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Tsinghua Science and Technology

Issue 1 • Date Feb. 2008

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Displaying Results 1 - 21 of 21
  • [Front cover]

    Publication Year: 2008 , Page(s): c1
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    Freely Available from IEEE
  • Contents

    Publication Year: 2008 , Page(s): 1
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    Freely Available from IEEE
  • Carrier frequency offset compensation for an interleaved OFDMA uplink

    Publication Year: 2008 , Page(s): 1 - 8
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (362 KB)  

    This paper reports an investigation of the carrier frequency offset (CFO) compensation in the uplink of the orthogonal frequency division multiple access (OFDMA) system with interleaved subcarrier assignment. The presence of CFOs between the transmitters and the uplink receiver will destroy the orthogonality among the different subcarriers, resulting in inter-carrier interference and multiuser interference. This paper proposes a pseudoinverse CFO compensation method based on the signal structure. The proposed method can compensate the CFOs of all users simultaneously and isolate the signals from all users at the same time. Compared with the existing CFO compensation methods, the new method provides a considerable signal-to-noise ratio gain on the bit error rate performance and has a relatively low implementation complexity. View full abstract»

    Open Access
  • Direct GPS P-code acquisition method based on FFT

    Publication Year: 2008 , Page(s): 9 - 16
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (310 KB)  

    Recently, direct acquisition of GPS P-code has received considerable attention to enhance the anti-jamming and anti-spoofing capabilities of GPS receivers. This paper describes a P-code acquisition method that uses block searches with large-scale FFT to search code phases and carrier frequency offsets in parallel. To limit memory use, especially when implemented in hardware, only the largest correlation result with its position information was preserved after searching a block of resolution cells in both the time and frequency domains. A second search was used to solve the code phase slip problem induced by the code frequency offset. Simulation results demonstrate that the probability of detection is above 0.99 for carrier-to-noise density ratios in excess of 40 dB· Hz when the predetection integration time is 0.8 ms and 6 non-coherent integrations are used in the analysis. View full abstract»

    Open Access
  • Adaptive hammerstein predistorter using the recursive prediction error method

    Publication Year: 2008 , Page(s): 17 - 22
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (285 KB)  

    The digital baseband predistorter is an effective technique to compensate for the nonlinearity of power amplifiers (PAs) with memory effects. However, most available adaptive predistorters based on direct learning architectures suffer from slow convergence speeds. In this paper, the recursive prediction error method is used to construct an adaptive Hammerstein predistorter based on the direct learning architecture, which is used to linearize the Wiener PA model. The effectiveness of the scheme is demonstrated on a digital video broadcasting-terrestrial system. Simulation results show that the predistorter outperforms previous predistorters based on direct learning architectures in terms of convergence speed and linearization. A similar algorithm can be applied to estimate the Wiener PA model, which will achieve high model accuracy. View full abstract»

    Open Access
  • Simple, high-performance fusion rule for censored decisions in wireless sensor networks

    Publication Year: 2008 , Page(s): 23 - 29
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    Data selection-based summation fusion (DSSF) was developed to overcome the shortcomings of previously developed likelihood ratio tests based on channel statistics (LRT-CS) for the problem of fusing censored binary decisions transmitted over Nakagami fading channels in a wireless sensor network (WSN). The LRT-CS relies on detection probabilities of the local sensors, while the detection probabilities are a priori unknown for uncooperative targets. Also, for Nakagami fading channels, the LRT-CS involves an infinite series, which is cumbersome for real-time application. In contrast, the DSSF only involves data comparisons and additions and does not require the detection probabilities of local sensors. Furthermore, the performance of DSSF is only slightly degraded in comparison with the LRT-CS when the detection probabilities of local sensors are a priori unknown. Therefore, the DSSF should be used in a WSN with limited resources. View full abstract»

    Open Access
  • Improved minimum detectable velocity in bistatic space-based radar

    Publication Year: 2008 , Page(s): 30 - 34
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (221 KB)  

    Single orbit bistatic space-based radar (SBR) is composed of two radars in the same orbit. The characteristics of the clutter Doppler-angle spectrum of a single orbit bistatic SBR show that the slope of the mainbeam clutter spectrum is highly sensitive to the cone angles. Therefore, the minimum detectable velocity of the bistatic system is dependent on the cone angle. Then a new combined working mode of single-orbit bistatic SBR system was developed in which one radar will act as the transmitter and another as the receiver to improve detection performance for all angles. Simulation results by space-time adaptive processing verify the improved detection performance. The new design also reduces the average power of each radar system and the size and weight of the on-board solar array-battery system. View full abstract»

    Open Access
  • Steady-State analysis of target tracker with constant input/bias constraint

    Publication Year: 2008 , Page(s): 35 - 42
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (315 KB)  

    Navigation and surveillance applications require tracking constant input/bias targets. When the target's trajectory follows a constant input/bias constraint, model mismatching caused by conventional tracking algorithms can be handled by a delayed update filter (DUF). The statistical convergence and stability properties of the delayed update filter were studied to insure the rationality of its steady-state analysis. A steady-state filter gain was then designed for a constant-gain DUF to reduce the computations without much performance loss. Simulations demonstrate the potential of the constant-gain DUF, and the CGDUF is nearly 60% faster than the DUF without much loss in steady-state tracking accuracy. View full abstract»

    Open Access
  • Temperature dependence of the spontaneous brillouin scattering spectrum in microstructure fiber with small core

    Publication Year: 2008 , Page(s): 43 - 46
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (236 KB)  

    The almost equal height dual peak spontaneous Brillouin scattering spectrum of a piece of microstructure fiber with a small core was investigated at various temperatures using the heterodyne method. The central frequencies of the two peaks increase linearly with increasing temperature with temperature coefficients of 1.05 MHz/°C and 1.13 MHz/°C. The height difference between the two peaks decreases linearly with a coefficient of −0.06 dB/°C. The results show that microstructure fibers with a small core have great potential for fiber Brillouin distributed sensing. View full abstract»

    Open Access
  • Soft sensing of overflow particle size distributions in hydrocyclones using a combined method

    Publication Year: 2008 , Page(s): 47 - 53
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (294 KB)  

    Precise, real-time measurements of overflow particle size distributions in hydrocyclones are necessary for accurate control of the comminution circuits. Soft sensing measurements provide real-time, flexible, and low-cost measurements appropriate for the overflow particle size distributions in hydrocyclones. Three soft sensing methods were investigated for measuring the overflow particle size distributions in hydrocyclones. Simulations show that these methods have various advantages and disadvantages. Optimal Bayesian estimation fusion was then used to combine three methods with the fusion parameters determined according to the performance of each method with validation samples. The combined method compensates for the disadvantages of each method for more precise measurements. Simulations using real operating data show that the absolute root mean square measurement error of the combined method was always about 2% and the method provides the necessary accuracy for beneficiation plants. View full abstract»

    Open Access
  • Efficient scheme for optimizing quantum fourier circuits

    Publication Year: 2008 , Page(s): 54 - 58
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (237 KB)  

    In quantum circuits, importing of additional qubits can reduce the operation time and prevent decoherence induced by the environment. However, excessive qubits may make the quantum system vulnerable. This paper describes how to relax existing qubits without additional qubits to significantly reduce the operation time of the quantum Fourier circuit compared to a circuit without optimization. The results indicate that this scheme makes full use of the qubits relaxation. The concepts can be applied to improve similar quantum circuits and guide the physical implementations of quantum algorithms or devices. View full abstract»

    Open Access
  • Computing nonlinear lts estimator based on a random differential evolution strategy

    Publication Year: 2008 , Page(s): 59 - 64
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (228 KB)  

    Nonlinear least trimmed squares (NLTS) estimator is a very important kind of nonlinear robust estimator, which is widely used for recovering an ideal high-quality signal from contaminated data. However, the NLTS estimator has not been widely used because it is hard to compute. This paper develops an algorithm to compute the NLTS estimator based on a random differential evolution (DE) strategy. The strategy which uses random DE schemes and control variables improves the DE performance. The simulation results demonstrate that the algorithm gives better performance and is more convenient than existing computing algorithms for the NLTS estimator. The algorithm makes the NLTS estimator easy to apply in practice, even for large data sets, e.g. in a data mining context. View full abstract»

    Open Access
  • Dynamic reconstruction-based fuzzy neural network method for fault detection in chaotic system

    Publication Year: 2008 , Page(s): 65 - 70
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (279 KB)  

    This paper presents a method for detecting weak fault signals in chaotic systems based on the chaotic dynamics reconstruction technique and the fuzzy neural system (FNS). The Grassberger-Procaccia algorithm and least squares regression were used to calculate the correlation dimension for the model order estimate. Based on the model order, an appropriately structured FNS model was designed to predict system faults. Through reasonable analysis of predicted errors, the disturbed signal can be extracted efficiently and correctly from the chaotic background. Satisfactory results were obtained by using several kinds of simulative faults which were extracted from the practical chaotic fault systems. Experimental results demonstrate that the proposed approach has good prediction accuracy and can deal with data having a −40 dB signal to noise ratio (SNR). The low SNR requirement makes the approach a powerful tool for early fault detection. View full abstract»

    Open Access
  • Intelligent scheduling controller design for networked control systems based on estimation of distribution algorithm

    Publication Year: 2008 , Page(s): 71 - 77
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (302 KB)  

    The use of communication networks in control loops has gained increasing attention in recent years due to its advantages and flexible applications. The network quality-of-service (QoS) in those so-called networked control systems always fluctuates due to changes of the traffic load and available network resources. This paper presents an intelligent scheduling controller design approach for a class of NCSs to handle network QoS variations. The sampling period and control parameters in the controller are simultaneously scheduled to compensate for the network QoS variations. The estimation of distribution algorithm is used to optimize the sampling period and control parameters for better performance. Compared with existing networked control methods, the controller has better ability to compensate for the network QoS variations and to balance network loads. Simulation results show that the plant setting time with the intelligent scheduling controller is reduced by about 64.0% for the medium network load and 49.1% for high network load and demonstrate the effectiveness of the proposed approaches. View full abstract»

    Open Access
  • Incremental placement-based clock network minimization methodology

    Publication Year: 2008 , Page(s): 78 - 84
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (239 KB)  

    Power is the major challenge threatening the progress of very large scale integration (VLSI) technology development. In ultra-deep submicron VLSI designs, clock network size must be minimized to reduce power consumption, power supply noise, and the number of clock buffers which are vulnerable to process variations. Traditional design methodologies usually let the clock router independently undertake the clock network minimization. Since clock routing is based on register locations, register placement actually strongly influences the clock network size. This paper describes a clock network design methodology that optimizes register placement. For a given cell placement result, incremental modifications are performed based on the clock skew specifications by moving registers toward preferred locations that may reduce the clock network size. At the same time, the side-effects to logic cell placement, such as signal net wirelength and critical path delay, are controlled. Test results on benchmark circuits show that the methodology can considerably reduce clock network size with limited impact on signal net wirelength and critical path delay. View full abstract»

    Open Access
  • Performance flexibility architecture of core service platform for next-generation network

    Publication Year: 2008 , Page(s): 85 - 90
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (257 KB)  

    The hardware and software architectures of core service platforms for next-generation networks were analyzed to compute the minimum cost hardware configuration of a core service platform. This method gives a closed form expression for the optimized hardware cost configuration based on the service requirements, the processing features of the computers running the core service platform software, and the processing capabilities of the common object request broker architecture middleware. Three simulation scenarios were used to evaluate the model. The input includes the number of servers for the protocol mapping (PM), Parlay gateway (PG), application sever (AS), and communication handling (CH) functions. The simulation results show that the mean delay meets requirements. When the number of servers for PM, PG, AS, and CH functions were not properly selected, the mean delay was excessive. Simulation results show that the model is valid and can be used to optimize investments in core service platforms. View full abstract»

    Open Access
  • Modeling of busbars in high power neutral point clamped three-level inverters

    Publication Year: 2008 , Page(s): 91 - 97
    Cited by:  Papers (4)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (433 KB)  

    The busbars in high power neutral point clamped three-level inverters are modeled using the Maxwell Q3D Extractor software, which is based on the partial element equivalent circuits method. The equivalent circuits of the busbars and devices model are simulated in the electric simulator PSIM to analyze the effects of the parasitic inductance on the switching characteristics of the integrated gate commutated thyristor (IGCT) in different topology positions. The simulation results agree well with the measured impedance analyzer results and the IGCT test results, which proves the effectiveness of the modeling method for the large, complex busbars. View full abstract»

    Open Access
  • Object-Oriented system-on-network-on-chip template and implementation: H.263 case study

    Publication Year: 2008 , Page(s): 98 - 105
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    Network-on-chip (NoC) technology enables a new system-on-chip paradigm, the system-on-network-on-chip (SoNoC) paradigm. One of the challenges in designing application-specific networks is modeling the on-chip system behavior and determining on-chip traffic characteristics. A universal object message level model for SoNoC was defined and an object-oriented methodology was developed to implement this model in hardware and software. The model supports “object to core” synthesis and “function invoking to network” mapping. A case study of an H.263 system verifies the model and methodology. System prototypes are easily built and on-chip traffic can be observed using the SoNoC model to provide real benchmarks for on-chip network design. View full abstract»

    Open Access
  • Fuzzy programming models for vendor selection problem in a supply chain

    Publication Year: 2008 , Page(s): 106 - 111
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (249 KB)  

    This paper characterizes quality, budget, and demand as fuzzy variables in a fuzzy vendor selection expected value model and a fuzzy vendor selection chance-constrained programming model, to maximize the total quality level. The two models have distinct advantages over existing methods for selecting vendors in fuzzy environments. A genetic algorithm based on fuzzy simulations is designed to solve these two models. Numerical examples show the effectiveness of the algorithm. View full abstract»

    Open Access
  • Image and video quality assessment using neural network and SVM

    Publication Year: 2008 , Page(s): 112 - 116
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (268 KB)  

    An image and video quality assessment method was developed using neural network and support vector machines (SVM) with the peak signal to noise ratio (PSNR) and the structure similarity indexes used to describe image quality. The neural network was used to obtain the mapping functions between the objective quality assessment indexes and subjective quality assessment. The SVM was used to classify the images into different types which were accessed using different mapping functions. Video quality was assessed based on the quality of each frame in the video sequence with various weights to describe motion and scene changes in the video. The number of isolated points in the correlations of the image and video subjective and objective quality assessments was reduced by this method. Simulation results show that the method accurately accesses image quality. The monotonicity of the method for images is 6.94% higher than with the PSNR method, and the root mean square error is at least 35.90% higher than with the PSNR. View full abstract»

    Open Access
  • Dependent-chance programming models for capital budgeting in fuzzy environments

    Publication Year: 2008 , Page(s): 117 - 120
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (205 KB)  

    Capital budgeting is concerned with maximizing the total net profit subject to budget constraints by selecting an appropriate combination of projects. This paper presents chance maximizing models for capital budgeting with fuzzy input data and multiple conflicting objectives. When the decision maker sets a prospective profit level and wants to maximize the chances of the total profit achieving the prospective profit level, a fuzzy dependent-chance programming model, a fuzzy multi-objective dependent-chance programming model, and a fuzzy goal dependent-chance programming model are used to formulate the fuzzy capital budgeting problem. A fuzzy simulation based genetic algorithm is used to solve these models. Numerical examples are provided to illustrate the effectiveness of the simulation-based genetic algorithm and the potential applications of these models. View full abstract»

    Open Access

Aims & Scope

Tsinghua Science and Technology (Tsinghua Sci Technol) aims to highlight scientific achievements in computer science, electronic engineering, and other IT fields. Contributions all over the world are welcome.

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