Faculty Publications
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Publications by NITK Faculty
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Item A Numerical Study on Interference Effects of Closely Spaced Strip Footings on Cohesionless Soils(Springer Science and Business Media Deutschland GmbH, 2021) Anaswara, S.; Shivashankar, R.Foundations of buildings often need to be placed at close spacings to meet the various structural or functional requirements. In such cases, the combined action of adjacent footings is different from that of a single foundation. The combined effect causes interference of the stress zones. Numerical analysis is carried out on two closely spaced strip footings on sands, by varying the affecting parameters, to study the interference effects. Interference effects are analysed in terms of bearing pressure, settlement and tilt of foundations. In this study, the interference effects of closely spaced strip footings on the surface of cohesionless soils are being investigated. Parametric studies are done for two foundations by varying the clear spacing between the foundations. The results are presented in terms of interference factors. New structures near to the old construction may alter the settlement, pressure and rotational characteristics of the old footing and could lead to its distress. Above all, the load-carrying capacity of the new foundation will be very different from what it would have carried if it were independent—without the interference of the other footing. First footing representing an already existing footing is loaded with half of the estimated failure load of single independent strip footing and second adjacent footing loaded up to failure. The effect of interference of the old foundation is observed to be particularly significant in terms of the settlement and tilt. © 2021, Springer Nature Singapore Pte Ltd.Item Studies on Tilt of Closely Spaced Strip Footings on Unreinforced and Reinforced Sands(Springer Science and Business Media Deutschland GmbH, 2021) Anaswara, S.; Shivashankar, R.Two or more strip footings are quite often built close to each other, due to which there will be overlapping of stresses in zones or at points between the footings. There is a non-uniform pressure distribution in the foundation soil beneath the footings, in the space between the footings and beyond. There is also an increase in confining pressure of the soils between the footings. All these result in the tilt of the footings. This numerical study looks into the tilt of the already existing strip footings due to the construction of an adjacent new strip footing on the surface of cohesionless soils. A parametric study is conducted including the effect of geogrid reinforcement/s beneath the new footing. One of the footings representing an already existing foundation is loaded with half of the estimated failure load of a single-strip footing, and adjacent new strip footing is loaded up to failure. The property boundary line is assumed to be midway between the two footings. Geogrid reinforcement layers beneath the new footing are considered to be extending equally beyond the footing on either side, up to the property line. Both unreinforced and reinforced sands are considered beneath the new footing for analyses. Tilts are observed to increase with the width of footing. At closer spacings, tilt was found to be more in case of loose sand. Results of this study indicate that there is a considerable increase in the tilt of the old footing in the presence of reinforcements beneath the new footing. © 2021, Springer Nature Singapore Pte Ltd.Item Enhanced Clustering and Channel Allocation in Wireless Mesh Networks(Springer Science and Business Media Deutschland GmbH, 2025) Sushma Reddy, C.V.; Harshini, V.; Rayala, A.; Chandavarkar, B.R.Wireless mesh networks (WMNs) are crucial for establishing adaptable and scalable communication infrastructures among interconnected devices. Effective clustering and channel allocation are vital for enhancing WMN performance by addressing energy efficiency, latency, throughput, and interference challenges. Proper clustering facilitates the organization of network nodes into cohesive groups, enhancing communication efficiency and resource utilization. Additionally, channel allocation strategies ensure minimized collisions and improved overall network throughput, enhancing network stability and reliability. Existing approaches, such as clique-based channel assignment (CCCA) and two-hop neighbor clustering, present complexity, and interference level limitations. The significant contribution of this paper is to introduce a novel approach focused on clustering and channel assignment, referred to as enhanced clustering and channel allocation (ECCA), to optimize WMN performance—the clustering technique groups nodes based on maximal cliques in one-hop neighbors. Furthermore, channel assignment strategies are employed to minimize collisions and improve overall network throughput. The performance of ECCA is compared with state-of-the-art clique-based channel assignment (CCCA) in terms of the modularity, average number of nodes per cluster, average node degree, and coefficient of variance. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.Item GNSS Spoofing Detection and Mitigation in Multireceiver Configuration via Tracklets and Spoofer Localization(Institute of Electrical and Electronics Engineers Inc., 2022) Pardhasaradhi, B.; Gunnery, G.; Vandana, G.S.; Srihari, P.; Aparna., P.Global navigation satellite systems (GNSS) sensors estimate its position, velocity, and time (PVT) using pseudorange measurements. When there is no interference, the pseudoranges are due to authentic satellites, and the bearings is distinguishable. Whereas, in the presence of any intentional interference source like spoofer, the pseudorange measurements owing to spurious signals and all the bearings from the same direction. These spurious attacks yield either no position or falsified position to the GNSS receiver. This paper proposes to install multiple GNSS receivers on a vehicle (assumed to be cooperative) to detect and mitigate the spoofing attack. While installing multiple GNSS receivers, we assume that each GNSS receiver's relative position vector (RPV) is assumed to be known to other GNSS receivers. The installed GNSS receivers use the extended Kalman filter (EKF) framework to estimate their PVT. We proposed to calculate the equivalent-measurement and equivalent-measurement covariance of each GNSS receiver in the Cartesian coordinates in the tracklet framework. These tracklets are translated to the vehicle center using RPV to obtain translated-Tracklets. The translated tracklet based generalized likelihood ratio test (GLRT) is derived to detect the spoofing attack at a given epoch. In addition to that, these translated-Tracklets are processed in a batch least square (LS) framework to obtain the vehicle position. Once the attack is detected at a specific epoch, it quantifies that the position information is false. Moreover, another spoofing test is also formulated using DOA of signals. Once both the tests confirm the spoofing attack, the spoofer localization is performed using pseudo-updated states of GNSS receivers and acquired bearings in the iterative least-squares (ILS) framework. Mitigation of spoofing attack can be achieved either by projecting a null beam in the direction of the spoofer or by launching a counter-Attack on the spoofer. The simulation results demonstrate that the proposed algorithm detects spoofing attacks and ensures continuity in the navigation track. As the number of satellite signals increases, the algorithms provide better position root mean square error (PRMSE) for GNSS receivers track, vehicle track, and spoofer localization. © 2013 IEEE.Item Tracking of Radar Targets With In-Band Wireless Communication Interference in RadComm Spectrum Sharing(Institute of Electrical and Electronics Engineers Inc., 2022) Gunnery, G.; Pardhasaradhi, B.; Prashantha Kumar, P.; Srihari, P.Radar and communication system (RadComm) spectrum sharing has received considerable attention from the research community in recent years. This paper considers the distributed radars present in the surveillance region with multiple in-band wireless communication transmitters (IWCTs). A new measurement model is proposed by considering both radar returns and returns due to IWCTs. The tracking performance is evaluated using the global nearest neighbor (GNN) tracker with an extended Kalman filter (EKF) for the received measurement set. A single radar case is considered, where near geometry scenario (IWCTs are placed near the radar and target) and far-geometry scenario (IWCTs are placed far from the radar and target) are considered to evaluate the tracking performance. It is observed that a large number of tracks are resulted due to IWCTs, and identifying the actual target track is ambiguous in a single radar case. Therefore, in the second case, multiple radars are placed to investigate the problem comprehensively. The track-to-track association (T2TA) is performed to identify the true target track on multiple tracks produced owing to the presence of IWCTs and the resulting tracks from all radars pertaining to the true targets. Once the true target tracks from each radar are identified, using the T2TA, the track-to-track fusion (T2TF) is carried out to improve the estimates of the true target. The simulation results are quantified with position root mean square error (PRMSE). The posterior Cramer-Rao lower bounds (PCRLBs) quantifying the achievable estimation accuracies are also presented. The simulation results reveal that the association and fusion of tracks from multiple radars identify the true target track with good accuracy and overcome the inability to determine the true track, as in the case of a single radar. Further, the results disclose that, as the number of radars increases, the T2TA and fusion improved the PRMSE. © 2022 IEEE.Item Performance Analysis of Spectrum Sharing Radar in Multipath Environment(Institute of Electrical and Electronics Engineers Inc., 2023) Gunnery, G.; Pardhasaradhi, B.; Mahipathi, A.C.; Prashantha Kumar, P.K.; Srihari, P.; Cenkarmaddi, L.R.Radar based sensing and communication systems sharing a common spectrum have become a potential research problem in recent years due to spectrum scarcity. The spectrum sharing radar (SSR) is a new technology that uses the total available bandwidth (BW) for both radar based sensing and communication. Unlike traditional radar, the SSR divides the total available BW into radar-only and mixed-use bands. In a radar-only band, only radar sensor signals can be transmitted and received. In contrast, radar and communication signals can both be transmitted and received in the mixed-use band. Taking such BW sharing into account, this paper investigates the performance of SSR in an information-theoretic sense. To evaluate performance, mutual information (MI), spectral efficiency (SE) and capacity (C) metrics are used. Initially, this paper considered a clean environment (no multipath) in order to evaluate performance metrics in the mixed-use band with and without successive interference cancellation. Following that, this paper addresses the performance of BW allocation by allocating low to high BW in mixed-band. Furthermore, the performance metrics are extended to account for the multipath environment, and the same analogy as in a clean environment is used. In addition, the MI and SE of traditional radar system is taken into account when comparing the performance of SSR with and without the use of the SIC. Finally, MI and capacity results show that using the SIC scheme in a mixed-use band yields performance comparable to traditional radar and communication system. In terms of SE, the SSR with SIC scheme outperforms traditional radar and communication system. © 2020 IEEE.Item An Iterative-Based Optimum Power and Resource Allocation in Application-Dependent Scenarios for One-to-One D2D Communication(Institute of Electrical and Electronics Engineers Inc., 2024) Raghu, T.V.; Manjappa, M.Efficient and timely sharing of critical information is crucial for Public Safety (PS) communications, which can be fulfilled using one of the cutting-edge technologies, Device-to-device (D2D) communication. During an emergency, the PS applications should be prioritized over other applications, ensuring the emergency messages reach the first responders in time. Due to its inherent characteristics, the evolved Node Base station will not prioritize or categorize the D2D communication based on its application type, thus treating all applications equally. Further, D2D communication introduces significant interference to cellular users and vice-versa while sharing resources, and it is vital to reduce the impact of these interferences to ensure the Quality of Service for all users in the network. Hence, this article proposes a novel interference management approach to increase the overall sum rate of the system. In addition, the proposed approach also allows more D2D communication in general, particularly PS application-based D2D communication, to be active in the network. As the formulated problem is a Mixed-Integer Non-Linear Programming (MINLP) type of problem, it is split into two sub-problems, namely, Iterative Resource Allocation and Sharing and Iterative Power Optimization to achieve a polynomial time complexity. The theoretical proofs adequately explain the algorithm's time complexity and convergence property. The simulation results show that the proposed system enhances the overall sum rate by allowing more active PS D2D applications in the network. © 2013 IEEE.Item Priority-Driven Resource Allocation and Power Optimization in D2D Communication(Institute of Electrical and Electronics Engineers Inc., 2024) Raghu, T.V.; Manjappa, M.This research proposes priority-driven application-based channel assignment and power optimization frameworks called Channel State Information-based Resource Allocation (CSIRA) and Binary Search Power Control Mechanism (BSPCM) in D2D-enabled cellular communication. The CSIRA framework is cluster-based and uses a K-means clustering algorithm to group the D2D users into clusters. CSIRA allows the D2D users to share the cellular user's resources without compromising the cellular user's Quality of Service (QoS) in each cluster. Also, CSIRA ensures that public safety communication will get an edge over commercial communication during resource allocation. In order to ensure the QoS for cellular users is maintained while also enhancing the sum rate of D2D communication, the CSIRA employs the BSPCM framework. BSPCM framework utilizes a binary search algorithm to determine the optimal transmission power required for guaranteed D2D transmission within a cluster, thereby mitigating interference effects. A theoretical proof is provided to show that the suggested frameworks converge to a stable matching and end after a finite number of iterations. Simulation results demonstrate that the proposed frameworks effectively prioritizes public safety over commercial applications while preserving optimal system efficiency and quality with minimal complications. © 2017 IEEE.