arXiv subjects

Vivek Ashok Bohara

Publications and source records attributed to Vivek Ashok Bohara.

At least 19 recordsLinked to original sources

arXiv2026

Energy-Efficient THz Sensing with Hybrid THz/VLC Communication Under Human Blockage Effects

This paper presents an energy-efficient indoor system integrating \ac{THz} with \ac{VLC}. \ac{THz} communication offers ultra-high-capacity links but is limited by severe path loss, atmospheric absorption, and susceptibility to blockages. In contrast, \ac{VLC} provides robust, wide indoor coverage with illumination support, thereby enabling reliable, high-speed hybrid connectivity. To leverage their respective strengths, we propose a hybrid framework that integrates \ac{$THz_s-AP$} with hybrid \ac{$THz_c/VLC_c-AP$}, enabling reliable coverage and enhancing the \ac{EE} from an \ac{ISAC} perspective. We first perform optimal power allocation between the \ac{$THz_s-AP$} and \ac{$THz_c-AP$} to optimized the set of users served by the \ac{$THz_c-AP$} link, considering monostatic sensing performance metrics such as \ac{$P_d$}, \ac{$FA_p$} and \ac{$SC_p$} under the impact of human blockages are evaluated. Subsequently, the overall network power consumption is minimized via a mixed-integer linear programming (MILP) optimization that optimally selects the active \ac{$VLC_c-APs$} and assigns transmit powers. Furthermore, extensive performance evaluations are conducted to analyze key metrics, including average energy efficiency, average spectral efficiency, average sensing rate, and average communication rate. Simulation results demonstrate that, under \ac{THz} sensing, most users are connected to the \ac{$THz_c-AP$} in the absence of blockages, whereas in the presence of blockages, the majority are served by the \ac{$VLC_c-APs$}. Overall, all users maintain reliable coverage with high \ac{EE}.

eess.SP↗

arXiv2025

UAV-Based Cell-Free Massive MIMO: Joint Placement and Power Optimization under Fronthaul Capacity Limitations

We consider a cell-free massive multiple-input multiple-output (mMIMO) network, where unmanned aerial vehicles (UAVs) equipped with multiple antennas serve as distributed UAV-access points (UAV-APs). These UAV-APs provide seamless coverage by jointly serving user equipments (UEs) with out predefined cell boundaries. However, high-capacity wireless networks face significant challenges due to fronthaul limitations in UAV-assisted architectures. This letter proposes a novel UAV-based cell-free mMIMO framework that leverages distributed UAV-APs to serve UEs while addressing the capacity constraints of wireless fronthaul links. We evaluate functional split Options 7.2 and 8 for the fronthaul links, aiming to maximize the minimum signal-to-interference-plus-noise ratio (SINR) among the UEs and minimize the power consumption by optimizing the transmit powers of UAV-APs and selectively activating them. Our analysis compares sub-6 GHz and millimeter wave (mmWave) bands for the fronthaul, showing that mmWave achieves superior SINR with lower power consumption, particularly under Option 8. Additionally, we determine the minimum fronthaul bandwidth required to activate a single UAV-AP under different split options.

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arXiv2025

Handover_Management_in_UAV_Networks_with_Blockages

We investigate the performance of unmanned aerial vehicle (UAV)-based networks in urban environments characterized by blockages, focusing on their capability to support the service demands of mobile users. The UAV-base stations (UAV-BSs) are modeled using a two-dimensional (2-D) marked- Poisson point process (MPPP), where the marks represent the altitude of each UAV-BS. Leveraging stochastic geometry, we analyze the impact of blockages on network reliability by studying the meta distribution (MD) of the signal-to-interference noise ratio (SINR) for a specific reliability threshold and the association probabilities for both line-of-sight (LoS) and non line-of-sight (NLoS) UAV-BSs. Furthermore, to enhance the performance of mobile users, we propose a novel cache-based handover management strategy that dynamically selects the cell search time and delays the received signal strength (RSS)-based base station (BS) associations. This strategy aims to minimize unnecessary handovers (HOs) experienced by users by leveraging caching capabilities at user equipment (UE), thus reducing latency, ensuring seamless connectivity, and maintaining the quality of service (QoS). This study provides valuable insights into optimizing UAV network deployments to support the stringent requirements in the network, ensuring reliable, low-latency, and high-throughput communication for next-generation smart cities.

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arXiv2025

Analysis of Climatic Trends and Variability in Indian Topography

The climatic change is one of the serious concerns nowadays. The impacts of climate change are global in scope and unprecedented in scale. Moreover, a small perturbation in climatic changes affects not only the pristine ecosystem but also the socioeconomic sectors. Specifically, the affect of climatic changes is related to frequent casualties. This makes it essential to dwelve deeper into analyzing the socio-climatic trends and variability. This work provides a comprehensive analysis of India's climatic trends, emphasizing on regional variations and specifically delving into the unique climate of Delhi. Specifically, this research unveils the temporal and spatial variations in temperature patterns by amalgamating extensive datasets encompassing India's diverse landscapes. The study uses advanced statistical tools and methodologies to scrutinize temperature's annual and seasonal variability. The insights drawn from this rigorous analysis may offer invaluable contributions to regional planning strategies, adaptive measures, and informed decision-making amidst the complex impacts of climate change. By bridging the gap between broader climatic trends and localized impacts, this research aims to facilitate more effective measures to mitigate and adapt to the multifaceted challenges of climate change, ensuring a more nuanced and tailored approaches. We utilized the Mann-Kendall test and Theil-Sen's slope estimator to analyze the trends and variability of the climatic conditions over the decades. The results demonstrate that temperature variations have increased over 0.58oC on average over the last decade. Moreover, over last decade the variability of Indian states shows that Lakshadweep faced the highest change (0.87oC), highlighting coastal vulnerability, while Tripura observed the least change of 0.07oC.

cs.SI↗

arXiv2024

Towards 6G-V2X: Aggregated RF-VLC for Ultra-Reliable and Low-Latency Autonomous Driving

We are witnessing a transition to a new era where driverless cars will be pervasively connected to deliver significantly improved safety, traffic efficiency, and travel experiences. A diverse set of advanced vehicular use cases including connected autonomous vehicles will be made possible by building upon the emerging sixth-generation (6G) wireless networks. Among many 6G wireless technologies, the principal objective of this paper is to introduce the potential benefits of the hybrid integration of Vehicular Visible Light Communication (V VLC) and Vehicular Radio Frequency (V RF) communication systems by studying the impact of interference as well as various meteorological phenomenon viz. rain, fog and dry snow. In particular, we show that regardless of any meteorological impact, a properly configured link-aggregated hybrid V-VLC/V-RF system is capable of meeting stringent ultra high reliability (>99.999%) and ultra-low latency (<3 ms) requirements, making it a promising candidate for 6G Vehicle-to-Everything (V2X) Communications. To stimulate future research in the hybrid RF-VLC V2X space, we also highlight the potential challenges and research directions.

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arXiv2022

Optical IRS Aided B5G V2V Solution for Road Safety Applications

In this work, we showcase the potential benefit of employing optical intelligent reflecting surfaces (O-IRS) for improving safety message dissemination for vehicular visible light communication (V-VLC) systems particularly at the road intersections. Buildings, roadside structures, signboards, and other impediments commonly hinder line-of-sight (LoS) communication between vehicles at urban crossroads scenarios. We propose using O-IRS at road intersection to improve the communication link's reliability. We compare the performance of proposed scheme with baseline scenarios such as optical relay and non line-of-sight (NLOS) road reflection (NRR) aided vehicle-to-vehicle (V2V) communication. From obtained results, it has been shown that O-IRS offers considerable performance enhancement as compared to the baseline scenarios. In particular, O-IRS can achieve longer communication range as compared to the optical relay aided V-VLC systems while ensuring desired quality-of-service (QoS).

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arXiv2022

Cache Enabled UAV HetNets Access xHaul Coverage Analysis and Optimal Resource Partitioning

We study an urban wireless network in which cache-enabled UAV-Access points (UAV-APs) and UAV-Base stations (UAV-BSs) are deployed to provide higher throughput and ad-hoc coverage to users on the ground. The cache-enabled UAV-APs route the user data to the core network via either terrestrial base stations (TBSs) or backhaul-enabled UAV-BSs through an xHaul link. First, we derive the association probabilities in the access and xHaul links. Interestingly, we show that to maximize the line-of-sight (LoS) unmanned aerial vehicle (UAV) association, densifying the UAV deployment may not be beneficial after a threshold. Then, we obtain the signal to interference noise ratio (SINR) coverage probability of the typical user in the access link and the tagged UAV-AP in the xHaul link, respectively. The SINR coverage analysis is employed to characterize the successful content delivery probability by jointly considering the probability of successful access and xHaul transmissions and successful cache-hit probability. We numerically optimize the distribution of frequency resources between the access and the xHaul links to maximize the successful content delivery to the users. For a given storage capacity at the UAVs, our study prescribes the network operator optimal bandwidth partitioning factors and dimensioning rules concerning the deployment of the UAV-APs.

cs.IT↗

arXiv2022

A Tutorial on Decoding Techniques of Sparse Code Multiple Access

Sparse Code Multiple Access (SCMA) is a disruptive code-domain non-orthogonal multiple access (NOMA) scheme to enable \color{black}future massive machine-type communication networks. As an evolved variant of code division multiple access (CDMA), multiple users in SCMA are separated by assigning distinctive sparse codebooks (CBs). Efficient multiuser detection is carried out at the receiver by employing the message passing algorithm (MPA) that exploits the sparsity of CBs to achieve error performance approaching to that of the maximum likelihood receiver. In spite of numerous research efforts in recent years, a comprehensive one-stop tutorial of SCMA covering the background, the basic principles, and new advances, is still missing, to the best of our knowledge. To fill this gap and to stimulate more forthcoming research, we provide a holistic introduction to the principles of SCMA encoding, CB design, and MPA based decoding in a self-contained manner. As an ambitious paper aiming to push the limits of SCMA, we present a survey of advanced decoding techniques with brief algorithmic descriptions as well as several promising directions.

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arXiv2022

Low-Complexity Codebook Design for SCMA based Visible Light Communication

Sparse code multiple access (SCMA), as a code-domain non-orthogonal multiple access (NOMA) scheme, has received considerable research attention for enabling massive connectivity in future wireless communication systems. In this paper, we present a novel codebook (CB) design for SCMA based visible light communication (VLC) system, which suffers from shot noise. In particular, we introduce an iterative algorithm for designing and optimizing CB by considering the impact of shot noise at the VLC receiver. Based on the proposed CB, we derive and analyze the theoretical bit error rate (BER) expression for the resultant SCMA-VLC system. The simulation results show that our proposed CBs outperform CBs in the existing literature for different loading factors with much less complexity. Further, the derived analytical BER expression well aligns with simulated results, especially in high signal power regions.

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arXiv2021

A Tutorial to Sparse Code Multiple Access

Sparse Code Multiple Access (SCMA) is an enabling code-domain non-orthogonal multiple access (NOMA)scheme for massive connectivity and ultra low-latency in future machine-type communication networks. As an evolved variant of code division multiple access (CDMA), multiple users in SCMA are separated by assigning distinctive codebooks which display certain sparsity. At an SCMA receiver, efficient multiuser detection is carried out by employing the message passing algorithm (MPA) which exploits the sparsity of codebooks to achieve error rate performance approaching to that of the maximum likelihood receiver. Despite numerous research efforts on SCMA in recent years, a comprehensive and in-depth tutorial to SCMA is missing, to the best of our knowledge. To fill this gap and to stimulate more forthcoming research, we introduce the principles of SCMA encoding, codebook design, and MPA based decoding in a self-contained manner for layman researchers and engineers.

cs.IT↗

arXiv2020

eSampling: Energy Harvesting ADCs

Analog-to-digital converters (ADCs) allow physical signals to be processed using digital hardware. The power consumed in conversion grows with the sampling rate and quantization resolution, imposing a major challenge in power-limited systems. A common ADC architecture is based on sample-and-hold (S/H) circuits, where the analog signal is being tracked only for a fraction of the sampling period. In this paper, we propose the concept of eSampling ADCs, which harvest energy from the analog signal during the time periods where the signal is not being tracked. This harvested energy can be used to supplement the ADC itself, paving the way to the possibility of zero-power consumption and power-saving ADCs. We analyze the tradeoff between the ability to recover the sampled signal and the energy harvested, and provide guidelines for setting the sampling rate in the light of accuracy and energy constraints. Our analysis indicates that eSampling ADCs operating with up to 12 bits per sample can acquire bandlimited analog signals such that they can be perfectly recovered without requiring power from the external source. Furthermore, our theoretical results reveal that eSampling ADCs can in fact save power by harvesting more energy than they consume. To verify the feasibility of eSampling ADCs, we present a circuit-level design using standard complementary metal oxide semiconductor (CMOS) 65 nm technology. An eSampling 8-bit ADC which samples at 40 MHZ is designed on a Cadence Virtuoso platform. Our experimental study involving Nyquist rate sampling of bandlimited signals demonstrates that such ADCs are indeed capable of harvesting more energy than that spent during analog-to-digital conversion, without affecting the accuracy.

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arXiv2019

eSampling: Rethinking Sampling with Energy Harvesting

In general, real world signals are analog in nature. To capture these signals for further processing, or transmission, signals are converted into digital bits using analog-to-digital converter (ADC). In this conversion, a good amount of signal energy is wasted because signal that is captured within the sampling duration is utilized, while rest of the signal waveform is discarded. In this context, this paper revisits the sampling process and proposes to utilize this discarded signal for energy harvesting, naming the method as eSampling, i.e., sampling with energy harvesting. The proposed idea of \textit{eSampling} is demonstrated via modifying the circuitry of the hold phase of ADC. The system is designed using standard Complementary Metal Oxide Semiconductor (CMOS) 65 nm technology and simulations are performed on Cadence Virtuoso platform with input signal at different frequencies (100 Hz and 40 MHz). These results show that 10\% of the sampling period is sufficient to sample the input analog signal, while the remaining 90\% can be used for harvesting the energy from the input analog signal. In order to validate eSampling for practical scenarios, results with hardware setup have also been added.

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arXiv2018

PCI-MDR: Missing Data Recovery in Wireless Sensor Networks using Partial Canonical Identity Matrix

Data loss in wireless sensor networks (WSNs) is quite prevalent. Since sensor nodes are employed for various critical applications, accurate recovery of missing data is important. Researchers have exploited different characteristics of WSN data, such as low rank, spatial and temporal correlation for missing data recovery. However, the performance of existing methods is dependent on various factors. For instance, correct rank estimation is required for exploiting the low-rank behaviour of WSNs, whereas correlation information among the nodes should be known for exploiting spatial correlation. Further, the amount of missing data should not be massive for exploiting temporal correlation. To overcome the above-mentioned drawbacks, a novel method PCI-MDR has been proposed in this paper. It utilizes compressive sensing with partial canonical identity matrix for the recovery of missing data in WSNs. To validate the proposed method, the results have been obtained on the real data set of temperature sensors from the Intel Lab. The proposed method is observed to perform superior to the existing methods, yielding significant improvement

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arXiv2018

D2D User Selection For Simultaneous Spectrum Sharing And Energy Harvesting

This paper presents a device-to-device (D2D) user selection protocol wherein multiple D2D pairs coexist with a cellular network. In the developed framework, certain D2D users harvest energy and share the spectrum of the cellular users by adopting a hybrid time switching and power splitting protocol. The D2D user which harvests the maximum energy and achieves the desired target rate for the cellular communication is selected to serve as a decode-and-forward (DF) relay for the cellular user. The proposed work analyzes the impact of increase in the number of D2D users on the performance of cellular user as well as derives an upper bound on the time duration of energy harvesting within which best possible rate for cellular user can be obtained. The performance of the proposed protocol has been quantified by obtaining the closed form expressions of outage probability.

cs.IT↗

arXiv2018

Cooperative Spectrum Sharing Relaying Protocols With Energy Harvesting Cognitive User

The theory of wireless information and power transfer in energy constrained wireless networks has caught the interest of researchers due to its potential in increasing the lifetime of sensor nodes and mitigate the environment hazards caused by conventional cell batteries. Similarly, the advancements in areas of cooperative spectrum sharing protocols has enabled efficient use of frequency spectrum between a licensed primary user and a secondary user. In this paper, we consider an energy constrained secondary user which harvests energy from the primary signal and relays the primary signal in exchange for the spectrum access. We consider Nakagami-m fading model and propose two key protocols, namely time-splitting cooperative spectrum sharing (TS-CSS) and power-sharing cooperative spectrum sharing (PS-CSS), and derive expressions for the outage probabilities of the primary and secondary user in decode-forward and amplify-forward relaying modes. From the obtained results, it has been shown that the secondary user can carry its own transmission without adversely affecting the performance of the primary user and that PS-CSS protocol outperforms the TS-PSS protocol in terms of outage probability over a wide range of Signal to noise ratio(SNRs). The effect of various system parameters on the outage performance of these protocols have also been studied.

cs.NI↗

arXiv2017

Powering Future Mobile Phones Through RF Energy Harvesting

In this paper we present the preliminary measurement results of harvesting radio frequency(RF) energy from the mobile phones. The aim is to revolutionize the way mobile phones are being charged and paving a way of charging the future mobile phones through RF energy harvesting. In order to measure the amount of energy that can be harvested, mobile phones from two different manufactures namely Asus and Samsung have been used. It was shown that depending on the manufacturer it is possible to harvest 1.53 joules amount of energy per day.

cs.NI↗

arXiv2016

A Proof-of-Concept Device-to-Device Communication Testbed

This paper presents the design and development of proof-of-concept Device-to-Device (D2D) Communication testbed. This testbed also seeks to address the design issues involved in the implementation of a D2D network in a realistic scenario. The performance of this testbed has been validated by emulating a Cellular network consisting of a Base Staion (BTS) and many D2D devices in its proximity. The devices and the BTS coordinate and communicate with each other to select the optimum communication range, mode of communication and transmit parameters. Through the experimental results it has been shown that the proposed testbed has a communication radius of 120m and a D2D communication range of 62m with over 90% efficiency.

cs.NI↗

arXiv2015

iDART-Intruder Detection and Alert in Real Time

In this work, we design and develop a smart intruder detection and alert system which aims to elevate the security as well as the likelihood of true positive identification of trespassers and intruders as compared to other commonly deployed electronic security systems. Using multiple sensors, this system can gauge the extent of danger exhibited by a person or animal in or around the home premises, and can forward various critical information regarding the event to home owners as well as other specified entities, such as relevant security authorities.

cs.CY↗