ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Multimedia systems 5 (1997), S. 347-357 
    ISSN: 1432-1882
    Keywords: Key words:Bandwidth allocation – MPEG – Statistical multiplexing – Video-on-demand
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract. We present efficient schemes for scheduling the delivery of variable-bit-rate MPEG-compressed video with stringent quality-of-service (QoS) requirements. Video scheduling is being used to improve bandwidth allocation at a video server that uses statistical multiplexing to aggregate video streams prior to transporting them over a network. A video stream is modeled using a traffic envelope that provides a deterministic time-varying bound on the bit rate. Because of the periodicity in which frame types in an MPEG stream are typically generated, a simple traffic envelope can be constructed using only five parameters. Using the traffic-envelope model, we show that video sources can be statistically multiplexed with an effective bandwidth that is often less than the source peak rate. Bandwidth gain is achieved without sacrificing the stringency of the requested QoS. The effective bandwidth depends on the arrangement of the multiplexed streams, which is a measure of the lag between the GOP periods of various streams. For homogeneous streams, we give an optimal scheduling scheme for video sources at a video-on-demand server that results in the minimum effective bandwidth. For heterogeneous sources, a sub-optimal scheduling scheme is given, which achieves acceptable bandwidth gain. Numerical examples based on traces of MPEG-coded movies are used to demonstrate the effectiveness of our schemes.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Multimedia systems 8 (2000), S. 20-36 
    ISSN: 1432-1882
    Keywords: Key words:MPEG – Video scheduling – Interactive video-on-demand – Scanning operations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract. In this paper, we present an efficient approach for supporting fast-scanning (FS) operations in MPEG-based video-on-demand (VOD) systems. This approach is based on storing multiple, differently encoded versions of the same movie at the server. A normal version is used for normal playback, while several scan versions are used for FS. Each scan version supports forward and backward FS at a given speedup. The server responds to an FS request by switching from the normal version to an appropriate scan version. Scanning versions are produced by encoding a sample of the raw frames using the same GOP pattern of the normal version. When a scanning version is decoded and played back at the normal frame rate, it gives a perceptual motion speedup. By being able to control the traffic envelopes of the scan versions, our approach can be integrated into a previously proposed framework for distributing archived, MPEG-coded video streams. FS operations are supported using no or little extra network bandwidth beyond what is already allocated for normal playback. Mechanisms for controlling the traffic envelopes of the scan versions are presented. The actions taken by the server and the client's decoder in response to various types of interactive requests are described in detail. The latency incurred in implementing various interactive requests is shown to be within an acceptable range. Striping and disk-scheduling strategies for storing various versions at the server are presented. Issues related to the implementation of our approach are discussed.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Telecommunication systems 9 (1998), S. 335-355 
    ISSN: 1572-9451
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Providing cost‐effective video‐on‐demand (VOD) services necessitates reducing the required bandwidth for transporting video over high‐speed networks. In this paper, we investigate efficient schemes for transporting archived MPEG‐coded video over a VOD distribution network. A video stream is characterized by a time‐varying traffic envelope, which provides an upper bound on the bit rate. Using such envelopes, we show that video streams can be scheduled for transmission over the network such that the per‐stream allocated bandwidth is significantly less than the source peak rate. In a previous work [13], we investigated stream scheduling and bandwidth allocation using global traffic envelopes and homogeneous streams. In this paper, we generalize the scheduling scheme in [13] to include the heterogeneous case. We then investigate the allocation problem under window‐based traffic envelopes, which provide tight bounds on the bit rate. Using such envelopes, we introduce three stream‐scheduling schemes for multiplexing video connections at a server. The performance of these schemes is evaluated under static and dynamic scenarios. Our results indicate a significant reduction in the per‐stream allocated bandwidth when stream scheduling is used. While this reduction is obtained through statistical multiplexing, the transported streams are guaranteed stringent, deterministic quality of service (i.e., zero loss rate and small, bounded delay). In contrast to video smoothing, our approach requires virtually no buffer at the set‐top box since frames are delivered at their playback rate.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Publication Date: 2019-07-13
    Description: In the last few years, radio technologies for unmanned aircraft vehicle (UAV) have advanced very rapidly. The increasing need to fly unmanned aircraft systems (UAS) in the national airspace system (NAS) to perform missions of vital importance to national security, defense, and science has pushed ahead the design and implementation of new radio platforms. However, a lot still has to be done to improve those radios in terms of performance and capabilities. In addition, an important aspect to account for is hardware cost and the feasibility to implement these radios using commercial off-the-shelf (COTS) components. UAV radios come with numerous technical challenges and their development involves contributions at different levels of the design. Cognitive algorithms need to be developed in order to perform agile communications using appropriate frequency allocation while maintaining safe and efficient operations in the NAS and, digital reconfigurable architectures have to be designed in order to ensure a prompt response to environmental changes. Command and control (C2) communications have to be preserved during "standard" operations while crew operations have to be minimized. It is clear that UAV radios have to be software-defined systems, where size, weight and power consumption (SWaP) are critical parameters. This paper provides preliminary results of the efforts performed to design a fully digital radio architecture as part of a NASA Phase I STTR. In this paper, we will explain the basic idea and technical principles behind our dynamic/adaptive frequency hopping radio for UAVs. We will present our Simulink model of the dynamic FH radio transmitter design for UAV communications and show simulation results and FPGA system analysis.
    Keywords: Air Transportation and Safety; Space Sciences (General); Communications and Radar
    Type: GRC-E-DAA-TN30791 , Integrated Communication Navigation Systems (ICNS 2016); Apr 19, 2017 - Apr 21, 2017; Herndon, VA; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...