A Cooperative QoS Management Scheme Based on DiffServ Network for Real-Time Service

In this paper,an improved scheme based on DiffServ network is proposed to provide a decentralized coopera-tive QoS management for real-time services'admission control and resources'monitoring.The proposed scheme consists of aQoS Control Server(QoSCS),a Service Management Server(SMS),a Network Management Server(NMS)and routersin the concerned management domain.When an application asks for a service with specific QoS requirements,a series ofcooperation are initiated among these components by means of a suit of signaling protocol.Once a service is admitted,itcan provide required QoS services more effectively than original DiffServ network.Monitoring per-flow states are movedfrom edge routers to the QoSCS server.The prototype implementation and experimental results show that this scheme canprovide enhanced manageability and scalability for providing per-flow management in such a distributed way.     

A Secure and Efficient Authentication Scheme for E-coupon Systems

Through the explosive growth of network technologies, electronic commercial businesses have made our lives easier and more convenient. The application of e-coupons is quite a novel issue but is becoming increasingly popular among electronic commercial businesses because the extensive use of e-coupons can help consumers to save money; however, the e-coupon has also brought security issues as attackers can obtain illegitimate benefits from imperfections of the design. Hence, the security of the e-coupon system has become important as well. In this paper, we propose a novel and complete chaotic maps-based authentication scheme for e-coupon systems. Security analysis shows that our scheme satisfies essential security and functionality requirements. Furthermore, performance analysis shows that the execution time of our scheme is efficient and suitable for practical implementation in real life. In other words, users such as shops and customers can use our e-coupon system conveniently and securely.     

Maximum Power Point Tracking Scheme for PV Systems Operating Under Partially Shaded Conditions

Current-voltage and power-voltage characteristics of large photovoltaic (PV) arrays under partially shaded conditions are characterized by multiple steps and peaks. This makes the tracking of the actual maximum power point (MPP) [global peak (GP)] a difficult task. In addition, most of the existing schemes are unable to extract maximum power from the PV array under these conditions. This paper proposes a novel algorithm to track the global power peak under partially shaded conditions. The formulation of the algorithm is based on several critical observations made out of an extensive study of the PV characteristics and the behavior of the global and local peaks under partially shaded conditions. The proposed algorithm works in conjunction with a DC-DC converter to track the GP. In order to accelerate the tracking speed, a feedforward control scheme for operating the DC-DC converter is also proposed, which uses the reference voltage information from the tracking algorithm to shift the operation toward the MPP. The tracking time with this controller is about one-tenth as compared to a conventional controller. All the observations and conclusions, including simulation and experimental results, are presented.     

A Multiple Criteria Decision-Making Knowledge-Based Scheme for Real-Time Power Voltage Control

A new real-time power voltage control strategy is proposed in this paper. This scheme utilizes a novel offline evolutionary multiobjective optimization algorithm called jumping genes for generating the widespread control solutions and be readily stored into a knowledge data base. A separate online multiple criteria decision-making scheme is established for selecting the appropriate control solution. This concept of power voltage control has been demonstrated by the New England 39-bus power system. The system output performance was speedy and accurate.     

Exploration of Soft-Output MIMO Detector Implementations on Massive Parallel Processors

Emerging Software Defined Radio (SDR) baseband platforms are based on multiple processors with massive parallelism. Although the computational power of these platforms would theoretically enable SDR solutions with advanced wireless signal processing, existing work implements still rather basic algorithms. For instance, current Multiple-Input Multiple-Output (MIMO) detector implementations are typically based on simple linear hard-output and not on advanced near-Maximum Likelihood (ML) soft-output detection. However, only the latter enables to exploit the full potential of MIMO technology. In this work, we explore the feasibility of advanced soft-output near-ML MIMO detectors on massive parallel processors. Although such detectors are considered to be very challenging due to their high computational complexity, we combine architecture-friendly algorithm design, application specific instructions and instruction-level/data-level parallelism explorations to make SDR solutions feasible. We show that, by applying the proposed combination of techniques, it is possible to obtain SDR implementations which can deliver data rates that are sufficient for future wireless systems. For example, a 2 × 4 Coarse Grain Array (CGA) processor with 16-way Single Instruction Multiple Data (SIMD) can deliver 192/368 Mbps throughput for 2 × 2 64/16-QAM transmissions. Finally, we estimate the area and power consumption of the programmable solution and compare it against a traditional Application Specific Integrated Circuit (ASIC) approach. This enables us to draw conclusions from the cost perspective.     

An OFDMA-Based Subcarrier and Power Allocation Scheme in Wireless Cooperative Cellular Systems

An OFDMA-based subcarrier and power allocation scheme is proposed in this paper in the wireless cooperative cellular system. It is assumed that users in this system have the ability to relay information to each other to improve the overall system performance. The formulation of this scheme is to maximize the uplink system throughput subject to the half-duplex, distributed power and queue state constraints of each user. A two-slot resource allocation structure is constructed to deal with the half-duplex constraint. A low-complexity suboptimal algorithm is developed to solve the problem efficiently. This algorithm first greedily allocates subcarriers and power to users and then decides the relay selection. Numerical examples demonstrate the good throughput performance of our propose scheme and the effectiveness of the low-complexity algorithm.

超标量处理器的转移预测方案研究

随着高性能超标量处理器的流水线深度和发射度的增加,为挖掘宽发射、深度流水线处理器的潜在性能,设计一个杰出的转移预测器已变得越来越重要.常规的两级转移预测器是根据局部转移历史信息或全局转移历史信息来预测转移的结果,文章给出了一种新的转移预测方案,称为LGshare,它同时使用全局和局部转移历史信息来改进超标量微处理器的转移预测准确度.当模式历史表（PHT）的大小固定时,与常规的两级预测器相比,LGshare能获得更高的转移预测准确度.     

Efficient Array Coding Scheme for Large-Scale Storage Systems

A family of array codes with a maximum distance separable(MDS) property, named L codes, is proposed. The greatest strength of L codes is that the number of rows (columns) in a disk array does not be re...     

An Efficient Adaptive Distributed Space-Time Coding Scheme for Cooperative Relaying

A non-regenerative dual-hop wireless system based on distributed Alamouti space-time coding is considered. It is assumed that each relay retransmits an appropriately scaled space-time coded version of its received signal. The main goal of this paper is to find a scaling function for each relay to minimize the outage probability. In the high signal-to-noise ratio (SNR) regime for the relay-destination link, it is shown that a threshold-based scaling function (i.e., the relay remains silent if its channel gain with the source is less than its predetermined threshold) is optimum from the outage probability point of view. Numerical results demonstrate a dramatic performance improvement as compared to the case that the relay stations forward their received signals with full power even for finite SNR scenarios.     

A Hardware Approach to Real-Time Program Trace Compression for Embedded Processors

Collecting the program execution traces at full speed is essential to the analysis and debugging of real-time software behavior of a complex system. However, the generation rate and the size of real-time program traces are so huge such that real-time program tracing is often infeasible without proper hardware support. This paper presents a hardware approach to compress program execution traces in real time in order to reduce the trace size. The approach consists of three modularized phases: 1) branch/target filtering; 2) branch/target address encoding; 3) Lempel-Ziv (LZ)-based data compression. A synthesizable RTL code for the proposed hardware is constructed to analyze the hardware cost and speed and typical multimedia benchmarks are used to measure the compression results. The results show that our hardware is capable of real-time compression and achieving compression ratio of 454:1, far better than 5:1 achieved by typical existing hardware approaches. Furthermore, our modularized approach makes it possible to trade off between the hardware cost (typically from 1 to 50K gates) and the achievable compression ratio (typically from 5:1 to 454:1)     

A Robust Cooperative Spectrum Sensing Scheme in Cognitive Radio Systems

Performance of cluster-based cooperative spectrum sensing is more greatly improved than that of the traditional cooperative spectrum sensing.However,the style of clusters is not pointed out on traditional cluster-based method.In view of all the fading in the cooperative spectrum sensing,space diversity,and selective diversity,a robust cooperative spectrum sensing scheme based on clusters is proposed.Simulation results show that the detection performance of this new scheme is more close to that of the ideal cluster-based cooperative spectrum sensing scheme,and the excellent performance with higher reliability is gained relative to the actual cluster-based cooperative spectrum sensing scheme.Finally,the number of users in a cluster of the proposed scheme is discussed.The two users in a cluster are not the optimal solution to the overall implementation of cognitive radio.     

Efficient Power Allocation for Coded OFDM Systems

In coded OFDM systems, the transmission power of each subchannel is the same. In this letter, a power optimization scheme is presented to minimize FER or BER of a coded OFDM system under constant transmission power constraint. The power optimization is shown to be a convex optimization problem.     

An Efficient CSI Feedback Scheme for MIMO-OFDM Wireless Systems

For antenna-array-based multiple-input multiple- output orthogonal-frequency-division-multiplexing (MIMO-OFDM) wireless systems, gain in channel throughput reduced through sufficient feedback of the channel state information (CSI) is significant, particularly when the number of transmit antennas is larger than the number of receive antennas. In this letter, we demonstrate that, in such scenarios, (1) the CSI of each OFDM sub-carrier can be parameterized into a short bit stream by a proposed low-complexity QR decomposition on the corresponding MIMO channel matrix, (2) the overall CSI can be reliably represented by a proposed parameter interpolation on the above bit streams of only a fraction of sub-carriers, and (3) a MIMO-OFDM system with a low-rate CSI feedback parameterized above can provide a channel throughput comparable to the channel capacity.     

An Efficient Adaptive Modulation Scheme for Wireless OFDM Systems

An adaptive modulation scheme is presented for multiuser orthogonal frequency‐division multiplexing systems. The aim of the scheme is to minimize the total transmit power with a constraint on the transmission rate for users, assuming knowledge of the instantaneous channel gains for all users using a combined bit‐loading and subcarrier allocation algorithm. The subcarrier allocation algorithm identifies the appropriate assignment of subcarriers to the users, while the bit‐loading algorithm determines the number of bits given to each subcarrier. The proposed bit‐loading algorithm is derived from the geometric progression of the additional transmission power required by the subcarriers and the arithmetic‐geometric means inequality. This algorithm has a simple procedure and low computational complexity. A heuristic approach is also used for the subcarrier allocation algorithm, providing a trade‐off between complexity and performance. Numerical results demonstrate that the proposed algorithms provide comparable performance with existing algorithms with low computational cost.     

Efficient Transmission Scheme for AWG-Based DWDM Millimeter-Wave Fiber-Radio Systems

We propose and demonstrate an upstream transmission scheme using a semiconductor optical amplifier (SOA) for arrayed waveguide grating (AWG)-based dense wavelength-division-multiplexed (DWDM) millimeter-wave fiber-radio systems and show improved link performance. In our scheme, unused optical carriers from the cyclic AWG in the downlink (DL) are tapped for uplink (UL) transmission. An SOA in conjunction with the AWG simultaneously amplifies the DL RF subcarriers and UL optical carrier, thus improving carrier-to-sideband ratio in the DL while also yielding an improved power budget for the UL. Our experimental results show that the proposed scheme can be a practical solution for future bidirectional wavelength interleaved DWDM transmission systems     

具有高阶分集的协作系统中的功率分配算法

针对具有高阶分集的协作系统采用平均功率分配(EPA),导致系统平均误比特率性能较低的问题,提出了以最小化系统平均误比特率为目标的功率优化分配(OPA)算法。首先,推导了协作系统端到端误比特率的上界以及高信噪比条件下的渐近近似。在此基础上,推导了使系统平均误比特率最小的最优功率分配系数的闭式表达式。仿真结果表明,在保证总发射功率一定的条件下,所提功率分配算法相比平均功率分配可以有效降低系统的平均误比特率。     

Simultaneous Dynamic Voltage Scaling of Processors and Communication Links in Real-Time Distributed Embedded Systems

Dynamic voltage scaling has been widely acknowledged as a powerful technique for trading off power consumption and delay for processors. Recently, variable-frequency (and variable-voltage) parallel and serial links have also been proposed, which can save link power consumption by exploiting variations in the bandwidth requirement. This provides a new dimension for power optimization in a distributed embedded system connected by a voltage-scalable interconnection network. At the same time, it imposes new challenges for variable-voltage scheduling as well as flow control. First, the variable-voltage scheduling algorithm should be able to trade off the power consumption and delay jointly for both processors and links. Second, for the variable-frequency network, the scheduling algorithm should not only consider the real-time constraints, but should also be consistent with the underlying flow control techniques. In this paper, we address joint dynamic voltage scaling for variable-voltage processors and communication links in such systems. We propose a scheduling algorithm for real-time applications that captures both data flow and control flow information. It performs efficient routing of communication events through multihops, as well as efficient slack allocation among heterogeneous processors and communication links to maximize energy savings, while meeting all real-time constraints. Our experimental study shows that on an average, joint voltage scaling on processors and links can achieve 32% less power compared with voltage scaling on processors alone     

一种多中继协作系统中的功率分配算法

提出了多中继无线通信系统的模型,研究其源节点和各中继节点间功率分配对系统容量的影响,在总功率一定的情况下,探讨了以容量最大化为准则的功率分配算法。对采用非再生协作中继方式的多中继协作通信系统进行了容量分析,并提出了一种低复杂度的最优功率分配算法(Optimum Power Allocation,OPA)。仿真结果表明,该算法相对于平均功率分配算法(Average Power Allocation,APA),系统容量得到了显著提高,在信道条件差的情况下,性能提高更明显。     

A Reliable and Power Efficient Beacon Structure for Cognitive Radio Systems

In this paper, an energy efficient structure for beacon signal transmission is proposed for incumbent wireless microphone protection in a cognitive radio system. The proposed structure consists of two consecutive parts: Synchronization with Index and Synchronization with Payload, transmitted as in-phase and quadrature components respectively. As opposed to the current beacon design, it can achieve more reliable and balanced error protection for the beacon components, while keeping the system complexity low.     

A Combined Hard and Soft Variable-Structure Control Scheme for a Class of Nonlinear Systems

This paper presents a novel variable-structure-based control scheme for nonlinear systems. First, a hard variable-structure control is constructed for achieving a uniform ultimate boundedness control. Then, a soft variable-structure control using fuzzy logic is incorporated to help improve dynamic responses when trajectories enter into the ultimate bound. For practical consideration, we added a genetic-algorithm-based alpha–beta filter in front of the fuzzy controller to suppress noise and obtain smooth input signals. For comparison purposes, an inverted pendulum system was first used as a simulated example to demonstrate the effectiveness of the design. Then, the performance of the control scheme was practically tested with an experimental PC-based magnetic levitation system. The simulation and experimental results strongly suggest that the newly proposed control scheme is encouraging for practical applications.