Tree pruning for MIMO sphere detection based on MMSE detection

Tree pruning is an effective algorithm to reduce the complexity of sphere detection(SD) for multiple-input multiple-output(MIMO) communication systems.How to determine the tree pruning rule,as well as by what the tradeoff between the performance and the complexity can be achieved,is still an open problem.In this paper,a tree pruning algorithm is proposed based on minimum mean square error(MMSE) detection.The proposed algorithm first preforms MMSE detection since the complexity of MMSE detection is very low.Then the pruning constraints will be set according to the scaled path metrics of the MMSE solution.The choice of the scale factors and their influences on the complexity and performance are also discussed.Through analysis and simulations,it is shown that the complexity is reduced significantly with negligible performance degradation and additional computations.     

P-Zone： Connectivity-based Packet Path Tracing in Wireless Sensor Networks

In large-scale Wireless sensor networks （WSNs）, the network status is complex and unpredictable, which brings great challenges to practical network design and management. Tracing the route path of each data packet in the network is an important way to observe network behaviors and understand network dynamics. However, tracing the full route path of each packet could be highly challenging, due to the hard resource con- straint in WSNs. Our previous work proposes a hash-based path tracing mechanism, and leverages network connectivity and node locations to reduce the computational complexity. However, the node locations may be unavailable in some scenarios. In this work, we further propose a location-free enhancement to the hash-based path tracing mechanism, called P-Zone. P-Zone requires only network connectivity information to reduce the computational complexity. Theoretical analysis and practical simulations are conducted to evaluate the effectiveness and performance of our design. The results indicate that P-Zone can significantly reduce the computational complexity of the hashbased path tracing mechanism, while effectively tracing the full route path of each packet in the network in a real-time manner, and outperforms the state-of-the-art methods.     

An efficient simulation of multiple correlated Rayleigh fading envelopes

In order to better assess the performance of wireless communication systems, it is desirable to produce multiple Rayleigh fading envelopes with specified correlations. In this paper, we analyze theoretically a procedure which generates correlated Gaussian random variables from independent Gaussian random variables and give a physical explanation for the limitation of this procedure. Then, based on some uncorrelated Rayleigh fading envelopes, a simple but efficient procedure for generating an arbitrary number of cross-correlated Rayleigh fading envelopes is proposed. Simulation results and computational complexity analysis are presented, which show that the proposed method has some advantages, such as high accuracy, low computational complexity and easy implementation, over the conventional simulation method.     

Low complexity detection algorithm based on optimized Neumann series for massive MIMO system

An optimized Neumann series ( NS ) approximation isdescribed based on Frobenius matrix decomposition, this method aims to reduce the high complexity, which caused by the large matrix inversion of detection algorithm in the massive multiple input multiple output (MIMO) system. The large matrix in the inversion is decomposed into the sum of the hollow matrix and a Frobenius matrix, and the Frobenius matrix has the diagonal elements and the first column of the large matrix. In order to ensure the detection performance approach to minimum mean square error (MMSE) algorithm, the first three terms of the series approximation are needed, which results in high complexity as O(K³), where K is the number of users. This paper further optimize the third term of the series approximation to reduce the computational complexity from O(K³) to O(K²). The computational complexity analysis and simulation results show that the performance of proposed algorithm can approach to MMSE algorithm with low complexity O(K²).     

THE FOURTH-ORDER CUMULANTS BASED SPECTRALESTIMATION METHOD AND ITS APPLICATIONTO DIRECTION-FINDING

Traditional approaches of spatial spectral estimation are usually based on the second-order statistics. The higher-order cumulants and the poly-spectrum contain more information and are capable of reducing the Gaussian noise. In this paper, we present a new spectrum estimation method for direction-finding, the FOMUSIC algorithm, which is based on the eigen-structure analysis of the fourth-order cumulants. The derivation of the algorithm is given in detail and its performance is illustrated by both the computer simulations and the experiments of a direction-finding system. The obtained results demonstrate that the fourth-order cumulants based method outperforms the traditional methods, especially when the noise is an unknown colored one.     

Coalition-based downlink resource allocation for LTE system with divide-and-conquer approach

To take advantage of the multiuser diversity resulted from the variation in channel conditions among the users,it has become an interesting and challenging problem to efficiently allocate the resources such as subcarriers,bits,and power.Most of current research concentrates on solving the resource-allocation problem for all users together in a centralized way,which brings about high computational complexity and makes it impractical for real system.Therefore,a coalitional game framework for downlink multi-user resource allocation in long term evolution(LTE) system is proposed,based on the divide-and-conquer idea.The goal is to maximize the overall system data rate under the constraints of each user’s minimal rate requirement and maximal transmit power of base station while considering the fairness among users.In this framework,a coalitional formation algorithm is proposed to achieve optimal coalition formation and a two-user bargaining algorithm is designed to bargain channel assignment between two users.The total computational complexity is greatly reduced in comparison with conventional methods.The simulation results show that the proposed algorithms acquire a good tradeoff between the overall system throughout and fairness,compared to maximal rate and max-min schemes.     

Study on the Complexity of the Bullwhip Effect

Recent years have witnessed a rapid growth of interest in the study of the dynamic behavior of replenishment rules of bullwhip effect. We prove that bullwhip effect and butterfly effect share a same the self-oscillation amplifying mechanism that is the ordering decisions the supplier self-oscillation amplify the perturbations brought by the errors in the processing of retailers' demand information. This results as an explicit self-similar structure of the sensitivity of the system to the initial values duty to the nonlinear mechanism. In this paper, the causes process of the bullwhip effect is described as the internal nonlinear mechanism and study on the complexity of bullwhip effect for order-up-to policy under demand signal processing. The methodology is based on fractal and chaotic theory and allows important insights to be gained about the complexity behavior of bullwhip effect.     

Low-complexity SAGE-based MMSE channel estimation for CoMP multi-user systems

Coordinated multiple point(CoMP) transmission/reception has been investigated recently as a promising technology to increase the cell-edge user performance of long term evolution-advanced(LTE-A),and channel estimation is a crucial technology for CoMP systems.In this paper,we consider a reduced-complexity minimum mean square error(MMSE) channel estimator for CoMP systems.The estimator uses space alternating generalized expectation maximization(EM)(SAGE) algorithm to avoid the inverse operation of the joint MMSE estimator.In the proposed scheme,the base stations(BSs) in the CoMP system estimate the channels of all the coordinated users serially and iteratively.We derive the SAGE-based estimators and analyze complexity.Simulation results verify that the performance of the proposed algorithm is close to the joint MMSE estimation algorithm while reducing the complexity greatly.     

Optimal power allocation for two-way relaying over OFDM using physical-layer network coding

In this paper,a network scenario of two-way relaying over orthogonal frequency division multiplexing(OFDM) is considered,in which two nodes intend to exchange the information via a relay using physical-layer network coding(PLNC).Assuming that the full channel knowledge is available,an optimization problem,which maximizes the achievable sum rate under a sum-power constraint,is investigated.It is shown that the optimization problem is non-convex,which is difficult to find the global optimum solution in terms of the computational complexity.In consequence,a low-complexity optimal power allocation scheme is proposed for practice implementation.A link capacity diagram is first employed for power allocation on each subcarrier.Subsequently,an equivalent relaxed optimization problem and Karush-Kuhn-Tucker(KKT) conditions are developed for power allocation among each subcarrier.Simulation results demonstrate that the substantial capacity gains are achieved by implementing the proposed schemes efficiently with a low-complexity computational effort.     

Channel Estimation for Cyclic Postfixed OFDM

A novel channel estimation algorithm is presented in this paper for the recently proposed cyclic postfix based on orthogonal frequency division multiplexing （OFDM） systems. Phase equalization with the erasure decision is used to reduce both the channel estimation error and the computational complexity. Simulation results show that the proposed channel estimation algorithm can effectively estimate the channel impulse response （CIR） and the performance of the proposed phase equalization with erasure decision is comparable with the minimal mean square error （MMSE） equalization, but it offers less computational complexity.     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

Teleportation of an arbitrary unknown N-qubit entangled state under the controlling of M controllers

A new quantum protocol to teleport an arbitrary unknown N-qubit entangled state from a sender to a fixed receiver under M controllers(M < N) is proposed. The quantum resources required are M non-maximally entangled Greenberger-Home-Zeilinger (GHZ) state and N-M non-maximally entangled Einstein-Podolsky-Rosen (EPR) pairs. The sender performs N generalized Bell-state measurements on the 2N particles. Controllers take M single-particle measurement along x-axis, and the receiver needs to introduce one auxiliary two-level particle to extract quantum information probabilistically with the fidelity unit if controllers cooperate with it.     

A rigorous proof of MIMO channel capacity’s increase with antenna number

It is well known that adding more antennas at the transmitter or at the receiver may offer larger channel capacity in the multiple-input multiple-output（MIMO） communication systems. In this letter, a simple proof is presented for the fact that the channel capacity increases with an increase in the number of receiving antennas. The proof is based on the famous capacity formula of Foschini and Gans with matrix theory.     

Diode-end-pumped Nd:YVO4/LBO lasers with 4.2W continuous-wave output at 457 nm

A continuous-wave (CW) 457 nm blue laser operating at the power of 4.2 W is demonstrated by using a fiber coupled laser diode module pumped Nd: YVO4 and using LBO as the intra-cavity SHG crystal With the optimization of laser cavity and crystal parameters, the laser operates at a very high efficiency. When the pumping power is about 31 W, the output at 457nm reaches 4.2 W, and the optical to optical conversion efficiency is about 13.5% accordingly. The stability of the out putpower is better than 1.2% for 8 h continuously working.     

Call for Papers

正Wireless Body-area Networks The last decade has witnessed the convergence of three giant worlds:electronics,computer science and telecommunications.The next decade should follow this convergence in most of our activities with the generalization of sensor networks.In particular with the progress in medicine,people live longer and the aging of population will push the development of wireless personal networks