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25th International Symposium on Stabilization, Safety, and Security of Distributed Systems, SSS 2023

作者： Das, Bibhuti Mukhopadhyaya, Krishnendu Advanced Computing and Microelectronics Unit Indian Statistical Institute Kolkata India

ISBN: (纸本)9783031442735

In this paper, we study the uniform k-circle formation by a swarm of mobile robots with dimensional extent. For some k> 0, the k-circle formation problem asks the robots to form disjoint circles. Each circle must be centered at one of the pre-fixed points given in the plane. Each circle should contain exactly k distinct robot positions. The k-circle formation problem has already been studied for punctiform robots in the plane. In this paper, the robots are represented by transparent unit disks in the plane. They are autonomous, anonymous, homogeneous, and silent. The robots are oblivious and execute Look-Compute-Move (LCM) cycle under a fair asynchronous scheduler. The direction and orientation of one of the axes are agreed upon by the robots. In this setting, we have characterized all the initial configurations and values of k for which the uniform k-circle formation problem is deterministically unsolvable. For the remaining configurations and values of k, a deterministic distributed algorithm has been proposed that solves the uniform k-circle formation problem within finite time. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.

关键词： Distributed computer systems

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LazyUAV: A Minimal Displacement Coverage Strategy for Multi-UAV mmWave Networks 3

LazyUAV: A Minimal Displacement Coverage Strategy for Multi-...

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3rd IEEE International Mediterranean Conference on Communications and Networking, MeditCom 2023

作者： Sarkar, Subhojit Dutta, Rathindra Nath Ghosh, Sasthi C. Indian Statistical Institute Advanced Computing and Microelectronics Unit Kolkata India

ISBN: (纸本)9798350333732

Unmanned Aerial Vehicles (UAVs) are a potential platform for deploying millimeter wave (mmWave) base stations. Their high spatial flexibility makes them an attractive choice for the deployment in disaster management scenarios, and for offloading in crowded areas. Apart from the stringent propagation requirements of mmWaves, one challenge that has to be addressed is the limited power onboard a UAV, which is used to hover and move the device, and of course, to transmit data. In this paper, we deal with the deployment of UAVs with an aim to minimising their displacement in subsequent time. We take into consideration user mobility, and propose LazyUAV, a Set-Cover based geometric approach to minimise UAV displacement, while maintaining maximal coverage. Via extensive simulations, we demonstrate the effectiveness of our approach. © 2023 IEEE.

关键词： Millimeter waves

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Joint Base Station and Reflector Placement in an urban mmWave Network 3

Joint Base Station and Reflector Placement in an urban mmWav...

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3rd IEEE International Mediterranean Conference on Communications and Networking, MeditCom 2023

作者： Dutta, Rathindra Nath Sarkar, Subhojit Ghosh, Sasthi C. Indian Statistical Institute Advanced Computing and Microelectronics Unit Kolkata India

ISBN: (纸本)9798350333732

Millimeter-wave (mmWave) technology is expected to be the backbone of future communication networks. However, for all its benefits, mmWave communication comes with its fair share of challenges. In this context, the obstacle free strict line-of-sight (LOS) requirement is one of the primary hurdles that has to be crossed. One way to deal with this problem is to densely deploy small range base stations, called gNBs, to overcome outage due to obstacles. Reflectors have been proposed to augment the transmission environment, and reflect mmWaves bypassing the obstacles. Evidently, they can be used to increase the coverage area that do not have LOS with the available gNBs. We argue that considering the placement of gNBs and reflectors independently may lead to suboptimal solution. In this paper, we consider an urban deployment scenario, and attempt to maximally cover it by jointly placing the gNBs and reflectors. Given the hardness of the joint problem, we first develop a set cover based greedy solution and also provide a linear programming (LP) relaxation based solution. With extensive simulations, we show that with fixed number of available gNBs and reflectors to be placed, both our joint placement solutions can achieve a larger coverage compared to an existing approach. © 2023 IEEE.

关键词： Base stations

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Improved Lower Bound for L(1, 2)-Edge-Labeling of Infinite 8-Regular Grid 9th

Improved Lower Bound for L(1, 2)-Edge-Labeling of Infinite ...

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The 9th International Conference on Mathematics and computing (ICMC 2023)

作者： Koley, Subhasis Ghosh, Sasthi C. Advanced Computing and Microelectronics unit Indian Statistical Institute 203 B. T. Road Kolkata700108 India

ISBN: (纸本)9789819930791

Let us take two given integers h and k where h, k≥ 0 and a graph G= (V(G), E(G) ). An L(h, k)-edge-labeling for G is defined as a function f′: E(G) → { 0, 1, ⋯, n} such that ∀ e1, e2∈ E(G), | f′(e1) - f′(e2) | ≥ h when d′(e1, e2) = 1 and | f′(e1) - f′(e2) | ≥ k when d′(e1, e2) = 2 where d′(e1, e2) denotes the distance between e1 and e2 in G. If there is no other way to connect e1 and e2 with less than k′- 1 number of edges in G, then d′(e1, e2) = k′. The objective is to find the span which is the least value of n obtained over all such L(h, k)-edge-labeling for G, and it is denoted as λh,k′(G). Motivated from the channel assignment problem in wireless network, L(h, k)-edge-labeling has been studied for various infinite regular grid graphs. For infinite 8-regular grid T8, it is known in the existing literature that 25≤λ1,2′(T8)≤28. But the lower and upper bounds obtained there are not identical. Here, we improve the lower bound and prove that λ1,2′(T8)≥28 and eventually it is proved that λ1,2′(T8)=28. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd 2023.

关键词： Combinatorial optimization

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Double reflections Assisted RIS Deployment and Energy-efficient Group Selection in mmWaves D2D Communication

arXiv

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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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A Study on the Problems of Dispersion and Exploration on Graph Topology 22

A Study on the Problems of Dispersion and Exploration on Gra...

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23rd International Conference on Distributed computing and Networking, ICDCN 2022

作者： Das, Archak Bose, Kaustav Sau, Buddhadeb Mathematics Jadavpur University India Advanced Computing and Microelectronics Unit Indian Statistical Institute Kolkata India

ISBN: (纸本)9781450395601

In this paper we discuss two important problems: Dispersion and Exploration. We have provided two optimal algorithms for each of them. For Dispersion we have provided an algorithm which is optimal in terms of memory complexity and for Exploration we have given an algorithm which is optimal in terms of number of robots in a dynamic ring. We give a brief idea about our algorithms and novelty of our techniques. © 2022 ACM.

关键词： Topology

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Priority aware grouping-based multihop routing scheme for RIS-assisted wireless networks

arXiv

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arXiv 2024年

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

Reconfigurable intelligent surfaces (RISs) is a novel communication technology that has been recognized and recently presented as a candidate for beyond fifth generation wireless communication technology. In this paper, we propose a priority aware user traffic dependent grouping based multihop routing scheme for a RIS-assisted millimeter wave (mmWave) device-to-device (D2D) communication network with spatially correlated channels. Specifically, the proposed scheme exploits the priority of the users (based on their respective delay constrained applications) and the aspect of spatial correlation in the narrowly spaced reflecting elements of the RISs. In this context, we establish a multihop connection for information transfer from one of the users to its desired receiver based on the other users in the neighbourhood, their respective traffic characteristics, and the already deployed RISs in the surroundings. Moreover, we also take into account the impact of considering practical discrete phase shifts at the RIS patches instead of its ideal continuous counterpart. Furthermore, we claim as well as demonstrate that the existing classic least remaining distance (LRD)-based approach is not always the optimal solution. Finally, numerical results demonstrate the advantages of the proposed strategy and that it significantly outperforms the existing benchmark schemes in terms of system performance metrics such as data throughput, energy consumption, as well as energy efficiency. © 2024, CC BY-NC-SA.

关键词： Millimeter waves

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Distributed Pattern Formation by Autonomous Robot Swarm 22

Distributed Pattern Formation by Autonomous Robot Swarm

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23rd International Conference on Distributed computing and Networking, ICDCN 2022

作者： Bose, Kaustav Adhikary, Ranendu Kundu, Manash Kumar Das, Archak Sau, Buddhadeb Advanced Computing and Microelectronics Unit Indian Statistical Institute India Jadavpur University India Gayeshpur Government Polytechnic India

ISBN: (纸本)9781450395601

Arbitrary Pattern Formation is a fundamental robot coordination problem. The problem asks for a distributed algorithm that allows a swarm of autonomous mobile robots to form any pattern given as input. The majority of the works in the literature investigate the problem under models with very idealistic assumptions regarding motion and sensing capabilities of the robots. We investigate the problem, aiming towards removing these assumptions and understanding their effect on the solvability of the problem. © 2022 ACM.

关键词： Robots

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Pattern Formation by Robots with Inaccurate Movements 25

Pattern Formation by Robots with Inaccurate Movements

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25th International Conference on Principles of Distributed Systems, OPODIS 2021

作者： Bose, Kaustav Das, Archak Sau, Buddhadeb Advanced Computing and Microelectronics Unit Indian Statistical Institute Kolkata India Department of Mathematics Jadavpur University Kolkata India

ISBN: (纸本)9783959772198

Arbitrary Pattern Formation is a fundamental problem in autonomous mobile robot systems. The problem asks to design a distributed algorithm that moves a team of autonomous, anonymous and identical mobile robots to form any arbitrary pattern F given as input. In this paper, we study the problem for robots whose movements can be inaccurate. Our movement model assumes errors in both direction and extent of the intended movement. Forming the given pattern exactly is not possible in this setting. So we require that the robots must form a configuration which is close to the given pattern F. We call this the Approximate Arbitrary Pattern Formation problem. With no agreement in coordinate system, the problem is unsolvable, even by fully synchronous robots, if the initial configuration 1) has rotational symmetry and there is no robot at the center of rotation or 2) has reflectional symmetry and there is no robot on the reflection axis. From all other initial configurations, we solve the problem by 1) oblivious, silent and semi-synchronous robots and 2) oblivious, asynchronous robots that can communicate using externally visible lights. © Kaustav Bose, Archak Das, and Buddhadeb Sau.

关键词： Mobile robots

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