共查询到19条相似文献,搜索用时 515 毫秒
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Turbo均衡是一种通过反复均衡和信道译码来提高接收性能的迭代接收机算法。通常的Turbo均衡算法采用均衡与软输出译码的迭代运算,由于均衡和译码的重复计算,使得复杂度大大提高。文中提出了2种降低复杂度的Turbo均衡器:第一种采用软判决维特比译码,第二种采用软输入硬输出的维特比译码。通过仿真表明,这2种算法在几乎没有损失接收性能的情况下,大大降低了计算复杂度,并且第二种的性能要好于第一种。 相似文献
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在滤波多音调制(FMT)系统中,为了消除由于原型滤波器非理想重构特性和多径信道所导致的符号间干扰,提出了一种联合迭代信道估计和Turbo均衡的FMT系统接收方法,通过对FMT系统中每个子信道的等效冲激响应进行迭代估计,然后采用基于线性滤波器结构的Turbo均衡器来消除符号间干扰.仿真结果表明,不论采用QPSK调制方式还是16QAM调制方式,经过2次以上的迭代后,相比较于传统的判决反馈均衡算法,新算法的误码率性能得到了大大改善. 相似文献
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为克服无线衰落信道中严重的符号间干扰(ISI)的影响,提出了一种新的利用信源冗余的Turbo均衡算法。该算法将联合信源信道译码技术与Turbo均衡技术结合起来,在均衡、译码、信源之间建立起软信息交互的环路,有效提高了整体接收的性能。外信息传递(EXIT)图分析与计算机仿真均表明,尽管信源冗余给译码器带来的性能提升较为有限,但是将这部分信息反馈回均衡器后,在严重ISI信道,信源冗余度为70%时,整体接收的性能改善约为9.5 dB,基本达到了理想加性高斯白噪声(AWGN)信道下的误码性能。 相似文献
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为克服无线衰落信道中严重的符号间干扰( ISI)的影响,提出了一种新的利用信源冗余的Turbo均衡算法。该算法将联合信源信道译码技术与Turbo均衡技术结合起来,在均衡、译码、信源之间建立起软信息交互的环路,有效提高了整体接收的性能。外信息传递( EXIT)图分析与计算机仿真均表明,尽管信源冗余给译码器带来的性能提升较为有限,但是将这部分信息反馈回均衡器后,在严重ISI信道,信源冗余度为70%时,整体接收的性能改善约为9.5 dB,基本达到了理想加性高斯白噪声( AWGN)信道下的误码性能。 相似文献
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Turbo均衡技术是水声相干通信克服信道多径、消除码间干扰(ISI)的有效工具。Turbo均衡实际使用时需要对时变、多径信道进行良好的估计。为了提高信道估计的效果,该文基于时变横向滤波和相位旋转信道模型,提出一种水声通信Turbo均衡中的软迭代信道估计算法。该算法采用快速自优化最小均方算法得到各数据符号处的横向滤波器系数矢量并与二阶锁相环联合优化计算。通过仿真比较,该算法明显优于硬迭代信道估计算法,且相位估计性能优于其他文献中的软迭代信道估计算法。在海上试验中,水声通信距离5 km,方向近似垂直,接收阵起伏周期10 s,起伏幅度5 m左右,在此情况下进行数据采集。将该算法用于对海试数据的单通道Turbo均衡处理,实现无误码输出,验证了所提算法在软迭代信道相位估计方面的优势。 相似文献
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This paper presents two equalizer structures for trellis-coded continuous phase modulation (TC-CPM) on multipath fading intersymbol interference (ISI) channels. An equivalent discrete-time (DT) model is developed by combining the tapped-delay-line (TDL) model of the frequency-selective channel and by oversampling at the receiver. The (noninterleaved) fractionally spaced maximum-likelihood sequence estimation (MLSE) equalizer performs continuous phase modulation (CPM) demodulation, trellis-coded modulation (TCM) decoding, and channel equalization by exploiting the finite state nature of the ISI-corrupted TC-CPM signal. Both simulation and analytical results show diversity-like improvement when performing joint MLSE decoding and equalization. For the interleaved soft-output equalizer, the soft symbol metric is delivered to the TCM decoder by using a forward and backward recursion algorithm. Three variants of the soft-output equalizer are examined. We conclude that the backward recursion is essential to partial response CPM schemes, and with moderate complexity, the soft-output equalizer can have a substantial advantage over a noninterleaved MLSE equalizer 相似文献
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Liang Dong 《Wireless Personal Communications》2010,55(4):631-644
Turbo equalization that cooperates with channel prediction and iterative channel estimation is investigated for mobile wireless
communications. Frames of information bits are encoded, interleaved, and mapped to symbols for transmission over time-varying
frequency-selective fading channels. At the receiver, the Turbo equalizer consists of a maximum a posteriori probability equalizer/demapper
and a soft-input soft-output maximum a posteriori probability decoder. With initial channel estimates and sparse pilot insertion
across a number of frames, the receiver predicts the channel of the current frame. The effect of error propagation of channel
prediction is mitigated by the de-interleaver that is embedded in the Turbo equalizer. The predicted and interpolated channel
is refined through a channel estimator that uses the soft estimates of data symbols at each Turbo iteration. Due to the bandlimiting
feature of channel variation, the channel estimation error can be smoothed by low-pass filters that follow the channel estimator.
Simulation results show that incorporating Turbo equalization with channel prediction and iterative channel estimation can
combat time- and frequency-selective fading and improve reception performance. 相似文献
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This paper addresses the design and performance evaluation with respect to capacity of M-PSK turbo-coded systems operating in frequency-flat time-selective Rayleigh fading. The receiver jointly performs channel estimation and turbo decoding, allowing the two processes to benefit from each other. To this end, we introduce a suitable Markov model with a finite number of states, designed to approximate both the values and the statistical properties of the correlated flat fading channel phase, which poses a more severe challenge to PSK transmission than amplitude hiding. Then, the forward-backward algorithm determines both the maximum a posteriori probability (MAP) value for each symbol in the data sequence and the MAP channel phase in each iteration. Simulations show good performance in standard correlated Rayleigh fading channels. A sequence of progressively tighter upper bounds to the capacity of a simplified Markov-phase channel is derived, and performance of a turbo code with joint iterative channel estimation and decoding is demonstrated to approach these capacity bounds 相似文献
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We introduce an iterative joint channel and data estimation receiver that exploits both the power of pilot-symbol assisted modulation (PSAM) and turbo coding for fading channels. The key innovation is a low-complexity soft channel estimator which divides a processing block into overlapped cells and performs maximum a posteriori (MAP) sequence estimation and MMSE filtering based on the received signal and extrinsic information delivered by the soft channel decoder. Simulation results show that for turbo-coded PSAM systems under time-variant fading the proposed receiver offers significant performance gains over a non-iterative receiver and two other cancellation schemes 相似文献