下行多用户多业务OFDM系统动态资源分配方法

针对未来无线通信系统必须能够同时支持多种业务类型的用户的问题,按照各用户服务质量(QoS)需求的不同将用户分为具有不同优先级的类,并基于子载波与功率分配联合优化的思想,提出了一种下行多用户OFDM系统动态资源分配方法.仿真结果表明,与现有方法相比,该方法在首先满足具有较高优先级用户的QoS需求的情况下,将更多的资源分配给优先级相对较低的用户,从而提高了资源利用率,进一步增加了系统的整体速率.     

一种新颖的多用户OFDM资源分配算法

在多用户正交频分复用(OFDM)系统中设计一种新颖的子载波-功率分配方法来最大化用户数据传输速率.这个方案分成两部分,子载波分配和功率分配.其中,子载波分配方法是在信道容量矩阵中将信道容量最好的子载波首先进行分配,功率分配采用注水方法.研究和模拟结果表明,该算法在只改变各个子载波增益系数的基础上,基本保持了较低的复杂度,并且极大地提高了用户数据传输速率.     

基于改进粒子群算法的分布式天线系统跨层功率分配方案

结合数据链路层的队列状态信息和物理层的信道状态信息定义了系统的吞吐量系数和公平性系数,建立了分布式天线系统跨层功率分配的离散速率集优化模型。对粒子群优化算法的初始群体产生、粒子更新等步骤进行了改进,形成了改进粒子群算法(IMPSO)。利用IMPSO进行了动态功率分配和跨层优化。数值仿真结果表明,IMPSO能够取得很好的队列时延性能,选取不同的权重可对系统吞吐量性能和公平性性能产生重要影响,IMPSO获得的系统吞吐量性能和公平性性能较之功率固定分配算法(AP)均有较大幅度的提高。     

基于效用函数的IEEE 802.16 OFDMA系统资源分配算法

针对IEEE 802.16系统中复杂的服务质量(quality of service,Qos)机制,设计了一种统一的效用函数作为资源分配的目标函数以平衡资源分配中的效率和公平性,使资源分配问题转化为基于系统效用最大化的系统优化问题.考虑到对算法的实时性要求和适用于IEEE802.16正交频分复用多址(OFDMA)系统的要求,提出了一种基于效用函数的资源分配(URA)的算法.仿真结果表明,所提出的URA算法在性能上非常接近于最优算法,而计算复杂度却大幅度降低;同时,URA算法能够在频谱效率和公平性之间取得良好的折衷,以满足IEEE 802.16系统中各业务类型不同的QoS要求.     

一种面向应用的光子网格资源联合分配策略

基于对业务驱动的光子网格系统的研究,提出了一种面向应用的光子网格服务提供模型,它将应用资源和光网络资源看作对等的实体,并将其抽象和封装为网格可以控制和共享的服务.基于对光子网格资源分配问题的研究,提出了一种用于资源联合分配的最小代价策略,它从最小化作业执行代价的角度解决了应用资源和光网络资源的联合分配问题.构建光子网格实验平台,并以网格计算业务在分布式岩心图像处理中的应用为例,对资源分配策略进行实验分析.结果表明,最小代价策略能够降低光子网格系统的业务阻塞率和平均处理时间,优化网格应用资源和光网络资源的使用.     

Shape memory materials and hybrid composites for smart systems: Part II Shape-memory hybrid composites

By hybridizing or incorporating shape-memory materials with other functional materials or structural materials, smart composites can be fabricated which may utilize the unique functions or properties of the individual bulk materials to achieve multiple responses and optimal properties, or, to tune their properties to adapt to environmental changes. A variety of shape-memory hybrid composites have been designed and manufactured, with shape-memory elements being either the matrix or the reinforcement. The hybrid composites provide tremendous potential for creating new paradigms for material–structural interactions and demonstrate varying success in many engineering applications. This review, from the standpoint of materials science, will give a state-of-the-art survey on the various shape-memory hybrid smart composites developed during the last decade. Emphasis is placed on the design, fabrication, characterization and performance of fibre-reinforced, particle-reinforced and multi-layered thin-film shape-memory composites.     

Cross-layer distributed approach for optimal rate allocation for homogeneous wireless multicast

Multicast-based data communication is an efficient communication scheme especially in multihop ad hoc networks where the MAC layer is based on one-hop broadcast from one source to multiple receivers. The problem of resource allocation for a set of homogeneous multicast sessions over multihop wireless network is addressed. An iterative algorithm is proposed that achieves the optimal rates for a set of multicast sessions such that the aggregate utility for all sessions is maximised. The authors demonstrate analytically and through simulations that the algorithm achieves optimal resource utilisation while guaranteeing fairness among multicast sessions. The algorithm in network environments with asynchronous distributed computations has been further analysed. Two implementations for the algorithm based on different network settings are presented and show that the algorithm not only converges to the optimal rates in all network settings but it also tracks network changing conditions, including mobility and dynamic channel capacity.     

协作分集OFDM系统的混合排序子载波配对算法

考虑到信源子载波和中继子载波的配对能在频率选择信道环境下提高协作分集系统的性能,对协作分集正交频分复用(OFDM)系统的子载波配对进行了研究,推导了2种特殊情况下的最佳子载波配对方法,即顺序配对和逆序配对,在此基础上,提出了一种基于混合排序的子载波配对算法.该算法根据信源-中继链路、信源-目标链路和中继-目标链路上的每个子载波的信噪比状态,自适应地选择顺序配对或逆序配对.仿真结果表明,提出的混合排序子载波配对算法能显著提高系统的平均可取得速率,性能明显优于顺序配对和逆序配对.     

Compact multiband planar monopole antennas for smart phone applications

A compact multiband planar monopole antenna is discussed. Tuning techniques, including offset feed, etching meandered slot and cutting tuning inset, are applied to the radiator in order to maximise the operating frequency range of the antenna. Experimental results demonstrate that the proposed design covers the operating bands of seven wireless services including the DCS/PCS/W-CDMA/2.4-/5-GHz WLANs/Bluetooth and the WiMAX in United States. The design concept, step-by-step guidelines, radiation mechanism and the simulated and experimental results are carefully investigated. The finite-size ground plane effect is taken into account as well. This antenna features multiband operations, almost omnidirectional radiation patterns in one of the principal cuts, and a compact size of 22.75 times 20 mm². It is especially suitable for smart phone applications which are involving in integrating multiple wireless services into a single hand-held unit.     

消除小区间干扰的OFDMA系统多小区上行资源分配方案

针对OFDMA系统多小区上行链路资源分配问题,提出了一种新的基于基站合作(BSC)和软频率复用(SFR)的资源分配方案。该方案通过相邻小区使用不同的子载波的软频率复用减少小区间干扰,利用基站合作对边缘用户的信号重构,使小区间干扰进一步消除,从而将多小区资源分配转化为单一小区资源分配。然后根据选择子载波避免冲突原则进行第一次子载波分配。最后根据速率要求,在不影响其他用户最低速率要求的前提下,对子载波进行二次分配。分析和仿真结果表明,该方案可以很好地解决小区边缘干扰严重的问题,降低用户的中断率,使多小区资源分配更加简单、公平、有效,尤其可保证边缘用户的服务质量,从而改善了系统的性能。     

Shape-memory materials and hybrid composites for smart systems: Part I Shape-memory materials

A review is presented of the current research and development of shape-memory materials, including shape-memory alloys, shape-memory ceramics and shape-memory polymers. The shape-memory materials exhibit some novel performances, such as sensoring (thermal, stress or field), large-stroke actuation, high damping, adaptive responses, shape memory and superelasticity capability, which can be utilized in various engineering approaches to smart systems. Based on an extensive literature survey, the various shape-memory materials are outlined, with special attention to the recently developed or emerged materials. The basic phenomena in the materials, that is, the stimulus-induced phase transformations which result in the unique performance and govern the remarkable changes in properties of the materials, are systematically lineated. The remaining technical barriers, and the challenges to improve the present materials system and develop a new shape memory materials are discussed.     

Optimal resource allocation on grid systems for maximizing service reliability using a genetic algorithm

Grid computing system is different from conventional distributed computing systems by its focus on large-scale resource sharing and open architecture for services. The global grid technologies and the Globus Toolkit in particular, are evolving toward an open grid service architecture (OGSA) with which a grid system provides an extensible infrastructure so that various organizations can offer their own services and integrate their resources. Hence, this paper aims at solving the problem of optimally allocating services on the grid to maximize the grid service reliability. Since no existing study has analyzed the grid service reliability, this paper develops initial modeling and evaluation algorithms to evaluate the grid service reliability. Based on the grid service reliability evaluation, we present an optimization model for the grid service allocation problem and develop a genetic algorithm (GA) to effectively solve it. A numerical example is given to show the modeling procedures and efficiency of the GAs.     

Cross-layer queuing analysis on multihop relaying networks with adaptive modulation and coding

Multihop relaying is one of the promising techniques in future generation wireless networks. The adaptive modulation and coding (AMC) mechanisms can be applied in order to increase the spectral efficiency of wireless multihop networks. However, most of these mechanisms concentrate on the physical layer without taking the queuing effects at the data link layer into account, whose performances are overestimated. Therefore the cross-layer analytical framework is presented in analysing the quality-of-service (QoS) performances of the decode-and-forward (DF) relaying wireless networks, where the AMC is employed at the physical layer under the conditions of unsaturated traffic and finite-length queue at the data link layer. Considering the characteristics of DF relaying protocol at the physical layer, the authors first propose modelling a two-hop DF relaying wireless channel with AMC as an equivalent Finite State Markov Chain (FSMC) in queuing analysis. Then, the performances in terms of queuing delay, packet loss rate and average throughput are derived. The numerical results show that the proposed analytical method can be efficiently applied for studying the issues including the relay deployment and the cross-layer design in the multihop relaying networks.     

网格环境下应用-系统平衡型资源分配优化策略

针对网格环境中资源分配如何同时优化应用执行性能和提高系统资源效率这个难点问题,提出了基于序贯博弈的执行时间最优目标下的Makespan-效率平衡型优化策略以及费用最优目标下的Cost-效率平衡型扩展策略.优化策略利用平衡的思想将资源分配过程分为活动分发和处理器分配两个阶段,通过有限次博弈后获得优化解.仿真实验以实际网格...     

Comparison of distributed methods for resource allocation

Resource allocation problems aim to achieve certain goals or objectives by allocating resources. Traditionally, centralized methods are applied to such problems. However, the inherent, decentralized nature of many corporates/companies/factories drives the investigation on decentralized or distributed methods. This paper provides an overview of research activities in the field of distributed methods for resource allocation problems. We concentrate on classifying the resource allocation problems, comparing different methods and discussing how these different methods can be applied to the problems. Finally, a range of open issues and future challenges are highlighted.     

Load management as a smart grid concept for sizing and designing of hybrid renewable energy systems

Optimal sizing of hybrid renewable energy systems (HRES) to satisfy load requirements with the highest reliability and lowest cost is a crucial step in building HRESs to supply electricity to remote areas. Applying smart grid concepts such as load management can reduce the size of HRES components and reduce the cost of generated energy considerably. In this article, sizing of HRES is carried out by dividing the load into high- and low-priority parts. The proposed system is formed by a photovoltaic array, wind turbines, batteries, fuel cells and a diesel generator as a back-up energy source. A smart particle swarm optimization (PSO) algorithm using MATLAB is introduced to determine the optimal size of the HRES. The simulation was carried out with and without division of the load to compare these concepts. HOMER software was also used to simulate the proposed system without dividing the loads to verify the results obtained from the proposed PSO algorithm. The results show that the percentage of division of the load is inversely proportional to the cost of the generated energy.     

IQ不平衡OFDM系统两种逼近最大似然性能的亚最大似然补偿算法

针对在同相正交IQ不平衡的正交频分复用(OFDM)系统中用传统的最大似然(ML)补偿算法需要二维复向量的搜索,从而导致计算复杂度较高的问题,提出了两种逼近ML算法性能的补偿算法,即一维实向量迭代搜索算法和二维实向量迭代搜索算法,它们通过在空间中迭代搜索一维或二维实向量来降低计算复杂度.仿真结果表明,上述改进的亚ML补偿算法的性能优于现有的频域和时域最小二乘补偿方法,逼近ML算法,其计算复杂度明显低于传统的ML算法,误比特性能与ML算法相当.     

Cost optimal segregated targeting for resource allocation networks

In this paper, a generalised methodology is proposed to target cost optimal allocation of resources in segregated targeting problems. Cost optimal segregated targeting problems are characterised by the existence of multiple zones; each consisting of a set of demands and using a unique resource with given cost and a single quality index (e.g., emissions factor, contaminant concentrations, etc.). All these zones share a common set of internal sources. This paper presents a rigorous mathematical proof of the decomposition principle that decomposes the problem into a sequence of sub-problems. Decomposition of the original problem is performed based on the prioritised costs for each external resource, attached to a particular zone. Prioritised cost of a resource depends on the pinch quality, quality of the resource and its cost. Applicability of the proposed methodology is illustrated by examples from carbon-constrained energy planning and water allocation networks.     

A network flow algorithm for optimal resource allocation

This paper introduces a network flow method for manpower scheduling and resource allocation. The network formulation of the problem permits the development of an algorithm that determines the minimal flow of resources through the network. The method presented here corresponds to the Simplex method, for in both methods the value of the objective function is optimized while the capacity limitations are preserved. The procedure proposed here, however, uses a more economical problem representation and is computationally more efficient. The efficacy of the minimal flow algorithm and its use is illustrated for a production system but the applicability of the procedure is sufficiently broad for it to work in other problem situations just as well.     

一个面向异构多核处理器Cell的资源分配模型

为了充分利用多核处理器提供的多级并行和解决多核资源分配问题,提出了一种将多任务并行程序映射到多核处理器平台上的模型驱动的方法。该方法首先创建一个三维优化空间来表示资源分配配置,而后通过搜索该空间为应用生成多种并行机制,最后对各种并行机制进行静态评估从而找出最优的机制。该方法同时考虑了任务并行、数据并行以及通讯开销。在异构多核处理器Cell上利用一个图像处理应用对此方法进行了测试。实验表明,这种模型驱动的方法能够很好地评估性能并为应用确定有效的并行机制。