Stability Analysis of Spatiotemporally Periodic Orbits in Spatially Extended Systems

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Joint Frequency Offset and Channel Estimation for MIMO Systems in the Presence of Timing Error

This paper deals with the problem of joint frequency offset (FO) and channel estimation for multi-input multi-output (MIMO) systems in the presence of a timing error. Two equivalent signal models with FO and a timing error are given, and then a joint estimation method is derived. The proposed estimation method consists of two steps. Firstly, a maximum likelihood (ML) FO estimator is proposed based on the second signal model. Secondly, based on the FO estimate, we formulate the timing error and channel estimation as a problem of composite hypothesis testing according to the first signal model, and then solve the problem using a composite hypothesis testing approach. Simulation results are performed to show the effectiveness of the proposed method.     

An Analysis of the Blockcipher-Based Hash Functions from PGV

Preneel, Govaerts, and Vandewalle (1993) considered the 64 most basic ways to construct a hash function $H{:\;\:}\{0,1\}^{*}\rightarrow \{0,1\}^{n}Preneel, Govaerts, and Vandewalle (1993) considered the 64 most basic ways to construct a hash function H:   {0,1}^*? {0,1}ⁿH{:\;\:}\{0,1\}^{*}\rightarrow \{0,1\}^{n} from a blockcipher E:   {0,1}ⁿ×{0,1}ⁿ? {0,1}ⁿE{:\;\:}\{0,1\}^{n}\times \{0,1\}^{n}\rightarrow \{0,1\}^{n}. They regarded 12 of these 64 schemes as secure, though no proofs or formal claims were given. Here we provide a proof-based treatment of the PGV schemes. We show that, in the ideal-cipher model, the 12 schemes considered secure by PGV really are secure: we give tight upper and lower bounds on their collision resistance. Furthermore, by stepping outside of the Merkle–Damg?rd approach to analysis, we show that an additional 8 of the PGV schemes are just as collision resistant (up to a constant). Nonetheless, we are able to differentiate among the 20 collision-resistant schemes by considering their preimage resistance: only the 12 initial schemes enjoy optimal preimage resistance. Our work demonstrates that proving ideal-cipher-model bounds is a feasible and useful step for understanding the security of blockcipher-based hash-function constructions.     

On the Realization of Simulated Inductors with Reduced Parasitic Impedance Effects

In this paper, a method for reducing the parasitic impedance effects of the current feedback operational amplifiers (CFOAs) in an inductor simulator at low frequencies is proposed. Also, two novel grounded inductors employing a current follower (CF) and a second generation current conveyor (CCII) are given to illustrate the parasitic reduction technique clearly. The low frequency restrictions of the proposed inductors due to terminal parasitic resistances can be improved by using the presented parasitic impedance reduction technique. SPICE simulations show that the presented inductor employing CFOAs in a voltage-mode (VM) band-pass and high-pass filter application has lower parasitic effects at low frequencies. In addition to simulation results, experimental test results are given to verify the theory.     

Finite-Time H ∞ Inverse Optimal Control of Affine Nonlinear Systems

This paper is focused on the problem of the finite-time H _∞ inverse optimal control for affine nonlinear systems. Based on the finite-time control Lyapunov function, we derive a sufficient condition for the existence of time-invariant, continuous, finite-time stabilizing and inverse optimal state feedback control law, and propose a universal formula for constructing the finite-time H _∞ inverse optimal control law. We investigate the relationship between the finite-time stabilization and the finite-time H _∞ inverse optimal control. Finally, some examples are given to illustrate the effectiveness of the presented results.     

Stability Analysis of Robust Adaptive Control of Continuous-Time Systems

1IntroductionRobuStadaptivecontroltheoryisaveryimpo~researchsubject.Inrecentyearsmanypapersconcernedaboutrobustnessoftheadaptivecoalalsystemshavebeenpresented.Thereasonsforthisresearchtrendarethatmanyconventionaladaptivecolltrollersfailtodealwiththes...     

New Solutions for Distributed Realization of 8 × 1 MISO channel with QOSTBC

We proposed new solutions for distributed realization of the quasi orthogonal space-time block coding (QOSTBC), which is designed for 8 × 1 multiple input–single output (MISO) system. The first proposed solution assumes that base station and relay stations are equipped with 2 antennas, while for the second solution base station is equipped with 4 antennas and relay stations are with one antenna. In both scenarios mobile unit is equipped with single antenna. The proposed solutions are compared with distributed QOSTBC which is used for 4 × 1 MISO system. The simulation results show BER performances improvements provided with the proposed solutions in comparison with distributed QOSTBC designed for 4 × 1 MISO. It was shown that the first proposed scheme provides lower BER values than the second solution. Also, beside ideal channel estimation, influence of real estimation errors on BER performances is considered.     

Improved Analysis of Co-Channel Interference in Cellular Communications Systems

1 Introduction The performance analysis of co-channel interferenceincellular systems has been actively researched in the lastfewyears , due to the rapid deployment and success ofsuch systems , and because of the scarce bandwidthwhich calls for very careful design tools in order to uti-lizeit most efficiently.Signal transmission over a mobilechannel often suffers fromshadowing effect ,causing byobstacles in the radio propagation, such as the build-ings .In a cellular mobile system,the problemis…     

An Analysis of Interchannel Interference of OFDM Systems in Time-Varying Channel

1　IntroductionRecentlyOFDMtechniquehasregainedlotsofinterestforitspromisingtosupportbroadbandwire lessaccesssystems[1～ 4] .Comparedwithsingle car riersystems,OFDMsystemshavemanyobviousad vantages,suchasrobustnessagainstmultipathdelayspread,feasibilityinhardwareimplementation ,flexibilityinsubcarrierallocationandadaptabilityinsubcarriermodulation[5～6] .However,thepriorityofOFDMsystemscomesfromtheorthogonaldivi sionofbandwidth .Themoredivision ,thelongerthesymbolperiodisandthemorerobustt…     

Realization of Tapered Waveguide by Stretching the Rod Waveguide

By stretching the rod waveguide with different velocities in opposite directions, the tapered waveguide can be fabricated. In condition of taking no account of volume expansion caused by heating and under the assumptions of volume conservation,the rod waveguide can be stretched freely in the heated region without being stretched outside of the heated region. A model,which shows the relation of the transition shape and the two factors, that is the ratio of two velocity and the heated region length, is presented for the shape of the taper transition through mathematic deduction. Based on this model, a desired tapered waveguide can be fabricated. The tapered waveguide are widely used for fabricating tapered fiber couplers and sensors. In addition, the conclusion can be used for fabricating fused fiber coupler.     

Stabilization of Discrete-Time Switched Systems with Input Time Delay and Its Applications in Networked Control Systems

In this paper, we focus on investigating the asymptotic stabilizability of switched systems with input time delay and its applications in networked control systems (NCSs). First, based on an important lemma, a linear matrix inequality (LMI)-based asymptotic stabilizability criterion is established. Stabilizing switched state feedback controllers can be designed by solving a set of LMIs, which can be easily tested with efficient LMI algorithms. Then, for NCSs with communication constraints, the NCS is modelled as a discrete-time switched system with input time delay. Thus, the asymptotic stabilizability criterion of switched system with input delay can be applicable to such NCSs. Finally, an example is given to illustrate our main results. This work is supported by the National Natural Science Foundation of China under grants (No. 60704015), a grant of Liuhui Center for Applied Mathematics of Nankai University and Tianjin University in China.     

Circuit Topology Analysis of CMOS LNA in Mobile Communication Systems

1　Introduction　Now ,mostoftheLNAinRFreceiversarede signedwithGaAsorbipolartechnologies,whichhavealargepowerdissipationandunfavorableper formanceofintegration .CMOStechnologiestakeincreasinglyadvantagesoftechnologyadvances,whichhaveverylow powerconsumptionandmakepossibletheintegrationofcompletecommunicationsystems[1 ] .Forexample ,mobilecommunicationsystemreceiversemployextensivedigitalsignalpro cessingtoperformacquisition ,tracking ,anddecod ingfunctions.TheuseofCMOStechnologiesforimpl…     

Perturbation-Based Fourier Series Analysis of Transistor Amplifier

A perturbation-based Fourier series model is proposed to approximate the nonlinear distortion in weakly nonlinear circuits. This general model is applicable to any set of multi-variable state equations that completely describe a nonlinear circuit. This model is applied to a common emitter amplifier circuit wherein the transistor is represented by Ebers–Moll nonlinear current equations. Appropriate state variables are defined, then the linear and nonlinear parts of the Ebers–Moll current equations are separated, and a small perturbation parameter is incorporated into the nonlinear part. Now these current equations are incorporated into the set of KCL, KVL equations defined for the circuit and the state variables are perturbatively expanded. Hence, multi-variable state equations are obtained from these equations. The state variables are approximated up to first order through Fourier series expansion, as described in the proposed model. The main advantage of the proposed model is that it is simple and straightforward approach to analyze weakly nonlinear circuits, as it involves matrix computations and the calculations of exponential Fourier coefficients.     

Performance Analysis of STFT Based Timing Approach to OFDM Systems

1　IntroductionMuchinteresthasbeenfocusedonOrthogonalFrequencyDivisionMultiplexing (OFDM)inmanyareas,suchaswiredandwirelessapplications[1～ 1 5] .Synchronizationinbothtimeandfrequencydo mainisacriticalprobleminOFDMsystems.WEILandSCHLEGELC ,etalhavediscussedtheeffectsofsynchronizationerrorsandcarrierfrequencyoff sets[1～3] .ThemostremarkableworkbyBEEKJ[3]isajointMLestimatoroftimeandfrequencyoffsetutilizingtheCyclicPrefix (CP)withouttheaidofadditionalpilots.ThenJOHANSSONS ,eta…     

Design and Realization of Uniform Fiber Bragg Grating Used in Dense Wavelength Division Multiplexing Systems

Relation of optical properties in a uniform fiber Bragg grating(FBG) with its grating parameters and the laser beam engraving conditions is analyzed.The principle and metod for designing the uniform FBTG used in dense wavelength divison multiplexing (DWDM) system is given,By adopting the double exposure technique,with a univform phase mask and Gaussian laser beam,the uniform FBG used in DWDM system is designed and engraved,whose bandwidth of the main relection band is about 0.4 nm and 0.7 nm at -5dB and-25dB respecively.     

Analysis of Postal Development of the World

What will the Post in the world be like in 2005? At first glance, in view of worldwide structural changes, market liberalization and technological development, this question seems very hard to answer. However,without being able to draw a precise picture of the future post services, it can be affirmed that all current providers of postal services will have to face a very different environment from the current one. The objective of this analysis is to contribute to the future development by examining at the worldwide and regional level the major variables influencing the postal industry' s core businesssector, the letter-post, through analyzing the data published by the Universal Postal Union.     

Authenticated Encryption: Relations among Notions and Analysis of the Generic Composition Paradigm

An authenticated encryption scheme is a symmetric encryption scheme whose goal is to provide both privacy and integrity. We consider two possible notions of authenticity for such schemes, namely integrity of plaintexts and integrity of ciphertexts, and relate them, when coupled with IND-CPA (indistinguishability under chosen-plaintext attack), to the standard notions of privacy IND-CCA and NM-CPA (indistinguishability under chosen-ciphertext attack and nonmalleability under chosen-plaintext attack) by presenting implications and separations between all notions considered. We then analyze the security of authenticated encryption schemes designed by “generic composition,” meaning making black-box use of a given symmetric encryption scheme and a given MAC. Three composition methods are considered, namely Encrypt-and-MAC, MAC-then-encrypt, and Encrypt-then-MAC. For each of these and for each notion of security, we indicate whether or not the resulting scheme meets the notion in question assuming that the given symmetric encryption scheme is secure against chosen-plaintext attack and the given MAC is unforgeable under chosen-message attack. We provide proofs for the cases where the answer is “yes” and counter-examples for the cases where the answer is “no.” M. Bellare’s work was supported in part by a 1996 Packard Foundation Fellowship in Science and Engineering, NSF CAREER Award CCR-9624439, NSF grants CNS-0524765 and CNS-0627779, and a gift from Intel Corporation. C. Namprempre’s work was supported in part by grants of the first author and the Thailand Research Fund.     

Outage Probability Analysis of Relay Systems over K-μ Fading Channels

This paper provides an analytical framework for the outage probability evaluation of dual-hop decode-and-forward relay systems operating over K-μfading channels in the presence of co-channel interference. The interferers are independent non-identically distributed K-μfading. An accurate analytical-form expression for the cumulative distribution function of the received signal power to interference and noise ratio is derived. Various numerical results are compared with Monte Carlo simulation results in order to corroborate the accuracy of the proposed expressions. Our results show that increasing the value of kappa of main links will decrease the outage probability of relay systems. Furthermore, the system performance degrades with the number of interferences.     

Analysis of KMM¯ Sequences as Spreading Codes for A-CDMA Systems

In this paper, the KMM¯ sequence (i.e., a clock-controlledsequence) is presented as a new spreading code for A-CDMA (Asynchronous CDMA)systems. The conditions, which PN sequence as spreading codes should satisfy,are given on the basis of an A-CDMA system model. The properties ofKMM¯ sequences are described and their feasibility as thespreading codes for an A-CDMA system are analysed. The computer simulationcompares the cross-correlation of m-sequence and KMM¯ sequenceto prove the good cross-correlation property of KMM¯ sequence.Numerical results show the impact of the m-sequence and the KMM¯sequence on the system performance, as well as the differences betweenm-sequences and KMM¯ sequences under different user number andprocessing gain for A-CDMA system.     

Analysis of the Spherical-Circular Patch Antenna

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