Susan Rea

Multi-metric routing decisions for ad hoc networks using fuzzy logic

Routing is an essential function for traffic management in ad hoc networks. Table-based routing algorithms used in proactive protocols are computationally intensive and require periodic transmission of status information amongst all network nodes. Also, routing table volume swells with network size and can be large for dense networks. Therefore to cope with possibly rapidly changing topology reactive protocols such as dynamic source routing (DSR) generate routes for unknown destination paths on an as needs be basis. So as to avoid the continual demand for route discovery in DSR, network nodes record previously determined routes in either path or link caches. A route discovery attempt can possibly result in several paths being uncovered for a single destination. As nodes often have a finite capacity path cache, it may not be possible to store all paths. So as to influence productive caching decisions a fuzzy logic system is applied to the route discovery technique to curb non-optimal network floods. This action causes a cessation in the generation of low quality routes as only paths with good routing metrics are selected for the rebroadcast of route discovery packets. Consequently, route query packets arriving at the necessary destination node, or at some intermediate node with knowledge of the destination node, generate high quality route replies. This paper presents a fuzzy logic based decision algorithm that weighs individual links as a path to the necessary destination is being constructed if this link is deemed suitable by the fuzzy logic system it is added to the path and route construction continue. The fuzzy controller is used to instruct caching decisions and to optimise route selection as only good quality links are recorded in source destination paths.

InRout - A QoS aware route selection algorithm for industrial wireless sensor networks

Wireless sensor networks are a key enabling technology for industrial monitoring applications where the use of wireless infrastructure allows high adaptivity and low cost in terms of installation and retrofitting. To facilitate the move from the current wired designs to wireless designs, concerns regarding reliability must be satisfied. Current standardization efforts for industrial wireless systems lack specification on efficient routing protocols that mitigate reliability concerns. Consequently, this work presents the InRout route selection algorithm, where local information is shared among neighbouring nodes to enable efficient, distributed route selection while satisfying industrial application requirements and considering sensor node resource limitations. Route selection is described as a multi-armed bandit task and uses Q-learning techniques to obtain the best available solution with low overhead. A performance comparison with existing approaches demonstrates the benefits of the InRout algorithm, which satisfies typical quality of service requirements for industrial monitoring applications while considering sensor node resources. Simulation results show that InRout can provide gains ranging from 4% to 60% in the number of successfully delivered packets when compared to current approaches with much lower control overhead.

Experimental Evaluation of Beacon Scheduling Mechanisms for Multihop IEEE 802.15.4 Wireless Sensor Networks

Recently, several scheduling techniques to enable multihop communications in the beacon enabled mode of the IEEE 802.15.4 standard have been proposed. Using the beacon enabled mode allows node synchronization and hence energy savings which is an important concern in wireless sensor networks (WSNs). However, and to the best of our knowledge, current available scheduling techniques have not been formally compared. This makes it difficult to decide which technique gives a better performance with regard to different WSN scenarios or applications. In this paper, we compare the two most popular methods for beacon enabled multihop IEEE 802.15.4 WSNs for different scenarios and performance parameters. Based on our findings, we propose recommendations for the use of each scheduling technique.

Load balancing for QoS optimisation in wireless LANs utilising advanced cell breathing techniques

Wireless local area networks (WLANs) have become increasingly popular over the last number of years. During this time, user requirements have evolved, resulting in a more diverse mix of services being carried over the wireless medium. In particular, delay sensitive real-time applications such as streaming multimedia and voice over IP are growing in importance. The widely accepted IEEE 802.11b standard, however, was not designed with sufficient quality of service (QoS) constraints for such applications. This paper attempts to optimise the received quality in 802.11b WLAN by balancing the load between various access points while changing the coverage area of each access point, a technique commonly known as cell breathing.

Event Suppression for Safety Message Dissemination in VANETs

With recent advances in vehicular technology, a variety sensors, radars and onboard computing systems have enabled vehicles to become powerful information gathering and processing platforms. Sensors can continuously monitor and interpret the vehicles local environment and quickly detect dangerous situations. As vehicles in close proximity detect the same dangerous situation they will inevitably broadcast messages relating to the same event. As all these vehicles report on the same event broadcasting leads to dramatically excessive message redundancy. In the paper we present the Event Suppression for Safety Message Dissemination (ESSMD) scheme that reduces the number of broadcasting vehicles reporting on the same event. This scheme was compared with existing aggregation strategies for safety-related message dissemination. Experimental results using the OPNET simulator demonstrate that ESSMD significantly reduces redundant data transmissions and does not add any extra end-to-end delay compared with existing aggregation strategies. However, ESSMD had a decreasing probability of event reception due to an unreliable broadcasting protocol. The reception rate was improved by the introduction of a scheme called ESSMD+Rep that increases the reliability of the broadcasting protocol by repeating broadcasts at the source vehicles.

Multi-objective Cross-Layer Algorithm for Routing over Wireless Sensor Networks

With Wireless Sensor Networks popularity growth, numerous cross-layer routing protocols have been proposed. These proposals are mainly designed to address the limitations in energy resources of the sensor nodes. However, advances in technology have led to a wide variety of possible applications with many different requirements. The routing protocol should not only take into account the energy resources but it also should be able to adapt to different application requirements making different routing decisions. Here we present a flexible cross-layer algorithm based on a cost function to provide multi-objective adaptability to existing routing protocols that aims to balance the requirements of multiple applications and the resource constrained sensor network nodes. Computer simulations and real hardware experiments demonstrate that the cross layer algorithm applied over a collection protocol improves the performance for different application requirements and shows that energy resources are conserved through dynamic parameter tuning.

Design and deployment tool for in-building wireless sensor networks: A performance discussion

The design and deployment of a wireless sensor network (WSN) for building automation applications is a complex operation that requires expert knowledge and experience. This paper presents an evaluation of a WSN deployment support framework for in-building wireless infrastructures. A case study consisting of a sample network deployment for environmental monitoring is used to investigate the need for such support tools. The network infrastructure design suggested by the deployment support tool is compared against designs done using basic planning guidelines and a design based on an extensive site survey and experience. It will be shown how the deployment support tools provide a WSN with a reduced infrastructure cost and improved sensing packet delivery ratio when compared to the designs using traditional approaches.

Fuzzy logic optimisation of MAC parameters and sleeping duty-cycles in wireless sensor networks

Quality-of-Service, fairness, low power consumption, low latency and high throughput are all desirable attributes of medium access control (MAC) protocols. MAC protocols for sensor networks are designed with one principal attribute in mind - low power consumption. Minimizing power usage becomes the principal objective of MAC protocol design. This paper proposes FuzzyMAC, a CSMA/CA based MAC protocol that utilizes two separate fuzzy logic controllers to optimize both, MAC parameters and a sleeping schedule duty-cycle. A second fuzzy logic controller attempts to optimize the size of the contention window using three performance metrics as inputs. The primary goal of both fuzzy logic controllers is to ensure maximum power efficiency of the network, which is demonstrated by the results. However, some increased latency results from the adaptive sleeping clycles.

Reliable Broadcasting for Active Safety Applications in Vehicular Highway Networks

Vehicular communication is regarded as a major innovative feature for in-car technology. While improving road safety is unanimously considered the major driving factor for the deployment of Active Safety Intelligent Vehicle Safety Systems, the challenges relating to reliable multi-hop broadcasting are many in vehicular networking. In fact, safety applications must rely on very accurate and up to date information about the surrounding environment, which in turn requires the use of accurate positioning systems and smart communication protocols for exchanging information. Communications protocols for vehicular ad hoc networks (VANETs) must guarantee fast and reliable delivery of information to all vehicles in the neighbourhood, where the wireless communication medium is shared and highly unreliable with limited bandwidth. In this paper, we present a geo-broadcasting extension to the Slotted Restricted Mobility-Based (SRMB) broadcasting protocol and compare it with existing geobroadcasting protocols in highway environments.

Open Framework Middleware for intelligent WSN topology adaption in smart buildings

Modern smart buildings utilize sensor networks for facilities management applications such as energy monitoring. However as buildings become progressively more embedded with sensor networks, the challenge of managing and maintaining the sensor networks themselves becomes ever more significant. As a cost-sensitive activity, facilities management deployments are less likely to deploy node redundancy and specialized technical staff to maintain these networks. Hence there are strong requirements for the network to efficiently self-diagnose, self-heal and integrate with standard buildings management systems. This paper introduces a solution for WSN management in smart buildings that addresses these issues. It is based on the deployment of the Open Framework Middleware for sensor networks coupled with a structured knowledge and rule-based fault analysis engine to perform network event correlation and root cause analysis. The system also explicitly interfaces with a Building Management System (BMS) or the scheduling of network maintenance activities such as sensor battery replacement.