1. Ph.D Theses
Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/1/11
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Item Optimized Void-Aware Routing Protocol For Underwater Acoustic Sensor Networks(National Institute Of Technology Karnataka Surathkal, 2023) Nazareth, Pradeep; Chandavarkar, B. R.Underwater Acoustic Sensor Networks (UASNs) are the technologies used to ex- plore underwater resources. UASNs have been used in numerous applications such as environmental monitoring, underwater surveillance, underwater exploration, detection of resources and disasters, etc. However, UASNs face several fundamental issues like low bandwidth due to the environmental noise, high bit error rate as a result of fading and multipath propagation, energy constraints on nodes, security as they are vulnerable to active and passive attacks, complicated routing due to dynamic network topology and variation of the link quality between nodes. The UASNs architecture consists of sensor nodes deployed underwater for sensing the events and forwarding or routing the data, in one or multiple hops, to the sink nodes deployed at the water’s surface. Wireless routing has three significant categories, that are proactive, reactive, and geographic routing. However, proactive routing requires transmission of more number control packets, thus increasing energy consumption and overhead on the network. The reactive routing results in increased end-to-end delay due to high propagation delay. Geographic routing forwards the data, using the position information of the neighbors and the sink. It uses greedy forwarding, and every node determines only its next hop, rather than the end-to-end path. Geographic routing is the most suitable protocol to forward data from the source to the sink node in UASNs. However, communication void or void node is one of the major challenges in UASNs to deliver the data to the sink reliably. The non-availability of a neighbor, in the positive progress to a source or forwarding node, results in a communication void. Communication void impacts the performance of the UASNs in terms of packet loss, high end-to-end delay, waste of energy, etc. Primary reasons for communication void are, node movement due to water current, ship movement, or a drop in Signal-to-Noise Ratio (SNR) between nodes. Many methods are proposed in the literature to deal with the communication void, such as backward forwarding, topologyadjustment, transmission power adjustment, etc. The major drawbacks of these methods are, void nodes as a part of routing, loops, unreachable data to the sink, more duplicate packets, hidden-node issues, and more energy consumption. This thesis mainly addresses the issues of the communication void in underwater routing. In existing void-aware routing protocols, the source/forwarder node decides the next hop using multiple attributes, such as hop count, residual energy, distance with the neighbor, depth, Packet Delivery Probability (PDP), status (void or normal), etc., of the neighboring nodes. However, the priorities of the individual attributes are not considered in determining the next hop(s). Hence, this thesis presents the selection or identification of an appropriate combination of attributes of neighboring nodes. Ac- cordingly, this thesis proposes the Enhanced-Void-Aware Routing (E-VAR) protocol, which uses a combination of the neighbor’s status and Euclidean distance between the neighbor to the sink attributes to decide the next hop for delay-sensitive applications. Further, Link Quality-based Routing Protocol (LQRP) proposed in this thesis uses link quality between source to neighbors and neighbor to its best hop as attributes. Addi- tionally, applying appropriate weights, a suitable neighbor is selected as its next hop. The LQRP protocol achieves better reliability than the state-of-the-art protocol. The Location-Free Void Avoidance Routing (LFVAR) protocol proposed in this thesis uses status, hop count, and depth of neighbor as attributes. Further, by computing the cost of neighbors, one of them is selected as the next hop. The Link and Void-Aware Routing (LVAR) protocol proposed in this thesis uses status, PDP, and hop count of neighbor as attributes to select the next hop. The state-of-the-art routing protocols proposed in the literature do not consider Mul- tiple Attribute Decision Making (MADM) techniques to evaluate the neighboring nodes using identified attributes. Hence, this study proposes a Cluster-based Multi-Attribute Routing (CMAR) protocol. CMAR is a sender-based, opportunistic routing protocol. The source/forwarder node evaluates its neighbors using the Technique for Order Pref- erence by Similarity to Ideal Solution (TOPSIS) method. Additionally, it forms the cluster(s) of neighboring nodes, consisting of a threshold number of nodes in the vicin- ity of each other. The source/forwarder node forwards the data to the cluster using iiopportunistic routing. The protocols (E-VAR, LQRP, LFVAR, LVAR, and CMAR) designed, as a part of this research work, are simulated and evaluated in industry-standard simulators such as MATLAB and UnetStack. UnetStack is an agent-based simulator used to develop and evaluate underwater protocols. Further, E-VAR, LQRP, LFVAR, LVAR, and CMAR are evaluated in terms of various metrics such as the number of nodes reachable to the sink, number of nodes not reachable to the sink due to loops, packet delivery ratio, hop count, propagation distance from source to the sink, throughput, number of the clusters formed, number of times a void node is part of the routing, etc. In conclusion, the major contribution of this thesis, focuses on identifying the most suitable combination of attributes of neighbors to select the next hop(s) with E-VAR, LQRP, LFVAR, and LVAR, further evaluating neighboring nodes, using the MADM approach with CMAR protocol. Additionally, designed protocols are evaluated using MATLAB or UnetStack and are compared with state-of-the-art routing protocols.Item Optimizing Vertical Handover Decision Making in Heterogeneous Wireless Networks(National Institute of Technology Karnataka, Surathkal, 2016) Chandavarkar, Beerappa Rama; Reddy, G. Ram MohanaEver-increasing demands of users and the development of modern communication technologies have led to the evolution of 4th Generation (4G) heterogeneous wireless networks. The integration of wireless networks of different characteristics and the demands of: user, mobile device, applications and service providers result in issues such as seamless mobility management, security, administration, billing, etc. The key issue among these challenges is the handover process of mobility management for seamless communication of mobile devices in heterogeneous wireless networks with maximized users’ satisfaction. Always Best Connected (ABC) services anywhere at anytime is one of the key objectives of 4G in integrating IEEE and cellular technologies. This thesis mainly addresses the Vertical Handover Decision (VHD) making in heterogeneous wireless networks for seamless communication of mobile devices. The dependency of VHD on multiple attributes in heterogeneous wireless networks demands an optimized handover process in terms of minimized complexity with improved reliability and flexibility. Several existing methods like fuzzy logic, neural networks, game theory and Multiple Attribute Decision Making (MADM) have been used for VHD. However there are still open issues such as, complexity, reliability and flexibility in these methods. MADM is one such method which supports multiple attributes based decision with minimum complexity for multiple criteria dependent VHD in heterogeneous wireless networks. The main problem with the MADM method is unreliable network selection and the rank reversal problem due to its dependency on attributes normalization and weight calculation methods. Hence, this thesis presents an optimized MADM method referred to as Simplified and Improved Multiple Attributes Alternate Ranking (SI-MAAR) for overcoming the limitations of classical MADM methods. Thus, SI-MAAR method is optimized in terms of minimized computational complexity and improved network selection reliability with the elimination of rank reversal problem. With MATLAB simulations, the analytical model of SI-MAAR method is demonstrated for 100% reliable VHD with the 0% rank reversal problem in heterogeneous wireless networks. iFurther, many of the classical MADM methods used in VHD in heterogeneous wireless networks depend on attributes weight computation techniques such as, Entropy, Variance, Analytical Hierarchy Process (AHP) etc. Expectations of users and applications during VHD in heterogeneous wireless networks is subjective in nature. AHP is one such popular method which supports computation of subjective attributes weight. The main problem with AHP is computation of reciprocal matrix through the involvement of the decision maker which will result in unreliable attributes weight and further to unreliable network selection in VHD. Hence, this thesis also presents an optimized AHP method referred to as Simplified and Improved Analytical Hierarchy Process (SI-AHP) to overcome unreliability in attributes weight computation. Thus, SI-AHP method is optimized in terms of minimum involvement of the decision maker resulting in reduced attributes weight computational complexity with the improved reliability. With MATLAB simulations, SI-AHP method is demonstrated for 100% reliable attributes weight computation used for VHD in heterogeneous wireless networks. In this thesis, SI-MAAR and SI-AHP methods are numerically analysed using MATLAB simulations and results demonstrate that SI-MAAR and SI-AHP methods are outperforming classical MADM and AHP methods respectively. Similarly, simulations using network simulators and further validation by testbed-based approaches are also required for justifying the proposed analytical solutions. Among the available open source network simulators such as NS2, NS3, OMNET++ and J-Sim, simulation of heterogeneous wireless networks is supported only in NS2’s distribution provided by National Institute of Science and Technology (NIST). The major problems with the NIST’s NS2 distribution are: (i) support for only one mobile node simulations (ii) minimal support for VHD and (iii) non-availability of configuration and result analysis tools such as TCP Performance Evaluation suite for simulations of heterogeneous wireless networks. Hence, this thesis also presents NS2 based Evaluation Suite for User Datagram Protocol applications referred to as “ES-UDP” for configuration, simulations and results analysis of multiple mobile nodes in heterogeneous wireless networks. Thus, ES-UDP tool provides both text and graphical results of handover, packets sent and received, throughput, packet delay and jitter of heterogeneous wireless networks simulations. iiOn the other hand, real time experimentation is subject to testbed’s deployment complexity, cost and time. The other major challenge of testbed experimentations is Linux kernel support for heterogeneous wireless networks. Although for handover execution, network layer protocol-Mobile IPv6 is supported by Linux kernel, the major issues are lack of testbed deployment informations, high cost, and nonavailability of testing checkpoints and debugging procedures. Thus, this thesis also presents a cost-effective testbed of Mobile IPv6 for handover execution in homogeneous and heterogeneous wireless networks. Further, this testbed can be used for VHD by deploying proposed solutions: SI-MAAR and SI-AHP in the Linux kernel. To summarize, the main contributions of the thesis are, improving the network selection reliability and the elimination of rank reversal problem of classical MADM methods used in VHD of heterogeneous wireless networks with “SI-MAAR”. Simplifying the attributes weight computation and improving the attributes weight reliability of AHP with “SI-AHP”. Ease of NS2’s configuration, simulation and results analysis of multiple mobile nodes experimentations in heterogeneous wireless networks with “ES-UDP” tool. Finally, simple and cost-effective Mobile IPv6 testbed for handover execution and further to handover decision in heterogeneous wireless networks