latter is in turn split into two subclasses: (1) passive wake-up MAC protocols versus (2) ultra low power active wake-up MAC protocols. Two schemes could be identified for the last category, (1) broadcast based wake-up versus (2) addressing based wake-up. All these classes are discussed and analyzed in this paper, and canonical protocols are investigated following the proposed taxonomy

Networking protocols for long life wireless sensor networks

My original contribution to knowledge is the creation of a WSN system that further improves the functionality of existing technology, whilst achieving improved power consumption and reliability. This thesis concerns the development of industrially applicable wireless sensor networks that are low-power, reliable and latency aware. This work aims to improve upon the state of the art in networking protocols for low-rate multi-hop wireless sensor networks. Presented is an application-driven co-design approach to the development of such a system. Starting with the physical layer, hardware was designed to meet industry specified requirements. The end system required further investigation of communications protocols that could achieve the derived application-level system performance specifications. A CSMA/TDMA hybrid MAC protocol was developed, leveraging numerous techniques from the literature and novel optimisations. It extends the current art with respect to power consumption for radio duty-cycled applications, and reliability, in dense wireless sensor networks, whilst respecting latency bounds. Specifically, it provides 100% packet delivery for 11 concurrent senders transmitting towards a single radio duty cycled sink-node. This is representative of an order of magnitude improvement over the comparable art, considering MAC-only mechanisms. A novel latency-aware routing protocol was developed to exploit the developed hardware and MAC protocol. It is based on a new weighted objective function with multiple fail safe mechanisms to ensure extremely high reliability and robustness. The system was empirically evaluated on two hardware platforms. These are the application-specific custom 868 MHz node and the de facto community-standard TelosB. Extensive empirical comparative performance analyses were conducted against the relevant art to demonstrate the advances made. The resultant system is capable of exceeding 10-year battery life, and exhibits reliability performance in excess of 99.9%

The deployment of extra relay nodes around the sink in order to solve the energy imbalanced problem in Wireless Sensor Networks

Wireless sensor networks are an emerging technology that has recently gained attention for their potential use in many applications such disaster management, combat field reconnaissance, border protection, object localization, harbors, coal mines, and so on. Sensors in these kind of applications are expected to be remotely deployed and to operate autonomously in unattended environments. Since sensors typically operate on batteries and are often deployed in harsh environment where human operators cannot access them easily, much of the research on wireless sensor networks has focused on the energy depletion in order to achieve energy efficiency to extend the network lifetime. In multihop wireless networks that are often characterized by many to one traffic patterns, it is very common to find problems related to energy depletion. Along the network, sensors experiment different traffic intensities and energy depletion rates. Usually, the sensors near the sink tend to deplete their energy sooner because they act as data originators and data relayers and are required to forward a large amount of traffic of the most remote sensors to the sink while the sensors located in the periphery of the network remain much of the time inactive. Therefore, these sensors located close to the sink tend to die early, leaving areas of the network completely disconnected from the sink reducing the functional network lifetime. In order to achieve equal power consumption at different levels of our network, we have decided to add extra relay nodes to reduce and balance the traffic load that normal nodes have to carry. As mentioned above, each level within the network faces a different amount of traffic, which becomes more intense as we approach the interior levels. This behavior causes that the external nodes, with less traffic to handle, stay more time at rest while the nodes in the inner rings face a great amount of traffic which forces them to be more active, generating a more accelerated exhaustion, reason why nodes located in the inner rings exhaust its battery faster causing the lifetime of the network to come to an end. This work presents a comprehensive analysis on the maximum achievable sensor network lifetime for different deployment strategies (linear, quadratic, and exponential ) in order to equalize the energy consumption rates of all nodes. More specifically the deployment of extra relay nodes around the sink in order to solve the energy imbalanced problem and guarantee that all nodes have balanced energy consumption and die almost at the same time

Energy-Efficient Boarder Node Medium Access Control Protocol for Wireless Sensor Networks

This paper introduces the design, implementation, and performance analysis of the scalable and mobility-aware hybrid protocol named boarder node medium access control (BN-MAC) for wireless sensor networks (WSNs), which leverages the characteristics of scheduled and contention-based MAC protocols. Like contention-based MAC protocols, BN-MAC achieves high channel utilization, network adaptability under heavy traffic and mobility, and low latency and overhead. Like schedule-based MAC protocols, BN-MAC reduces idle listening time, emissions, and collision handling at low cost at one-hop neighbor nodes and achieves high channel utilization under heavy network loads. BN-MAC is particularly designed for region-wise WSNs. Each region is controlled by a boarder node (BN), which is of paramount importance. The BN coordinates with the remaining nodes within and beyond the region. Unlike other hybrid MAC protocols, BN-MAC incorporates three promising models that further reduce the energy consumption, idle listening time, overhearing, and congestion to improve the throughput and reduce the latency. One of the models used with BN-MAC is automatic active and sleep (AAS), which reduces the ideal listening time. When nodes finish their monitoring process, AAS lets them automatically go into the sleep state to avoid the idle listening state. Another model used in BN-MAC is the intelligent decision-making (IDM) model, which helps the nodes sense the nature of the environment. Based on the nature of the environment, the nodes decide whether to use the active or passive mode. This decision power of the nodes further reduces energy consumption because the nodes turn off the radio of the transceiver in the passive mode. The third model is the least-distance smart neighboring search (LDSNS), which determines the shortest efficient path to the one-hop neighbor and also provides cross-layering support to handle the mobility of the nodes. The BN-MAC also incorporates a semi-synchronous feature with a low duty cycle, which is advantageous for reducing the latency and energy consumption for several WSN application areas to improve the throughput. BN-MAC uses a unique window slot size to enhance the contention resolution issue for improved throughput. BN-MAC also prefers to communicate within a one-hop destination using Anycast, which maintains load balancing to maintain network reliability. BN-MAC is introduced with the goal of supporting four major application areas: monitoring and behavioral areas, controlling natural disasters, human-centric applications, and tracking mobility and static home automation devices from remote places. These application areas require a congestion-free mobility-supported MAC protocol to guarantee reliable data delivery. BN-MAC was evaluated using network simulator-2 (ns2) and compared with other hybrid MAC protocols, such as Zebra medium access control (Z-MAC), advertisement-based MAC (A-MAC), Speck-MAC, adaptive duty cycle SMAC (ADC-SMAC), and low-power real-time medium access control (LPR-MAC). The simulation results indicate that BN-MAC is a robust and energy-efficient protocol that outperforms other hybrid MAC protocols in the context of quality of service (QoS) parameters, such as energy consumption, latency, throughput, channel access time, successful delivery rate, coverage efficiency, and average duty cycle.https://doi.org/10.3390/s14030507

Wake-up radio systems : design, development, performance evaluation and comparison to conventional medium access control protocols for wireless sensor networks

During the recent years, the research related to Wake-up Radio (WuR) systems has gained noticeable interest. In WuR systems, a node initiating a communication first sends a Wake-up Call (WuC) by means of its Wake-up Transmitter (WuTx), to the Wake-up Receiver (WuRx) of a remote node to activate it in an on-demand manner. Until the reception of the WuC, the node's MCU and main data transceiver are in sleep mode. Hence, WuR drastically reduce the power required by wireless nodes. This thesis provides a complete analysis of several WuR designs vs. conventional MAC protocols for Wireless Sensor Networks (WSN). The research is performed in an incremental fashion and includes hardware, softwar and simulation topics. WuR systems enable energy savings in plenty of different applications, e.g., retrieving information from environmental pollution sensors placed in a city by a mobile collector node, or activating a sleeping wireless AP. They are easy to program in and provide implicit synchronization. However, achieving a good WuRx design may become a challenge because power amplifiers cannot be used for the sake of energy. The system proposed in chapter 2 is a successful WuR system prototype. The so-called SµA-WuRx is less complex than commercial WuR systems, it is cheaper from the monetary point of view, requires several times less energy and allows for up to 15 meters of communication, an adequate value for WuR systems. However, the system can be improved by including several desirable features, such as longer operational ranges and/or addressing mechanisms. The so-called Time-Knocking (TicK) addressing strategy, analyzed in chapter 3, enables energy efficient node addressing by varying the time between WuCs received by a MCU. TicK allows for variable length addresses and multicast. A WuR system may not fit any possible application. Thus, while the SµA-WuRx and TicK efficiently solved many of the requirements of single-hop and data-collector applications, they lack of flexibility. Instead, SCM-WuR systems in chapter 4 feature an outstanding trade-off between hardware complexity, current consumption and operational range, and even enable multi-hop wake-up for long remote sensor measure collection. To contextualize the WuR systems developed, chapter 5 provides an overview of the most important WuR systems as of 2014. Developing a MAC protocol which performs acceptably in a wide range of diverse applications is a very difficult task. Comparatively, SCM-WuR systems perform properly in all the use cases (single and multi-hop) presented in chapter 6. Bluetooth Low Energy, or BLE, appears as a duty-cycled MAC protocol mainly targeting single-hop applications. Because of its clearly defined use cases and its integration with its upper application layers, BLE appears as an extremely energy-efficient protocol that cannot be easily replaced by WuR. Because of all these aspects, the performance of BLE is analyzed in chapter 7. Finally, chapter 8 tries to solve one of the issues affecting WuR systems, that is, the need for extra hardware. While this issue seems difficult to solve for WuRx, the chapter provides ideas to use IEEE 802.11-enabled devices as WuTx.Durant els últims anys, la investigació relativa als sistemes de Ràdios de Wake-up (de l'anglès Wake-up Radio, WuR) ha experimentat un interès notable. En aquests sistemes, un node inicia la comunicació inal.làmbrica transmetent una Wake-up Call (WuC), per mitjà del seu transmissor de Wake-up (WuTx), dirigida al receptor de Wake-up (WuRx) del node remot. Aquesta WuC activa el node remot, el microcontrolador (MCU) i la ràdio principals del qual han pogut romandre en mode "sleep" fins el moment. Així doncs, els sistemes WuR permeten un estalvi dràstic de l'energia requerida pels nodes sense fils. Aquesta tesi proposa diferents sistemes WuR i els compara amb protocols MAC existents per a xarxes de sensors sense fils (Wireless Sensor Networks, WSN). La investigació es realitza de forma progressiva i inclou hardware, software i simulació. Els sistemes WuR permeten un estalvi energètic notable en moltes aplicacions: recol¿lecció d'informació ambiental, activació remota de punts d'accés wi-fi, etc. Són fàcils de programar en software i comporten una sincronització implícita entre nodes. Malauradament, un consum energètic mínim impossibilita l'ús d'amplificadors de potència, i dissenyar-los esdevé un repte. El sistema presentat en el capítol 2 és un prototip exitós de sistema WuR. De nom SµA-WuR, és més senzill que alternatives comercials, és més econòmic, requereix menys energia i permet distàncies de comunicació WuR majors, de fins a 15 metres. L'estratègia d'adreçament Time-KnocKing, presentada en el capítol 3, permet dotar l'anterior SµA-WuR d'una forma d'especificar el node adreçat, permetent estalvi energètic a nivell de xarxa. TicK opera codificant el temps entre diferents WuC. Depenent del temps entre intervals, es desperten el/s node/s desitjats d'una forma extremadament eficient. Tot i els seus beneficis, hi ha aplicacions no implementables amb el sistema SµA-WuR. Per a aquest motiu, en el capítol 4 es presenta el sistema SCM-WuR, que ofereix un rang d'operació de 40 a 100 metres a canvi d'una mínima complexitat hardware afegida. SCM-WuR cobreix el ventall d'aplicacions del sistema SµA-WuRx, i també les que requereixen multi-hop a nivell WuR. El capítol 5 de la tesi compara els dos sistemes WuR anteriors vers les propostes més importants fins el 2014. El capítol 6 inclou un framework de simulació complet amb les bases per a substituir els sistemes basats en duty-cycling a WuR. Degut a que desenvolupar un protocol MAC que operi acceptablement bé en multitud d'aplicacions esdevé una tasca pràcticament impossible, els sistemes WuR presentats amb anterioritat i modelats en aquest capítol representen una solució versàtil, interessant i molt més eficient des del punt de vista energètic. Bluetooth Low Energy, o Smart, o BLE, representa un cas d'aplicació específica on, degut a la gran integració a nivell d'aplicació, la substitució per sistemes de WuR esdevé difícil Per a aquesta raó, i degut a que es tracta d'un protocol MAC extremadament eficient energèticament, aquesta tesi conté una caracterització completa de BLE en el capítol 7. Finalment, el capítol 8 soluciona un dels inconvenients del sistemes WuR, el disseny de WuTx específics, presentant una estratègia per a transformar qualsevol dispositiu IEEE 802.11 en WuTx

Optimal power control in green wireless sensor networks with wireless energy harvesting, wake-up radio and transmission control

Wireless sensor networks (WSNs) are autonomous networks of spatially distributed sensor nodes which are capable of wirelessly communicating with each other in a multi-hop fashion. Among different metrics, network lifetime and utility and energy consumption in terms of carbon footprint are key parameters that determine the performance of such a network and entail a sophisticated design at different abstraction levels. In this paper, wireless energy harvesting (WEH), wake-up radio (WUR) scheme and error control coding (ECC) are investigated as enabling solutions to enhance the performance of WSNs while reducing its carbon footprint. Specifically, a utility-lifetime maximization problem incorporating WEH, WUR and ECC, is formulated and solved using distributed dual subgradient algorithm based on Lagrange multiplier method. It is discussed and verified through simulation results to show how the proposed solutions improve network utility, prolong the lifetime and pave the way for a greener WSN by reducing its carbon footprint

Energy Harvesting Wireless Sensor Networks: From Characterization to Duty Cycle Dimensioning

International audienceEnergy harvesting capabilities are challenging our understanding of wireless sensor networks by adding recharging capacity to sensor nodes. This has a significant impact on the communication paradigm, as networking mechanisms can benefit from these potentially infinite renewable energy sources. In this work, we study the consequences of implementing photovoltaic energy harvesting on the duty cycle of a wireless sensor node, in both outdoor and indoor scenarios. We show that for the static duty cycle approach in outdoor scenarios, very high duty cycles, in the order of tens of percents, are achieved. This further eliminates the need for additional energy conservation schemes. In the indoor case, our analysis shows that the dynamic duty cycle approach based solely on the battery residual energy does not necessarily achieve better results than the static approach. We identify the main reasons behind this behavior, and test new design considerations by adding information on the battery level variation to the duty cycle computation. We demonstrate that this approach always outperforms static solutions when perfect knowledge of the harvestable energy is assumed, as well as in realistic deployments, where this information is not available