Modelling Clock Synchronization in the Chess gMAC WSN Protocol

We present a detailled timed automata model of the clock synchronization algorithm that is currently being used in a wireless sensor network (WSN) that has been developed by the Dutch company Chess. Using the Uppaal model checker, we establish that in certain cases a static, fully synchronized network may eventually become unsynchronized if the current algorithm is used, even in a setting with infinitesimal clock drifts

Evaluation of WiseMAC and extensions onwireless sensornodes

In the past five years, many energy-efficient medium access protocols for all kinds of wireless networks (WSNs) have been proposed. Some recently developed protocols focus on sensor networks with low traffic requirements are based on so-called preamble sampling or low-power listening. The WiseMAC protocol is one of the first of this kind and still is one of the most energy-efficient MAC protocols for WSNs with low or varying traffic requirements. However, the high energy-efficiency of WiseMAC has shown to come at the cost of a very limited maximum throughput. In this paper, we evaluate the properties and characteristics of a WiseMAC implementation in simulation and on real sensor hardware. We investigate on the energy-consumption of the prototype using state-of-the-art evaluation methodologies. We further propose and examine an enhancement of the protocol designed to improve the traffic-adaptivity of WiseMAC. By conducting both simulation and real-world experiments, we show that the WiseMAC extension achieves a higher maximum throughput at a slightly increased energy cost both in simulation and real-world experiment

WiseMAC protocol for wireless sensor network-an energy efficient protocol

Wireless Sensor Networks are very useful in case of distance or unreachable areas. WSN are having large number of nodes (sensors) which are randomly distributed. These sensors are primarily used to process data and connected through wireless channel. The processing, transmission and reception and sensing the channel need power. This power is given to nodes by their batteries. So the problem in front of us is to reduce power consumption by these nodes. Some areas are very far and some areas are unreachable like valley or hill areas. Thus it is not possible in some cases to replace or change the battery. Our focus is to make a protocol which makes these nodes work with lesser battery power. There are so many MAC layer protocols which work for this purpose but they too are not energy efficient. These protocols are based on CSMA. Here in this report we have proposed WiseMAC protocol which is also based on CSMA but with preamble sampling. This protocol shows very good reduction in power consumption. For this we used some more schemes with the existing WiseMAC protocol, these schemes are more bit and extended more bit. Our WiseMAC protocol is an asynchronous protocol and works very well in case of adaptive traffic conditions. To make WiseMAC energy efficient we are here focusing to reduce preamble sampling duration and this done with reducing duty cycle and contention window of our proposed protocol. As we have implemented Adaptive WiseMAC protocol so we are focusing that this will help in body are network (BAN) for medical purposes. Although a lot of works have been done but still more work has to be don

Energy-efficient MAC protocol for wireless sensor networks

A Wireless Sensor Network (WSN) is a collection of tiny devices called sensor nodes which are deployed in an area to be monitored. Each node has one or more sensors with which they can measure the characteristics of their surroundings. In a typical WSN, the data gathered by each node is sent wirelessly through the network from one node to the next towards a central base station. Each node typically has a very limited energy supply. Therefore, in order for WSNs to have acceptable lifetimes, energy efficiency is a design goal that is of utmost importance and must be kept in mind at all levels of a WSN system. The main consumer of energy on a node is the wireless transceiver and therefore, the communications that occur between nodes should be carefully controlled so as not to waste energy. The Medium Access Control (MAC) protocol is directly in charge of managing the transceiver of a node. It determines when the transceiver is on/off and synchronizes the data exchanges among neighbouring nodes so as to prevent collisions etc., enabling useful communications to occur. The MAC protocol thus has a big impact on the overall energy efficiency of a node. Many WSN MAC protocols have been proposed in the literature but it was found that most were not optimized for the group of WSNs displaying very low volumes of traffic in the network. In low traffic WSNs, a major problem faced in the communications process is clock drift, which causes nodes to become unsynchronized. The MAC protocol must overcome this and other problems while expending as little energy as possible. Many useful WSN applications show low traffic characteristics and thus a new MAC protocol was developed which is aimed at this category of WSNs. The new protocol, Dynamic Preamble Sampling MAC (DPS-MAC) builds on the family of preamble sampling protocols which were found to be most suitable for low traffic WSNs. In contrast to the most energy efficient existing preamble sampling protocols, DPS-MAC does not cater for the worst case clock drift that can occur between two nodes. Rather, it dynamically learns the actual clock drift experienced between any two nodes and then adjusts its operation accordingly. By simulation it was shown that DPS-MAC requires less protocol overhead during the communication process and thus performs more energy efficiently than its predecessors under various network operating conditions. Furthermore, DPS-MAC is less prone to become overloaded or unstable in conditions of high traffic load and high contention levels respectively. These improvements cause the use of DPS-MAC to lead to longer node and network lifetimes, thus making low traffic WSNs more feasible.Dissertation (MEng)--University of Pretoria, 2008.Electrical, Electronic and Computer EngineeringMEngUnrestricte

Real-time SIL Emulation Architecture for Cooperative Automated Vehicles

This thesis presents a robust, flexible and real-time architecture for Software-in-the-Loop (SIL) testing of connected vehicle safety applications. Emerging connected and automated vehicles (CAV) use sensing, communication and computing technologies in the design of a host of new safety applications. Testing and verification of these applications is a major concern for the automotive industry. The CAV safety applications work by sharing their state and movement information over wireless communication links. Vehicular communication has fueled the development of various Cooperative Vehicle Safety (CVS) applications. Development of safety applications for CAV requires testing in many different scenarios. However, the recreation of test scenarios for evaluating safety applications is a very challenging task. This is mainly due to the randomness in communication, difficulty in recreating vehicle movements precisely, and safety concerns for certain scenarios. We propose to develop a standalone Remote Vehicle Emulator (RVE) that can reproduce V2V messages of remote vehicles from simulations or from previous tests, while also emulating the over the air behavior of multiple communicating nodes. This is expected to significantly accelerate the development cycle. RVE is a unique and easily configurable emulation cum simulation setup to allow Software in the Loop (SIL) testing of connected vehicle applications in a realistic and safe manner. It will help in tailoring numerous test scenarios, expediting algorithm development and validation as well as increase the probability of finding failure modes. This, in turn, will help improve the quality of safety applications while saving testing time and reducing cost. The RVE architecture consists of two modules, the Mobility Generator, and the Communication emulator. Both of these modules consist of a sequence of events that are handled based on the type of testing to be carried out. The communication emulator simulates the behavior of MAC layer while also considering the channel model to increase the probability of successful transmission. It then produces over the air messages that resemble the output of multiple nodes transmitting, including corrupted messages due to collisions. The algorithm that goes inside the emulator has been optimized so as to minimize the communication latency and make this a realistic and real-time safety testing tool. Finally, we provide a multi-metric experimental evaluation wherein we verified the simulation results with an identically configured ns3 simulator. With the aim to improve the quality of testing of CVS applications, this unique architecture would serve as a fundamental design for the future of CVS application testing

Low-power epidemic communication in wireless ad hoc networks

Steen, M.R. van [Promotor]Voulgaris, S. [Copromotor

Energy efficient medium access control for wireless sensor networks

A wireless sensor network designates a system composed of numerous sensor nodes distributed over an area in order to collect information. The sensor nodes communicate wirelessly with each other in order to self-organize into a multi-hop network, collaborate in the sensing activity and forward the acquired information towards one or more users of the information. Applications of sensor networks are numerous, ranging from environmental monitoring, home and building automation to industrial control. Since sensor nodes are expected to be deployed in large numbers, they must be inexpensive. Communication between sensor nodes should be wireless in order to minimize the deployment cost. The lifetime of sensor nodes must be long for minimal maintenance cost. The most important consequence of the low cost and long lifetime requirements is the need for low power consumption. With today's technology, wireless communication hardware consumes so much power that it is not acceptable to keep the wireless communication interface constantly in operation. As a result, it is required to use a communication protocol with which sensor nodes are able to communicate keeping the communication interface turned-off most of the time. The subject of this dissertation is the design of medium access control protocols permitting to reach a very low power consumption when communicating at a low average throughput in multi-hop wireless sensor networks. In a first part, the performance of a scheduled protocol (time division multiple access, TDMA) is compared to the one of a contention protocol (non-persistent carrier sensing multiple access with preamble sampling, NP-CSMA-PS). The preamble sampling technique is a scheme that avoids constant listening to an idle medium. This thesis presents a low power contention protocol obtained through the combination of preamble sampling with non-persistent carrier sensing multiple access. The analysis of the strengths and weaknesses of TDMA and NP-CSMA-PS led us to propose a solution that exploits TDMA for the transport of frequent periodic data traffic and NP-CSMA-PS for the transport of sporadic signalling traffic required to setup the TDMA schedule. The second part of this thesis describes the WiseMAC protocol. This protocol is a further enhancement of CSMA with preamble sampling that proved to provide both a low power consumption in low traffic conditions and a high energy efficiency in high traffic conditions. It is shown that this protocol can provide either a power consumption or a latency several times lower that what is provided by previously proposed protocols. The WiseMAC protocol was initially designed for multi-hop wireless sensor networks. A comparison with power saving protocols designed specifically for the downlink of infrastructure wireless networks shows that it is also of interest in such cases. An implementation of the WiseMAC protocol has permitted to validate experimentally the proposed concepts and the presented analysis

Cascading Tournament Algorithm: Low Power, High Capacity Medium Sharing for Wireless Sensor Networks

Existing Medium Access Control protocols for Wireless Sensor Networks reduce the radio activity to improve network lifetime, at the expense of a reduced network capacity. Those protocols are ill-suited for energy constrained sensor networks that must support spatially and temporally heterogeneous traffic loads. This paper proposes a novel multi-ressource allocation algorithm and describes its implementation as a medium access control protocol for Wireless Sensor Networks. The algorithm, named Cascading Tournament (CT), is a localized, dynamic, joint contention/allocation algorithm. It relies on cascading iterations of tournaments to allocate a multiplicity of ressources to a multiplicity of winners. CT-MAC is an implementation of CT as a medium access protocol. By allocating multiple logicals channels allocation at each competition, CT-MAC improves the network capacity at a given duty-cycle or decreases the energy expenditure of the MAC layer at a given network capacity. Extensive simulations highlight the benefits of CT-MAC in both single-hop and multiple-hop scenarios through the computation of relevant performance metrics: power consumption, network capacity, delay and retransmissions. CT-MAC offers an unprecedented trade-off between network capacity, energy efficiency and delay and stands out as a solid candidate for energy constrained sensor networks that must support heterogeneous traffic loads. Our simulations show that CT-MAC significantly outperforms the state-of-the-art SCP-MAC protocol.Les protocoles d'accès au medium radio existants pour réseaux de capteurs sans-fil réduisent l'activité de la radio afin d'améliorer la durée de vie du réseau, et ce, au prix d'une diminution de la capacité du réseau. Ces protocoles sont peu adaptés pour les réseaux de capteurs contraints en énergie qui doivent supporter des trafics spatialement et temporellement hétérogènes. Ce rapport propose un algorithme d'allocation multi-ressources et décrit son implémentation sous forme de protocole de contrôle d'accès (MAC) au canal radio pour réseaux de capteurs. L'algorithme, appelé Cascading Tour- nament (CT), est un algorithme combiné de gestion de la contention/allocation localisé, dynamique et localisé. Il se repose sur des itérations de tournois en cascade pour allouer une pluralité de ressources à une pluralité de vainqueurs. CT-MAC est une implémentation de CT en tant que protocole MAC. En al- louant plusieurs canaux logiques à chaque compétition, CT-MAC améliore la capacité du réseau pour un cycle d'endormissement donné ou diminue la con- sommation énergétique de la couche MAC pour une capacité du réseau donnée. Une étude complète par simulation montre l'intérêt de CT-MAC dans des scé- narios de voisinage unique et multi-sauts. Ces simulations ont permis le calcul de métriques de performances pertinentes: consommation énergétique, capacité du réseau, délai et retransmissions. CT-MAC offre un compromis entre capacité du réseau et efficacité énergétique qui n'a pas de précédent. Il se présente donc comme un candidat sérieux pour les réseaux de capteurs contraints en énergie qui doivent supporter des trafics hétérogènes. Nos simulations ont montré que CT-MAC surpasse le protocole de l'état de l'art SCP-MAC