An Energy-efficient Rate Adaptive Media Access Protocol (RA-MAC) for Long-lived Sensor Networks

We introduce an energy-efficient Rate Adaptive Media Access Control (RA-MAC) algorithm for long-lived Wireless Sensor Networks (WSNs). Previous research shows that the dynamic and lossy nature of wireless communications is one of the major challenges to reliable data delivery in WSNs. RA-MAC achieves high link reliability in such situations by dynamically trading off data rate for channel gain. The extra gain that can be achieved reduces the packet loss rate which contributes to reduced energy expenditure through a reduced numbers of retransmissions. We achieve this at the expense of raw bit rate which generally far exceeds the application’s link requirement. To minimize communication energy consumption, RA-MAC selects the optimal data rate based on the estimated link quality at each data rate and an analytical model of the energy consumption. Our model shows how the selected data rate depends on different channel conditions in order to minimize energy consumption. We have implemented RA-MAC in TinyOS for an off-the-shelf sensor platform (the TinyNode) on top of a state-of-the-art WSN Media Access Control Protocol, SCP-MAC, and evaluated its performance by comparing our implementation with the original SCP-MAC using both simulation and experiment

Design Aspects of An Energy-Efficient, Lightweight Medium Access Control Protocol for Wireless Sensor Networks

This document gives an overview of the most relevant design aspects of the lightweight medium access control (LMAC) protocol [16] for wireless sensor networks (WSNs). These aspects include selfconfiguring and localized operation of the protocol, time synchronization in multi-hop networks, network setup and strategies to reduce latency.\ud The main goal in designing a MAC protocol for WSNs is to minimize energy waste - due to collisions of messages and idle listening - , while limiting latency and loss of data throughput. It is shown that the LMAC protocol performs well on energy-efficiency and delivery ratio [19] and can\ud ensure a long-lived, self-configuring network of battery-powered wireless sensors.\ud The protocol is based upon scheduled access, in which each node periodically gets a time slot, during which it is allowed to transmit. The protocol does not depend on central managers to assign time slots to nodes.\ud WSNs are assumed to be multi-hop networks, which allows for spatial reuse of time slots, just like frequency reuse in GSM cells. In this document, we present a distributed algorithm that allows nodes to find unoccupied time slots, which can be used without causing collision or interference to other nodes. Each node takes one time slot in control to\ud carry out its data transmissions. Latency is affected by the actual choice of controlled time slot. We present time slot choosing strategies, which ensure a low latency for the most common data traffic in WSNs: reporting of sensor readings to central sinks

An Energy-conscious Transport Protocol for Multi-hop Wireless Networks

We present a transport protocol whose goal is to reduce power consumption without compromising delivery requirements of applications. To meet its goal of energy efficiency, our transport protocol (1) contains mechanisms to balance end-to-end vs. local retransmissions; (2) minimizes acknowledgment traffic using receiver regulated rate-based flow control combined with selected acknowledgements and in-network caching of packets; and (3) aggressively seeks to avoid any congestion-based packet loss. Within a recently developed ultra low-power multi-hop wireless network system, extensive simulations and experimental results demonstrate that our transport protocol meets its goal of preserving the energy efficiency of the underlying network.Defense Advanced Research Projects Agency (NBCHC050053

On channel adaptive energy management in wireless sensor networks

Energy constraints in a wireless sensor network are crucial issues critically affecting the network lifetime and connectivity. To realize true energy saving in a wireless environment,the time varying property of the wireless channel should also be taken into account. Unfortunately, this factor has long been ignored in most existing state-of-the-art energy saving protocols. Neglecting the effects of varying channel quality can lead to an unnecessary waste of precious battery resources, and, in turn, can resultin the rapid depletion of sensor energy and partitioning of the network. In this paper, we propose a channel adaptiveenergy managementprotocol, called CAEM, that can exploit this time varying nature of the wireless link. Specifically, CAEM leverages on the synergistically cross-layer interaction between physical and MAC layers. Thus, each sensor node can intelligently access the wireless medium according to the current wireless link quality and the predicted traffic load, to realize an efficient utilization of the energy. Extensivesimulation results indicate that CAEM can achieve as much as 40% reductionin energy dissipation compared with traditional protocols without channel adaptation. © 2005 IEEE.published_or_final_versio

A Unified Architecture for Flexible Radio Power Management in Wireless Sensor Networks

A challenge for many wireless sensor networks is to remain operational for long periods of time on a very limited power supply. While many power management protocols have been proposed, a solution does not yet exist that allows them to be seamlessly integrated into the existing systems. In this paper we study the architectural support required to resolve this issue. We propose a framework that separates sleep scheduling from the basic MAC layer functionality and provide a set of unified interfaces between them. This framework enables different sleep scheduling policies to be easily implemented on top of multiple MAC layers. Such a flexibility allows applications to choose the best sleep scheduling policy based on their own particular needs. We demonstrate the practicality of our approach by implementing this framework on top of both the mica2 and telosb radio stacks in TinyOS 2.0. Our micro-benchmark results show that at the cost of a slight increase in code size, our framework significantly eases the development of new radio power management protocols across multiple WSN platform

Spectrum-efficient Architecture for Cognitive Wireless Sensor Networks

Projecte realitzat en col.laboració amb el centre Université Libre de BruxellesHoy en día existe la creencia de que en unos pocos años las actuales Redes Inalámbricas de Sensores estarán presentes en muchas aplicaciones. Mientras estas sigan actuando en la banda sin licencia de ISM 2,4GHz, tendrán que coexistir con otras exitosas tecnologías como Wi-Fi o Bluetooth. En consecuencia, resulta obvio asegurar que la banda en cuestión estará superpoblada en un futuro próximo. Sin embargo y gracias a las nuevas técnicas de Radio Cognitiva, que permitirán la aplicación de un eficiente Acceso al Espectro Dinámico, se conseguirá una distribución racional, dentro del espectro disponible en ese momento y lugar, de las comunicaciones inalámbricas que se estén llevando a cabo. Esta actuación permitirá acceder a frecuencias menos pobladas para poder transmitir con menos interferencias e incluso con menos pérdidas de propagación. A lo largo de este trabajo se va a presentar una arquitectura eficiente, espectralmente hablando, para Redes Inalámbricas de Sensores y Cognitivas. Este esquema desarrolla un protocolo de recolección de datos, para una red con topología de árbol, totalmente escalable y con finalidades genéricas. A través de las pruebas realizadas, podemos afirmar que nuestro esquema, sin alterar el ciclo normal de recolección de datos, puede detectar la presencia de otras Redes Inalámbricas de Sensores y, consecuentemente, migrar la red a nueva frecuencia mientras que todas estas operaciones están ocultas al usuario final. También es eficiente a nivel de energía, ya que no se realizan comprobaciones redundantes de la presencia de otras redes. De esta manera, nuestra propuesta asegura un mejor comportamiento en caso de la existencia de una Red Inalámbrica de Sensores externa, sin realizar operaciones complicadas ni añadiendo más tráfico a la red

Performance of data aggregation for wireless sensor networks

This thesis focuses on three fundamental issues that concern data aggregation protocols for periodic data collection in sensor networks: which sensor nodes should report their data, when should they report it, and should they use unicast or broadcast based protocols for this purpose. The issue of when nodes should report their data is considered in the context of real-time monitoring applications. The first part of this thesis shows that asynchronous aggregation, in which the time of each node’s transmission is determined adaptively based on its local history of past packet receptions from its children, outperforms synchronous aggregation by providing lower delay for a given end-to-end loss rate. Second, new broadcast-based aggregation protocols that minimize the number of packet transmissions, relying on multipath delivery rather than automatic repeat request for reliability, are designed and evaluated. The performance of broadcast-based aggregation is compared to that of unicast-based aggregation, in the context of both real-time and delay-tolerant data collection. Finally, this thesis investigates the potential benefits of dynamically, rather than semi-statically, determining the set of nodes reporting their data, in the context of applications in which coverage of some monitored region is to be maintained. Unicast and broadcast-based coverage-preserving data aggregation protocols are designed and evaluated. The performance of the proposed protocols is compared to that of data collection protocols relying on node scheduling

JTP, an energy-aware transport protocol for mobile ad hoc networks (PhD thesis)

Wireless ad-hoc networks are based on a cooperative communication model, where all nodes not only generate traffic but also help to route traffic from other nodes to its final destination. In such an environment where there is no infrastructure support the lifetime of the network is tightly coupled with the lifetime of individual nodes. Most of the devices that form such networks are battery-operated, and thus it becomes important to conserve energy so as to maximize the lifetime of a node. In this thesis, we present JTP, a new energy-aware transport protocol, whose goal is to reduce power consumption without compromising delivery requirements of applications. JTP has been implemented within the JAVeLEN system. JAVeLEN [RKM+08], is a new system architecture for ad hoc networks that has been developed to elevate energy efficiency as a first-class optimization metric at all protocol layers, from physical to transport. Thus, energy gains obtained in one layer would not be offset by incompatibilities and/or inefficiencies in other layers. To meet its goal of energy efficiency, JTP (1) contains mechanisms to balance end-toend vs. local retransmissions; (2) minimizes acknowledgment traffic using receiver regulated rate-based flow control combined with selected acknowledgments and in-network caching of packets; and (3) aggressively seeks to avoid any congestion-based packet loss. Within this ultra low-power multi-hop wireless network system, simulations and experimental results demonstrate that our transport protocol meets its goal of preserving the energy efficiency of the underlying network. JTP has been implemented on the actual JAVeLEN nodes and its benefits have been demonstrated on a real system

ENERGY CONSERVATION FOR WIRELESS AD HOC ROUTING

Self-configuring wireless ad hoc networks have attracted considerable attention in the last few years due to their valuable civil and military applications. One aspect of such networks that has been studied insufficiently is the energy efficiency. Energy efficiency is crucial to prolong the network lifetime and thus make the network more survivable.Nodes in wireless ad hoc networks are most likely to be driven by battery and hence operate on an extremely frugal energy budget. Conventional ad hoc routing protocols are focused on handling the mobility instead of energy efficiency. Energy efficient routing strategies proposed in literature either do not take advantage of sleep modes to conserve energy more efficiently, or incur much overhead in terms of control message and computing complexity to schedule sleep modes and thus are not scalable.In this dissertation, a novel strategy is proposed to manage the sleep of the nodes in the network so that energy can be conserved and network connectivity can be kept. The novelty of the strategy is its extreme simplicity. The idea is derived from the results of the percolation theory, typically called gossiping. Gossiping is a convenient and effective approach and has been successfully applied to several areas of the networking. In the proposed work, we will developa sleep management protocol from gossiping for both static and mobile wireless ad hoc networks. Then the protocol will be extended to the asynchronous network, where nodes manage their own states independently. Analysis and simulations will be conducted to show thecorrectness, effectiveness and efficiency of the proposed work. The comparison between analytical and simulation results will justify them for each other. We will investigate the most important performance aspects concerning the proposed strategy, including the effect ofparameter tuning and the impacts of routing protocols. Furthermore, multiple extensions will be developed to improve the performance and make the proposed strategy apply to different network scenarios