FFH/BFSK选择分集合并接收机在部分频带干扰Nakagami-m信道下的性能分析

快速跳频通信系统选择分集合并接收机可以有效减轻干扰及衰落对系统带来的性能损伤。该文给出了快速跳频BFSK系统在部分频带干扰下的选择分集合并接收机模型,并对该接收机在同时存在部分频带干扰以及加性高斯白噪声的非频率选择性Nakagami-m衰落信道下的性能进行了推导,给出了误码率的闭合表达式。最后进行了仿真验证,仿真结果与理论分析结果完全一致。分析表明:具有高分集度的选择分集合并接收机受干扰影响较小;在干扰功率较大时,其性能要好于其它几种分集合并接收机;在一定的信道条件下,存在一个最佳分集度。最后针对选择分集合并接收机在弱干扰信号下的性能不足,提出相应的改进措施。     

Optimization of Linearly Equalized QAM

A QAM signal transmitted over a channel with linear distortion and additive white Gaussian noise can be linearly equalized at the receiver to eliminate intersymbol interference. If the QAM signal is power constrained and a given symbol error rate is required, we show that it is possible to maximize the bit rate of this system by optimizing the symbol rate and the number of bits/symbol. Ideal linear equalization is assumed at the receiver to overcome the distortion introduced by the channel. As an example, a Gaussian channel is chosen, and the bit rate is maximized for this channel. The QAM maximization is especially useful for channels with slowly decaying channel attenuation characteristics, e.g., the twisted-pair channel.     

Maximum-likelihood receiver of FFH/BFSK systems with multitonejamming and AWGN over Rayleigh-fading channels

A maximum-likelihood receiver for fast frequency-hopped binary frequency-shift-keying (FFH/BFSK) systems which operates in an additive white Gaussian noise (AWGN) environment and is subjected to multitone jamming over Rayleigh-fading channels is derived. Simulation results show that the proposed maximum-likelihood receiver outperforms existing receivers with the same channel and jamming conditions     

Multitone jamming rejection of FFH/BFSK spread-spectrum system overfading channels

Analytical expressions for bit-error probability are derived for a fast frequency-hopping binary frequency-shift keying (FFH/BFSK) spread-spectrum communication system over a fading channel with worst-case band multitone jamming (MTJ) and additive white Gaussian noise (AWGN). An FFH system employing either a linear-combining receiver or a clipper receiver is investigated. The desired signal and MTJ are assumed to undergo independent fading, and our analysis, validated with simulation results, shows that the performance of the system is slightly improved as the severity of the MTJ fading is increased. The clipper receiver is found to be superior to the linear-combining receiver when the jamming power is strong. The worst-case MTJ is shown to be more harmful than the corresponding worst-case partial-band noise jamming over a fading channel with AWGN     

Probability of error in frequency-hop spread-spectrummultiple-access communication systems with noncoherent reception

Expressions are developed for the probability of error for asynchronous frequency-hop spread-spectrum multiple-access networks using Markov hopping patterns and binary frequency shift keying (BFSK) with one symbol transmitted per hop. The expressions are exact when there is one interfering user and orthogonal BFSK is used. They provide excellent approximations when there are more than one interfering user. It is also shown that the error probability when Markov hopping patterns are used is a good approximation to the error probability when memoryless hopping patterns are used. By computing the channel capacity and the associated throughput, a simple hard decision receiver is shown to perform much better than a receiver using perfect side-information to erase the symbols transmitted on hops that were hit when all the users have the same power and one binary symbol is transmitted per hop     

Probability of Error Analyses of a BFSK Frequency-Hopping System with Diversity Under Partial-Band Jamming Interference--Part I: Performance of Square-Law Linear Combining Soft Decision Receiver

In this paper, error probability analyses are performed for a binary frequency-shift-keying (BFSK) system employingLhop/bit frequency-hopping (FH) spread-spectrum waveforms transmitted over a partial-band Gaussian noise jamming channel. The error probabilities for theLhop/bit BFSK/FH systems are obtained as the performance measure of the square-law linear combining soft decision receiver under the assumption of the worst-case partial-band jamming. The receiver in our analysis assumes no knowledge of jamming state (side information). Both exact and approximate (multiple bound-parameter Chernoff bound) solutions are obtained under two separate assumptions: with and without the system's thermal noise in the analyses. Numerical results of the error rates are graphically displayed as a function of signal-to-jamming power ratio withLand signal-to-noise ratio as parameters. All of our results, exact and approximate, indicated that the higher number of hops per bit produced higher error probabilities as a result of increased combining losses when the square-law linear combining soft decision receiver is employed in demodulating the multihop-per-bit waveform.     

SER Computation in M-QAM Systems with Phase Noise

This paper presents an exact closed-form expression for the symbol error rate of the square and rectangular quadrature amplitude modulation (QAM) constellations, under the assumption that the transmitted and/or received signals are corrupted by the phase noise fluctuation. Phase noise is one of the most important radio frequency (RF) imperfections which usually comes from the local oscillator (LO) at the transmitter and/or receiver. In this paper, the additive white Gaussian noise (AWGN) channel is assumed. Although AWGN is a simple channel, but our exact analysis of the symbol error rate in this paper can be led to the precise study of the real communication systems in the fading channel. Hence, an exact closed-form solution for the symbol error rate is derived here as a finite summation of the two-dimensional Q-function and verified by the simulation.     

Performance Study of an FFH/BFSK Self-Normalizing Receiver with Multitone Jamming's Frequency Offsets

This study investigates how frequency offsets of multitone jamming affect the fast frequency-hopped binary frequency shift keying (FFH/BFSK)self-normalizing (SNZ) receiver under additive white Gaussian noise (AWGN). The average bit-error-rate (BER) expressions of the FFH/BFSK SNZ receiver and the average BER expressions of an FFH/BFSK spread-spectrum (SS) communication system with frequency offsets of multitone jamming for the sake of understanding the simulation results better. Simulation results show that BER performance of the FFH/BFSK SNZ receiver with diversity under the worst casemultitone jamming (MTJ) and AWGN suffers from multitone jamming's frequency offsets when the jamming power is moderate, which is validated by several simulations with different frequency offsets configured in multitone jamming. Therefore, an FFH/BFSK SNZ receiver under multitone jamming can be combated with the help of frequency offsets of multitone jamming.     

Improved auxiliary particle filter‐based synchronization of chaotic Colpitts circuit and its application to secure communication

In this paper, we propose a synchronization scheme based on an improved auxiliary particle filter (IAPF) for chaotic Colpitts circuit and conduct an experimental study on the synchronization performance with application to secure communications. Specifically, with the synchronization scheme, when the chaotic signals generated by an analog Colpitts circuit are transmitted through a nonideal channel, the distorted signals are processed digitally by the novelly designed IAPF at the receiver, in order to obtain the synchronized signals of the transmitter circuit. Experimental results indicate that synchronization can be achieved over both the additive white Gaussian noise channel and the multipath fading channel with low signal‐to‐noise ratio, even if there exist severe circuit parameter mismatches between the transmitter and the receiver. Furthermore, a chaos‐masking secure communication system is constructed and verified over both the additive white Gaussian noise channel and the multipath fading channel, and the bit error rate is evaluated versus different signal‐to‐noise ratios and symbol periods. It is shown that the achievable bit error rate can reach the order of magnitude of 10 ^{− 4} without error correction coding techniques. In addition, security analysis demonstrates that the proposed chaotic secure communication system is resistant to the brute‐force attack. Copyright © 2013 John Wiley & Sons, Ltd.     

Impact of large Doppler on error performance of FH/MFSK with RS orBCH coding in Rayleigh and Rician fading

The degradation of performance caused by Doppler shift to frequency hopped (FH)/M-ary frequency shift keying (MFSK) Reed-Solomon (RS) coded signal over a Rayleigh and Rician channel is analyzed. The receiver employs a digital processing scheme, consisting of an analog-to-digital (A/D) converter followed by quadrature decomposition and complex-valued envelope discrete Fourier transformation (DFT). Predecoder symbol error probability and post-decoder word error probability are presented as a function of Doppler shift, channel randomness parameter, and the symbol energy-to-noise ratio. The noise is assumed to be white and Gaussian distributed. Results show that for a typical symbol error rate of 10^-3, the margin for 8-ary uncoded transmission must be increased by 8 dB to account for Doppler in a Rician fading channel     

On the design of universal receivers for nonselective Rician-fadingchannels

The purpose of this paper is to illustrate the issues involved in designing the demodulator portion of a universal receiver for unknown or time-varying channels by means of a specific example. We consider the class of nonselective Rician fading channels with additive white Gaussian noise. The optimal receiver for a Rician channel depends on the parameters of the channel, and the collection of optimal receivers for channels in the class of interest forms an infinite receiver class. We find a finite number of receivers in this receiver class with the property that, regardless of the parameters of the channel in effect, at least one of these receivers provides a symbol error probability that is within a specified deviation from the optimal symbol error probability for the channel. These receivers are then used in parallel to perform a symbol-by-symbol demodulation of the received signal. The receiver output that gives the most reliable reproduction of the transmitted sequence is identified by means of a data verification mechanism. The resulting system is a universal receiver. Methods for data verification are developed in other papers. In this paper, we develop an algorithm for finding the required finite set of receivers. Typical issues, such as the tradeoff between the number of parallel receivers and the allowed deviation from optimality, are discussed     

A fully digital noncoherent and coherent GMSK receiver architecturewith joint symbol timing error and frequency offset estimation

We propose a fully digital noncoherent and coherent Gaussian minimum shift keying (GMSK) receiver architecture with joint frequency offset compensation and symbol timing recovery. Carrier phase offset can be estimated if the coherent demodulation mode is adopted. The converted base-band complex signal is first frequency discriminated and then passed through a digital filter which performs a fast Fourier transform (FFT). The frequency offset can be estimated from the DC component of the FFT, and the symbol timing error can be estimated from the phase angle of the FFT at a specified frequency which is equal to an integral multiple of half the bit rate. These two estimated parameters are then used for frequency offset compensation and symbol timing recovery during a preamble period. Coarse carrier phase can be estimated by averaging sampled in-phase and quadrature-phase signals and finding its phase angle within the preamble period after carrier frequency offset is estimated and compensated. The bit error rate (BER) performance of this GMSK receiver architecture is assessed for an additive white Gaussian noise (AWGN) channel by computer simulation     

Multitone jamming of FH/BFSK in Rician channels

A new bit error rate (BER) expression for a noncoherent frequency-hopped binary-frequency-shift-keying (FH/BFSK) receiver in Rician channels, subjected to independent multitone and wideband noise interference, is derived. Unlike previously published analyzes, we combine the signal and jammer multipath components, the additive white Gaussian noise (AWGN), and other wideband interference as a single Gaussian process. This method leads to a BER expression which consists of only a single rather than a triple integral requiring numerical computation. We also present a new derivation of the probability density function (PDF) of the ratio of two Rician random variables, used in a previously published approximate BER analysis     

基于Monte Carlo模型的FFH/BFSK合并技术研究

分析了FFH/BFSK接收机的两种合并方式:平方律线性合并和具有自适应增益控制(AGC)的平方律非线性合并;在部分频带噪声干扰下,使用Monte Carlo模型对这两种合并方式进行仿真得到误码率曲线,仿真结果与理论误码率吻合,并得出结论:在热噪声功率受限的情况下,使用AGC合并能有效的抑制部分频带噪声干扰.     

An information theoretic foundation of synchronized detection

The constrained capacity of a coherent coded modulation (CM) digital communication system with data-aided channel estimation and a discrete, equiprobable symbol alphabet is derived under the assumption that the system operates on a flat fading channel and uses an interleaver to combat the bursty nature of the channel. It is shown that linear minimum mean square error channel estimation directly follows from the derivation and links average mutual information to the channel dynamics. Based on the assumption that known training symbols are transmitted, the achievable rate of the system is optimized with respect to the amount of training information needed. Furthermore, the results are compared to the additive white Gaussian noise channel, and the case when ideal channel state information is available at the receiver     

Extended MLSE receiver for the frequency-flat, fast-fading channel

This paper develops a maximum likelihood sequence estimation (MLSE) receiver for the frequency-flat, fast-fading channel corrupted by additive Gaussian noise when linear modulations (M-ASK, M-PSK, and M-QAM) are employed. This paper extends Ungerboeck's derivation of the extended MLSE receiver for the purely frequency-selective channel to the time-selective channel. Although the new receiver's structure and metric assume ideal channel state information (CSI) at the receiver, the receiver structure can be used wherever high-quality CSI is available. The receiver is maximum likelihood for a variety of channels, including Ricean, Rayleigh, lognormal, and additive white Gaussian noise (AWGN) channels. Bounds on the receiver's bit error rate (BER) are deduced for ideal and pilot tone CSI for fast Rayleigh fading. A crude lower bound is developed on the BER of predictor-based receivers for the same channel. This paper offers insight into matched filtering and receiver processing for the fast-fading channel and shows how pilot symbols and tones should be exploited     

Shaping gain of the partially coherent additive white Gaussiannoise channel

We derive necessary conditions on the channel input and output probability density functions (PDFs) to achieve channel capacity for the additive white Gaussian noise (AWGN) channel with Tikhonov distributed phase error. We show that the Gaussian input does not achieve capacity, and we obtain a lower bound on the shaping gain. The shaping gain can be as large as 2.4 dB at rates as low as 0.5 b/symbol/Hz. This contrasts with the well-known shaping gain for the AWGN channel, which is small at low transmission rates and 1.53 dB at higher rates     

Average symbol error probability for M-ary DDPSK

A unified and exact analysis of the symbol error probability (SEP) for M-ary doubly-differential phase-shift keying (M-DDPSK) is presented. The SEP is expressed in terms of Fourier coefficients of the probability density function of the composite phase at the receiver input which are available for several channel scenarios including the additive white Gaussian noise, the fading, the fading-shadowing and the cochannel interference type of channel. Useful numerical results, obtained through the analytical expressions derived, are presented to compare the performance of 8-DDPSK and 8-DPSK over a channel in which, in addition to additive noise, a constant carrier frequency shift and Nakagami fading affect the transmission.     

Maximum Likelihood Sequence Estimation of Binary Sequences Transmitted Over Bandlimited Nonlinear Channels

The problem of designing and evaluating the performance of a maximum likelihood sequence receiver for binary PSK transmission over bandlimited nonlinear channels is considered in this paper. The effects of intersymbol interference followed by AM/AM and AM/PM conversions are taken into account while optimizing the performance in the presence of white Gaussian noise. A new representation for the output of a bandpass nonlinearity is given when the input consists of a carrier signal modulated by a sum of binary overlapping pulses. The structure of a maximum likelihood sequence receiver for a bandlimited nonlinear channel is derived using this representation. The receiver uses a modified Viterbi algorithm to determine the most likely sequence of data symbols transmitted. An upperbound on the probability of symbol error for this receiver is obtained. Numerical results illustrating the applicability of the present work to optimizing the performance of a digital satellite communications link are also presented.     

Design of turbo-coded modulation for the AWGN channel with Tikhonov phase error

We design 1-b/symbol/Hz parallel concatenated turbo-coded modulation (PCTCM) for the additive white Gaussian noise (AWGN) channel with Tikhonov phase error. Constituent recursive convolutional codes are optimized so that the turbo codes have low error floors and low convergence thresholds. The pairwise error probability based on the maximum-likelihood decoding metric is used to select codes with low error floors. We also present a Gaussian approximation method that accurately predicts convergence thresholds for PCTCM codes on the AWGN/Tikhonov channel. Simulation results show that the selected codes perform within 0.6 dB of constellation constrained capacity, and have no detectable error floor down to bit-error rates of 10/sup -6/.