移动通信环境中多媒体服务的动态资源分配

由于需求的显著增加，产生了在移动通信环境中提供多媒体服务的问题。本文根据对支持多媒体服务的基站的系统要求，介绍一个动态资源分配方案，该方案可以为陆基和移动环境间的接口提供一个框架。     

Replication Requirements in Mobile Environments

Replication is extremely important in mobile environments because nomadic users require local copies of important data. However, today's replication systems are not mobile-ready. Instead of improving the mobile user's environment, the replication system actually hinders mobility and complicates mobile operation. Designed for stationary environments, the replication services do not and cannot provide mobile users with the capabilities they require. Replication in mobile environments requires fundamentally different solutions than those previously proposed, because nomadicity presents a fundamentally new and different computing paradigm. Here we outline the requirements that mobility places on the replication service, and briefly describe ROAM, a system designed to meet those requirements.     

An Enhanced Load Balancing Approach for Dynamic Resource Allocation in Cloud Environments

Cloud computing is one of the distributed resource-sharing technology that offers resources on a pay-as-you-use basis. Platform as a service, Infrastructure as a service, and Software as a Service are services provided by the Cloud. Each end user's Quality of service must be ensured by the cloud service provider. In recent days, cloud utilization is rapidly increasing. To avoid congestion and to preserve the Service Level Agreement, the large workload must be balanced across the network. In this research work, a new load balancing approach is proposed for the dynamic resource allocation process to improve stability and to increase profit. PBMM algorithm is devised for an effective load balancing process through which, resource scheduling is performed. Task size and the bidding value coded by each customer are taken into account. To optimize the waiting time, resource tables and task tables are employed. The average waiting time and response time of the special users are minimized. The simulation results show that the proposed load balancing technique ensures the maximum profit and it enhances load balancing stability by increasing the number of special users.

     

Mixed Reality Applications in Urban Environments

Mixed reality applications are concerned with blurring the divide between the real and virtual, where the user perception of the real world is contextually enhanced with additional information. This paper will provide an overview of three related projects that explore opportunities for how virtual reality and mixed reality technologies can be effectively used across consumer, industrial and military domains. A common theme is dealing with the amount of data that can be potentially displayed in the applications.     

Nano-Underfills for High-Reliability Applications in Extreme Environments

Silica particles are used as a filler material in electronic underfills to reduce coefficient of thermal expansion of the underfill-epoxy matrix. In traditional underfills, the size of silica particles is in the micrometer range. Reduction in particle sizes into the nanometer range has the potential of attaining higher volume fraction particle loading in the underfills and greater control over underfill properties for higher reliability applications. Presently, no-flow underfills have very low or no filler content because micron-size filler particles hinder solder joint formation. Nano-silica underfills have the potential of attaining higher filler loading in no-flow underfills without hindering solder interconnect formation. In this paper, property prediction models based on representative volume element (RVE) and modified random spatial adsortion have been developed. The models can be used for development of nano-silica underfills with desirable thermo-mechanical properties. Temperature dependent thermo-mechanical properties of nano-underfills have been evaluated and correlated with models in a temperature range of -175degC to 150degC. Properties investigated include, temperature dependent stress-strain, creep and stress relaxation behavior. Nano-underfills on 63Sn37Pb eutectic and 95.5Sn3.5Ag1.0Cu leadfree flip-chip devices have been subjected to thermal shock tests in the range of -55degC to 125degC and -55degC to 150degC, respectively. The trade-offs between using nano-fillers instead of micron-fillers on thermo-mechanical properties and reliability has been benchmarked.     

Sensors for Applications in Magnetic Resonance Environments

This paper analyzes sensing methods compatible with magnetic resonance imaging (MRI) and functional MRI (fMRI) reported in the literature, and presents the three generations of MR-compatible force/torque sensors we have developed for robotic systems to interact with human motion. Conventional sensors such as camera-based measurement systems, strain gauges or commercial force/torque sensors, and optical encoders may be used, if placed sufficiently away from the imaging region and equipped with adequate shielding and filtering in order to minimize electromagnetic interference caused by electric cables, the transducer, and electronics of surrounding equipment. However, electromagnetic interference can be avoided by using light transmission over optical fibers, in which case sensitive and noisy electronic components can be placed outside the MR room, and the MR compatibility issue is restricted to the used materials. Good performance can be obtained with sensing elements made from materials adapted to the location of use, combined with reflected or differential light intensity measurement over optical fibers. We have developed various force and position sensors based on this principle, ranging from MR Safe (for a definition and discussion of the terms MR Safe and MR Conditional, see Gassert , IEEE Eng. Med. Biol. Mag., pp. 12--14, May/Jun. 2008) milled polymer probes to MR Conditional assemblies combining beryllium copper blades with a polymer body, as well as smaller aluminum probes realized through a combination of milling and electric discharge machining. It appears that, in contrast to actuators, good performance is not in tradeoff with MR compatibility.     

Dynamic Video Transcoding in Mobile Environments

A transcoder with dynamic feedback addresses interactivity, packet loss, and client power constraints in mobile communication systems.     

基于网格的资源查找算法分析

文章对网格环境下已有的资源查找算法，通过建模分别在时间复杂度、空间复杂度上进行对比分析，指出了这些算法各自存在的优势和不足。     

一种确定多媒体应用程序内层循环的子字并行编译方法

多媒体程序是数据密集型应用，其核心代码部分占用了大部分的执行时间，因此，对多媒体应用程序的研究大多针对其核心代码部分．本文围绕多媒体应用程序的核心内层循环，分析其子字并行特点，提出了一种新颖的按位数据流分析方法，能够确定程序的内层循环，为进一步深入研究奠定基础．     

面向动态AdHoc网络异构多播业务流最优资源控制策略

无线多播最优资源分配策略是无线AdHoc网络的核心问题.本文提出自适应多播控制算法(AMCAdaptive Multicast Control),采用分段效用函数精确量化用户感知,降低无效带宽分配次数,使之适应中速及高速移动Ad Hoc网络;引入单位资源效用参数和接入判决机制,改善原有模型中带宽平均分配造成的资源浪费;...     

Exploiting Thread‐Level Parallelism in Lockstep Execution by Partially Duplicating a Single Pipeline

In most parallel loops of embedded applications, every iteration executes the exact same sequence of instructions while manipulating different data. This fact motivates a new compiler‐hardware orchestrated execution framework in which all parallel threads share one fetch unit and one decode unit but have their own execution, memory, and write‐back units. This resource sharing enables parallel threads to execute in lockstep with minimal hardware extension and compiler support. Our proposed architecture, called multithreaded lockstep execution processor (MLEP), is a compromise between the single‐instruction multiple‐data (SIMD) and symmetric multithreading/chip multiprocessor (SMT/CMP) solutions. The proposed approach is more favorable than a typical SIMD execution in terms of degree of parallelism, range of applicability, and code generation, and can save more power and chip area than the SMT/CMP approach without significant performance degradation. For the architecture verification, we extend a commercial 32‐bit embedded core AE32000C and synthesize it on Xilinx FPGA. Compared to the original architecture, our approach is 13.5% faster with a 2‐way MLEP and 33.7% faster with a 4‐way MLEP in EEMBC benchmarks which are automatically parallelized by the Intel compiler.     

Dynamic Current Requirements in Single-Ended Log-Domain Filters

Single-ended log-domain filters must operate Class A: the amplitude of any symmetric signal must be less than the bias current. Even so, peak internal dynamic current requirements can be much greater than the bias currents. Worst-case peak current demands in a second-order log-domain filter are related to modulation index by simple expressions that allow transistor geometries to be optimized for specified signal levels. Several circuit topologies are considered, and some circuit topologies are shown to be better able to supply larger internal currents than others.     

一种满足通用和高性能应用的新时钟技术

随着时钟频率的持续增加,以及应用对越来越多不同频率的需要,传统的石英振荡器正在达到极限.IDT公司的系列硅时钟发生器正在成为低成本、通用应用及高性能数据通信、光纤网络和存储系统应用的晶振的有力替代品.     

Fiber-Optic Link Design Considerations for Applications in Noisy Industrial Environments

Industrial system considerations suggest the need for fiberoptic data links that have the ability to reduce susceptibility to noise from EMI or RFI, to isolate a system from high voltages and transmit reliable data. This paper deals with the design aspects of a fiber-optic system link, suitable for industrial process applications, and addresses process environments with slowly changing parameters such as: pressure, temperature, position (both rotary and linear), etc., available at the output of system interfacing sensors in the form of voltages, where less attention has been paid thus far. The approach used involves a voltage-pulse frequencyvoltage conversion technique with a VCO in the modulator and a PLL circuit in the demodulator. By changing a few components, the system can be converted into a simplex intercommunication optical link.     

On Exploiting Dynamic Trusted Routing Scheme in Delay Tolerant Networks

Wireless Personal Communications - Delay tolerant network routing is characterized by sparsely or densely populated nodes. In such network routing with limited resource like buffer space is a...     

动态环境下载波锁相跟踪环的信号级仿真

在接收信号载噪比一定的前提下,针对GPS软件接收机在不同运动状态下载波环跟踪的问题,仿真研究了不同环路的跟踪性能:在低加速度动态下采用2阶锁相环跟踪更佳,在高加速度动态下则应该采用3阶锁相环跟踪。通过仿真验证了环路的有效性。此外通过仿真发现当载噪比和滤波器噪声带宽一定的情况下,选择合适的预检测积分时间可以有利于载波跟踪。     

Enforcing Cooperative Resource Sharing in Untrusted P2P Computing Environments

Peer-to-Peer (P2P) computing is widely recognized as a promising paradigm for building next generation distributed applications. However, the autonomous, heterogeneous, and decentralized nature of participating peers introduces the following challenge for resource sharing: how to make peers profitable in the untrusted P2P environment? To address the problem, we present a self-policing and distributed approach by combining two models: PET, a personalized trust model, and M-CUBE, a multiple-currency based economic model, to lay a foundation for resource sharing in untrusted P2P computing environments. PET is a flexible trust model that can adapt to different requirements, and provides the solid support for the currency management in M-CUBE. M-CUBE provides a novel self-policing and quality-aware framework for the sharing of multiple resources, including both homogeneous and heterogeneous resources. We evaluate the efficacy and performance of this approach in the context of a real application, a peer-to-peer Web server sharing. Our results show that our approach is flexible enough to adapt to different situations and effective to make the system profitable, especially for systems with large scale.     

高动态条件下测控系统载波跟踪环路优化设计

航天测控系统中载波跟踪误差主要来源于热噪声和航天器动态应力,对载波跟踪环路的优化一般通过调整环路等效噪声带宽来实现.分析了航天测控系统中航天器的动态应力特性及环路跟踪误差特性,导出由载噪比和动态应力决定的环路最佳带宽表达式,提出一种通过环路自身状态估计载噪比和动态应力的方法,通过对载噪比和动态应力的实时估计实现对环路参数的实时调整.仿真结果表明,该算法在动态应力和载噪比时变的高动态场合可以实现稳定的载波跟踪,测量精度得到明显改善.     

Secure Transmission of Mobile Agent in Dynamic Distributed Environments

Huang et al. has recently proposed an efficient key management and access control scheme for mobile agent environments based on Elliptic Curve Cryptosystem (ECC). Although their scheme provides superior efficiency in comparison with the previous works, however some active attacks threaten its security. In this paper a new dynamic key management scheme based on ECC is proposed that is secure and also is efficient in computation cost. Analyzing the security criteria and performance confirms suitability of the proposed scheme for mobile agent environments.     

环树型TWDM-PON动态资源调度方法研究

针对基于波长变换型远端节点(RN)的环树型时分波分复用无源光网络(TWDM PON)接入网方案,提出了最大带宽利用率算法和最小切换次数算法等两种波长与时隙联合带宽分配算法。仿真结果显示了两种算法的有效性,最大带宽利用率算法可有效提高系统带宽利用率;最小切换次数算法可有效延长系统运行寿命,在现有光开关运行次数条件下系统可保证10年以上的有效运行时间。