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In this paper design of very thin and broadband electromagnetic absorbers is described. For normal incidence a five-layer absorber with 7.6 mm thickness with reflection coefficient below 20 dB over the frequency range 0.1 < f (GHz) < 10 has been achieved. Genetic Algorithms (GA) and three variants of particle swarm optimization (PSO) are applied to this problem. In order to show the capabilities...
The pattern synthesis technique described here is unique in that it allows the power pattern to be optimized in a very useful sense over the desired operating band of the array. This is an improvement over previous techniques involving constraints on such artificial parameters as source norm and superdirectivity ratio which do not in fact ensure a useful pattern bandwidth. The procedure described...
Vectorization has been an important method of using data-level parallelism to accelerate scientific workloads on vector machines such as Cray for the past three decades. In the last decade it has also proven useful for accelerating multimedia and embedded applications on short SIMD architectures such as MMX, SSE and AltiVec. Most of the focus has been directed at innermost loops, effectively executing...
The problem of spectrum sharing between two operators in a dynamic network is considered. We allow both operators to share (a fraction of) their licensed spectrum band with each other by forming a common spectrum band. The objective is to maximize the gain in profits of both operators by sharing their licensed spectrum bands rather than using them exclusively, while considering the fairness among...
The memory wall continues to be a major performance bottleneck. While small on-die caches have been effective so far in hiding this bottleneck, the ever-increasing footprint of modern applications renders such caches ineffective. Recent advances in memory technologies like embedded DRAM (eDRAM) and High Bandwidth Memory (HBM) have enabled the integration of large memories on the CPU package as an...
The use of curved reflectarrays for telecommunication applications is presented in this paper. For contoured beam applications, the curvature of the reflectarray surface can be used to enhance the bandwidth significantly, yielding reflectarray designs that are equivalent in performance compared to traditional shaped reflector antennas. For multiple spot beam applications, the curvature of the reflectarray...
In this paper, a bandpass filter (BPF) at 60 GHz band based on new design procedure is presented. The BPF is constructed by quartz-based post-wall waveguide (PWW) due to its lower dielectric loss. Filter design is achieved by optimization theory and burden for design is reduced by modeling filter as two dimensional structure. The 2D model is analyzed by using the method of moment (MoM) with global...
We report the design of a metamaterial-based antenna beamformer that transforms 7 stipulated inputs to 7 prescribed output beams. The beamformer is printed and exhibits a broad bandwidth of operation. It is modeled as an inhomogeneous, anisotropic 2D medium, and is designed using an constrained optimization approach. This design technique offers improved flexibility and feasibility over coordinate-transformation...
The virtualized network functions placement and chaining problem is formulated as a decision tree to reduce significantly the complexity of service function chaining (SFC) in clouds. Each node in the tree corresponds to a virtual resource embedding and each tree branch to the mapping of a client request in some physical candidate. This transforms the placement problem to a decision tree search. We...
Cost-effective cloud storage services attract users with their convenience; there is a trade-off between the service availability and the usage cost. We develop two cloud provider selection models for cloud storage services to minimize the total cost of usage. The models select multiple cloud providers with considering unavailability to meet the user requirements. The first model, called a user-copy...
This paper relates to the problem statement of distribution of heterogeneous information and communication system capacity among multiple service flows. We consider the case study of multi-commodity flow problem in terms of utility functions maximization. This approach differs from previously known by separating the optimization problem into layers based on Bellman's Principle of Optimality. It simplifies...
Bandwidth and Efficiency enhancement by multiport loading of a double notched small antenna is presented in this paper. The technique used is based on the combination of the Network Characteristic Modes (NCM) with an optimization algorithm, in order to find the optimal load values at specified positions. The required loads are found to be simple capacitive loads.
Multi-granularity memory system provides multiple access granularities for the applications with various spatial localities. In the multi-granularity access pattern, the one-size-bandwidth NoC design cannot utilize the bandwidth efficiently. We propose a novel NoC design, called BoDNoC, which can merge multiple narrow subnets to provide various bandwidths for access data. The new design also adopts...
This paper investigates resource allocation algorithms that use limited communication - where the supplier of a resource broadcasts a coordinating signal using one bit of information to users per iteration. Rather than relay anticipated consumption to the supplier, the users locally compute their allocation, while the supplier measures the total resource consumption. Since the users do not compare...
Nature-inspired approaches are powerful methods to solve many tough optimization problems. This paper proposes the two optimization approaches named, Big bang-big crunch and Firefly optimization algorithm to solve the optical channel-allocation problem in the optical wavelength division multiplexing systems by using the optimal Golomb ruler sequences. The simulation results conclude that both approaches...
Spectral efficiency and energy efficiency are important design criteria for green communications. In this paper, spectral efficiency and energy efficiency are addressed for transmission over channels that are orthogonal in frequency. The maximum sum rate is used in measuring the spectral- and energy-efficiency. The combined spectral- and energy-efficiency of particular total bandwidth and total transmit...
Regarding the bandwidth allocation of IEEE 802.16j two-hop relay networks, a Dynamic Bandwidth Allocation (DBA) algorithm based on the utility optimization is proposed. During the bandwidth allocation process of relay links, DBA algorithm takes the Quality-of-Service (QoS) requirements of different services into account by means of utility functions came from economic theories. Under the certain constraints,...
This paper presents a novel technique to extend the bandwidth of oversampled Analog-to-Digital Converters and a method to optimize their design to avoid instability, when oversampling has to be preserved and clock frequency cannot be increased. This proposal allows the converter to increase the resolution only introducing minor circuit modifications when processing input signals in the extended band...
A 25Gb/s CMOS optical receiver with superior noise performance is presented. The fully integrated receiver comprises a transimpedance amplifier (TIA), a main amplifier (MA), auxiliary analog loops and on-chip bias circuitry. The receiver employs a novel noise optimization technique for BJT-based shunt-feedback TIA, together with gain and bandwidth boosting methods to achieve low noise. Designed and...
Modern Cloud computing environments are rapidly evolving, leading to a growing adoption of dynamic pricing for virtual resources and of speedier deployment tools and to the emergence of hybrid Cloud scenarios. These trends suggest the opportunity to investigate a new generation of Cloud-based IT services, capable of adapting to changes in their operating conditions and deployment environment by dynamically...
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