Noise immunity of a quasi-optimal correlation receiver of noiselike signals with minimum frequency-shift keying

A quasi-optimal algorithm for correlation processing of noiselike signals with minimum frequency-shift keying is proposed and its noise immunity is analyzed. It is shown that the immunity of the quasi-optimal receiver to a structural noise is the same as that of the optimal correlation receiver and, in the case of a fluctuation noise, the loss in the signal-to-noise ratio is ～ 1 dB relative to the optimal algorithm.     

A differentially coherent receiver for minimum shift keying signal

The author extends to the case of minimum-shift-keying (MSK) modulation the differentially coherent reception theory established for phase-shift-keying modulation. A novel differentially coherent detector for MSK is thus derived. The receiver filter is equivalent to the cascade of a matched filter and an equalizer in order to suppress inherent intersymbol interference. It is shown that performance can be improved when the delay between signals, multiplied by the differential detector, is increased from one to M bit time intervals. This decreases the effect of noise correlation and, thus, the bit error probability. The bit error probability of the proposed receiver is calculated. It is found that almost all potential improvement due to the delay M is obtained with M=3     

Wideband frequency-shift keying with a spectrally bistable cleaved-coupled-cavity semiconductor laser

By operating a cleaved-coupled-cavity (C3) laser in a spectrally bistable regime with large hysteresis we demonstrate a new kind of high-speed FSK transmitter. This scheme can tolerate large fluctuations in modulation signal amplitude and show a detection limited switching time of 1 ns, indicating the possibility of high-speed high-reliability FSK systems.     

An ultraviolet laser communication system using frequency-shift keying modulation scheme

A communication system based on an ultraviolet(UV) laser at 266 nm is presented to improve the communication distance. The pulse frequency-shift keying(FSK) modulation scheme is studied and improved in order to reduce the bit error rate(BER), and is put into practice on a field programmable gate array(FPGA). The mathematical models of the modulation and demodulation are established. A test platform is set up to measure the energy density and pulse response under different distances and receiver elevation angles. It is shown that the omnibearing communication can be realized, and the bit rate is limited to 12.5 Mbit/s. The BER is estimated to be less than 10-7 at distance of 300 m in line-of-sight(LOS) communication model and to be less than 10-6 at distance of 80 m in non-line-of-sight(NLOS) communication model.     

Digital transmission by frequency-shift keying with zero intersymbol interference

A general criterion is derived that must be satisfied by the frequency characteristic of a transmission channel if a recovered f.s.k. signal is to exhibit zero i.s.i. It is shown that the bandwidth over which nonzero transmission is required is at least three times the Nyquist bandwidth for the given signalling rate, except for the special case of a frequency shift equal to the signalling rate. A minimal-bandwidth solution is given for a symmetrical bandpass channel of small fractional bandwidth.     

AN IMPROVED GENETIC ALGORITHM FOR SEARCHING OPTIMAL PARAMETERS IN n—DIMENSIONAL SPACE

An improved genetic algorithm for searching optimal parameters in n-dimensional space is presented,which encodes movement direction and distance and searches from coarse to precise.The algorithm can realize global optimization and improve the search efficiency,and can be applied effectively in industrial optimization ,data mining and pattern recognition.     

Classification of multiple M-ary frequency-shift keying signalsover a Rayleigh fading channel

We develop and analyze classifiers for multiple M-ary frequency-shift keying (MFSK) signals traveled over a static frequency nonselective Rayleigh fading channel. The classifier is based on approximating the likelihood function (LF) of the frequency modulated digital signals and is derived for both synchronous and asynchronous waveforms. Two cases are considered; the first one is concerned with the signals that have identical modulation type [for example, binary FSK (BFSK) or quaternary FSK (QFSK)]. The second case deals with the signals with different modulation type. We use complex envelope representation of the signals and noise to derive the LF. Simulation experiments are illustrated to validate the theoretical developments     

A wideband frequency-shift keying wireless link for inductively powered biomedical implants

A high data-rate frequency-shift keying (FSK) modulation protocol, a wideband inductive link, and three demodulator circuits have been developed with a data-rate-to-carrier-frequency ratio of up to 67%. The primary application of this novel FSK modulation/demodulation technique is to send data to inductively powered wireless biomedical implants at data rates in excess of 1 Mbps, using comparable carrier frequencies. This method can also be used in other applications such as radio-frequency identification tags and contactless smartcards by adding a back telemetry link. The inductive link utilizes a series-parallel inductive-capacitance tank combination on the transmitter side to provide more than 5 MHz of bandwidth. The demodulator circuits detect data bits by directly measuring the duration of each received FSK carrier cycle, as well as derive a constant frequency clock, which is used to sample the data bits. One of the demodulator circuits, digital FSK, occupies 0.29 mm/sup 2/ in the AMI 1.5-/spl mu/m, 2M/2P, standard CMOS process, and consumes 0.38 mW at 5 V. This circuit is simulated up to 4 Mbps, and experimentally tested up to 2.5 Mbps with a bit error rate of 10/sup -5/, while receiving a 5/10-MHz FSK carrier signal. It is also used in a wireless implantable neural microstimulation system.     

最小移频键控信号的检测和误码性能分析

首先介绍了MSK信号差分检测原理。其次,分析了存在相关高斯噪声和信道有瑞利衰落时MSK的抗噪声性能。结果表明,在高斯噪声时的差分MSK的误码率与DPSK相同;而当信道存在瑞利衰落时将严重影响系统的抗噪声性能。所得结论能为系统的设计提供重要依据。     

Serial concatenated coding scheme with minimum shift keying

A novel serially concatenated coding scheme for use with minimum shift keying (MSK) is proposed. The novelty is to use a mixture of recursive and non-recursive realisations for the MSK modulator. It is shown that this improves the performance of iterative demodulation and decoding of convolutionally encoded MSK signals with a slight decrease in the decoder complexity     

Optimal phase discriminator of a spread-spectrum frequency-shift keyed signal

An optimal phase discrimination algorithm for phase tracking of a spread-spectrum signal with minimum frequency-shift keying is proposed. The noise immunity of the algorithm is analyzed.     

一种改进的矢量量化码字搜索算法

该文利用图像矢量的平均值和方差,结合了最近邻域搜索算法,构造了一种新的快速矢量量化编码算法。将一个输入矢量分为两个子矢量,分别计算原始矢量、两个子矢量的和以及方差值,利用在这些数值基础上建立的一组三角不等式来排除不可能的码字。仿真结果表明新算法在所需时间和计算复杂度方面优于改进的EENNS算法,为矢量量化算法的研究提供了一种新的思路。     

An optimal tandem active-passive suspension system for roadvehicles with minimum power consumption

The authors examine the problem of the synthesis of an optimal control law for active suspensions of road vehicles, based on a model with two degrees of freedom. The possibility of realizing the desired optimal control law with a tandem active-passive suspension is considered. The procedure for determining the desired optimal control law on the basis of suitable design specification is outlined. In the case of a suspension with two degrees of freedom, the possibility of realizing a control law with an active suspension in tandem with a conventional passive one consisting of a spring and a damper is examined. The characteristic parameters of the passive part of the suspension are identified with the aim of minimizing the power required by the active part. The expressions for calculating the values of the elastic constant of the spring and of the characteristic coefficient of the damper, which are both assumed to be linear, are provided. An example of the application is presented     

An optimal signal design for band-limited asynchronous DS-CDMAcommunications

An optimal signal design for band-limited, asynchronous, direct-sequence code-division multiple-access (DS-CDMA) communications with aperiodic random spreading sequences and a conventional matched filter receiver is considered in an additive white Gaussian noise (AWGN) channel. With bandwidth defined in the strict sense, two optimization problems are solved under finite bandwidth and zero interchip interference constraints. First, a chip waveform optimization is performed given the system bandwidth, the data symbol transmission rate, and the processing gain. A technique to characterize a band-limited chip waveform with a finite number of parameters is developed, and it is used to derive optimum chip waveforms which minimize the effect of multiple-access interference (MAI) for any energy and delay profile of users. Next, a joint optimization of the processing gain and the chip waveform is performed, given the system bandwidth and the data symbol transmission rate. A sufficient condition for a system to have lower average probability of bit error for any energy profile is found, and it is used to derive some design strategies. It is shown that the flat spectrum pulse with the processing gain leading to zero excess bandwidth results in the minimum average probability of bit error. Design examples and numerical results are also provided     

An optimal training signal structure for frequency-offset estimation

This paper addresses an optimal training-signal design for frequency-offset estimation. Based on minimizing the Cramer-Rao lower bound for frequency-offset estimation with constraints on the peak and the total training signal energies, and the training block length, the optimal training-signal structure is developed. An approximate version of the optimal training-signal structure is proposed, which has practically the same performance as the optimal one, and provides convenience in training-signal generation and estimator derivation. Two robust reduced-complexity frequency-offset estimation methods for the proposed training structures are presented. In order to handle larger frequency offsets, modified training-signal structures are proposed. Frequency-offset estimation methods suitable for these training signals are also derived, based on the best linear unbiased estimation principle. Analytical and simulation results show that the proposed training-signal structures improve the estimation performance significantly.     

An asymptotic optimal algorithm for modulation classification

A suboptimal algorithm for modulation classification was proposed for classifying the modulation type of general M-ary phase-shifted keying (MPSK) signals. Yang and Soliman (see IEEE Trans. Aerosp. Electron. Syst., vol.33, no.1, p.38-45, 1997) approximated the phase probability density function of a received signal to be the Tikhonov function. Instead, we employ the exact phase density function and derive an asymptotic optimal classification algorithm. We show a structure of this proposed classifier for continuous wave (CW), binary phase-shift keying (BPSK), quaternary phase-shift keying (QPSK), and 8PSK. Besides, we give an example to demonstrate the capability of this algorithm and compare its performance to that in Yang and Soliman. It is shown that the performance is more effective     

An ant colony algorithm for minimum unsatisfiable core extraction

Explaining the causes of infeasibility of Boolean formulas has many practical applications in electronic design automation and formal verification of hardware. Furthermore, a minimum explanation of infeasibility that excludes all irrelevant information is generally of interest. A smallest-cardinality unsatisfiable subset called a minimum unsatisfiable core can provide a succinct explanation of infeasibility and is valuable for applications. However, little attention has been concentrated on extraction of minimum unsatisfiable core. In this paper, the relationship between maximal satisfiability and minimum unsatisfiability is presented and proved, then an efficient ant colony algorithm is proposed to derive an exact or nearly exact minimum unsatisfiable core based on the relationship. Finally, experimental results on practical benchmarks compared with the best known approach are reported, and the results show that the ant colony algorithm strongly outperforms the best previous algorithm.     

An optimal vector-network-analyzer calibration algorithm

We present an iterative algorithm for calibrating vector network analyzers based on orthogonal distance regression. The algorithm features a robust, yet efficient, search algorithm, an error analysis that includes both random and systematic errors, a full covariance matrix relating calibration and measurement errors, 95% coverage factors, and an easy-to-use user interface that supports a wide variety of calibration standards. We also discuss evidence that the algorithm outperforms the MultiCal software package in the presence of measurement errors and accurately estimates the uncertainty of its results.     

An optimal distributed routing algorithm

A distributed optimal one-level routing algorithm is presented. The algorithm is based on Newton's method. Using the variable reduction method, the Hessian matrix becomes diagonal. An example shows that the algorithm has a much faster convergence rate, more accurate results, and better transient behavior than previous work. The algorithm is shown to be convergent, stable, robust, and loop free     

An efficient algorithm for the minimum cost min-max load terminal assignment problem

One of the main issues to be addressed in topological design of centralized networks is that of assigning terminals to concentrators in such a way that each terminal is assigned to one (and only one) concentrator and the total number of terminals assigned to any concentrator (which is referred to as load in this paper) does not overload that concentrator, i.e. is within the concentrator's capacity. Under these constraints, an assignment with the lowest possible cost is sought. An assignment of terminals to concentrators which minimizes the maximum load among the concentrators (which qualitatively represents congestion at some hot spots in a network service area) is referred to as a min-max load assignment. In this paper, we consider the problem of finding a min-max load assignment with the-lowest cost. We call this problem the Minimum Cost Min-Max Load Terminal Assignment Problem (MCMLTAP). We present an algorithm for MCMLTAP and prove that the problem is optimally solvable in polynomial time using our proposed algorithm.