Subir Halder

Enhancement of wireless sensor network lifetime by deploying heterogeneous nodes

Abstract Energy is one of the scarcest resources in wireless sensor network (WSN). One fundamental way of conserving energy is judicious deployment of sensor nodes within the network area so that energy flow remains balanced throughout the network. This avoids the problem of occurrence of ‘energy holes’ and ensures prolonged network lifetime. We have first investigated the problem for enhancing network lifetime using homogeneous sensor nodes. From our observation it is revealed that energy imbalance in WSN occurs due to relaying of data from different parts of the network towards sink. So for improved energy balance instead of using only sensor nodes it is desirable to deploy relay nodes in addition to sensor nodes to manage such imbalance. We have also developed a location-wise pre-determined heterogeneous node deployment strategy based on the principle of energy balancing derived from this analysis, leading to an enhancement of network lifetime. Exhaustive simulation is performed primarily to measure the extent of achieving our design goal of enhancing network lifetime while attaining energy balancing and maintaining coverage. The simulation results also show that our scheme does not compromise with other network performance metrics such as end-to-end delay, packet loss, throughput while achieving the design goal. Finally all the results are compared with two competing schemes and the results confirm our schemes supremacy in terms of both design performance metrics as well as network performance metrics.

A survey on mobility-assisted localization techniques in wireless sensor networks

Identifying locations of sensor nodes in wireless sensor networks (WSNs) is significant for both network operations and most application level tasks. Although geographical positioning system (GPS) based localization schemes are used for determining node locations but the cost of GPS devices and non-availability of GPS signals in indoor environments prevent their use in large scale WSNs. A substantial amount of research work exist that intend at obtaining precise and relative spatial locations of sensor nodes without requiring large amount of specialized hardware. Mobility-assisted localization is one typical approach that significantly reduces the implementation cost by using limited number of mobile anchors. In this survey, we present key issues and inherent challenges faced by the mobility-assisted localization techniques in WSNs. We take a closer look at the algorithmic approaches of various important fine-grained mobility-assisted localization techniques applicable in WSNs. In addition, we highlight the error refinement mechanisms adopted by the state-of-the-art works associated with their approaches. Well known mobile anchor trajectories presented in existing works are also reviewed. Finally, open research issues are discussed for future research scope in this field.

A survey on mobile anchor assisted localization techniques in wireless sensor networks

Identifying locations of sensor nodes in wireless sensor networks (WSNs) is significant for both network operations and most application level tasks. Although, geographical positioning system (GPS) based localization schemes are used for determining node locations but the cost of GPS devices and non-availability of GPS signals in indoor environments prevent their use in large scale WSNs. A substantial amount of research work exist that intend at obtaining precise and relative spatial locations of sensor nodes without requiring large amount of specialized hardware. Mobile anchor assisted localization is one typical approach that significantly reduces the implementation cost by using limited number of mobile anchors. In this survey, we present key issues and inherent challenges faced by the mobile anchor assisted localization techniques in WSNs. We take a closer look at the algorithmic approaches of various important fine-grained mobile anchor assisted localization techniques applicable in WSNs. In addition, we highlight the error refinement mechanisms adopted by the state-of-the-art works associated with their approaches. Well known mobile anchor trajectories presented in existing works are also reviewed. Finally, open research issues are discussed for future research scope in this field.

A dynamic TDMA based scheme for securing query processing in WSN

Nodes in a wireless sensor network (WSN) are generally deployed in unattended environments making the nodes susceptible to attacks. Therefore, the need of defending such attacks becomes a big challenge. We propose a scheme to build a security mechanism in a query-processing paradigm within WSN. The scheme is capable of protecting replay attack while preserving essential properties of security such as authentication, data integrity and data freshness. The solution is made lightweight using symmetric key cryptography with very short-length key. Further, the key used in our scheme is neither pre-deployed nor is transmitted directly. The key information is established among nodes through an efficient use of one variant of dynamic TDMA mechanism which ensures security of key. Another variant of dynamic TDMA is used to make the scheme bandwidth saving, an essential quality of WSN. Performance of the scheme is analyzed in terms of storage, computation and communication overhead. Finally the analytical results are compared with two of the existing schemes including the previous version of the present scheme that show significant reduction of all such overheads thereby proving the suitability of the proposed scheme for a resource-constrained network like WSN.

A Location-Wise Predetermined Deployment for Optimizing Lifetime in Visual Sensor Networks

Visual sensor networks are receiving significant attention due to their potential applications ranging from surveillance to tracking domains. Nevertheless, due to the funneling effect, the unbalanced energy usage among visual sensor nodes (SNs) increases and leads to premature decrease in network lifetime. First, considering Rayleigh fading channel and routing models, we analyze the optimization of network lifetime by balancing the energy consumption among different SNs. From the analysis, it is revealed that the number of SNs and relay nodes and their locations have significant influence on limiting the energy hole problem and optimization of network lifetime. Based on the derived principle of energy balancing, we develop a heterogeneous SNs deployment strategy leading to optimization in network lifetime. Exhaustive simulation is performed, primarily to measure the extent of achieving our design goal of optimizing network lifetime while attaining energy balancing. We also measure the effect of placement errors on the performance and robustness of the scheme. The results show that even in the presence of placement error the performance is comparable and provides better robustness compared with the competing scheme. Further, the simulation results show that our scheme does not compromise with other performance metrics, e.g., end-to-end delay and throughput, while achieving the design goal. Finally, all the comparative results confirm our schemes supremacy over the competing schemes.

Design of a Probability Density Function Targeting Energy-Efficient Node Deployment in Wireless Sensor Networks

In wireless sensor networks the issue of preserving energy requires utmost attention. One primary way of conserving energy is judicious deployment of sensor nodes within the network area so that the energy flow remains balanced throughout the network and prevents the problem of occurrence of energy holes. Firstly, we have analyzed network lifetime, found node density as the parameter which has significant influence on network lifetime and derived the desired parameter values for balanced energy consumption. Then to meet the requirement of energy balancing, we have proposed a probability density function (PDF), derived the PDFs intrinsic characteristics and shown its suitability to model the network architecture considered for the work. A node deployment algorithm is also developed based on this PDF. Performance of the deployment scheme is evaluated in terms of coverage-connectivity, energy balance and network lifetime. In qualitative analysis, we have shown the extent to which our proposed PDF has been able to provide desired node density derived from the analysis on network lifetime. Finally, the scheme is compared with three existing deployment schemes based on various distributions. Simulation results confirm our schemes supremacy over all the existing schemes in terms of all the three performance metrics.

Is sensor deployment using Gaussian distribution energy balanced

Energy is one of the scarcest resources in wireless sensor network (WSN). One fundamental way of conserving energy is judicious deployment of sensor nodes within the network area so that energy flow remains balanced throughout the network. Node deployment using Gaussian distribution is a standard practice and is widely acceptable when random deployment is used. Initially, an analysis is done to establish that Gaussian distribution based node deployment is not energy balanced. Standard deviation has been identified as the parameter responsible for energy balancing. A deployment strategy is proposed for energy balancing using customized Gaussian distribution by discretizing the standard deviation. Performance of the deployment scheme is evaluated in terms of energy balance and network lifetime. Simulation results demonstrate that the proposed deployment strategy significantly outperforms conventional Gaussian distribution based node deployment scheme in terms of the two performance metrics.

Localization with enhanced location accuracy using RSSI in WSN

Recent advances in wireless communication, low power sensors and microcontrollers enable the deployment of large-scale wireless sensor networks. A fundamental problem in wireless sensor networks is localization i.e. determination of geographical locations of sensor nodes. This paper addresses the problem of location discovery of the nodes in wireless sensor network. We propose a localization technique by means of which a sensor node can determine its location with enhanced accuracy by listening wireless transmissions from three or more beacons. The proposed method is based on RSSI technique that does not require any additional complexity in construction of the sensor nodes. Performance of the proposed localization scheme is compared with one of the existing schemes. Qualitative analysis is done considering communication, storage and computational overhead as performance metrics, whereas quantitative analysis is done considering localization error as a performance metric. The results confirm our schemes supremacy over the competing scheme.

Ensuring basic security and preventing replay attack in a query processing application domain in WSN

Nodes in a wireless sensor network are susceptible to various attacks primarily due to their nature of deployment. Therefore, providing security to the network becomes a big challenge. We propose a scheme considering cluster architecture based on LEACH protocol to build a security mechanism in a query-processing paradigm within wireless sensor network. The scheme is capable of thwarting replay attack while ensuring essential properties of security such as authentication, data integrity and data freshness. Our scheme is lightweight as it employs symmetric key cryptography with very short-length key. We simulate our scheme to show its efficacy of providing basic security to the network as well as detecting replay attack in the sensor network. Further we compare our scheme with one of the existing schemes taking packet loss and packet rejection ratio as performance metrics.

A jamming defending data-forwarding scheme for delay sensitive applications in WSN

Wireless sensor network (WSN) has emerged as an important application area where nodes are generally placed in an unattended environment and therefore are vulnerable to attack by adversaries. Moreover in real time application domains delay even by fraction of a second may deceive the purpose of the application. Therefore, designing an attack-defending scheme for WSN without involving any additional delay in data-forwarding is an important challenge in this domain. The present work proposes a data-forwarding scheme having no additional delay to defend jamming attack in WSN. The scheme considers a multilayer architecture where the layers are made up of hexagonal cells each containing sensor nodes in the form of clusters. The nodes are randomly deployed throughout the network and clusters are formed so that every cell hosts two sets of clusters operating in two different predefined frequencies. We have provided design guideline to determine cell size in terms of network parameters. This guideline ensures that for a cluster head there is at least another cluster head at one-hop distance towards the sink and thereby ensures data-forwarding in shortest path. During data-forwarding, if a frequency is jammed, the cluster operating in that frequency becomes inoperative and the other cluster acts as back-up. We claim that the scheme defends jamming attack without incurring any additional delay and the claim is substantiated through simulation.