The Experts below are selected from a list of 4512 Experts worldwide ranked by ideXlab platform
Erik G Strom - One of the best experts on this subject based on the ideXlab platform.
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performance analysis of receivers using sector antennas for Broadcast vehicular communications
IEEE Transactions on Communications, 2019Co-Authors: Keerthi Kumar Nagalapur, Fredrik Brannstrom, Erik G StromAbstract:In this paper, we analyze a carrier-sense multiple access system with all-to-all Broadcast data traffic to assess the performance gain obtained by using multiple sector antennas and a receiver setup that can decode multiple packets simultaneously when packets arrive in narrow angle of arrivals. In the Broadcast Mode of IEEE 802.11p-based vehicle-to-vehicle communications, acknowledgment messages are absent and a fixed contention window is used in medium access. As a result, the probability of multiple vehicles simultaneously transmitting a packet increases with the number of vehicles. In the case of a simultaneous transmission, a receiver with omnidirectional antennas receives power from all the transmitting vehicles and the probability of successfully decoding a packet decreases. This problem can be alleviated by using sector antennas when the simultaneously transmitted packets arrive at a receiver in the narrow angle of arrivals. We show through analysis and simulations that the packet success rate (PSR) can be improved significantly by using the sector antennas’ setup instead of an omnidirectional antenna. Numerical results show that a several-fold increase in the PSR can be achieved in a setup with four sector antennas compared with an omnidirectional antenna when the density of vehicles is large.
Keerthi Kumar Nagalapur - One of the best experts on this subject based on the ideXlab platform.
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performance analysis of receivers using sector antennas for Broadcast vehicular communications
IEEE Transactions on Communications, 2019Co-Authors: Keerthi Kumar Nagalapur, Fredrik Brannstrom, Erik G StromAbstract:In this paper, we analyze a carrier-sense multiple access system with all-to-all Broadcast data traffic to assess the performance gain obtained by using multiple sector antennas and a receiver setup that can decode multiple packets simultaneously when packets arrive in narrow angle of arrivals. In the Broadcast Mode of IEEE 802.11p-based vehicle-to-vehicle communications, acknowledgment messages are absent and a fixed contention window is used in medium access. As a result, the probability of multiple vehicles simultaneously transmitting a packet increases with the number of vehicles. In the case of a simultaneous transmission, a receiver with omnidirectional antennas receives power from all the transmitting vehicles and the probability of successfully decoding a packet decreases. This problem can be alleviated by using sector antennas when the simultaneously transmitted packets arrive at a receiver in the narrow angle of arrivals. We show through analysis and simulations that the packet success rate (PSR) can be improved significantly by using the sector antennas’ setup instead of an omnidirectional antenna. Numerical results show that a several-fold increase in the PSR can be achieved in a setup with four sector antennas compared with an omnidirectional antenna when the density of vehicles is large.
Taira Kunihiko - One of the best experts on this subject based on the ideXlab platform.
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Network Broadcast Mode analysis and control of turbulent flows
2020Co-Authors: Yeh Chi-an, Meena, Muralikrishnan Gopalakrishnan, Taira KunihikoAbstract:We present a network-based modal analysis that identifies the key dynamical paths along which perturbations amplify in an isotropic turbulent flow. This analysis is built upon the Katz centrality, which reveals the flow structures that can effectively spread perturbations over the time-evolving network of vortical elements that constitute the turbulent flow field. Motivated by the resolvent form of the Katz function, we take the singular value decomposition of the resulting communicability matrix, complementing resolvent analysis. The right-singular vector, referred to as the Broadcast Mode, gives insights into the sensitive regions where introduced perturbations can be effectively spread over the entire fluid-flow network as it evolves over time. The Broadcast Mode reveals that vortex dipoles are the important structures in spreading perturbations. By perturbing the flow with the Broadcast Mode, we demonstrate its capability to effectively modify the evolution of turbulent flows. The current network-inspired work presents a novel use of network analysis to guide flow control efforts, in particular for time-varying turbulent base flows
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Network Broadcast analysis and control of turbulent flows
'Cambridge University Press (CUP)', 2020Co-Authors: Yeh Chi-an, Meena, Muralikrishnan Gopalakrishnan, Taira KunihikoAbstract:We present a network-based modal analysis technique that identifies key dynamical paths along which perturbations amplify over a time-varying base flow. This analysis is built upon the Katz centrality, which reveals the flow structures that can effectively spread perturbations over a time-evolving network of vortical interactions on the base flow. Motivated by the resolvent form of the Katz function, we take the singular value decomposition of the resulting communicability matrix, complementing the resolvent analysis for fluid flows. The right-singular vectors, referred to as the Broadcast Modes, give insights into the sensitive regions where introduced perturbations can be effectively spread and amplified over the entire fluid-flow network that evolves in time. We apply this analysis to a two-dimensional decaying isotropic turbulence. The Broadcast Mode reveals that vortex dipoles are important structures in spreading perturbations. By perturbing the flow with the principal Broadcast Mode, we demonstrate the utility of the insights gained from the present analysis to effectively modify the evolution of turbulent flows. The current network-inspired work presents a novel use of network analysis to guide flow control efforts, in particular for time-varying base flows
Fredrik Brannstrom - One of the best experts on this subject based on the ideXlab platform.
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performance analysis of receivers using sector antennas for Broadcast vehicular communications
IEEE Transactions on Communications, 2019Co-Authors: Keerthi Kumar Nagalapur, Fredrik Brannstrom, Erik G StromAbstract:In this paper, we analyze a carrier-sense multiple access system with all-to-all Broadcast data traffic to assess the performance gain obtained by using multiple sector antennas and a receiver setup that can decode multiple packets simultaneously when packets arrive in narrow angle of arrivals. In the Broadcast Mode of IEEE 802.11p-based vehicle-to-vehicle communications, acknowledgment messages are absent and a fixed contention window is used in medium access. As a result, the probability of multiple vehicles simultaneously transmitting a packet increases with the number of vehicles. In the case of a simultaneous transmission, a receiver with omnidirectional antennas receives power from all the transmitting vehicles and the probability of successfully decoding a packet decreases. This problem can be alleviated by using sector antennas when the simultaneously transmitted packets arrive at a receiver in the narrow angle of arrivals. We show through analysis and simulations that the packet success rate (PSR) can be improved significantly by using the sector antennas’ setup instead of an omnidirectional antenna. Numerical results show that a several-fold increase in the PSR can be achieved in a setup with four sector antennas compared with an omnidirectional antenna when the density of vehicles is large.
Warrior Jay - One of the best experts on this subject based on the ideXlab platform.
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CheepSync: A Time Synchronization Service for Resource Constrained Bluetooth Low Energy Advertisers
'Institute of Electrical and Electronics Engineers (IEEE)', 2016Co-Authors: Sridhar Sabarish, Misra Prasant, Gill, Gurinder Singh, Warrior JayAbstract:Clock synchronization is highly desirable in distributed systems, including many applications in the Internet of Things and Humans (IoTH). It improves the efficiency, modularity and scalability of the system, and optimizes use of event triggers. For IoTH, Bluetooth Low Energy (BLE) - a subset of the recent Bluetooth v4.0 stack - provides a low-power and loosely coupled mechanism for sensor data collection with ubiquitous units (e.g., smartphones and tablets) carried by humans. This fundamental design paradigm of BLE is enabled by a range of Broadcast advertising Modes. While its operational benefits are numerous, the lack of a common time reference in the Broadcast Mode of BLE has been a fundamental limitation. This paper presents and describes CheepSync: a time synchronization service for BLE advertisers, especially tailored for applications requiring high time precision on resource constrained BLE platforms. Designed on top of the existing Bluetooth v4.0 standard, the CheepSync framework utilizes low-level timestamping and comprehensive error compensation mechanisms for overcoming uncertainties in message transmission, clock drift and other system specific constraints. CheepSync was implemented on custom designed nRF24Cheep beacon platforms (as Broadcasters) and commercial off-the-shelf Android ported smartphones (as passive listeners). We demonstrate the efficacy of CheepSync by numerous empirical evaluations in a variety of experimental setups, and show that its average (single-hop) time synchronization accuracy is in the 10us range
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CheepSync: A Time Synchronization Service for Resource Constrained Bluetooth LE Advertisers
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2016Co-Authors: Sridhar Sabarish, Misra Prasant, Gill, Gurinder Singh, Warrior JayAbstract:Clock synchronization is highly desirable in distributed systems, including many applications in the Internet of Things and Humans. It improves the efficiency, modularity, and scalability of the system, and optimizes use of event triggers. For IoTH, BLE - a subset of the recent Bluetooth v4.0 stack - provides a low-power and loosely coupled mechanism for sensor data collection with ubiquitous units (e.g., smartphones and tablets) carried by humans. This fundamental design paradigm of BLE is enabled by a range of Broadcast advertising Modes. While its operational benefits are numerous, the lack of a common time reference in the Broadcast Mode of BLE has been a fundamental limitation. This article presents and describes CheepSync, a time synchronization service for BLE advertisers, especially tailored for applications requiring high time precision on resource constrained BLE platforms. Designed on top of the existing Bluetooth v4.0 standard, the CheepSync framework utilizes low-level time-stamping and comprehensive error compensation mechanisms for overcoming uncertainties in message transmission, clock drift, and other system-specific constraints. CheepSync was implemented on custom designed nRF24Cheep beacon platforms (as Broadcasters) and commercial off-the-shelf Android ported smartphones (as passive listeners). We demonstrate the efficacy of CheepSync by numerous empirical evaluations in a variety of experimental setups, and show that its average (single-hop) time synchronization accuracy is in the 10 mu s range
