61,575 research outputs found
MHP-VOS: Multiple Hypotheses Propagation for Video Object Segmentation
We address the problem of semi-supervised video object segmentation (VOS),
where the masks of objects of interests are given in the first frame of an
input video. To deal with challenging cases where objects are occluded or
missing, previous work relies on greedy data association strategies that make
decisions for each frame individually. In this paper, we propose a novel
approach to defer the decision making for a target object in each frame, until
a global view can be established with the entire video being taken into
consideration. Our approach is in the same spirit as Multiple Hypotheses
Tracking (MHT) methods, making several critical adaptations for the VOS
problem. We employ the bounding box (bbox) hypothesis for tracking tree
formation, and the multiple hypotheses are spawned by propagating the preceding
bbox into the detected bbox proposals within a gated region starting from the
initial object mask in the first frame. The gated region is determined by a
gating scheme which takes into account a more comprehensive motion model rather
than the simple Kalman filtering model in traditional MHT. To further design
more customized algorithms tailored for VOS, we develop a novel mask
propagation score instead of the appearance similarity score that could be
brittle due to large deformations. The mask propagation score, together with
the motion score, determines the affinity between the hypotheses during tree
pruning. Finally, a novel mask merging strategy is employed to handle mask
conflicts between objects. Extensive experiments on challenging datasets
demonstrate the effectiveness of the proposed method, especially in the case of
object missing.Comment: accepted to CVPR 2019 as oral presentatio
Relieving the Wireless Infrastructure: When Opportunistic Networks Meet Guaranteed Delays
Major wireless operators are nowadays facing network capacity issues in
striving to meet the growing demands of mobile users. At the same time,
3G-enabled devices increasingly benefit from ad hoc radio connectivity (e.g.,
Wi-Fi). In this context of hybrid connectivity, we propose Push-and-track, a
content dissemination framework that harnesses ad hoc communication
opportunities to minimize the load on the wireless infrastructure while
guaranteeing tight delivery delays. It achieves this through a control loop
that collects user-sent acknowledgements to determine if new copies need to be
reinjected into the network through the 3G interface. Push-and-Track includes
multiple strategies to determine how many copies of the content should be
injected, when, and to whom. The short delay-tolerance of common content, such
as news or road traffic updates, make them suitable for such a system. Based on
a realistic large-scale vehicular dataset from the city of Bologna composed of
more than 10,000 vehicles, we demonstrate that Push-and-Track consistently
meets its delivery objectives while reducing the use of the 3G network by over
90%.Comment: Accepted at IEEE WoWMoM 2011 conferenc
ABC: A Simple Explicit Congestion Controller for Wireless Networks
We propose Accel-Brake Control (ABC), a simple and deployable explicit
congestion control protocol for network paths with time-varying wireless links.
ABC routers mark each packet with an "accelerate" or "brake", which causes
senders to slightly increase or decrease their congestion windows. Routers use
this feedback to quickly guide senders towards a desired target rate. ABC
requires no changes to header formats or user devices, but achieves better
performance than XCP. ABC is also incrementally deployable; it operates
correctly when the bottleneck is a non-ABC router, and can coexist with non-ABC
traffic sharing the same bottleneck link. We evaluate ABC using a Wi-Fi
implementation and trace-driven emulation of cellular links. ABC achieves
30-40% higher throughput than Cubic+Codel for similar delays, and 2.2X lower
delays than BBR on a Wi-Fi path. On cellular network paths, ABC achieves 50%
higher throughput than Cubic+Codel
Indoor wireless communications and applications
Chapter 3 addresses challenges in radio link and system design in indoor scenarios. Given the fact that most human activities take place in indoor environments, the need for supporting ubiquitous indoor data connectivity and location/tracking service becomes even more important than in the previous decades. Specific technical challenges addressed in this section are(i), modelling complex indoor radio channels for effective antenna deployment, (ii), potential of millimeter-wave (mm-wave) radios for supporting higher data rates, and (iii), feasible indoor localisation and tracking techniques, which are summarised in three dedicated sections of this chapter
Active Queue Management for Fair Resource Allocation in Wireless Networks
This paper investigates the interaction between end-to-end flow control and MAC-layer scheduling on wireless links. We consider a wireless network with multiple users receiving information from a common access point; each user suffers fading, and a scheduler allocates the channel based on channel quality,but subject to fairness and latency considerations. We show that the fairness property of the scheduler is compromised by the transport layer flow control of TCP New Reno. We provide a receiver-side control algorithm, CLAMP, that remedies this situation. CLAMP works at a receiver to control a TCP sender by setting the TCP receiver's advertised window limit, and this allows the scheduler to allocate bandwidth fairly between the users
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