Distributed Optimal Rate-Reliability-Lifetime Tradeoff in Wireless Sensor Networks

The transmission rate, delivery reliability and network lifetime are three fundamental but conflicting design objectives in energy-constrained wireless sensor networks. In this paper, we address the optimal rate-reliability-lifetime tradeoff with link capacity constraint, reliability constraint and energy constraint. By introducing the weight parameters, we combine the objectives at rate, reliability, and lifetime into a single objective to characterize the tradeoff among them. However, the optimization formulation of the rate-reliability-reliability tradeoff is neither separable nor convex. Through a series of transformations, a separable and convex problem is derived, and an efficient distributed Subgradient Dual Decomposition algorithm (SDD) is proposed. Numerical examples confirm its convergence. Also, numerical examples investigate the impact of weight parameters on the rate utility, reliability utility and network lifetime, which provide a guidance to properly set the value of weight parameters for a desired performance of WSNs according to the realistic application's requirements.Comment: 27 pages, 10 figure

National economic and environmental development study: the case of Pakistan

Pakistan is a developing country bracing for significant economic growth and development in the future. In this regards, the country is poised to shift towards an increased reliance upon its indigenous coal reserves to fuel its development in the 2010-2050 time frame. Although this will significantly raise its projected greenhouse gas emissions, the present study has identified numerous measures which can be taken to shift this future development pathway on to a lower carbon and more climate friendly trajectory. The country, however, requires this shift to be supported through the access and transfer of appropriate technologies and finance. The ensuing “additional” financial needs for mitigation for a cleaner development future range from between U$8 billion and U$ 17 billion. These have been identified in this report along with a potential of 18% and 40% reduction of emissions between below “Business As Usual” scenario which is possible with a shift towards cleaner technologies. These clean development investments, however, need to be made in the near future as otherwise the energy future of Pakistan will get locked into the lower cost - higher carbon options. This mitigation costing estimate will, however, need to be refined and focused further as Pakistan identifies not only the specific technologies that it needs for this low carbon shift (through carrying out the “Technology Needs Assessment”) but also the programmatic, sectoral as well as project specific NAMAs (Nationally Appropriate Mitigation Actions) in the near future. Pakistan is also highly vulnerable to the impacts of climate change and faces immense associated challenges in coping with its unavoidable effects and economic implications. This study has highlighted the need to treat adaptation to climate change as a primary development issue for Pakistan. The potential impacts and sectors demanding prioritized adaptation have been identified in this study and the, associated, costs of adaptation have been estimated utilizing three diverse modeling methodologies – using GDP projections, per-capita figures and “flood” disaster modeling. The resulting adaptation cost figures range from between U$6 billion to U$ 14 billion/year that Pakistan would have to spend at an average in the 2010-2050 time frame to cope with the effects of climate change while it will be also left to, unavoidably, bear significant “residual damage” costs induced due to climate change. The top-down adaptation costing analysis applied in this report is aimed at providing a reasonable first approximation that can be refined over time as relevant and reliable local data becomes available especially from research focusing on sector specific adaptation costing. Most significantly the report reinforces the fact that the issue of climate change is, thus, not only an environmental issue challenging the country but an issue which will directly impinge upon the country’s economic, financial and development future as it deals with its extreme vulnerability to climate change. The significant climate costs identified in this study inextricably shows that climate change is an issue which Pakistan can ill afford to ignore in the future. Finally the report has identified the major financing options available for climate change related activities in Pakistan as well as the significant unilateral climate resources, U$ 4.5 billion in 2007-2009 alone, that the country is already committing to climate change without getting any global recognition for its efforts. In future, global financing will need to augment and leverage such national financial commitments. Also, as climate finance becomes increasingly available at the global level, it would be essential to enact appropriate assimilative national capacity in Pakistan to direct this finance towards nationally identified priorities as well as channelize it transparently and efficiently through consolidated financial mechanisms like a National Climate Change Fund which has been proposed through this study.climate change Pakistan

A Survey on Various Congestion Control Techniques in Wireless Sensor Networks

Wireless Sensor Networks (WSNs) are made up of small battery-powered sensors that can sense and monitor a variety of environmental conditions. These devices are self-contained and fault tolerant. The majority of WSNs are built to perform data collection tasks. These data are gathered and then sent to the sink node. Small packets are sent towards the sink node in such cases, and as a result, the areas near the sink node become congested, becoming the bottleneck of the entire network. In this paper, a survey of existing techniques or methods for detecting and eliminating congestions is conducted. Finally, a comparison in the form of a table based on various matrices is presented

Enabling reliable and power efficient real-time multimedia delivery over wireless sensor networks

There is an increasing need to run real-time multimedia applications, e.g. battle field and border surveillance, over Wireless Sensor Networks (WSNs). In WSNs, packet delivery exhibits high packet loss rate due to congestion, wireless channel high bit error rate, route failure, signal attenuation, etc... Flooding conventional packets over all sensors redundantly provides reliable delivery. However, flooding real-time multimedia packets is energy inefficient for power limited sensors and causes severe contentions affecting reliable delivery. We propose the Flooding Zone Initialization Protocol (FZIP) to enhance reliability and reduce power consumption of real-time multimedia flooding in WSNs. FZIP is a setup protocol which constrains flooding within a small subset of intermediate nodes called Flooding Zone (FZ). Also, we propose the Flooding Zone Control Protocol (FZCP) which monitors the session quality and dynamically changes the FZ size to adapt to current network state, thus providing a tradeoff of good quality and less power consumption

Modular Energy-Efficient and Robust Paradigms for a Disaster-Recovery Process over Wireless Sensor Networks

Robust paradigms are a necessity, particularly for emerging wireless sensor network (WSN) applications. The lack of robust and efficient paradigms causes a reduction in the provision of quality of service (QoS) and additional energy consumption. In this paper, we introduce modular energy-efficient and robust paradigms that involve two archetypes: (1) the operational medium access control (O-MAC) hybrid protocol and (2) the pheromone termite (PT) model. The O-MAC protocol controls overhearing and congestion and increases the throughput, reduces the latency and extends the network lifetime. O-MAC uses an optimized data frame format that reduces the channel access time and provides faster data delivery over the medium. Furthermore, O-MAC uses a novel randomization function that avoids channel collisions. The PT model provides robust routing for single and multiple links and includes two new significant features: (1) determining the packet generation rate to avoid congestion and (2) pheromone sensitivity to determine the link capacity prior to sending the packets on each link. The state-of-the-art research in this work is based on improving both the QoS and energy efficiency. To determine the strength of O-MAC with the PT model; we have generated and simulated a disaster recovery scenario using a network simulator (ns-3.10) that monitors the activities of disaster recovery staff; hospital staff and disaster victims brought into the hospital. Moreover; the proposed paradigm can be used for general purpose applications. Finally; the QoS metrics of the O-MAC and PT paradigms are evaluated and compared with other known hybrid protocols involving the MAC and routing features. The simulation results indicate that O-MAC with PT produced better outcomes.https://doi.org/10.3390/s15071616

OPTIMIZATION MODELS AND METHODOLOGIES TO SUPPORT EMERGENCY PREPAREDNESS AND POST-DISASTER RESPONSE

This dissertation addresses three important optimization problems arising during the phases of pre-disaster emergency preparedness and post-disaster response in time-dependent, stochastic and dynamic environments. The first problem studied is the building evacuation problem with shared information (BEPSI), which seeks a set of evacuation routes and the assignment of evacuees to these routes with the minimum total evacuation time. The BEPSI incorporates the constraints of shared information in providing on-line instructions to evacuees and ensures that evacuees departing from an intermediate or source location at a mutual point in time receive common instructions. A mixed-integer linear program is formulated for the BEPSI and an exact technique based on Benders decomposition is proposed for its solution. Numerical experiments conducted on a mid-sized real-world example demonstrate the effectiveness of the proposed algorithm. The second problem addressed is the network resilience problem (NRP), involving an indicator of network resilience proposed to quantify the ability of a network to recover from randomly arising disruptions resulting from a disaster event. A stochastic, mixed integer program is proposed for quantifying network resilience and identifying the optimal post-event course of action to take. A solution technique based on concepts of Benders decomposition, column generation and Monte Carlo simulation is proposed. Experiments were conducted to illustrate the resilience concept and procedure for its measurement, and to assess the role of network topology in its magnitude. The last problem addressed is the urban search and rescue team deployment problem (USAR-TDP). The USAR-TDP seeks an optimal deployment of USAR teams to disaster sites, including the order of site visits, with the ultimate goal of maximizing the expected number of saved lives over the search and rescue period. A multistage stochastic program is proposed to capture problem uncertainty and dynamics. The solution technique involves the solution of a sequence of interrelated two-stage stochastic programs with recourse. A column generation-based technique is proposed for the solution of each problem instance arising as the start of each decision epoch over a time horizon. Numerical experiments conducted on an example of the 2010 Haiti earthquake are presented to illustrate the effectiveness of the proposed approach