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Next Generation Routing and Data Dissemination Techniques for Vehicular Ad-hoc Networks
(Indian Institute of Technology, Jodhpur, 2024-07-23) Das, Debasis; Das, Sajal K.
Consider a driver on a busy highway where their vehicle immediately receives alerts about a collision occurring three cars ahead, well before it comes into their line of sight. Or imagine a navigation system dynamically rerouting the driver to avoid a newly formed traffic jam just a few kilometers away. This is the capability offered by Vehicular Ad-hoc Networks (VANETs), which enable direct communication between vehicles and roadside infrastructure, establishing a real-time digital network that enhances road safety and optimizes traffic flow. However, deploying VANETs is complex. On actual roads, particularly in developing countries, traffic is highly heterogeneous ranging from cars and buses to motorcycles and auto-rickshaws, all traveling at varying speeds, frequently changing lanes unpredictably, and constantly joining or leaving the network. Traditional communication protocols, originally designed for relatively stable and homogeneous networks, struggle under these conditions: communication links frequently break, message flooding occurs in dense traffic scenarios (known as "broadcast storms"), and critical safety messages that require delivery within 100 milliseconds often fail to meet the stringent latency requirements. This thesis addresses these fundamental networking challenges (packet routing) by developing and validating next-generation routing and data dissemination techniques that maintain reliability despite high node mobility and diverse traffic conditions. Our contributions encompass three different directions: direction-aware forwarding mechanisms,metaheuristic-based clustering frameworks, and hypergraph-based communication models. We first propose three orientation-informed routing protocols, Cosine Similarity-Based Routing (CSBR), Orientation-Based QoS Routing (OBQR), and SDCast leveraging vehicles’movement direction and road context to improve data dissemination. Unlike conventional broadcast or shortest-path schemes, these protocols dynamically bias message forwarding along the direction of traffic flow, reducing redundant transmissions and avoiding relays on vehicles that are likely to move out of range. In CSBR, a cosine similarity metric between vehicle velocity vectors is used to select relay candidates, ensuring that only vehicles with aligned directions participate in rebroadcasting. OBQR builds on this by incorporating multi-constraint QoS metrics (link stability, transit delay, etc.) into routing decisions, using a weighted optimization to find routes that honor safety-critical latency and reliability requirements. Finally, SDCast introduces a hybrid Software-Defined Networking (SDN) architecture into the VANET: a two-tier controller system (a central controller working with local Roadside Units) that orchestrates cluster-based forwarding policies. To improve communication stability and QoS in dynamic conditions, we next develop advanced clustering and routing optimization techniques using metaheuristics. Two frameworks, i.e., MetaLearn and Multi-constraint Routing using Hybrid Metaheuristics (MRMH) are introduced to intelligently organize vehicles into semi-stable clusters and optimize multi-hop routes within and between these clusters. MetaLearn employs a hybrid learning approach: it uses meta-heuristic algorithms (Grey Wolf Optimization (GWO)) to bootstrap efficient clustering, and then applies reinforcement-learning principles (fast adaptation based on prior outcomes) to continually refine routing policies as conditions change. This enables the routing strategy to “learn” from the network’s behavior, quickly adapting to recurring traffic patterns (e.g., rush hour flows) and thereby improving long-term performance. MRMH, on the other hand, hybridizes multiple optimization techniques (GWO and Sequential Quadratic Programming (SQP)) to solve the routing problem under multiple constraints (such as latency, link durability, and bandwidth) simultaneously. By hybridizing metaheuristics methods, MRMH avoids the pitfalls of single-metaheuristic approaches (like premature convergence or high computational cost) and finds high-quality routes that satisfy all QoS requirements even as the network scales. Finally, we present an approach using Spatio-Temporal Information-Aware Hypergraph formulation that generalizes the traditional network graph model to a hypergraph structure. In a hypergraph, an edge (now called a hyperedge) can connect any number of vertices, which in our context means a communication event can directly involve multiple vehicles. This representation is paired with a deep learning-driven routing strategy that uses spatial (geographic/positional) and temporal (time-dependent) dynamics of vehicles and network conditions to make optimized decisions. By capturing higher-order relationships (beyond simple pairwise links) and feeding them into a deep learning algorithm, the network can better anticipate and adapt to changes. Further, we introduce a Software-Defined Fog Computing (SDFC) framework for VANETs,which pushes computational intelligence and control closer to the network edge (the vehicles and roadside units). This enables data processing and decision-making to occur in proximity to where data is generated. By doing so, fog computing can drastically reduce end-to-end communication delays and offload traffic from the core network. In our SDFC framework, VANET management functions (such as cluster formation,routing control, and load balancing) are distributed across a hierarchy of cloud, fog, and edge layers. This design improves scalability and reliability by avoiding single points of failure and by adapting to local conditions. To ensure experimental validations, all proposed techniques were implemented using standard VANET simulation tools and real hardware. Simulations leveraged frameworks like NS-2/NS-3 and OMNeT++ (with the Vehicle in Network Simulations (VEINS) open source library) for network-layer behavior, standard Vehicle-to-Everything (V2X) communication technology (IEEE 802.11p, Cellular-V2X) and Simulation of Urban Mobility (SUMO) for generating realistic vehicle mobility on road layouts imported from OpenStreetMap (openly-licensed data from national mapping agencies and other sources). We seeded simulations with actual city road maps and traffic patterns (including heterogeneous vehicle types, intersections and traffic lights) to closely mirror real-world conditions. Key performance metrics, end-to-end latency, packet delivery ratio, routing overhead, cluster membership time, throughput, and route discovery time were measured across a range of scenarios (urban environments, highways, varying vehicle densities from sparse to congested). Furthermore, the algorithms were tested on a physical testbed: our Duckietown setup (miniature autonomy test bed) and anedge computing platform with Raspberry Pi and JetsonNano devices (working as Onboard Units and Roadside Units) allowed us to verify that the protocols run within real-time constraints on resource-constrained hardware.
Xurography- Based Microfluidic Platform for Mimicking Neuronal cytoarchitecture and Exploring its Application in Neurodegenerative Disease Research
(Indian Institute of Technology, Jodhpur, 2025-01-03) Ghosh, Surajit
The brain is an intricate system composed of millions of neural networks. Deciphering its overall dynamics and the underlying significance of several cues that direct neuronal development, the formation of axons, dendrites, and synapses during wiring and re-wiring remains a formidable challenge in developmental and cellular neuroscience. Although traditional in vitro macroscopic cell culture techniques are easy to perform, they often fail to mimic the complex phenomenon of brain microenvironments. Recent advancements in microfluidic device-based cell culture technologies have successfully overcome the limitations of conventional cell culture methods, enabling the reconstitution of neural cytoarchitecture through precise spatiotemporal regulation of compartmentalized cell culture microenvironments. These lab-on-chip technologies can aid in elucidating the fundamental principles of brain function and provide innovative platforms for screening neurotherapeutics. This thesis offers a succinct overview of the structural and functional aspects of the human nervous system by the reconstitution of the central and peripheral nervous systems on the chip. It highlights the neurological disorders associated with dysfunctions in both systems. It also reviews the several strategies researchers have adopted to mimic neurogenesis on a chip. Additionally, we have designed and developed an economical, innovative microfluidic device utilizing a state-of-the-art Xurography technique. Thereafter, we performed on-chip cell culture studies with primary neurons and SH-SY5Y cells to validate the cytocompatibility of the device. Furthermore, we demonstrated the application of the fabricated device as a coculture model using astrocytes and neurons. The device also served as a drug screening platform for a multi-targeted compound in the differentiated SH-SY5Y cells in the context of Lastly, we also developed a Ferroptosis model that can be linked to neurodegenerative disorders. In this regard, we also investigated the efficacy of a synthesized small molecule inside our fabricated microfluidic device. All these lead to the conclusion that our simple and cost-effective Xurography-based microfluidic device can open gateways to decipher neuronal events inside the human brain and serve as potential platforms for neurodegenerative disease modelling and screening novel therapeutic agents.
Studies on Beam Steerable Dipole Antenna
(Indian Institute of Technology, Jodhpur, 2025-02-01) Yadav, Sandeep Kumar; Mukherjee, Soumava
HF communication using sky wave propagation through ionosphere plays a vital role for short and long distance communication specially in the fields of Defence, maritime role, police and remote sensing. For reliable and efficient HF communication various adaptive data transmission schemes have been formulated. This require selection of best channel frequency through ALE (Automatic Link Establishment) and choosing of best modulation to provide highest possible bit rate. Optimum deployment of HF antenna after predicting accurate frequency spots for real-time communication at various ranges is essential due to HF link limitation of impulsive atmospheric noise, multipath propagation, limited band width and interference. However, changes in HF dipole antenna height with respect to range and time was still needed to be addressed. Height of HF antenna above ground plays a vital role for establishing successful HF contact. Effective HF communication is dependent on accurate radiation / take off angle achieved by the transmitting antenna. The height of HF antenna to be adjusted either while variation of frequency during different time slots or variation of distance between transmitting and receiving stations. Desired radiation / take of angle can be achieved by adjusting the antenna height above ground while variation of operating frequency during different time slots i.e. Day, Night, Transition1 and Transition2. The variation in take of angle is maintained by modifying the radiation pattern of the antenna by changing the height or other critical dimensions of the antenna system. Several techniques are being adapted for variation of antenna height e.g. mechanical/physical variation of the antenna height, deployment of various height of multiple HF Antenna at different time slots etc. These methods require additional infrastructure and assets resulting in enhancement of time, cost and complexity. To address this limitation, a beam steerable inverted V HF dipole antenna has been proposed in thesis as an effective solution for beam steering of HF antenna without changing antenna height. To provide adequate beam steering a reactive circuit with parallel variable capacitor and inductor has been positioned at one end of dipole. Tilting of antenna pattern has been controlled by variable capacitor keeping fixed value of parallel inductor. Continuous beam steering of 60 degree (± 30 degree) has been achieved by changing the capacitive value from 26.6 PF to 27.7 PF at 9.3 MHz frequency by adjusting the Capacitor biasing voltage from 1.24 V to 1.10 V. The present work provides novel technique for electronically adjusting radiation beam take off angle to maximize HF coverage throughout the elevation plane with no variation in physical height of HF antenna. The steering of ± 30 degree beam takes off angle has been achieved electronically without varying physical height of HF antenna. In thesis, an efficient solution for selection of HF frequencies along with optimum deployment of antenna system for various ranges has been proposed. The optimum HF prediction presented in previous works provides contours of the probability of successful HF transmission as a function of frequency and time of day which presents means for HF spectrum utilization, giving a probability number to any assigned frequency at a given time of day. However external environment strongly influences HF communication frequencies due to variation of ionosphere layers along with variation of time as well as environmental changes. Therefore, it is not always feasible to change the height of antenna with variation in time. Present work considers different sets of frequencies at four different time slots and subsequently selection of frequencies carried out based on maximum usable frequency (MUF), frequency of optimum traffic (FOT) predicted from HF prediction software. The proposed work provides efficient solution for finding out optimum frequencies during various time slots and HF antenna height estimated accordingly for different path lengths. Based on linear approximation between effective antenna height and frequency of operation, a new set of equations has been proposed in thesis which can directly be used to calculate effective height of the HF antenna for all distances between transmitting and receiving stations during various ranges of HF communication. Various past research work with respect to HF frequency tuning focuses on either electrically small antennas or narrow band, dual band frequency tuning. However long-range wide band HF antenna frequency tuning needed to be addressed. In the thesis, a frequency tunable HF antenna with feeding network modification technique has been proposed to vary the long range inverted ‘V’ HF dipole antenna resonant frequency while maintaining the fixed dipole length. With the implementation of feeding network modification technique most of day/night frequencies can be covered in a particular time slot resulting in highly effective and accurate HF contact with least variation of antenna height. Resonance frequency shifting (3 MHz) from 7.5 MHz to 10.5 MHz has been demonstrated with gain of 5.4 dB by varying length of feeding network for 10 MHz inverted ‘V’ HF dipole antenna. Extensive trials were conducted to validate the performance results and same found as desired. Open Space radiation pattern measurement of wide band HF dipole antenna is a cumbersome process due to its long dipole length in meters and possible usage of Unmanned Arial Vehicle (UAV) or airborne object based systems for antenna measurements. This is a complex and expensive setup. To verify the concept of proposed beam steerable HF antenna, a low cost, small form factor model at ISM band has also been proposed as beam steerable printed dipole antenna. The radiation pattern of beam steerable printed dipole antenna has been measured and same concept can be extended to beam steerable HF antenna also. Hence, there was a need to study on novel approaches to design beam steerable antenna for different operating frequency with reduced complexity. Similar to design topology of inverted V HF antenna, a small form factor model as beam steerable inverted V printed dipole antenna has been proposed in thesis using single dipole integrated with a varactor diode and parallel inductor in one arm of antenna. Most of previously fabricated electrically tuned antennas requires more than one dipole and multiple tuning elements mounted on common platform for scanning between two angles / switching at different elevation angles. Proposed Planar Inverted V Dipole Antenna is capable of continuous beam steering (± 30 degree) electronically using Single Printed Dipole and single varactor diode. Hence, resistive and parasitic losses of proposed antenna is considerably low along with low design cost and the least space requirements. Steering angle for antenna radiation pattern has been controlled by gradually varying the capacitance value keeping fixed value of parallel inductance. Required biasing circuit for varactor diode is intentionally placed on substrate at back side of dipole arm to avoid losses. Antenna gain for proposed design observed to be 4.1 dB with less than 1 dB scan loss and cross-pol well below -25 dB. The antenna is capable of steering beam ± 30 degree in elevation plane at 2.35 GHz by tuning varactor diode bias voltage to achieve various capacitance values. Beam steerable printed antennas are useful for various applications e.g. mobile communication, Internet of Things (IoT) application, vehicular communication, sensor etc. For such applications large phased array or reflect array antennas are less suitable in comparison to compact planar tunable antennas. Several designs topologies have been proposed to achieve beam steering using phase shifter, varactor diode and PIN diode-based feeding network. However, such circuits have limitation of high parasitic loss, high insertion loss and space complexity. A digitally controlled beam steerable printed dipole antenna operating in Industrial, Scientific, and Medical (ISM) band has been proposed at 2.45 GHz operating frequency with 120 MHz bandwidth and 4.57 dB max gain using PIN diodes switching mechanism. The fabricated antenna provides effective solution of beam steering by establishing adequate coverage in elevation plane using a single dipole element. The beam steering of antenna has been digitally controlled by varying the effective length of one dipole arm by switching the PIN diodes integrated on it. For effective digitally controlled beam steering, the DC biasing voltage applied for switching PIN diodes is regulated by Pulse Width Modulation (PWM) signal generated from microcontroller through RC filter. Biasing elements for antenna is intentionally placed on back side of substrate through via to minimize the effect on radiation pattern. The proposed antenna is capable of steering beam up to 45 degrees in elevation plane. The present method eases the fabrication and measurement setup. However, the concept can be rescaled to other frequency of interest including HF communication for conventional HF horizontal dipole antenna. The proposed work in thesis will definitely enhance the efficiency of short and long range communication, especially in the field of HF communication to provide a novel platform for optimum deployment of HF antenna ensuring the high operational efficiency of defense and other strategic fields of national security.
Calix[4] arene Derived Catalysts for Asymmetric Organic Transformations
(Indian Institute of Technology, Jodhpur, 2024-09-06) Sharma, Rakesh Kumar
This study draws attention to supramolecular catalysts. Cram, Lehn, and Pedersen’s pioneering works evolved around the use of supramolecules for molecular recognition and catalysis. Supramolecules offer defined binding pockets and noncovalent interactions such as hydrogen bonding, van der Waals forces, and π-π interactions, thus generating a reaction microenvironment for catalysis. Moreover, macrocycles can provide a preorganized arrangement of functional groups, such as binding sites or catalytically active groups, thus enabling a defined and possibly multivalent binding and activation of substrates. Various supramolecules such as calixarene, cryptands, cucurbiturils, and COFs, have been studied for a variety of applications for environmental and catalytic applications. Among various supramolecules, calixarene is the most important molecule for constructing conformationally rigid supramolecular catalysts. The unique properties of calix[4]arene lead to a rational design of homogeneous catalysts and due to the absence of metals, these methods are attractive for the preparation of pharmaceutical compounds, and chemical reactions that are of high value in the biological, and chemical industries. With the increasing demand for chiral products, many efficient catalysts have been developed for a wide range of organic transformations. The major part of asymmetric catalysis is homogeneous catalysts as they facilitate molecular reactions in an efficient manner with high chirality transfer. Calix[4]arene appended catalysts are easily recoverable, separable, and can be purified as well and these catalysts could be recycled with a good number of recyclable cycles. Out of various studies on asymmetric homogeneous organocatalyzed reactions, asymmetric Michael addition of acetylacetone to β-nitrostyrene is one of the key reactions with wide applications in pharmaceutical industries. Mono and dicationic Cinchona alkaloid-anchored calix[4]arenes as organocatalysts were effective and gave high enantiomeric induction (∼99% yield and >99% ee). Phase Transfer catalysts (PTC) based on calixarene supramolecules offer special advantages due to their unique properties with a rigid and stable aromatic cavity. Additionally, four phenolic hydroxyl groups of calix [4] arene provide synthetic adaptability and noncovalent interactions and a new catalyst designed utilizing quaternary ammonium Cinchona-functionalized crown ether-strapped calix[4]arenes as PTCs for asymmetric α-alkylation of glycine imines to α-alkylated glycinates with remarkable selectivity under ambient conditions (∼98% yield and >99% ee). Another PTC designed a highly selective α-methylbenzylamine functionalized crown-ether-appended calix [4]arene is harnessed for asymmetric nitroaldol reaction to provide nitroaldol adducts in high yields (up to 99 % yield) with good to excellent enantioselectivities (up to 99.8 % ee). Organocatalysis has gained noteworthy attention due to its efficiency, selectivity, and gratifying results at sub-stoichiometric amounts of the chiral catalyst and calixarene-derived enantioselective organocatalytic one-pot Strecker reaction catalyzed by camphor sulfonyl functionalized crown-ether-tethered calix [4] arene and provide the desired cyano adducts in high yields up to 99.9% yield and 99.2% ee. The synthetic utility of the Strecker reaction was used in the synthesis of Clopidogrel.
Flexible Resistive Memory Devices for Eco_friendly Electronics: Fabrication, Modeling, and Circuit Implementation
(Indian Institute of Technology, Jodhpur, 2025-06-20) Tiwari, Shree Parkash
The domain of flexible electronics has experienced an unprecedented rise in research and development activities, owing to its wide applications such as wearable devices, flexible displays, and sensors for biomedical purposes. This has motivated researchers to actively explore a suitable flexible memory device for storing the data generated or received by the flexible electronic circuit(s), to achieve monolithic integration i.e., fabrication of different flexible devices on the same substrate. Resistive random access memory (RRAM), a two terminal metal-insulator-metal structure device, with its various advantages such as ease of fabrication, low cost, high speed, ease of integration, and high scalability has emerged as a promising memory device for flexible electronic systems. Moreover, in view of ever increasing electronic waste, nature originated materials are being explored for the fabrication of different organic devices, and flexible electronics provide an added advantage of incorporating the organic materials in fabrication process, as most of these materials have properties such as solution processability and mechanical flexibility, along with non-toxicity, biocompatibility, and biodegradability which further instill eco-friendliness in devices. In this work, initially, natural proteins gelatin and egg-albumen, were investigated separately as a switching layer of RRAM devices. The prepared solutions of gelatin and albumen were deposited on the Indium-doped tin oxide coated polyethylene terephthalate substrate, and silver was used as the top electrode. The fabricated flexible RRAM devices with gelatin switching layer, have exhibited excellent switching behavior with Ion=Io f f ratio of greater than 105 and retention time of more than 104 seconds. Similarly, the albumen switching layer devices have also shown excellent resistive switching with high current on/off ratio of around 105 and memory retention time of 103 s without showing relevant degradation. The devices were then subjected to a mechanical bending of radius 7.5 mm, and it was observed that the device maintained the memory window of greater than 103 for more than 103 seconds. These results suggested that these organic proteins should further be explored for fabrication of flexible organic memory devices. Furthermore, to enhance the multiple cycle switching (endurance) of the devices, these proteins were investigated in hybrid bilayer combination with an ultrathin (5nm) layer of HfO2 as switching layer. Hybrid bilayer Ag/Gelatin/HfO2/ITO devices have shown a very high memory window of greater than 105 and data retention of 104 s without any degradation in a pristine state. Moreover, after bending the devices at a 12 mm radius followed by 7 mm, it was observed that the devices have maintained the memory window of 105 without any degradation in data retention, indicating excellent electromechanical stability of the devices. Similarly, Ag/Albumen/HfO2/ITO devices have demonstrated excellent switching characteristics with a current on/off ratio of greater than 104, stable retention of both low resistance and high resistance states, reliable multiple cycle switching, and very low switching power (with set power as 0.5 mW and reset power as 3.1 mW). The devices have also shown excellent electro-mechanical stability, with bending radii of 7.5 mm, 5 mm, and 2.5 mm. Additionally, to enable simulation based study of the fabricated device, a mathematical model of RRAM device has been studied and investigated. The model is then calibrated with the median of experimental results to extract the values of fitting parameters with less than 5% rms error. This ensures that the model can be utilized to simulate the switching characteristics of the fabricated device with greater accuracy. The model was further improved by introducing parameters for multiple layers of insulator, and multiple cycle variation parameters to make the model more robust. This improved RRAM model was then utilized to design a simple flexible hybrid electronic (FHE) circuit that is capable of generating 4 bit random numbers by utilizing intrinsic randomness of the device. The circuit is designed with 65nm technology node and the RRAM model with cyclic variation is utilized as the source of entropy. To verify the randomness of the proposed FHE circuit, the generated outputs have been test with NIST SP 800-22 test suits, a widely accepted set of tests to verify randomness of a bitstream. The outputs of this circuit have passed all the applicable tests of NIST SP 800-22, indicating the presence of randomness. This not only represents taht the output bitstreams are random in nature but also reflects that the improved model is capable of taking care of cyclic variations to a larger extent. Recently, Pectin was extracted from orange peel, and utilized as a switching layer. The fabricated flexible devices have demonstrated good resistive switching behavior with high current on/off ratio of 104 and retention time of 103 seconds. The fabricated device has then been investigated for synaptic behavior, probably for the first time, and it demonstrated depression characteristics with 10 ms input pulse, and the PPF relaxation time constants t1 = 0.3 ms and t2 = 4.1 ms are obtained. The results show a similar trend as that of a biological synapse, and thus it may be concluded that the fabricated device with pectin can be utilized for neuromorphic applications.