1,668 research outputs found
Analysis of DVB-H network coverage with the application of transmit diversity
No full textThis paper investigates the effects of the Cyclic Delay Diversity (CDD) transmit diversity scheme on DVB-H networks. Transmit diversity improves reception and Quality of Service (QoS) in areas of poor coverage such as sparsely populated or obscured locations. The technique not only povides robust reception in mobile environments thus improving QoS, but it also reduces network costs in terms of the transmit power, number of
infrastructure elements, antenna height and the frequency reuse factor over indoor and outdoor environments. In this paper, the benefit and effectiveness of CDD transmit diversity is tackled
through simulation results for comparison in several scenarios of coverage in DVB-H networks. The channel model used in the simulations is based on COST207 and a basic radio planning
technique is used to illustrate the main principles developed in this paper. The work reported in this paper was supported by
the European Commission IST project—PLUTO (Physical Layer DVB Transmission Optimization)
Cloned Access Point Detection and Point Detection and Prevention Mechanism in IEEE 802.11 Wireless Mesh Networks
No full textIEEE 802.11 Wireless Mesh Network (WMN) is an
emerging low cost, decentralized community-based broadband technology, which is based on self-healing and multi-hop deployment of Access Points (APs), so that to increase the coverage area with maximum freedom to end-users to join or leave the
network from anywhere anytime having low deployment and maintenance cost. Such kind of decentralized structure and multihop architecture increases its security vulnerabilities especially
against the APs. One of such possible security attack is the placement of cloned AP to create serious performance degradation in IEEE 802.11 WMN. In this paper, we discuss the different
security vulnerabilities of AP in IEEE 802.11 WMN along with possible research directions. We also propose a mutual cooperation mechanism between the multi-hop APs and serving gateway so that
to detect and prevent the possibility of cloned AP. In this way the large scale exploitation of IEEE 802.11 WMN can be eliminated
Enabling error-resilient internet broadcasting using motion compensated spatial partitioning and packet FEC for the dirac video codec
No full textVideo transmission over the wireless or wired
network require protection from channel errors since compressed video bitstreams are very sensitive to transmission errors because of the use of predictive coding and variable length coding. In this paper, a simple, low complexity and patent free error-resilient coding is proposed. It is based upon the idea of using spatial partitioning on the motion compensated residual frame without employing the transform coefficient coding. The proposed scheme is intended for open source Dirac video codec in order to enable the codec to be used for Internet
broadcasting. By partitioning the wavelet transform coefficients of the motion compensated residual frame into groups and independently processing each group using arithmetic coding and Forward Error Correction (FEC), robustness to transmission errors over the packet erasure
wired network could be achieved. Using the Rate
Compatibles Punctured Code (RCPC) and Turbo Code
(TC) as the FEC, the proposed technique provides
gracefully decreasing perceptual quality over packet loss rates up to 30%. The PSNR performance is much better when compared with the conventional data partitioning only methods. Simulation results show that the use of multiple
partitioning of wavelet coefficient in Dirac can achieve up to 8 dB PSNR gain over its existing un-partitioned method
User preference aware caching deployment for device-to-device caching networks
No full textContent caching in the device-to-device (D2D) cellular networks can be utilized to improve the content delivery efficiency and reduce traffic load of cellular networks. In such cache-enabled D2D cellular networks, how to cache the diversity contents in the multiple cache-enabled mobile terminals, namely, the caching deployment, has a substantial impact on the network performance. In this paper, a user preference aware caching deployment algorithm is proposed for D2D caching networks. First, the definition of the user interest similarity is given based on the user preference. Then, a content cache utility of a mobile terminal is defined by taking the transmission coverage region of this mobile terminal and the user interest similarity of its adjacent mobile terminals into consideration. A general cache utility maximization problem with joint caching deployment and cache space allocation is formulated, where the special logarithmic utility function is integrated. In doing so, the caching deployment and the cache space allocation can be decoupled by equal cache space allocation. Subsequently, we relax the logarithmic utility maximization problem, and obtain a low complexity near-optimal solution via a dual decomposition method. Compared with the existing caching placement methods, the proposed algorithm can achieve significant improvement on cache hit ratio, content access delay, and traffic offloading gain
Laboratory measurement campaign of DVB-T signal with transmit delay diversity
No full textThe requirements for future DVB-T/H networks demand that broadcasters design and deploy networks that provide ubiquitous reception in challenging indoors and other obstructed situations. It is essential that such networks are designed cost-effectively and with minimized environmental impact. The EC funded project PLUTO has since its start in 2006 explored the use of diversity to improve coverage in these difficult situations. The purpose of this paper is to investigate the performance of Transmit Delay Diversity (DD) with two antennas to improve the reception of DVB-T/H systems operating in different realistic propagation conditions through a series of tests using a SPIRENT SR5500 dual channel emulator. The relationship between correlation coefficient between channels, receiver velocity and diversity gain is nvestigated. It is shown that transmit delay diversity significantly improves the quality of reception particularly in simulated fast fading mobile broadcasting applications. This paper documents research conducted by Brunel University and Broadreach Systems
Denial of service attacks and challenges in broadband wireless networks
No full textBroadband wireless networks are providing internet and related services to end users. The three most important broadband wireless technologies are IEEE 802.11, IEEE 802.16, and
Wireless Mesh Network (WMN). Security attacks and
vulnerabilities vary amongst these broadband wireless networks because of differences in topologies, network operations and physical setups. Amongst the various security risks, Denial of Service (DoS) attack is the most severe security threat, as DoS can compromise the availability and integrity of broadband
wireless network. In this paper, we present DoS attack issues in broadband wireless networks, along with possible defenses and future directions
Evaluating WAIC and PSIS-LOO for Bayesian Diagnostic Classification Model Selection
No full textBayesian diagnostic classification models (Bayesian DCMs) are effective for diagnosing students\u27 skills. Research on the evaluation of relative model fit indices for DCMs using Bayesian estimation, however, is deficient. This study introduces the performance of Bayesian relative model fit indices, the widely applicable information criterion (WAIC) and leave-one-out cross-validation using Pareto-smoothed importance sampling (PSIS-LOO), in comparison to simpler and more widely used deviance information criterion (DIC). The simulation study evaluates the performance of WAIC and PSIS-LOO by detecting the true model with varying sample sizes, item qualities, and prior information levels. The results of the study indicate that WAIC and PSIS-LOO primarily favored the generating model; however, occasional inconsistencies were observed. This study recommends using WAIC and PSIS-LOO when the data is assumed to follow a simpler model and the models are estimated under uninformative priors, and DIC when the data is assumed to follow a more complex model
Loo - Looking back, Theatre - Statement or Show
No full textThe paper focuses mainly on the meaning of contemporary theatre- its role in the society today. The notions statement and show are the principal viewpoints. The issue is based on the reflection of the Loo - Looking back, staged poem about the World. The paper covers both the staging process and the author´s study and stage experience, which determined the approach to the production. The paper also analyzes the influences leading to the origin of Looking back, reflecting the statement/show koncept: eg. Having to stage poetry (as assigned), taking account of the contemporary thinking and contemporary theatre, and last but not least of the audience
Intrusion Detection and Security Mechanisms for Wireless Sensor Networks
No full textKhan, S.; Lloret, J.; Loo, J. (2014). Intrusion Detection and Security Mechanisms for Wireless Sensor Networks. International Journal of Distributed Sensor Networks. 2014:1-3. doi:10.1155/2014/747483S13201
Lastman kijkt naar Caravaggio en inspireert Rembrandt en Van Loo
No full textAbstractThe fact that Pieter Lastman was Rembrandt's teacher was published way back in 1641. However, general similarities between the master's and pupil's work were not observed until 1854 by Kolloff. In 1895 Hofstcdc de Groot was the first to note a direct borrowing from a Lastman in a particular Rembrandt. Since then more than 70 of such direct borrowings have been noted. The present author adds that the figure of Delilah in Rembrandt's Blinding of Samson of 1636 (fig. 4) was inspired by the fleeing girl on the left at the top of Lastman's Ulysses and Nausicaä of 1619 (fig. 3) (In an earlier version of this theme by Lastman - fig. 1 - the very similar fleeing lady was inspired by the running boy on the right in Caravaggio's Martyrdom of Matthew - fig. 2 and thus represented the first instance of Carravagio's influence on Dutch art). The same figure from Lastman's second Ulysses and Nausicaä (fig. 3) was similarly used as the top of a pyramid of action by the 'classicist' Jacob van Loo in his Bacchanal of 1653 (fig.6). Both Rembrandt and Van Loo interpreted Lastman's 'Caravaggesque' figure in a new way, serving their own subject and purpose. Additionally, the author supports C. Lenz's idea that the composition of Rubens's oilsketch fig.5 also influenced Rembrandt's Blinding of Samson.
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