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Video transmission over IEEE 802.11e wireless networks still shows poor performance for large bandwidth demand and frequently changed environments. Thus, several enhancements of IEEE 802.11e were proposed. On the other hand, big frames and simultaneous sending of adjacent frames always cause packet dropping for buffer overflow. In the past, we proposed an IEEE 802.11e enhancement named DFAA and a content aware mechanism to solve the above problems. The motivation of this paper is to find a proper way to integrate these two mechanisms. A DFAA enhancement (DFAA-E) is proposed to make up the insufficiency of content aware mechanism. Experiments results show that the combination of DFAA-E and content aware mechanism improves the video decoded quality greatly. And its performance can be further enhanced by selecting the suitable settings of certain parameters. 相似文献
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Mobile Networks and Applications - With the rapid development of Internet of things, the traditional city model is no longer applicable. Therefore, the emerging concept of smart city meets the... 相似文献
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Jizi Li Naixue Xiong Jong Hyuk Park Chunling Liu Shihua MA SungEon Cho 《Journal of Intelligent Manufacturing》2012,23(4):917-931
Intelligent model design of complex system becomes a key issue for organization responsiveness to uncertainties. In the real business world, the rule of competition between one firm verse another is replaced by a chain verse another chain, the cooperation is the same, where does it occur? At industrial cluster, there are a multiple of rivals or potential competitors for each member of value chain, industrial cluster location not only contains a couple of focal firms locating at the same tier, but includes the corresponding upstream and downstream firms as well, all of which concentrate on a close geographical site. For adopting to ever-changing market and sever competition, it is most likely to form multiple paralleled single supply chains for each focal firm of industrial cluster, these paralleled single supply chains compete and cooperate with each other. Recent researches regarding supply chain design mainly focus on a limited tier in single supply chain, which only take into account vertical cooperation and ignore the across-chain horizontal one. This paper, based on cluster supply chain, provides a novel framework and approach to design cluster supply chain without across-chain horizontal cooperation, then by introducing item allocation proportion of vertical and horizontal cooperation (α: 1?α), the cluster supply chain design with across-chain horizontal cooperation is developed, then presents a hybrid method to find solution, at last, computational study is presented to investigate values of decision variables and their influence on cluster supply chain design. 相似文献
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Jiao Feng Naixue Xiong Laurence T. Yang Yan Yang 《Multimedia Tools and Applications》2012,56(2):227-243
With the advent of Next Generation Network (NGN), services that are currently provided by multiple specific network-centric
architectures. NGN provides AAA (Anytime, Anywhere and Always on) access to users from different service providers with consistent
and ubiquitous provision of services as necessary. This special issue of NGN includes pervasive, grid, and peer-to-peer computing
to provide computing and communication services at anytime and anywhere. In fact, the application of NGN includes digital
image processing, multimedia systems/services, and so on. Here we focus on the digital image processing technology in NGN
environments. Low-contrast structure and heavy noise in NGN environments can be found in many kinds of digital images, which
makes the images vague and uncertainly, especially in x-ray images. As result, some useful tiny characteristic are weakened—which
are difficult to distinguish even by naked eyes. Based on the combination of no-linear grad-contrast operator and multi-resolution
wavelet analysis, a kind of image enhancement processing algorithm for useful tiny characters is presented. The algorithm
can enhance the tiny characters while confine amplifying noise. The analysis of the results shows that local regions of the
image are enhanced by using the concept of the grad contrast to make image clearer adaptively. Experiments were conducted
on real pictures, and the results show that the algorithm is flexible and convenient. 相似文献
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Naixue Xiong Jong Hyuk Park Laurence T. Yang Byoung-Soo Koh Yingshu Li 《Journal of Intelligent Manufacturing》2011,22(2):333-342
Information security management has become an important research issue in distributed systems, and the detection of failures
is a fundamental issue for fault tolerance in large distributed systems. Recently, many people have come to realize that failure
detection ought to be provided as some form of generic service, similar to IP address lookup. However, this has not been successful
so far; one of the reasons being the fact that classical failure detectors were not designed to satisfy several application
requirements simultaneously. More specifically, traditional implementations of failure detectors are often tuned for running
over local networks and fail to address some important problems found in wide-area distributed systems with a large number
of monitored components, such as Grid systems. In this paper, we study the security management scheme for failure detector
distributed systems. We first identify some of the most important QoS problems raised in the context of large wide-area distributed
systems. Then we present a novel failure detector scheme combined with self-tuning control theory that can help in solving
or optimizing some of these problems. Furthermore, this paper discusses the design and analysis of implementing a scalable
failure detection service for such large wide-area distributed systems considering dynamically adjusting the heartbeat streams,
so that it satisfies the bottleneck router requirements. The basic z-transformation stability test is used to achieve the stability criterion, which ensures the bounded rate allocation without
steady state oscillation. We further show how the online failure detector control algorithm can be used to design a controller,
analyze the theoretical aspects of the proposed algorithm and verify its agreement with the simulations in the LAN and WAN
case. Simulation results show the efficiency of our scheme in terms of high utilization of the bottleneck link, fast response
and good stability of the bottleneck router buffer occupancy as well as of the controlled sending rates. In conclusion, the
new security management failure detector algorithm provides a better QoS than an algorithm that is proposed by Stelling et al.
(Proceedings of 7th IEEE symposium on high performance distributed computing, pp. 268–278, 1998), Foster et al. (Int J Supercomput
Appl, 2001). 相似文献
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Active queue management (AQM) is an effective method used in Internet routers for congestion avoidance, and to achieve a tradeoff between link utilization and delay. The de facto standard, the random early detection (RED) AQM scheme, and most of its variants use average queue length as a congestion indicator to trigger packet dropping. This paper proposes a novel packet dropping scheme, called self-tuning proportional and integral RED (SPI-RED), as an extension of RED. SPI-RED is based on a self-tuning proportional and Integral feedback controller, which considers not only the average queue length at the current time point, but also the past queue lengths during a round-trip time to smooth the impact caused by short-lived traffic dynamics. Furthermore, we give theoretical analysis of the system stability and give guidelines for selection of feedback gains for the TCP/RED system to stabilize the average queue length at a desirable level. The proposed method can also be applied to the other variants of RED. Extensive simulations have been conducted with ns2. The simulation results have demonstrated that the proposed SPI-RED algorithm outperforms the existing AQM schemes in terms of drop probability and stability. 相似文献
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Weiwei Fang Xiangmin Liang Shengxin Li Luca Chiaraviglio Naixue Xiong 《Computer Networks》2013,57(1):179-196
In recent years, the power costs of cloud data centers have become a practical concern and have attracted significant attention from both industry and academia. Most of the early works on data center energy efficiency have focused on the biggest power consumers (i.e., computer servers and cooling systems), yet without taking the networking part into consideration. However, recent studies have revealed that the network elements consume 10–20% of the total power in the data center, which poses a great challenge to effectively reducing network power cost without adversely affecting overall network performance. Based on the analysis on topology characteristics and traffic patterns of data centers, this paper presents a novel approach, called VMPlanner, for network power reduction in the virtualization-based data centers. The basic idea of VMPlanner is to optimize both virtual machine placement and traffic flow routing so as to turn off as many unneeded network elements as possible for power saving. We formulate the optimization problem, analyze its hardness, and solve it by designing VMPlanner as a stepwise optimization approach with three approximation algorithms. VMPlanner is implemented and evaluated in a simulated environment with traffic traces collected from a data center test-bed, and the experiment results illustrate the efficacy and efficiency of this approach. 相似文献
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Xiang Lu Linlin Tu Xinyun Zhou Naixue Xiong Limin Sun 《The Journal of supercomputing》2017,73(8):3562-3578
The telepresence service (TPS) leverages advanced communication, virtual reality, and cooperative web technologies to provide remote engaged users an immersive experience of being fully present, which are widely used in teleconferencing, remote surgery, and hazardous environment exploration. The common feature of TPS-based applications lies in that the users’ experiences heavily depend on the quality of interactive multimedia services, that is, most deliveries of multimedia contents are mission-critical, as well as time-critical, to ensure the control and operation accuracy for telerobots. Therefore, the delivery performance of multimedia contents over heterogeneous networks becomes the primary concern in the TPS system design, especially for those delay sensitive applications, like remote surgery and environment exploration. In this paper, we incorporate video processing tools with the network simulator to design and implement a joint emulation system, named as the virtual media network (ViMediaNet), through which, the TPS designer can readily deploy the TPS system over a heterogeneous network virtualized by the network emulator, investigate the critical network performance metrics in the multimedia content delivery, such as transmission delay and packet jitter, and observe control results in real time. To verify the capability of ViMediaNet in emulating the real-setting TPS system, we take a mobile device based vision navigation system as an example to evaluate performance impacts of the rate adaptation technology in the telerobot control. The experimental results reveal that the adaptive video streaming is a promising solution to significantly enhance the control accuracy of telerobots in TPS systems. 相似文献