Reliable routing for low-power smart space communications

Smart Space (SS) communications has rapidly emerged as an exciting new paradigm that includes ubiquitous, grid, and pervasive computing to provide intelligence, insight, and vision for the emerging world of intelligent environments, products, services and human interaction. Dependable networking of a smart space environment can be ensured through reliable routing, efficient selection of error free links, rapid recovery from broken links and the avoidance of congested gateways. Since link failure and packet loss are inevitable in smart space wireless sensor networks, we have developed an efficient scheme to achieve a reliable data collection for smart spaces composed of low capacity wireless sensor nodes. Wireless Sensor Networks (WSNs) must tolerate a certain lack of reliability without a significant effect on packet delivery performance, data aggregation accuracy or energy consumption. In this paper we present an effective hybrid scheme that adaptively reduces control traffic with a metric that measures the reception success ratio of representative data packets. Based on this approach, our proposed routing scheme can achieve reduced energy consumption while ensuring minimal packet loss in environments featuring high link failure rates. The performance of our proposed routing scheme is experimentally investigated using both simulations and a test bed of TelosB motes. It is shown to be more robust and energy efficient than the network layer provided by TinyOS2.x. Our results show that the scheme is able to maintain better than 95% connectivity in an interference-prone medium while achieving a 35% energy saving

Traffic eavesdropping based scheme to deliver time-sensitive data in sensor networks

Due to the broadcast nature of wireless channels, neighbouring sensor nodes may overhear packets transmissions from each other even if they are not the intended recipients of these transmissions. This redundant packet reception leads to unnecessary expenditure of battery energy of the recipients. Particularly in highly dense sensor networks, overhearing or eavesdropping overheads can constitute a significant fraction of the total energy consumption. Since overhearing of wireless traffic is unavoidable and sometimes essential, a new distributed energy efficient scheme is proposed in this paper. This new scheme exploits the inevitable overhearing effect as an effective approach in order to collect the required information to perform energy efficient delivery for data aggregation. Based on this approach, the proposed scheme achieves moderate energy consumption and high packet delivery rate notwithstanding the occurrence of high link failure rates. The performance of the proposed scheme is experimentally investigated a testbed of TelosB motes in addition to ns-2 simulations to validate the performed experiments on large-scale network

Reliable routing scheme for indoor sensor networks

Indoor Wireless sensor networks require a highly dynamic, adaptive routing scheme to deal with the high rate of topology changes due to fading of indoor wireless channels. Besides that, energy consumption rate needs to be consistently distributed among sensor nodes and efficient utilization of battery power is essential. If only the link reliability metric is considered in the routing scheme, it may create long hops routes, and the high quality paths will be frequently used. This leads to shorter lifetime of such paths; thereby the entire network's lifetime will be significantly minimized. This paper briefly presents a reliable load-balanced routing (RLBR) scheme for indoor ad hoc wireless sensor networks, which integrates routing information from different layers. The proposed scheme aims to redistribute the relaying workload and the energy usage among relay sensor nodes to achieve balanced energy dissipation; thereby maximizing the functional network lifetime. RLBR scheme was tested and benchmarked against the TinyOS-2.x implementation of MintRoute on an indoor testbed comprising 20 Mica2 motes and low power listening (LPL) link layer provided by CC1000 radio. RLBR scheme consumes less energy for communications while reducing topology repair latency and achieves better connectivity and communication reliability in terms of end-to-end packets delivery performance

Reliable load-balancing routing for resource-constrained wireless sensor networks

Wireless sensor networks (WSNs) are energy and resource constrained. Energy limitations make it advantageous to balance radio transmissions across multiple sensor nodes. Thus, load balanced routing is highly desirable and has motivated a significant volume of research. Multihop sensor network architecture can also provide greater coverage, but requires a highly reliable and adaptive routing scheme to accommodate frequent topology changes. Current reliability-oriented protocols degrade energy efficiency and increase network latency. This thesis develops and evaluates a novel solution to provide energy-efficient routing while enhancing packet delivery reliability. This solution, a reliable load-balancing routing (RLBR), makes four contributions in the area of reliability, resiliency and load balancing in support of the primary objective of network lifetime maximisation. The results are captured using real world testbeds as well as simulations. The first contribution uses sensor node emulation, at the instruction cycle level, to characterise the additional processing and computation overhead required by the routing scheme. The second contribution is based on real world testbeds which comprises two different TinyOS-enabled senor platforms under different scenarios. The third contribution extends and evaluates RLBR using large-scale simulations. It is shown that RLBR consumes less energy while reducing topology repair latency and supports various aggregation weights by redistributing packet relaying loads. It also shows a balanced energy usage and a significant lifetime gain. Finally, the forth contribution is a novel variable transmission power control scheme which is created based on the experience gained from prior practical and simulated studies. This power control scheme operates at the data link layer to dynamically reduce unnecessarily high transmission power while maintaining acceptable link reliability

Reliable data delivery in low energy ad hoc sensor networks

Reliable delivery of data is a classical design goal for reliability-oriented collection routing protocols for ad hoc wireless sensor networks (WSNs). Guaranteed packet delivery performance can be ensured by careful selection of error free links, quick recovery from packet losses, and avoidance of overloaded relay sensor nodes. Due to limited resources of individual senor nodes, there is usually a trade-off between energy spending for packets transmissions and the appropriate level of reliability. Since link failures and packet losses are unavoidable, sensor networks may tolerate a certain level of reliability without significantly affecting packets delivery performance and data aggregation accuracy in favor of efficient energy consumption. However a certain degree of reliability is needed, especially when hop count increases between source sensor nodes and the base station as a single lost packet may result in loss of a large amount of aggregated data along longer hops. An effective solution is to jointly make a trade-off between energy, reliability, cost, and agility while improving packet delivery, maintaining low packet error ratio, minimizing unnecessary packets transmissions, and adaptively reducing control traffic in favor of high success reception ratios of representative data packets. Based on this approach, the proposed routing protocol can achieve moderate energy consumption and high packet delivery ratio even with high link failure rates. The proposed routing protocol was experimentally investigated on a testbed of Crossbow's TelosB motes and proven to be more robust and energy efficient than the current implementation of TinyOS2.x MultihopLQI

Real-Time Cross-Layer Routing Protocol for Ad Hoc Wireless Sensor Networks

Reliable and energy efficient routing is a critical issue in Wireless Sensor Networks (WSNs) deployments. Many approaches have been proposed for WSN routing, but sensor field implementations, compared to computer simulations and fully-controlled testbeds, tend to be lacking in the literature and not fully documented. Typically, WSNs provide the ability to gather information cheaply, accurately and reliably over both small and vast physical regions. Unlike other large data network forms, where the ultimate input/output interface is a human being, WSNs are about collecting data from unattended physical environments. Although WSNs are being studied on a global scale, the major current research is still focusing on simulations experiments. In particular for sensor networks, which have to deal with very stringent resource limitations and that are exposed to severe physical conditions, real experiments with real applications are essential. In addition, the effectiveness of simulation studies is severely limited in terms of the difficulty in modeling the complexities of the radio environment, power consumption on sensor devices, and the interactions between the physical, network and application layers. The routing problem in ad hoc WSNs is nontrivial issue because of sensor node failures due to restricted recourses. Thus, the routing protocols of WSNs encounter two conflicting issue: on the one hand, in order to optimise routes, frequent topology updates are required, while on the other hand, frequent topology updates result in imbalanced energy dissipation and higher message overhead. In the literature, such as in (Rahul et al., 2002), (Woo et al., 2003), (TinyOS, 2004), (Gnawali et al., 2009) and (Burri et al., 2007) several authors have presented routing algorithms for WSNs that consider purely one or two metrics at most in attempting to optimise routes while attempting to keep small message overhead and balanced energy dissipation. Recent studies on energy efficient routing in multihop WSNs have shown a great reliance on radio link quality in the path selection process. If sensor nodes along the routing path and closer to the base station advertise a high quality link to forwarding upstream packets, these sensor nodes will experience a faster depletion rate in their residual energy. This results in a topological routing hole or network partitioning as stated and resolved in and (Daabaj 2010). This chapter presents an empirical study on how to improve energy efficiency for reliable multihop communication by developing a real-time cross-layer lifetime-oriented routing protocol and integrating useful routing information from different layers to examine their joint benefit on the lifetime of individual sensor nodes and the entire sensor network. The proposed approach aims to balance the workload and energy usage among relay nodes to achieve balanced energy dissipation, thereby maximizing the functional network lifetime. The obtained experimental results are presented from prototype real-network experiments based on Crossbow’s sensor motes (Crossbow, 2010), i.e., Mica2 low-power wireless sensor platforms (Crossbow, 2010). The distributed real-time routing protocol which is proposed In this chapter aims to face the dynamics of the real world sensor networks and also to discover multiple paths between the base station and source sensor nodes. The proposed routing protocol is compared experimentally with a reliability-oriented collection-tree protocol, i.e., the TinyOS MintRoute protocol (Woo et al., 2003). The experimental results show that our proposed protocol has a higher node energy efficiency, lower control overhead, and fair average delay

Politics and aspects of the development of Libya's air transport systems : A geographical analysis.

The aim of this thesis is to analyse the developments of Libya's air transport systems and infrastructures by analysing the evolution of these spatial organisations. Certain underlying factors are examined in order to explain these developments including the political element influencing the changing flows in, and structures of, the networks. The Study emphasises the need to examine similar systems in other developing countries in the light of internal political forces, and the impact of the policies of the major suppliers of air transport technology. The Preface defines the subject matter and methodology. The Introduction deals with the topic in order to introduce the ideas presented in the subsequent chapters of this thesis. The remainder of this thesis is divided into six chapters so that each covers a distinctive aspect of development. Chapter 1 investigates air transport in Libya in the pre-independence period before 1951, concentrating on the immediate pre-Independence years. Chapter 2 examines the impact of oil as an indigenous factor enabling the development of the Libyan air transport systems and infrastructure. The macro planning processes in Libyan air transport are considered in Chapter 3. Chapter 4 places the contemporary developments in Libya's international and domestic air networks in their wider geographical con-text with special reference to the four North African national airlines. Chapter 5 analyses the geographical and political aspects of the organisation of the Libyan air transport systems with emphasis on the predictions for changes in their organisation as a consequence of the removal of the administrative centre of the country from the historic location of Tripoli. This chapter also considers the revival of the strategic significance of the Libyan airport system. Chapter 6 considers the aircraft fleet aspect of Libyan air transport and throws light on the ability of the US Government to single handedly prevent its updating and to obstruct efforts towards an efficient system

Integrating wireless Sensor Network with Networked Control Systems

The integration of Wireless Sensor Networks (WSNs) into industrial networked monitoring and control systems has become an essential factor to effectively regulate and manage industrial automation operations. The automation of monitoring and control systems is an important function for many utility companies such as oil/gas and electricity companies in order to reduce operating cost and to increase efficiency. There are many issues that have to be dealt with concerning the integration of WSNs into such systems and these issues have to be addressed in an application-specific manner. One of the most widely used control systems in industrial control automation is the Supervisory Control And Data Acquisition (SCADA) systems, and with the aim of improving productivity of monitored sites (e.g., oil/gas well and pipelines) at minimal costs, it is very significant to enable the interoperability of SCADA systems with new technologies such as WSNs and extensibility of future SCADA systems for new applications. Furthermore, a new approach of in-network processing system is essential to successfully monitor, detect, identify, and localize anomalies such as blockage and leakage. This new approach should consider the benefits of low cost, flexible deployment, continuous monitoring, and accurate problem detection, identification, and localization quickly, reliably, and accurately, thereby improving the current SCADA system

Reliable load-balancing routing algorithm for wireless sensor networks

The most critical routing-related issue of wireless sensor network (WSNs) is the quality of the underlying links. While most routing protocols are formulated in a graphtheoretical manner, it is often by no means clear which sensor nodes are connected by a wireless link. Links fluctuate in reliability and can have relatively high packet error rates. Using flooding-based protocols over such links can result in rather convoluted routing tables where nodes are considered to be neighbors only because a flooding packet happened to go through despite actually poor link quality. To overcome these problems, the proposed routing scheme advocate a careful selection of actual parents for a routing tree toward the base station, using information that the link layer can provide. In addition, the determined routes evidently influence the lifetime of the network. Hence, the proposed routing scheme goes a step further in that it attempts to provide guarantee on the lifetime of the network. The initial experimental results, on Crossbow’s Mica2 sensor nodes, show that the proposed routing scheme achieves an overall average of over 30% energy savings over the standard network layer provided by TinyOS, i.e., MintRoute and achieves greater than 60% connectivity to neighboring nodes and communication reliability. Particularly, it shows a higher success rate of packet delivery and moderate energy consumption

LBR: Load balancing routing algorithm for wireless sensor networks

Homogeneous wireless sensor networks (WSNs) are organized using identical sensor nodes, but the nature of WSNs operations results in an imbalanced workload on gateway sensor nodes which may lead to a hot-spot or routing hole problem. The routing hole problem can be considered as a natural result of the tree-based routing schemes that are widely used in WSNs, where all nodes construct a multi-hop routing tree to a centralized root, e.g., a gateway or base station. For example, sensor nodes on the routing path and closer to the base station deplete their own energy faster than other nodes, or sensor nodes with the best link state to the base station are overloaded with traffic from the rest of the network and experience a faster energy depletion rate than their peers. Routing protocols for WSNs are reliability-oriented and their use of reliability metric to avoid unreliable links makes the routing scheme worse. However, none of these reliability oriented routing protocols explicitly uses load balancing in their routing schemes. Since improving network lifetime is a fundamental challenge of WSNs, we present, in this chapter, a novel, energy-wise, load balancing routing (LBR) algorithm that addresses load balancing in an energy efficient manner by maintaining a reliable set of parent nodes. This allows sensor nodes to quickly find a new parent upon parent loss due to the existing of node failure or energy hole. The proposed routing algorithm is tested using simulations and the results demonstrate that it outperforms the MultiHopLQI reliability based routing algorithm