1,721,051 research outputs found
An empirical model of multiview video coding efficiency for wireless multimedia sensor networks
Full text linkWe develop an empirical model of the Multiview Video Coding (MVC) performance that can be used to identify and separate situations when MVC is beneficial from cases when its use is detrimental in wireless multimedia sensor networks (WMSN). The model predicts the compression performance of MVC as a function of the correlation between cameras with overlapping fields of view. We define the common sensed area (CSA) between different views, and emphasize that it depends not only on geometrical relationships among the relative positions of different cameras, but also on various object-related phenomena, e. g., occlusions and motion, and on low-level phenomena such as variations in illumination. With these premises, we first experimentally characterize the relationship between MVC compression gain (with respect to single view video coding) and the CSA between views. Our experiments are based on the H. 264 MVC standard, and on a low-complexity estimator of the CSA that can be computed with low inter-node signaling overhead. Then, we propose a compact empirical model of the efficiency of MVC as a function of the CSA between views, and we validate the model with different multiview video sequences. Finally, we show how the model can be applied to typical scenarios in WMSN, i.e., to clustered or multi-hop topologies, and we show a few promising results of its application in the definition of cross-layer clustering and data aggregation procedures
A cross-layer bandwidth allocation scheme for HTTP-based video streaming in LTE cellular networks
No full textThis paper investigates the benefits of flexible
resource allocation when performing HTTP-based Adaptive
Streaming (HAS) across cellular systems such as Long Term
Evolution (LTE). To guarantee video fluidity in the presence of
fluctuations of the instantaneous video source rate and channel
capacity, we consider a HAS based proxy video manager and
resource controller located at the cellular base station. Based
on the channel quality observed by mobile clients, the manager
allocates the wireless bandwidth to mobile clients for transmitting
the video streams. We propose a cross-layer bandwidth allocation
scheme that takes into account the channel quality as well as
the video quality requirements and encoding rate fluctuations of
the HAS video stream and minimizes the transmission delays
experienced by users. This cross-layer bandwidth allocation
achieves the optimum in terms of HAS streams delays and
it outperforms different bandwidth allocations procedures and
state-of-the-art LTE schedulers
Performance evaluation of sender-assisted HTTP-based video streaming in wireless ad hoc networks
No full textHTTP Adaptive Streaming (HAS) delivers video streaming services according to a client-server architecture where the client originates consecutive HTTP requests to download chunks of encoded video. In state-of-the-art systems, the client selects the chunk out of a finite set of differently encoded versions of the same video made available at the server site; the selection is driven by a client-centered buffer management procedure. Still, dynamic bitstream switching may have drawbacks in terms of undesirable visual quality fluctuations artifacts at the final user; besides, it may result in oscillatory behavior of the overall traffic in case of multiple users. Therefore, this paper proposes a sender-assisted procedure for HTTP Adaptive Streaming (HAS) services with improved user Quality of Experience (QoE) that proactively avoids buffer underflow events at the receiver side, thus reducing the need for dynamic bitstream switching. In the proposed sender-assisted approach, HAS leverages information on the encoded video available at the server side to assist the client in originating the data requests. Specifically, the sender-assisted HAS procedure exploits information on the encoded video content available at the sender side to regulate the interval between consecutive client-originated download requests. Significant QoE improvements brought by the proposed sender-assisted video streaming procedure are demonstrated in challenging fluctuating throughput conditions encountered in wireless ad hoc networks
Autonomous Driving From the Sky: Design and End-to-End Performance Evaluation
Full text linkFor autonomous vehicles to operate without human intervention, information
sharing from local sensors plays a fundamental role. This can be challenging to
handle with bandwidth-constrained communication systems, which calls for the
adoption of new wireless technologies, like in the mmwave bands, to solve
capacity issues. Another approach is to exploit uav, able to provide human
users and their cars with an aerial bird's-eye view of the scene otherwise
unavailable, thus offering broader and more centralized observations. In this
article we combine both aspects and design a novel framework in which uav,
operating at mmwave, broadcast sensory information to the ground as a means to
extend the (local) perception range of vehicles. To do so, we conduct a
full-stack end-to-end simulation campaign with ns-3 considering real UAV data
from the Stanford Drone Dataset, and study four scenarios representing
different uav-to-ground communication strategies. Our results focus on the
trade-off between centralized data processing in the sky vs. distributed local
processing on the ground, with considerations related to the throughput,
latency and reliability of the communication process
Optimizing and Managing Wireless Backhaul for Resilient Next-Generation Cellular Networks
No full textNext-generation wireless networks target high network availability, ubiquitous coverage, and extremely high data rates for mobile users. This requires exploring new frequency bands, e.g., mmWaves, moving toward ultra-dense deployments in urban locations, and providing ad hoc, resilient connectivity in rural scenarios. The design of the backhaul network plays a key role in advancing how the access part of the wireless system supports next-generation use cases. Wireless backhauling, such as the newly introduced Integrated Access and Backhaul (IAB) concept in 5G, provides a promising solution, also leveraging the mmWave technology and steerable beams to mitigate interference and scalability issues. At the same time, however, managing and optimizing a complex wireless backhaul introduces additional challenges for the operation of cellular systems. This paper presents a strategy for the optimal creation of the backhaul network considering various constraints related to network topology, robustness, and flow management. We evaluate its feasibility and efficiency using synthetic and realistic network scenarios based on 3D modeling of buildings and ray tracing. We implement and prototype our solution as a dynamic IAB control framework based on the Open Radio Access Network (RAN) architecture, and demonstrate its functionality in Colosseum, a large-scale wireless network emulator with hardware in the loop
Timely delivery versus bandwidth allocation for DASH-based video streaming over LTE
No full textWe study HTTP video streaming over a wireless access cell, such as LTE. We derive a closed form expression for the probability of timely delivery of the streamed video packets as a function of the bandwidth allocated to the user. The probability expression uses application, transport, and physical layer parameters relating to the employed video stream rate and to the quality of the communications channel. We validate the analytical results via numerical simulations based on the execution of real video traces and with LTE channel quality index trace modeling. The attained results allow the system designer, scheduler, and manager to calculate the bandwidth level that should be allocated to maintain acceptable system performance, expressed by two quality-of-experience (QoE) metrics, namely the video rate and the probability of timely delivery of video packets. The model provides a rationale and tools for performing admission procedures, bandwidth pricing policies, and cell dimensioning designs
HIRO-NET: Heterogeneous intelligent robotic network for internet sharing in disaster scenarios
Full text linkThis article describes HIRO-NET, an Heterogeneous Intelligent
Robotic Network. HIRO-NET is an emergency infrastructure-less
network that aims to address the problem of providing connectivity in
the immediate aftermath of a natural disaster, where no cellular or
wide area network is operational and no Internet access is available.
HIRO-NET establishes a two-tier wireless mesh network where the
Lower Tier connects nearby survivors in a self-organized mesh via
Bluetooth Low Energy (BLE) and the Upper Tier creates long-range
VHF links between autonomous robots exploring the disaster stricken
area. HIRO-NET’s main goal is to enable users in the disaster area to
exchange text messages to share critical information and request help
from first responders. The mesh network discovery problem is analyzed
and a network protocol specifically designed to facilitate the exploration
process is presented. We show how HIRO-NET robots successfully
discover, bridge and interconnect local mesh networks. Results show
that the Lower Tier always reaches network convergence and the Upper
Tier can virtually extend HIRO-NET functionalities to the range of a
small metropolitan area. In the event of an Internet connection still being
available to some user, HIRO-NET is able to opportunistically share and
provide access to low data-rate services (e.g., Twitter, Gmail) to the
whole network. Results suggest that a temporary emergency network
to cover a metropolitan area can be created in tens of minutes.
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