389 research outputs found
Distributed delivery system for time-shifted streaming systems
International audienceIn live streaming systems (IPTV, life-stream services, etc.), an attractive feature consists in allowing users to access past portions of the stream. This is called a time-shifted streaming sys- tem. We address in this paper the design of a large-scale delivery system for a time-shifted streaming application. We highlight the challenging characteristics of time-shifted applications that prevent known delivery systems to be used. Then, we describe the turntable structure, the first structure that has been specifically designed to cope with the properties of time-shifted systems. A set of preliminary simulations confirm the interest for this structure
A Wideband MIMO Channel Model for Aerial Intelligent Reflecting Surface-Assisted Wireless Communications
Compared to traditional intelligent reflecting surfaces(IRS), aerial IRS
(AIRS) has unique advantages, such as more flexible deployment and wider
service coverage. However, modeling AIRS in the channel presents new challenges
due to their mobility. In this paper, a three-dimensional (3D) wideband channel
model for AIRS and IRS joint-assisted multiple-input multiple-output (MIMO)
communication system is proposed, where considering the rotational degrees of
freedom in three directions and the motion angles of AIRS in space. Based on
the proposed model, the channel impulse response (CIR), correlation function,
and channel capacity are derived, and several feasible joint phase shifts
schemes for AIRS and IRS units are proposed. Simulation results show that the
proposed model can capture the channel characteristics accurately, and the
proposed phase shifts methods can effectively improve the channel statistical
characteristics and increase the system capacity. Additionally, we observe that
in certain scenarios, the paths involving the IRS and the line-of-sight (LoS)
paths exhibit similar characteristics. These findings provide valuable insights
for the future development of intelligent communication systems.Comment: 6 pages, 7 figure
AerialVLN: Vision-and-Language Navigation for UAVs
Recently emerged Vision-and-Language Navigation (VLN) tasks have drawn
significant attention in both computer vision and natural language processing
communities. Existing VLN tasks are built for agents that navigate on the
ground, either indoors or outdoors. However, many tasks require intelligent
agents to carry out in the sky, such as UAV-based goods delivery,
traffic/security patrol, and scenery tour, to name a few. Navigating in the sky
is more complicated than on the ground because agents need to consider the
flying height and more complex spatial relationship reasoning. To fill this gap
and facilitate research in this field, we propose a new task named AerialVLN,
which is UAV-based and towards outdoor environments. We develop a 3D simulator
rendered by near-realistic pictures of 25 city-level scenarios. Our simulator
supports continuous navigation, environment extension and configuration. We
also proposed an extended baseline model based on the widely-used
cross-modal-alignment (CMA) navigation methods. We find that there is still a
significant gap between the baseline model and human performance, which
suggests AerialVLN is a new challenging task. Dataset and code is available at
https://github.com/AirVLN/AirVLN.Comment: Accepted by ICCV 202
Pervasive Detection of Sleep Apnea using Medical Wireless Sensor Networks
Abstract-The sleep apnea is a sleep disorder characterized by cessation of respiratory flow (apnea) or a reduction in the flow (hypopnea). This disorder is often invalidating and may in some cases lead to death. During the night, symptoms can include nocturnal choking, heavy snoring, sweating, restless sleep, impotence, and witnessed apnea. As the sleep centers for apnea detection are usually overloaded and inaccessible, an automatic apnea detection algorithm for portable devices is required for inhome detection. In this paper, we propose a lightweight approach for pervasive detection of sleep apnea using Wireless Sensor Networks. The experimental results show that our proposed approach achieves good detection accuracy with low delay and low false alarm rate
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