新型MFSK最佳相干解调器

本文推广了作者在1999年提出的方法和结论[1],讨论了在信号各频率振幅受到的衰减不一致并存在有色加性高斯噪声(IGDF-ACGN)信道条件下,M进制FSK(MFSK)信号的最佳相干解调问题。导出了最佳解调器的结构,说明了该解调器中有关参数的估计方法,以及实现时遇到的矢量、矩阵运算的有关快速算法。从理论和计算机模拟实验两方面说明了所导得的最佳解调器,不仅在IGDF-ACGN信道条件下是最佳的,而且在加性高斯白噪声(AWGN)信道条件下也是最佳的。文中给出了误码率的计算机模拟曲线。     

新型MFSK最佳相干解调器

本文推广了作者在１９９９年提出的方法和结论，讨论了在信号各频率振幅受到的衰减不一致并存在有色加性高斯噪声（ＩＧＤＦ－ＡＣＧＮ）信道条件下，Ｍ进修ＦＳＫ（ＭＦＳＫ）信号的最佳相干解调问题。导出了最佳解调器的结构，说明了该解调器中有关参数的估计方法，以及实现时遇到的矢量，矩阵运算的有关快速算法。从理论和计算机模拟实验两方面说明了所导得的最佳解调器，不仅在ＩＧＤＦ－ＡＣＧＮ信道条件下是最佳的，而且在加性     

基于MMSE准则的最佳相干FSK解调器

 本文提出用MMSE准则 设计最佳相干FSK解调器.在信道噪声分布未知条件下,导出了该解调器的结构.并给出了分析和计算机模拟实验结果,证明了该解调器在AWGN信道条件下与普通FSK解调器误码性能相同,在信号各个频率振幅受到的衰减不一致,并且为ACGN信道条件下误码性能优于普通FSK解调器,与文献[2]基于MAP准则的改进型FSK解调器的误码性能十分接近;在信道中的噪声为其它分布(如均匀分布)情况下,也有类似上述的结果.     

基于重叠与正交信号的超宽带系统性能研究

文章首先介绍了跳时超宽带(TH-UWB)信号,推导了在加性高斯白噪声(AWGN)信道条件和多径条件(MP)下,基于重叠和正交脉冲信号的系统误码率公式,并给出了仿真结果.仿真结果表明,在AWGN信道条件下,基于重叠脉冲信号的跳时二进制脉位调制(TH-BPPM)系统的性能优于基于正交脉冲信号的系统.多径条件下的正交TH-BPPM系统的性能优于AWGN信道条件下的系统性能.     

基于对消解调的时相调制误码率分析

以二进制为例,从对消解调的角度,导出了时相调制(TPM)信号在加性白高斯噪声信道下的误码率解析表达式.可以发现:TPM信号误码率与码元突变后的波形持续时间成反比,即相同信噪比条件下持续对间越长则误码率越小.通过对比判决统计量,可以发现对消解调是相关解调的简洁实现方式.仿真结果验证了上述理论推导.其结论可为进一步分析时相调制的其他解调方法性能提供参照和依据.     

UWB信号多径性能分析

分析了超宽带(UWB)信号抗多径衰落的原理,比较了UWB信号在只有加性高斯白噪声(AWGN)信道和AWGN室内密集多径信道两种环境下的误码率性能,得出UWB信号比窄带信号具有更低的多径衰落储备。     

脉冲超宽带在AWGN中的误码率性能分析

针对跳时超宽带(TH-UWB)和直接序列超宽带(DS-UWB)在加性高斯白噪声干扰下(AWGN)的误码率性能进行了分析,并对超宽带信号脉冲位置调制(PPM)和脉冲幅度调制(PAM)的误码率做了比较。通过理论分析和软件仿真,结果说明在加性高斯白噪声干扰下,对于TH-UWB调制和DS-UWB调制,PAM的误码率性能都优于PPM,并在此基础上给出了几种方法来提高超宽带脉冲信号抗加性高斯白噪声的能力。     

一种用于短波通信的新的频域差分解调器

在短波通信中,传输信号遭受延时、扩展、时变干扰以及接收机加性高斯噪声的影响。常规的差分解调器在恶劣的短波信道环境下性能很差。该文提出一种新的频域差分解调器,通过盲相位估计来消除延时扩展造成的相位误差的影响。仿真了常规差分解调器和新的差分解调器在恶劣短波信道环境下的性能对比。结果表明在快速衰落短波信道环境下,新的频域差分解调器的性能优于传统的差分解调器。     

一种用于短波通信的新的频域差分解调器

在短波通信中,传输信号遭受延时`扩展、时变干扰以及接收机加性高斯噪声的影响。常规的差分解调器在恶劣的短波信道环境下性能很差。该文提出一种新的频域差分解调器,通过盲相位估计来消除延时扩展造成的相位误差的影响。仿真了常规差分解调器和新的差分解调器在恶劣短波信道环境下的性能对比。结果表明在快速衰落短波信道环境下,新的频域差分解调器的性能优于传统的差分解调器。     

不同相位噪声谱对QPSK的性能影响分析

研究了相位噪声对QPSK系统的性能影响,利用高斯信道下带有相位噪声的条件误码率公式,分析了不同相位噪声谱所带来的解调损失。相位调制是一种恒包络调制方式,它对调制信号的相位偏移非常敏感,在单频相位噪声模型基础上,把相位噪声功率谱密度与相干解调的误码率公式相联系起来,计算了高斯信道条件下不同相位噪声谱对不同速率QPSK信号的解调损失。     

Optimal coherent detection of FSK signals with imbalance amplitudes in the presence of colored gaussian noise

The problem of optimal coherent detection of frequency-shift keying (FSK) signals transmitted over an additive colored Gaussian noise channel with imbalance gains in different frequencies (IGDF-ACGN channel) is studied. The structure of the optimal coherent detector is derived. Theoretical analysis and computer simulation results show that the detector is optimal in either additive colored Gaussian noise environment or additive white Gaussian noise environment.     

The optimum constant false alarm probability detector for relatively coherent multichannel signals in Gaussian noise of unknown power

In this paper, the method of "most powerful similar tests" is used to obtain the optimum (largest probability of detection) constant false alarm probability detector for multichannel signals received in the presence of additive Gaussian noise of unknown power. The signals are assumed to contain a common random phase angle, and hence are relatively coherent over the multiple channels. The noise is assumed to be correlated from channel to channel. The performance of the optimum detector is calculated. Finally, for illustrative purposes, the technique is applied to the detection of a signal in the presence of a jammer, and to the detection of a single channel signal in white and colored noise of unknown power.     

Duality theorems for joint source-channel coding

We consider joint source-channel coding for a memoryless Gaussian source and an additive white Gaussian noise (AWGN) channel. For a given code defined by an encoder-decoder pair (α, β), its dual code is obtained by interchanging the encoder and decoder: (β, α). It is shown that if a code (α, β) is optimal at rate p channel uses per source sample and if it satisfies a certain uniform continuity condition, then its dual code (β, α) is optimal for rate 1/ρ channel uses per source sample. Further, it is demonstrated that there is a code which is optimal but its dual code is not optimal. Finally, using random coding, we show that there is an optimal code which has an optimal dual. The duality concept is also presented for the cases of (i) binary memoryless equiprobable source and binary-symmetric channel (BSC), and (ii) colored Gaussian source and additive colored Gaussian noise (ACGN) channel     

Noncoherent detection of convolutionally encoded continuous phasemodulation

The authors consider the error probability at large signal-to-noise ratios of rate-1/2 convolutionally encoded CPFSK (continuous-phase frequency-shift keying) with an optimum noncoherent detector on an additive white Gaussian noise channel. The performance is given in terms of a parameter called the minimum squared normalized equivalent Euclidean distance which plays the same role mathematically as the minimum squared normalized Euclidean distance used for coherent detectors. It is shown that by introducing convolutional coding the error performance is significantly improved. The authors propose a decoding algorithm for these convolutionally encoded CPM schemes which is based on a limited tree search algorithm and uses the maximum-likelihood decision rule for noncoherent detection. Computer simulations show that the degradation in error performance compared to the performance of the optimum coherent Viterbi detector is less than 1 dB with a relatively simple noncoherent detector on an additive white Gaussian noise channel for most of the schemes considered     

Multiuser detection for square-law receiver under Gaussian channel noise with applications to fiber-optic communications

In fiber-optic wavelength-division multiplexing (WDM) communications systems, the nonlinearity of the channel and the limitations of optical filters result in received channel signals that are correlated. Furthermore, the square-law nature of the detector converts the additive fiber amplifier noise to a data-dependent asymmetric and non-Gaussian noise. The optimal multiuser detector for a Gaussian approximation is compared to the actual statistics and found to give a close performance estimate. Through bounds on the error probability and the asymptotic multiuser efficiency, the optimal multiuser detector based on a Gaussian approximation is found to improve significantly performance in highly correlated data cases. This result is applied to a practical optical WDM system.     

BER Calculation and Investigation of Optimal Single User Detector for a BPSK Signal Contaminated by Cochannel Interferer

We propose an optimal single user detector (OSUD) for a binary phase shift keying (BPSK) signal corrupted by a cochannel interferer and additive white Gaussian noise (AWGN). We obtain an analytical expression for the detector bit error rate (BER). The capacity of this channel is also investigated to interpret the BER performance of the optimal detectors.     

Information rates for photocount detection systems

A model that allows one to calculate information rates for optical communication systems that use photocount detection is presented. This model has its basis in the coherent states of the field. It consists of a source that places the field in a coherent state, a channel that can introduce additive Gaussian noise, and a photodetector that produces the number of photocounts in the detection interval as output symbols. The capability of introducing additive Gaussian noise can also be used to represent a physical source. The model is applied to several examples to illustrate its use. The rate of flow of information through the channel is calculated for a binary channel with and without additive Gaussian noise. The information rate for a noiseless channel is also obtained for the case in which the signals sent by a single-mode coherent source are selected from a Gaussian distribution.     

Optimum detection and signal selection for partially coherent binary communication

The optimum detectors for coherent and noncoherent reception of binary signals in additive Gaussian noise and the resuiting error probabilities were obtained by Helstrom [1]. In many practical communication systems a reasonable estimate of the phase of the received signal is available as the result of an auxiliary tracking operation of the carrier signal by a coherent tracking device such as a phase-locked loop. It is shown that the optimum detector for this case, which we refer to as partially coherent reception, is a linear combination of the correlation detector and the squared envelope correlation detector, which are optimum for the coherent and noncoherent cases, respectively. The error probabilities are also obtained as a function of the energy-to-noise ratio of the channel and the variance of the error in the phase estimate, which is a function of the signal-to-noise (SNR) in the tracking loop. The signal selection problem is considered in terms of these parameters.