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Mutual visibility by robots with persistent memory 1

13th International Workshop on Frontiers in Algorithmics, FAW 2019

作者： Bhagat, Subhash Mukhopadhyaya, Krishnendu Advanced Computing and Microelectronics Unit Indian Statistical Institute Kolkata India

ISBN: (数字)9783030181260

ISBN: (纸本)9783030181253

This paper addresses one of the fundamental geometric formation problems, namely the mutual visibility problem, for a set of semi-synchronous, opaque robots occupying distinct positions in the Euclidean plane. Since robots are opaque, if three robots lie on a line, the middle robot obstructs the visions of the two other robots. The mutual visibility problem requires the robots to coordinate their movements to form a configuration, within finite time and without collision, in which no three robots are collinear. We assume that robots are endowed with constant bits of persistent memory. We consider the computational model [4] in which the persistent memory is used by the robots only to remember their previous internal states. This piece of information is not communicated or visible to the other robots. Except from this persistent memory, robots are oblivious i.e., they do not carry forward any other information from their previous computational cycles. The paper presents a distributed algorithm to solve the mutual visibility problem for a set of semi-synchronous robots using only 1 bit of persistent memory. The proposed algorithm also provides a self-stabilizing solution to the problem. The algorithm does not impose any other restriction on the capability of the robots and guarantees collision-free movements for the robots. © Springer Nature Switzerland AG 2019.

关键词： Robots

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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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Query complexity of global minimum cut 24

Query complexity of global minimum cut

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24th International Conference on Approximation Algorithms for Combinatorial Optimization Problems, APPROX 2021 and 25th International Conference on Randomization and Computation, RANDOM 2021

作者： Bishnu, Arijit Ghosh, Arijit Mishra, Gopinath Paraashar, Manaswi Advanced Computing and Microelectronics Unit Indian Statistical Institute Kolkata India

ISBN: (纸本)9783959772075

In this work, we resolve the query complexity of global minimum cut problem for a graph by designing a randomized algorithm for approximating the size of minimum cut in a graph, where the graph can be accessed through local queries like Degree, Neighbor, and Adjacency queries. Given ϵ ∈ (0, 1), the algorithm with high probability outputs an estimate t satisfying the following (1 − ϵ)t ≤ t ≤ (1 + ϵ)t, where t is the size of minimum cut in the graph. The expected number of local queries used by our algorithm is min {m + n, mt poly (log n, 1ϵ) where n and m are the number of vertices and edges in the graph, respectively. Eden and Rosenbaum showed that Ω(m/t) local queries are required for approximating the size of minimum cut in graphs, but no local query based algorithm was known. Our algorithmic result coupled with the lower bound of Eden and Rosenbaum [APPROX 2018] resolve the query complexity of the problem of estimating the size of minimum cut in graphs using local queries. Building on the lower bound of Eden and Rosenbaum, we show that, for all t ∈ N, Ω(m) local queries are required to decide if the size of the minimum cut in the graph is t or t − 2. Also, we show that, for any t ∈ N, Ω(m) local queries are required to find all the minimum cut edges even if it is promised that the input graph has a minimum cut of size t. Both of our lower bound results are randomized, and hold even if we can make Random Edge queries in addition to local queries. © Arijit Bishnu, Arijit Ghosh, Gopinath Mishra, and Manaswi Paraashar;licensed under Creative Commons License CC-BY 4.0

关键词： Parallel processing systems

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Uniform k-Circle Formation by Fat Robots 25th

Uniform k-Circle Formation by Fat Robots

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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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Largest triangle inside a terrain 31

Largest triangle inside a terrain

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31st Canadian Conference on Computational Geometry, CCCG 2019

作者： Das, Arun Kumar Das, Sandip Mukherjee, Joydeep Advanced Computing and Microelectronics Unit Indian Statistical Institute Calcutta India

In this paper, we present an O(n2) time algorithm to find a largest area triangle contained inside a terrain with n vertices. We also present an O(n log n) time 1/2-factor approximation for the same. © CCCG 2019....

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Fast Estimation of Coverage Area in a Pervasive computing Environment

Fast Estimation of Coverage Area in a Pervasive Computing En...

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2nd International Conference on advanced computing, Networking and Informatics, ICACN 2014

作者： Saha, Dibakar Das, Nabanita Bhattacharya, Bhargab B. Advanced Computing and Microelectronics Unit Indian Statistical Institute Kolkata India

ISBN: (纸本)9783319073491

In many applications of pervasive computing and communication, it is often mandatory that a certain service area be fully covered by a given deployment of nodes or access points. Hence, a fast and accurate method of estimating the coverage area is needed. However, in a scenario with a limited computation and communication capability as in self-organized mobile networks, where the nodes are not static, computation-intensive algorithms are not suitable. In this paper, we have presented a simple algorithm for estimating the area covered by a set of nodes randomly deployed over a 2-D region. We assume that the nodes are identical and each of them covers a circular area. For fast estimation of the collective coverage of n such circles, we approximate each real circle by the tightest square that encloses it as well as by the largest square that is inscribed within it, and present an O(n logn) time algorithm for computation. We study the variation of the estimated area between these two bounds, for random deployment of nodes. In comparison with an accurate digital circle based method, the proposed algorithms estimate the area coverage with only 10% deviation, while reducing the complexity of area computation significantly. Moreover, for an over-deployed network, the estimation provides an almost exact measure of the covered area. © Springer International Publishing Switzerland 2014.

关键词： Sensor nodes

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Pre-emptive Spectrum Access in Cognitive Radio for Better QoS 4th

Pre-emptive Spectrum Access in Cognitive Radio for Better Q...

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4th International Conference on advanced computing and Intelligent Engineering, ICACIE 2019

作者： Das, Avirup Karar, Sandip Das, Nabanita Ghosh, Sasthi C. Advanced Computing & Microelectronics Unit Indian Statistical Institute Kolkata India

ISBN: (纸本)9789811565830

Cognitive radio techniques are becoming very popular to overcome the spectrum scarcity. For dynamic channel access, spectrum latency is a major bottleneck to achieve good QoS. In this paper, we have proposed distributed proactive channel scanning for different channel assignment policies of primary users (PUs). From periodic channel scanning, secondary users (SUs) store recent history of channel occupancy, and based on that decide the order of channel selection when demand comes, and switch channels proactively, if any better channel appears. For various channel allocation strategies of primary users, different channel selection algorithms are presented for secondary users to improve the spectrum latency as well as the channel switching overhead per call. Through simulation, the performance of the proposed strategies is compared with that of conventional cognitive radio. Results show that by the proposed scheme, the call drop/block rate decreases by more than 30 % with significant reduction in interference, and hence improving the QoS of the system. © 2021, Springer Nature Singapore Pte Ltd.

关键词： Cognitive radio

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Obstacle Aware Link Selection for Stable Multicast D2D Communications 3rd

Obstacle Aware Link Selection for Stable Multicast D2D Comm...

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3rd International Conference on Computer and Communication Engineering, CCCE 2023

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

ISBN: (纸本)9783031352980

The rapid growth of multimedia applications requiring high bandwidth has paved the way for millimeter-wave (mmWave) device-to-device (D2D) communications. In many modern applications, such as video streaming, same data packets need to be delivered to a group of users. Multicasting these packets has a clear advantage over repeated unicast. Establishing a stable multicast route for mmWave D2D communications is a challenging task as presence of obstacles can easily break a link. In this work we devise a mechanism for constructing a stable route for D2D multicast communications in presence of static as well as dynamic obstacles. This requires some knowledge about the blockage probabilities due to the obstacles. We then present a way of learning these blockage probabilities using the Dempster-Shafer evidential theory framework. We show the effectiveness of our proposed scheme over an existing approach through extensive simulations. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.

关键词： Multicasting

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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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