Overcoming Adversaries in Sensor Networks: A Survey of Theoretical Models and Algorithmic Approaches for Tolerating Malicious Interference <s> A. Communication and Medium Access Control <s> Wireless distributed microsensor systems will enable the reliable monitoring of a variety of environments for both civil and military applications. In this paper, we look at communication protocols, which can have significant impact on the overall energy dissipation of these networks. Based on our findings that the conventional protocols of direct transmission, minimum-transmission-energy, multi-hop routing, and static clustering may not be optimal for sensor networks, we propose LEACH (Low-Energy Adaptive Clustering Hierarchy), a clustering-based protocol that utilizes randomized rotation of local cluster based station (cluster-heads) to evenly distribute the energy load among the sensors in the network. LEACH uses localized coordination to enable scalability and robustness for dynamic networks, and incorporates data fusion into the routing protocol to reduce the amount of information that must be transmitted to the base station. Simulations show the LEACH can achieve as much as a factor of 8 reduction in energy dissipation compared with conventional outing protocols. In addition, LEACH is able to distribute energy dissipation evenly throughout the sensors, doubling the useful system lifetime for the networks we simulated. <s> BIB001 </s> Overcoming Adversaries in Sensor Networks: A Survey of Theoretical Models and Algorithmic Approaches for Tolerating Malicious Interference <s> A. Communication and Medium Access Control <s> This paper proposes S-MAC, a medium-access control (MAC) protocol designed for wireless sensor networks. Wireless sensor networks use battery-operated computing and sensing devices. A network of these devices will collaborate for a common application such as environmental monitoring. We expect sensor networks to be deployed in an ad hoc fashion, with individual nodes remaining largely inactive for long periods of time, but then becoming suddenly active when something is detected. These characteristics of sensor networks and applications motivate a MAC that is different from traditional wireless MACs such as IEEE 802.11 in almost every way: energy conservation and self-configuration are primary goals, while per-node fairness and latency are less important. S-MAC uses three novel techniques to reduce energy consumption and support self-configuration. To reduce energy consumption in listening to an idle channel, nodes periodically sleep. Neighboring nodes form virtual clusters to auto-synchronize on sleep schedules. Inspired by PAMAS, S-MAC also sets the radio to sleep during transmissions of other nodes. Unlike PAMAS, it only uses in-channel signaling. Finally, S-MAC applies message passing to reduce contention latency for sensor-network applications that require store-and-forward processing as data move through the network. We evaluate our implementation of S-MAC over a sample sensor node, the Mote, developed at University of California, Berkeley. The experiment results show that, on a source node, an 802.11-like MAC consumes 2-6 times more energy than S-MAC for traffic load with messages sent every 1-10 s. <s> BIB002 </s> Overcoming Adversaries in Sensor Networks: A Survey of Theoretical Models and Algorithmic Approaches for Tolerating Malicious Interference <s> A. Communication and Medium Access Control <s> Studies of ad hoc wireless networks are a relatively new field gaining more popularity for various new applications. In these networks, the Medium Access Control (MAC) protocols are responsible for coordinating the access from active nodes. These protocols are of significant importance since the wireless communication channel is inherently prone to errors and unique problems such as the hidden-terminal problem, the exposed-terminal problem, and signal fading effects. Although a lot of research has been conducted on MAC protocols, the various issues involved have mostly been presented in isolation of each other. We therefore make an attempt to present a comprehensive survey of major schemes, integrating various related issues and challenges with a view to providing a big-picture outlook to this vast area. We present a classification of MAC protocols and their brief description, based on their operating principles and underlying features. In conclusion, we present a brief summary of key ideas and a general direction for future work. <s> BIB003 </s> Overcoming Adversaries in Sensor Networks: A Survey of Theoretical Models and Algorithmic Approaches for Tolerating Malicious Interference <s> A. Communication and Medium Access Control <s> In this paper we investigate the performance of mica2 and mica2dot Berkeley motes by means of an extensive experimental analysis. This study is aimed at analyzing the main elements that characterize the performance of a sensor network, e.g., power consumption in different operating conditions, impact of weather conditions, interference between neighboring nodes, etc. Even if the analysis is related to a specific technology it provides some general useful information. Specifically, we found that the transmission range of mote sensor nodes decreases significantly in the presence of fog or rain. We also investigated the interference between neighboring nodes and, based on the experimental results, we propose a channel model for mote sensor nodes. This model is very similar to the channel model of IEEE 802.11 networks. <s> BIB004 </s> Overcoming Adversaries in Sensor Networks: A Survey of Theoretical Models and Algorithmic Approaches for Tolerating Malicious Interference <s> A. Communication and Medium Access Control <s> We present Telos, an ultra low power wireless sensor module ("mote") for research and experimentation. Telos is the latest in a line of motes developed by UC Berkeley to enable wireless sensor network (WSN) research. It is a new mote design built from scratch based on experiences with previous mote generations. Telos' new design consists of three major goals to enable experimentation: minimal power consumption, easy to use, and increased software and hardware robustness. We discuss how hardware components are selected and integrated in order to achieve these goals. Using a Texas Instruments MSP430 microcontroller, Chipcon IEEE 802.15.4-compliant radio, and USB, Telos' power profile is almost one-tenth the consumption of previous mote platforms while providing greater performance and throughput. It eliminates programming and support boards, while enabling experimentation with WSNs in both lab, testbed, and deployment settings. <s> BIB005 </s> Overcoming Adversaries in Sensor Networks: A Survey of Theoretical Models and Algorithmic Approaches for Tolerating Malicious Interference <s> A. Communication and Medium Access Control <s> Recently, several MAC protocols, such as S-MAC and T-MAC, have exploited scheduled sleep/wakeup cycles to conserve energy in sensor networks. Until now, most protocols have assumed all nodes in the network were configured to follow the same schedule, or have assumed border nodes would follow multiple schedules, but those cases have not been evaluated. The paper develops two new algorithms to control and exploit the presence of multiple schedules to reduce energy consumption and latency. The first one is the global schedule algorithm (GSA). Through experiments, we demonstrate that, because of radio propagation vagaries, large sensor networks have very ragged, overlapping borders where many nodes listen to two or more schedules. GSA is a fully distributed algorithm that allows a large network to converge on a single global schedule to conserve energy. Secondly, we demonstrate that strict schedules incur a latency penalty in a multi-hop network when packets must wait for the next schedule for transmission. To reduce latency in multi-hop paths, we develop the fast path algorithm (FPA). FPA provides fast data forwarding paths by adding additional wake-up periods on the nodes along paths from sources to sinks. We evaluate both algorithms through experiments on Berkeley motes and demonstrate that the protocols accomplish their goals of reducing energy consumption and latency in large sensor networks. <s> BIB006 </s> Overcoming Adversaries in Sensor Networks: A Survey of Theoretical Models and Algorithmic Approaches for Tolerating Malicious Interference <s> A. Communication and Medium Access Control <s> For wireless sensor networks to reach their full potential they need to be able to interoperate with external IPv6 based networks. This can be achieved using the light-weight 6LoWPAN (IPv6 over Low power Wireless Personal Area Networks) communications protocol that has been designed to operate within the limited processing, memory and energy power constraints associated with Wireless Sensor Networks. In this paper the TinyOS Berkeley 6LoWPAN implementation is configured, deployed and tested on both the MICAz and the TelosB sensor architectures. A performance evaluation of point-to-point communications from a computer to a sensor mote is then carried out over an IPv6/6LoWPAN network. <s> BIB007
Devices are assumed to possess a transceiver that operates on a single-channel or multiple-channels; however, typically, transmitting and receiving are assumed not to occur simultaneously. This is in line with current technology such as the MICA2, MICAz, MICA2dot BIB004 and Telos motes BIB005 , BIB007 . The models in this survey assume a time division multiple access (TDMA)-like medium access control (MAC) protocol. For example, the well-known LEACH BIB001 protocol for sensor networks is TDMA-based. Of course, the literature on MAC protocols is vast and we refer the reader to the survey by Kumar et al. BIB003 for an overview of the area. The discretization of time appears to be a common aspect of the theoretical models present in the literature since it facilitates an analysis of various performance metrics. Therefore, such discretization is a common feature of the models we examine in this survey. In our discussion of multi-hop networks, the notion of a global broadcast schedule appears in several works. It seems likely that this is not essential so long as we are willing to suffer an increase in latency and energy expenditure assuming nodes can hold multiple schedules that are locally synchronized; such is the case for S-MAC BIB002 . However, the exact implications of such an approach is an open question. In any event, global scheduling (and the resulting advantages in terms of energy efficiency) has been clearly demonstrated by experimental work in BIB006 .