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arXiv 2025年

作者： Sau, Lakshmikanta Ghosh, Sasthi C. The Advanced Computing & Microelectronics Unit Indian Statistical Institute Kolkata700108 India

Reconfigurable intelligent surfaces (RISs) offer a viable way to improve the performance of the multi-hop device-to-device (D2D) communication. However, due to the substantial propagation and penetration losses of the millimeter waves (mmWaves), a direct line of sight (LoS) link and close proximity of a device pair are required for a high data rate. Static obstacles like trees and buildings can easily impede the direct LoS connectivity between a device pair. Hence, RIS placement plays a crucial role in establishing an indirect LoS link between them. Therefore, in this work, we propose a set cover-based RIS deployment strategy for both single and double RIS-assisted D2D communication. In particular, we have demonstrated that permitting reflections via two consecutive RISs can greatly lower the RIS density in the environment, preventing resource waste and enabling the service of more obstructed device pairs. After the RIS deployment, for information transfer, we also propose an energy-efficient group selection criteria. Moreover, we prove that sometimes double reflections are more beneficial than single reflection, which is counter-intuitive. Numerical results show that our approach outperforms a random and a recent deployment strategy. © 2025, CC BY-NC-SA.

关键词： Clutter (information theory)

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Energy-efficient UAV movement and user-UAV association in multi-UAV networks

arXiv

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arXiv 2025年

作者： Ghosh, Subhadip Mukherjee, Priyadarshi Ghosh, Sasthi C. Advanced Computing and Microelectronics Unit Indian Statistical Institute Kolkata700108 India

These days, unmanned aerial vehicle (UAV)-based millimeter wave (mmWave) communication systems have drawn a lot of attention due to the increasing demand for faster data rates. Given the susceptibility of mmWave signals to obstacles and high propagation loss of mmWaves, ensuring line-of-sight (LoS) connectivity is critical for maintaining robust and efficient communication. Furthermore, UAVs have limited power resource and limited capacity in terms of number of users it can serve. Most significantly different users have different delay requirements and they keep moving while interacting with the UAVs. In this paper, first, we have provided an efficient solution for the optimal movement of the UAVs, by taking into account the energy efficiency of the UAVs as well as the mobility and delay priority of the users. Next, we have proposed a greedy solution for the optimal user-UAV assignment. After that, the numerical results show how well the suggested solution performs in comparison to the current benchmarks in terms of delay suffered by the users, number of unserved users, and energy efficiency of the UAVs. © 2025, CC BY-NC-SA.

关键词： Unmanned aerial vehicles (UAV)

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Constructing Rectilinear Steiner Minimum Tree with Conditional Generative Adversarial Network 38

Constructing Rectilinear Steiner Minimum Tree with Condition...

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38th International Conference on VLSI Design, VLSID 2025

作者： Saha, Kritanta Banerjee, Pritha Sur-Kolay, Susmita Indian Statistical Institute Advanced Computing and Microelectronics Unit Kolkata India Sister Nivedita University Department of Computer Science and Engineering Kolkata India University of Calcutta Department of Computer Science and Engineering Kolkata India

ISBN: (纸本)9798331522445

Given n points in the 2D plane which are the pins of a net, a Rectilinear Steiner Minimum Tree (RSMT) which consists only of vertical and horizontal line segments is the shortest network to interconnect the pins along with a few extra (Steiner) points. An RSMT for a net has a minimum total wirelength in Manhattan distance and acts as a backbone to many state-of-the-art global routers. However, finding an RSMT is NPcomplete. In this work, we propose a method for constructing an RSMT with an image-to-image translation using a conditional generative adversarial network (cGAN) based model. Images of RSMTs with optimal wirelength for randomly generated nets form our training dataset. Experimental results show that, after training, our model generates RSMTs with = 0.348% wirelength error on average compared with the optimal solution for nets with degrees up to 50. This is the first successful attempt to solve the RSMT construction problem as an image-to-image translation problem using a cGAN based model. © 2025 IEEE.

关键词： Generative adversarial networks

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Time varying channel estimation for RIS assisted network with outdated CSI: Looking beyond coherence time

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Computer Communications 2025年 240卷

作者： Deb, Souvik Ghosh, Sasthi C. Advanced Computing & Microelectronics Unit Indian Statistical Institute West Bengal Kolkata700108 India

The channel estimation (CE) overhead for unstructured multipath-rich channels increases linearly with the number of reflective elements of reconfigurable intelligent surface (RIS). This results in a significant portion of the channel coherence time being spent on CE, reducing data communication time. Furthermore, due to the mobility of the user equipment (UE) and the time consumed during CE, the estimated channel state information (CSI) may become outdated during actual data communication. In recent studies, the timing for CE has been primarily determined based on the coherence time interval, which is dependent on the velocity of the UE. However, the effect of the current channel condition and pathloss of the UEs can also be utilized to control the duration between successive CE to reduce the overhead while still maintaining the quality of service. Furthermore, for multi-user systems, the appropriate coherence time intervals of different users may be different depending on their velocities. Therefore CE carried out ignoring the difference in coherence time of different UEs may result in the estimated CSI being detrimentally outdated for some users. In contrast, others may not have sufficient time for data communication. To this end, based on the throughput analysis on outdated CSI, an algorithm has been designed to dynamically predict the next time instant for CE after the current CSI acquisition. In the first step, optimal RIS phase shifts to maximize channel gain is computed. Based on this and the amount of degradation of signal to interference plus noise ratio due to outdated CSI, transmit powers and bandwidth are allocated for the UEs and finally the next time instant for CE is predicted such that the aggregated throughput is maximized. Simulation results confirm that our proposed algorithm outperforms the coherence time-based strategies and an existing algorithm that adaptively changes inter CE duration. © 2025 Elsevier B.V.

关键词： Bandwidth

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DCSK-based Waveform Design for Self-sustainable RIS-aided Noncoherent SWIPT

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IEEE Transactions on Communications 2025年

作者： Mukherjee, Priyadarshi Psomas, Constantinos Krikidis, Ioannis Indian Statistical Institute Advanced Computing and Microelectronics Unit Kolkata India University of Cyprus Department of Electrical and Computer Engineering Nicosia1678 Cyprus

This paper investigates the problem of transmit waveform design in the context of a chaotic signal-based self-sustainable reconfigurable intelligent surface (RIS)-aided system for simultaneous wireless information and power transfer (SWIPT). Specifically, we propose a differential chaos shift keying (DCSK)-based RIS-aided point-to-point set-up, where the RIS is partitioned into two non-overlapping surfaces. The elements of the first sub-surface perform energy harvesting (EH), which in turn, provide the required power to the other sub-surface operating in the information transfer (IT) mode. In this framework, by considering a generalized frequency-selective Nakagami-m fading scenario as well as the nonlinearities of the EH process, we derive closed-form analytical expressions for both the bit error rate (BER) at the receiver and the harvested power at the RIS. Our analysis demonstrates, that both these performance metrics depend on the parameters of the wireless channel, the transmit waveform design, and the number of reflecting elements at the RIS, which switch between the IT and EH modes, depending on the application requirements. Moreover, we show that, having more reflecting elements in the IT mode is not always beneficial and also, for a given acceptable BER, we derive a lower bound on the number of RIS elements that need to be operated in the EH mode. Furthermore, for a fixed RIS configuration, we investigate a trade-off between the achievable BER and the harvested power at the RIS and accordingly, we propose appropriate transmit waveform designs. Finally, our numerical results illustrate the importance of our intelligent DCSK-based waveform design on the considered framework. © 1972-2012 IEEE.

关键词： Energy harvesting

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Constructing Rectilinear Steiner Minimum Tree with Conditional Generative Adversarial Network

Constructing Rectilinear Steiner Minimum Tree with Condition...

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International Conference on VLSI Design

作者： Kritanta Saha Pritha Banerjee Susmita Sur-Kolay Advanced Computing and Microelectronics Unit Indian Statistical Institute Kolkata India Department of Computer Science and Engineering Sister Nivedita University Kolkata India Department of Computer Science and Engineering University of Calcutta Kolkata India

ISBN: (数字)9798331522445

ISBN: (纸本)9798331522452

Given n points in the 2D plane which are the pins of a net, a Rectilinear Steiner Minimum Tree (RSMT) which consists only of vertical and horizontal line segments is the shortest network to interconnect the pins along with a few extra (Steiner) points. An RSMT for a net has a minimum total wirelength in Manhattan distance and acts as a backbone to many state-of-the-art global routers. However, finding an RSMT is NPcomplete. In this work, we propose a method for constructing an RSMT with an image-to-image translation using a conditional generative adversarial network (cGAN) based model. Images of RSMTs with optimal wirelength for randomly generated nets form our training dataset. Experimental results show that, after training, our model generates RSMTs with $\leq 0.348\%$ wirelength error on average compared with the optimal solution for nets with degrees up to 50. This is the first successful attempt to solve the RSMT construction problem as an image-to-image translation problem using a cGAN based model.

关键词： Training Steiner trees Translation Computational modeling Machine learning Very large scale integration Generative adversarial networks Generators Pins Testing

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Efficient and Fault-Tolerant Memristive Neural Networks with In-Situ Training

SSRN

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SSRN 2025年

作者： Prajapati, Santlal Mondal, Manobendra Nath Sur-Kolay, Susmita Indian Statistical Institute Advanced Computing and Microelectronics Unit West Bengal Kolkata700108 India UPES School of Computer Science Uttarakhand Dehradun248007 India Ashoka University Department of Computer Science Haryana Sonipat131029 India

In an artificial neural network (ANN), the most frequent and demanding operations are matrix-vector multiplication, vector-vector outer product, and weight matrix updates. These operations require parallel and in-memory processing hardware architectures to accelerate the training of the ANN. This article introduces a novel memristor-based multi-layer neural network (memristive MLNN) architecture featuring an efficient in-situ supervised training method based on gradient descent backpropagation. The proposed memristive MLNN can execute the aforementioned operations in O(1) time by leveraging in-memory and parallel computing capabilities. A single memristor without transistors is sufficient to realize a synapse. The performance of our architecture is evaluated by training and testing the memristive MLNN using the LTspice simulator, which achieved accuracies of 98.22%, 90.43%, and 98.59% on the IRIS, NASA asteroid, and Breast Cancer Wisconsin data sets respectively. The resilience of the architecture to memristor faults owing to a stuck-at-a-conducting state is assessed by injecting faults at certain percentages of randomly chosen memristors. The impact of nonlinearity, present in the memristor's conductance, on the accuracy of memristive MLNN is analyzed. We also evaluate the memristive MLNN's performance with a 10% variation in memristors. The simulation results establish that the network's performance is not affected significantly by non-linearity, device variation, and faulty memristors. © 2025, The Authors. All rights reserved.

关键词： NASA

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Growth rates of the number of empty triangles and simplices

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Computational Geometry 2026年 130卷

作者： Bhaswar B. Bhattacharya Sandip Das Sk Samim Islam Saumya Sen Department of Statistics and Data Science University of Pennsylvania USA Advanced Computing and Microelectronics Unit Indian Statistical Institute Kolkata India

Given a set P of n points in R 2 , in general position, denote by N 2 ( P ) the number of empty triangles with vertices in P . In this paper we investigate by how much N 2 ( P ) changes if a point x is removed from P . By constructing a graph G 2 ( x , P ) based on the arrangement of the empty triangles incident on x , we transform this geometric problem to the problem of counting triangles in the graph G 2 ( x , P ) . We study properties of the graph G 2 ( x , P ) and, in particular, show that it is diamond-free. This relates the growth rate of the number of empty triangles to the famous Ruzsa–Szemerédi problem. We also derive similar bounds for the growth rate of the number of empty simplices for point sets in R d .

关键词： Discrete geometry Empty triangles and simplices Extremal combinatorics Diamond-free graphs

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On L(k, k-1, ..., 1) labeling of triangular lattice

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Electronic Notes in Discrete Mathematics 2015年 48卷 281-288页

作者： Nandi, Soumen Sen, Sagnik Ghosh, Sasthi C. Das, Sandip Advanced Computing and Microelectronics Unit Indian Statistical Institute Kolkata India

An n - L(k, k-1, ..., 1) labeling of a simple graph G is a mapping f: V(G) → {0, 1, ..., n} such that |f(u) - f(v)| ≥ k+1 - d(u,v), for all u,v∈V(G), where d(u,v) is the length of the shortest path connecting u and v. The L(k, k-1, ..., 1) labeling span λk(F) of a family of graphs F is the minimum n for which each G∈F admits an n - L(k, k-1, ..., 1) labeling. For the family L3 of all subgraphs of an infinite triangular lattice we provide upper and lower bounds of λk(L3) for general k and show that the ratio of the upper and lower bound is at most 43. The upper bound is given by providing an assignment algorithm to the vertices of the infinite triangular lattice. © 2015 Elsevier B.V.

关键词： Approximation ratio Assignment algorithm Distance k - clique L(k, k-1, ..., 1) labeling span Triangular lattice

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Classification of long-bone fractures based on digital-geometric analysis of X-ray images

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Pattern Recognition and Image Analysis 2016年第4期26卷 742-757页

作者： Bandyopadhyay, O. Biswas, A. Bhattacharya, B.B. Advanced Computing and Microelectronics Unit Indian Statistical Institute Kolkata India Department of Information Technology Indian Institute of Engineering Science and Technology Shibpur India

The classification of fractured of a patient plays an important role in orthopaedic evaluation and diagnosis. It not only aids in assessing the severity of the disease or injury but also serves as a basis of treatment or surgical correction. This paper proposes a novel approach to automated classification of long-bone fractures based on the analysis of an input X-ray image. The method consists of four major steps: (i) extraction of the bone-contour from a given X-ray image, (ii) identification of fracture-points or cracks, (iii) determination of an equivalent set of geometric features in tune with the Müller-AO clinical classification of fractures, and (iv) identification and detailed assessment of the fracture-type. The decision procedure makes use of certain geometric properties of digital curves such as relaxed digital straight line segments (RDSS), arcs, discrete curvature, and concavity index. The proposed method for the analysis of fractures is applied on different types of bone-images and is observed to have produced correct classification in most of the test-cases. © 2016, Pleiades Publishing, Ltd.

关键词： Fracture

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