1,721,008 research outputs found
Transmission Control of Variable-Bit-Rate Video Streaming in UMTS Networks
No full textVariable-Bit-Rate (VBR) video transmission over UMTS networks is assuming an ever growing importance, then scheduling VBR data over wireless channels attracts great interest today. This paper proposes an on-line PI control algorithm for easily and suitably scheduling interactive multimedia transmission of VBR video streams. It dynamically adapts the transmitted bit rate to the user's actions that can suddenly and highly modify the client buffer level. The Real-time Transport Control Protocol (RTCP) packets periodically feed back the buffer level to the server for keeping the free buffer space at 50% of its capacity, so as to prevent both buffer overflow and underflow. Numerical results of different simulated scenarios show the effectiveness of the proposed controller in comparison with two well-established algorithms, enhanced with RTCP information
Dynamic Burst Variation for Multiservice Transmission of Variable Bit Rate Streams in DVB SH Systems
No full textA New MBAC Algorithm for Video Streaming based on AutoRegressive Adaptive Filtering
No full textA novel strategy of measurement based admission control (MBAC) for video distribution systems has been developed, aimed at obtaining the needed quality of service (QoS), expressed in terms of loss probability. The developed algorithm is based on an autoregressive (AR) adaptive filter taking into account slow and quick time bit rate variations of video stream aggregation. A simple admission control strategy is presented, able to shift from the server to the client the decision about the admission of a new video stream. Simulation results, based on real MPEG encoded videos justify the applicatio
An Efficient Scheduling Algorithm for Multiservice Variable Bit Rate Video Transmission In DVB SH Systems
No full textAn extensive survey on the Internet of Drones
Full text linkThe Internet of Drones (IoD) recently gained momentum due to its high adaptability to a wide variety of complex scenarios. Indeed, Unmanned Aerial Vehicles (UAVs) can successfully be employed in different applications, such as agriculture, search and rescue missions, surveillance systems, mission-critical services, among others, thanks to some technological and practical advantages: high mobility, capability to extend wireless coverage areas, or ability to reach places inaccessible to humans. Moreover, the employment of drones promisingly improves the performance parameters of different network architectures, e.g., reliability, connectivity, throughput, and delay. Nevertheless, the adoption of networks of drones gives rise to several issues related to the intrinsic unreliability of the wireless medium, the duration of batteries, and the high mobility degree, which may cause frequent topology changes. Also security and privacy issues need to be properly investigated. This explains the very large number of works produced in the recent literature on IoD-related topics. With respect to other surveys on IoD-related topics, the goal of the present work is to categorize the multifaceted aspects of IoD, proposing a classification approach of the IoD environment that develops along two main directions. The IoD is initially introduced according to the possible applications and reference operating scenarios. On top of that, this work discussed with its applicability with a dedicated focus on the economical/social implications that the adoption of drones at scale may have. At a macroscopic level, it follows the structure of the Internet protocol stack, starting from the physical layer and extending to the upper layers, without neglecting cross-layer and optimization approaches. At a finer level, all the most relevant works belonging to each layer of the stack are further classified, according to the different issues that propose a peculiar challenges for each layer, and highlighting the most relevant differences with the other surveys present in literature. To provide a deeper insight, the present work embraces many facets of the IoD, with a thorough examination of privacy and security considerations. Finally, a discussion on the main research challenges and possible future directions is carried out, focusing on both open issues and the most promising technologies that deserve to be further developed in the IoD field
A Markov Model for characterizing IEEE 802.15.4 MAC Layer in Noisy Environments
No full textThe IEEE 802.15.4 standard represents one
of the most successful technologies for enabling low-rate
wireless personal area networks (LR-WPANs). Accordingly,
the properties of its protocols (at physical and MAC layers)
have been widely studied in the scientific literature to derive
performance bounds on throughput, delays, and frame
losses. At the same time, to the best of the authors’ knowledge,
a complete characterization of the frame-error-rate
process, including also the correlation among loss events,
is still missing. This kind of investigation is particularly
relevant in noisy industrial environments, which, as well
known, introduce bursty frame losses. To this end, this
paper proposes a Markov model to account for the different
changing conditions under which an IEEE 802.15.4 channel
is seen at the MAC layer. The model is able to reproduce
synthetic traces having a cumulative distribution function
and an autocorrelation coefficient that closely resemble
experimental measurements. In this way, it becomes a valuable
tool for further refining existing theoretical models and
simulation platforms for IEEE 802.15.4 LR-WPANs and for
helping the designer and researcher working on industrial
Internet of things
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