Showing papers by "Samir R. Das published in 2021"

Adaptive Streaming of 360-Degree Videos with Reinforcement Learning

Abstract: For bandwidth-efficient streaming of 360-degree videos, the streaming technique must adapt both to the changing viewport of the user and variations of the available network bandwidth. The state-of-the-art streaming techniques for this problem attempt to solve an optimization using simplified rules that do not adapt very well to the uncertainties related to the viewport or network. We adopt a 3D-Convolutional Neural Networks (3DCNN) model to extract spatio-temporal features of videos and predict the viewport. Given the sequential decision-making nature of such streaming technique, we then apply a Reinforcement Learning (RL) based adaptive streaming approach. We address the challenges of using RL in this scenario, such as large action space and delayed reward evaluation. Comprehensive evaluations with real network traces show that the proposed method outperforms three tile-based streaming techniques for 360-degree videos. Compared to the tile-based streaming techniques, the average user-perceived bitrate of the proposed method is 1.3-1.7 times higher and the average quality of experience of the proposed method is also 1.6-3.4 times higher. Subjective user studies further confirm the superiority of the proposed approach.

Mosaic : Advancing User Quality of Experience in 360-Degree Video Streaming With Machine Learning

Abstract: Conventional streaming solutions for streaming 360-degree panoramic videos are inefficient in that they download the entire 360-degree panoramic scene, while the user views only a small sub-part of the scene called the viewport. This can waste over 80% of the network bandwidth. We develop a comprehensive approach called Mosaic that combines a powerful neural network-based viewport prediction with a rate control mechanism that assigns rates to different tiles in the 360-degree frame such that the video quality of experience is optimized subject to a given network capacity. We model the optimization as a multi-choice knapsack problem and solve it using a greedy approach. We also develop an end-to-end testbed using standards-compliant components and provide a comprehensive performance evaluation of Mosaic along with five other streaming techniques – two for conventional adaptive video streaming and three for 360-degree tile-based video streaming. Mosaic outperforms the best of the competitions by as much as 47-191% in terms of average video quality of experience. Simulation-based evaluation as well as subjective user studies further confirm the superiority of the proposed approach.

Enabling Passive Backscatter Tag Localization Without Active Receivers

Abstract: Backscattering tags transmit passively without an on-board active radio transmitter. Almost all present-day backscatter systems, however, rely on active radio receivers. This presents a significant scalability, power and cost challenge for backscatter systems. To overcome this barrier, recent research has empowered these passive tags with the ability to reliably receive backscatter signals from other tags. This forms the building block of passive networks wherein tags talk to each other without an active radio on either the transmit or receive side. For wider functionality, accurate localization of such tags is critical. All known backscatter tag localization techniques rely on active receivers for measuring and characterizing the received signal. As a result, they cannot be directly applied to passive tag-to-tag networks. This paper overcomes the gap by developing a localization technique for such passive networks based on a novel method for phase-based ranging in passive receivers. This method allows pairs of passive tags to collaboratively determine the inter-tag channel phase while effectively minimizing the effects of multipath and noise in the surrounding environment. Building on this, we develop a localization technique that benefits from large link diversity uniquely available in a passive tag-to-tag network. We evaluate the performance of our techniques with extensive micro-benchmarking experiments in an indoor environment using fabricated prototypes of tag hardware. We show that our phase-based ranging performs similar to active receivers, providing median 1D ranging error

Selection of Sensors for Efficient Transmitter Localization

Abstract: We address the problem of localizing an (unauthorized) transmitter using a distributed set of sensors. Our focus is on developing techniques that perform the transmitter localization in an efficient manner, wherein the efficiency is defined in terms of the number of sensors used to localize. Localization of unauthorized transmitters is an important problem which arises in many important applications, e.g., in patrolling of shared spectrum systems for any unauthorized users. Localization of transmitters is generally done based on observations from a deployed set of sensors with limited resources, thus it is imperative to design techniques that minimize the sensors' energy resources. In this paper, we design greedy approximation algorithms for the optimization problem of selecting a given number of sensors in order to maximize an appropriately defined objective function of localization accuracy. The obvious greedy algorithm delivers a constant-factor approximation only for the special case of two hypotheses (potential locations). For the general case of multiple hypotheses, we design a greedy algorithm based on an appropriate auxiliary objective function--and show that it delivers a provably approximate solution for the general case. We develop techniques to significantly reduce the time complexity of the designed algorithms by incorporating certain observations and reasonable assumptions. We evaluate our techniques over multiple simulation platforms, including an indoor as well as an outdoor testbed, and demonstrate the effectiveness of our designed techniques--our techniques easily outperform prior and other approaches by up to 50-60% in large-scale simulations and up to 16% in small-scale testbeds.

RF Energy Harvesting and Management for Near-Zero Power Passive Devices

Abstract: We present RF energy harvester and management strategy tailored for the passive near-zero power devices. Radio- less RF-powered backscattering tags that have the ability to recognize and localize activities in the surrounding environment are example of such devices. We propose a management strategy that determines the operation regime of the harvester based on the input power level at which harvester provides the instantaneous supply voltage for device operation. As the input power exceeds this level, the storage of the excess energy is managed by an adaptive capacitor charging circuit that keeps the voltage at the input of voltage regulator constant. We demonstrate that backscatter-based RF tag in the listening mode of operation can instantaneously operate with an input power of −34.4 dBm. Due to the adaptive capacitor charging circuit, the power efficiency of the energy harvester is higher than 50% over a range of input powers from −25 dBm up to −5 dBm.

RF Backscatter-Based Sensors for Structural Health Monitoring

Abstract: There is a growing need for accurate and reliable assessment of conditions of a variety of engineering structures and for monitoring of their performance. Miniaturized, passive, backscatter-based RF sensors with embedded computational capabilities could enable advanced structural health monitoring at high fidelity and at large-scale. Specifically, these RF-powered devices, pervasively embedded and dispersed within the structural material, can sense parameters of interest throughout large volumes of instrumented structure, perform modest local computations to infer structural conditions, and communicate via backscatter modulation while consuming near-zero power. We demonstrate that the backscatter channel phase sensing enables quantification of a size of air gap between two RF sensors embedded in sand. Additionally, we demonstrate the sensitivity of the phase to the strain of the sand.

MAVERICK: Proactively detecting network control plane bugs using structural outlierness.

Abstract: Proactive detection of network configuration bugs is important to ensure its proper functioning and reduce cost of network administrator. In this research, we propose to build the control plane verification engine MAVERICK that detects the bugs in the network control plane i.e., network device configurations and control plane states. MAVERICK automatically infers signatures for the control plane configurations (e.g., ACLs, route-maps, route-policies and so on) and states that allows administrators to automatically detect bugs with minimal human intervention. MAVERICK achieves this by effectively leveraging any structural deviation i.e., outliers in the network configurations that is organized as simple or complexly nested key-value pairs. The outliers that are calculated using signature-based outlier detection mechanism are further characterized for its severity and ranked or re-prioritized according to their criticality. We consider a wide set of heuristics and domain expertise factors for effectively to reduce both false positives and false negatives.Our evaluation on four medium to large-scale enterprise networks show that MAVERICK can automatically detect the bugs present in the network with approximately 75% accuracy. Further-more, With minimal administrator input i.e., with a few minutes of signature re-tuning, MAVERICK allows the administrators to effectively detect approximately 94 - 100% of the bugs present in the network, thereby ranking down less severe bugs and removing false positives.