共查询到16条相似文献,搜索用时 436 毫秒
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水声信道的典型特点为多普勒频移严重、可利用带宽窄以及强多径干扰。空间分集均衡技术是相干水声通信中克服信道多径干扰,消除码间干扰的一种有效手段。为了极大化地输出阵增益,结合无源相位共轭方法和多通道均衡算法,本文设计了组合信噪干比的全新信道评价方法。利用改进的Sigmoid函数对各通道接收信号的幅度进行加权处理;采用二阶锁相环跟踪各通道信号的相位变化,实现各通道信号同相累加。将各通道低通滤波后的信号能量归一化,采用了分数阶-判决反馈分集均衡器,加入各通道权重系数实现了水声通信系统的分集均衡接收。仿真结果和湖试数据处理结果均表明,优化的幅相加权分集均衡接收算法能抵消多径和噪声的干扰,性能优于等增益合并接收算法。湖试数据处理结果误码率降低了1.8%。 相似文献
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基于对修正的常数模算法(MCMA)进行分析,提出了一种用于QPSK(四进制相移键控)信号的快速载波恢复盲均衡算法。该算法中构造了一种与MCMA算法不同的、能够快速收敛的误差函数,在消除码间干扰(ISI)、纠正相位误差的同时,进一步改善了收敛性能。该算法对输出信号的实部和虚部分别进行非线性变换。最后利用实测的水声信道数据,对这几种算法进行了数值分析研究,结果表明:所提出的算法不仅能够很好地克服相位旋转,而且其收敛速度明显高于MCMA,剩余均方误差更小,而计算量并没有明显的增加。 相似文献
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信号在超长线缆传输中, 线缆的线间串扰及温度梯度变化造成噪声干扰, 特别是线缆介电损耗和肌肤效应的影响, 导致接收端信号频率色散失真严重, 难以恢复原始信号, 限制了传输速度. 另外, 在页岩气、煤层气等资源勘探领域, 在用长缆传输数据时, 还要求传输高精度同步脉冲信号, 用于采集数据相位的标定. 线缆的传输效应及噪声干扰严重影响了接收端的信号同步, 造成采集数据相位失真. 本文针对信号在长缆传输中的非线性失真及衰减问题, 提出了一种新型均衡结构, 并针对新模型给出了最优系数组合. 在此基础上针对改进的结构提出了一种基于反正切函数的变步长算法, 该算法配合三误差因子, 形成收敛函数, 该函数具有收敛速度快, 稳态误差小的优点. 改进后的自适应组合均衡器计算复杂度低, 收敛快, 信道跟踪能力强, 加快了数据处理速度, 同时能较好地应对信道的时变性. 仿真结果表明, 基于新变步长算法的自适应组合均衡器, 性能上提高了50%, 并且消除了噪声干扰和码间干扰, 测试实验表明, 在无中继超长缆(7 km以上)传输中, 信号速度提高了一倍. 相似文献
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针对稀疏水声信道的长时延扩展及梯度下降的权值迭代方案导致的神经网络均衡器收敛速度慢的问题,提出了近似L0范数约束的BP神经网络均衡器。首先在传统BP网络均衡器基础上增加判决反馈项,然后在代价函数中对均衡器输入层到隐含层的权值增加L0范数约束,构造新的代价函数,利用高斯族函数近似L0范数约束,并根据不同隐层神经元节点输出权值的L2范数设定近似参数。仿真结果表明,稀疏信道条件下,本方法相比传统的BP网络均衡器收敛速度更快,误码率更低,可以有效提升神经网络均衡器的性能。 相似文献
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Emerging evidence indicates that orthogonal time–frequency space (OTFS) modulation is a potential candidate modulation scheme for high mobility wireless communications. However, OTFS may experience significant inter-symbol interference (ISI) and inter-Doppler interference (IDI) in the receiver. In this paper, we propose a soft decision feedback turbo equalization for OTFS transmission over delay-Doppler channels to jointly combat both interferences. A novel block decision feedback equalization (BDFE) algorithm is constructed using the band feature of the channels in the delay-Doppler domain. The feedforward and feedback filters are designed by the delay-time channels coefficients. According to the designed filter, an equivalent system model is employed to allow turbo equalization. The posterior probability is established using the soft prior information and feedback filter, and then fed back to the channel decoder as external information. Both theoretical analysis and simulation results demonstrate the effectiveness of the proposed scheme in improving the bit error rate (BER) performance and combat various interference. Numerical simulations are finally provided to justify the validity of the proposed scheme in improving the bit error rate (BER) performance and combating various interference. 相似文献
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A communication system is implemented on digital signal processors (DSPs) for the underwater acoustic environment. The implemented receiver uses time reversal multi-channel combining followed by a single-channel decision feedback equalizer. Periodic channel estimation is employed to track the channel fluctuations. These techniques are used to mitigate time-varying inter-symbol interference, which is the main challenge in the underwater acoustic channel at operating frequencies greater than 10 kHz. Various optimization tasks are performed to reduce the receiver computational complexity. A fast implementation of the matching pursuit algorithm is tested on the DSP platform. Its performance, in terms of accuracy and run-time, is compared with that of the basic matching pursuit algorithm. Experimental results of the transmission and demodulation of binary phase-shift keying signals at three different symbol rates were obtained in the local Delaware Bay. The low bit error rates demonstrate the effectiveness of our implementation. 相似文献
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Channel noise is often assumed to be Gaussian in most of the existing channel equalization algorithms. The performance of these algorithms will degrade seriously when the noise is non-Gaussian. This paper deals with the problem of blind channel equalization in impulsive noise environment that is modeled as α-stable process. A modified adaptive error-constrained constant modulus algorithm (MAECCMA) is proposed by soft-limiting the amplitude of the equalizer input and transforming the error signal of the original adaptive error-constrained constant modulus algorithm (AECCMA) nonlinearly to suppress the influence of α-stable noise. Computer simulation results of two underwater acoustic channels show that, MAECCMA has almost the same performance as AECCMA and they both have faster convergence rate than constant modulus algorithm (CMA) and normalized least mean absolute deviation (NLMAD) algorithm in Gaussian noise, while MAECCMA provides the best performance of those four algorithms in α-stable noise. 相似文献