Hassaan Khaliq Qureshi

Energy management in Wireless Sensor Networks

Energy management in Wireless Sensor Networks (WSNs) is of paramount importance for the remotely deployed energy stringent sensor nodes. These nodes are typically powered by attached batteries. Several battery-driven energy conservation schemes are proposed to ensure energy efficient network operation. The constraints associated to the limited battery capacity shifted the research trend towards finding alternate sources by harvesting ambient energy. This survey presents a high level taxonomy of energy management in WSNs. We analyze different battery-driven energy consumption based schemes and energy harvesting based energy provisioning schemes. We also highlight the recent breakthrough of wireless energy transference to a sensor node as an alternative to typical batteries. We recommend taking into account recent energy provisioning advancements in parallel with the traditional energy conservation approaches for a sensor network while designing energy efficient schemes.

Review: A1: An energy efficient topology control algorithm for connected area coverage in wireless sensor networks

Energy consumption in Wireless Sensor Networks (WSNs) is of paramount importance, which is demonstrated by the large number of algorithms, techniques, and protocols that have been developed to save energy, and thereby extend the lifetime of the network. However, in the context of WSNs routing and dissemination, Connected Dominating Set (CDS) principle has emerged as the most popular method for energy-efficient topology control (TC) in WSNs. In a CDS-based topology control technique, a virtual backbone is formed, which allows communication between any arbitrary pair of nodes in the network. In this paper, we present a CDS based topology control algorithm, A1, which forms an energy efficient virtual backbone. In our simulations, we compare the performance of A1 with three prominent CDS-based algorithms namely energy-efficient CDS (EECDS), CDS Rule K and A3. The results demonstrate that A1 performs better in terms of message overhead and other selected metrics. Moreover, the A1 not only achieves better connectivity under topology maintenance but also provides better sensing coverage when compared with other algorithms.

Poly: A reliable and energy efficient topology control protocol for wireless sensor networks

Energy efficiency and reliability are the two important requirements for mission-critical wireless sensor networks. In the context of sensor topology control for routing and dissemination, Connected Dominating Set (CDS) based techniques proposed in prior literature provide the most promising efficiency and reliability. In a CDS-based topology control technique, a backbone - comprising a set of highly connected nodes - is formed which allows communication between any arbitrary pair of nodes in the network. In this paper, we show that formation of a polygon in the network provides a reliable and energy-efficient topology. Based on this observation, we propose Poly, a novel topology construction protocol based on the idea of polygons. We compare the performance of Poly with three prominent CDS-based topology construction protocols namely CDS-Rule K, Energy-efficient CDS (EECDS) and A3. Our simulation results demonstrate that Poly performs consistently better in terms of message overhead and other selected metrics. We also model the reliability of Poly and compare it with other CDS-based techniques to show that it achieves better connectivity under highly dynamic network topologies.

Evaluation and improvement of CDS-based topology control for wireless sensor networks

The connected dominating set (CDS) principle has emerged as the predominant method for energy-efficient discovery and clustering of power-/location-unaware WSN nodes. While many CDS discovery protocols have been proposed recently, a one-to-one comparative evaluation of these protocols has not been performed on judicious metrics. In this paper, we perform a simulation-based evaluation of three prominent CDS based protocols (CDS Rule K, EECDS and A3) on the basis of message and energy overhead, residual energy, number of unconnected nodes, and convergence time. Our analysis shows that the protocols’ performances vary significantly with different maintenance techniques and none of the existing protocols can outperform the others on all metrics. Based on this result, we identify some performance-improving guidelines for CDS-based topology discovery and utilize them to propose a new protocol, clique-based CDS discovery (CCDS). We show that CCDS provides considerably better performance than existing protocols in most operational scenarios.

Variable rate adaptive modulation (VRAM) for introducing small-world model into WSNs

Data communication has a strong impact on the design of a Wireless Sensor Network (WSN), since the data transmission energy cost is typically higher than the data processing cost. In order to reduce the data transmission cost, small world phenomenon is introduced into WSNs. Networks that do not have the small world structure can be converted to achieve a small world property by the addition of few extra links. The problem is that most large scale WSNs are inherently unstructured and a node has no precise information of the overall model of the network and thus has to rely on the knowledge of its neighbor. For this reason, in most unstructured networks, information is propagated using gossiping. In this paper, we exploit this information propagation mechanism and use Neighbor Avoiding Walk (NAW), where the information is propagated to node that has not been visited previously and which is not the neighbor of a previously visited node. Using this, a novel approach is presented, in which nodes with highest betweenness centrality form a long distance relay path by using a lower order modulation scheme and therefore resulting in a relatively reduced data rate, but maintaining the same bit error rate. Our empirical and analytical evaluations demonstrate that this leads to a significant reduction in average path length and an increase in node degree.

Topology Control for Harvesting Enabled Wireless Sensor Networks: A Design Approach

While there has been a lot of research on energy efficient topology control protocols destined for different applications, topology control has never been explored in the presence of harvesting enabled sensors. Largely, researchers in this domain have considered a fixed battery design. We argue that arrival of harvesting enabled sensors necessitates rethink of topology control. The objective of topology control in this context should not be to minimize the spent energy and maintain a reduced topology, but to maximize fault tolerance in the network and increase the sensing coverage region. In this work, we first describe a taxonomy of existing topology control schemes and analyze the impact of reduced topology over fault tolerance and sensing coverage. We then describe the necessity of new design parameters in the presence of harvest-able ambient energy. We also outline guiding principles for designing a harvesting enabled topology control scheme. To cater for whether such a scheme is feasible or not, an insight is also provided onto the solar energy availability from solar radiations for near perpetual operation—as an example of available ambient energy. Based on the insight gained from the solar radiations availability, we explain why new design parameters are required for performance measurement of harvesting enabled sensors. The mathematical and empirical findings reveal that the topology control strategies, which do not take into account harvesting opportunity, are unable to provide better results in terms of fault tolerance and sensing coverage.

A Cycle-based Clustering Algorithm for Wireless Sensor Networks

In energy constrained wireless sensor networks, it is important that a routing protocol provides network redundancy and reliability at a minimum energy consumption cost. To satisfy these conflicting constraints, wireless sensor networks (WSN) routing protocols generally employ a clustering algorithm in which the entire network does not have to be active at all times. In this paper, we propose a novel graph-theoretic clustering algorithm that exploits cycles in a connected and undirected WSN graph to provide redundancy and reliability in an energy efficient manner. The proposed algorithm also facilitates cluster head rotation for load distribution, thereby extending the network lifetime. Our performance evaluation shows that the proposed algorithm performs better than existing graph- theoretic clustering algorithms.

Performance Analysis of Contention-Based Random Access Procedure in Clustered LTE Networks

Long Term Evolution (LTE) is a 4G standard for mobile networks, and has proven to be the only viable solution. In this paper, we have presented a new analytical model that describes the contention-based random access request procedure of LTE networks for dynamic request generation, including clustering and non-clustering schemes. The model takes into account the uniform back-off as well as the waiting period for the resource assignment and possible message delivery failures because of the collisions and resource starvation. The proposed model is empirically verified under simulation environment by measuring the collision probability, throughput and resource utilization. The results demonstrate that, when the network load is high, the clustering scheme performs better than non-clustering scheme.

Transmission power management for throughput maximization in harvesting enabled D2D network

Unlike traditional cellular networks, the multi-tier architecture of 5G networks supports Device-to-Device (D2D) communication, which allows devices to communicate with each other autonomously. Consequently, D2D-enabled Internet of Things (IoT) promise to provide higher bandwidth through frequency spectrum sharing. However, energy efficient operation of the network becomes a major challenge due to unattended operation of devices. In this study, we propose a solar energy harvesting based model for throughput maximization of an overlay in-band D2D network and consider an energy prediction model for optimal power management. Sum rate maximization problem subject to energy and power constraints is formulated for multiple D2D pairs and maximum achievable throughput is investigated by employing optimal power allocation at transmitters. The proposed model is analysed using real world solar energy harvesting data. The results show that consistently high throughput can be achieved by scheduling the energy arrival duration, while at the same time, energy inefficiency can also handled by optimal power allocation at the devices.

Combined Banzhaf & Diversity Index (CBDI) for critical node detection

Critical node discovery plays a vital role in assessing the vulnerability of a computer network to malicious attacks and failures and provides a useful tool with which one can greatly improve network security and reliability. In this paper, we propose a new metric to characterize the criticality of a node in an arbitrary computer network which we refer to as the Combined Banzhaf & Diversity Index (CBDI). The metric utilizes a diversity index which is based on the variability of a nodes attributes relative to its neighbours and the Banzhaf power index which characterizes the degree of participation of a node in forming shortest paths. The Banzhaf power index is inspired from the theory of voting games in game theory. The proposed metric is evaluated using analysis and simulations. The criticality of nodes in a network is assessed based on the degradation in network performance achieved when these nodes are removed. We use several performance metrics to evaluate network performance including the algebraic connectivity which is a spectral metric characterizing the connectivity robustness of the network. Extensive simulations in a number of network topologies indicate that the proposed CBDI index chooses more critical nodes which, when removed, degrade network performance to a greater extent than if critical nodes based on other criticality metrics were removed.