共查询到20条相似文献,搜索用时 15 毫秒
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In this paper, a doubly iterative receiver is proposed for joint turbo equalization, demodulation, and decoding of coded binary continuous-phase modulation (CPM) in multipath fading channels. The proposed receiver consists of three soft-input soft-output (SISO) blocks: a front-end soft-information-aided minimum mean square error (MMSE) equalizer followed by a CPM demodulator and a back-end channel decoder. The MMSE equalizer, combined with an a priori soft-interference canceler (SIC) and an a posteriori probability mapper, forms a SISO processor suitable for iterative processing that considers discrete-time CPM symbols which belong to a finite alphabet. The SISO CPM demodulator and the SISO channel decoder are both implemented by the a posteriori probability algorithm. The proposed doubly iterative receiver has a central demodulator coupled with both the front-end equalizer and the back-end channel decoder. A few back-end demodulation/decoding iterations are performed for each equalization iteration so as to improve the a priori information for the equalizer. As presented in the extrinsic information transfer (EXIT) chart analysis and simulation results for different multipath fading channels, this provides not only faster convergence to low bit error rates, but also lower computational complexity. 相似文献
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基于分层空时结构的多码CDMA系统中一种新的迭代均衡接收算法的研究 总被引:1,自引:1,他引:0
为了提高基于垂直结构的分层空时结构(V-BLAST, vertical bell-laboratories layered space-time)的多码 CDMA 系统的抗干扰能力与系统容量,文章提出了一种将 MMSE 均衡与 Turbo 译码联合运算进行的方法,得到了一种针对该系统的迭代均衡接收算法。该接收算法包含两个连续的软输入软输出模块,首先经过 MMSE 均衡后得到第一个软输出,然后从 Turbo 译码器得到第二个软输出。每一次迭代过程中,从均衡和译码中得到的外赋信息作为第二次迭代的先验信息。仿真结果表明,文章提出的迭代均衡接收算法相比较传统非迭代接收算法,性能有非常可观的改善。 相似文献
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Seok-Jun Lee Naresh R. Shanbhag Andrew C. Singer 《Journal of Signal Processing Systems》2005,39(1-2):49-62
In this paper, energy efficient VLSI architectures for linear turbo equalization are studied. Linear turbo equalizers exhibit dramatic bit error rate (BER) improvement over conventional equalizers by enabling a form of joint equalization and decoding in which soft information is iteratively exchanged between the equalizer and decoder. However, turbo equalizers can be computationally complex and hence require significant power consumption. In this paper, we present an energy-efficient VLSI architecture for such linear turbo equalizers. Key architectural techniques include elimination of redundant operations and early termination. Early termination enables powering down parts of the soft-input soft-output (SISO) equalizer and decoder thereby saving power. Simulation results show that energy savings in the range 30–60% and 10–60% are achieved in equalization and decoding, respectively. Furthermore, we present finite precision requirements of the linear turbo equalizer and an efficient rescaling method to prevent overflow. 相似文献
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水声通信网络的快速发展对多用户水声物理层通信技术提出了迫切的需求。本文主要针对水声多用户下行通信链路中存在严重码间干扰和多址干扰的问题,提出了一种交织多址(IDMA)水声多用户下行通信链路迭代接收算法,能够根据译码器输出的软信息对估计的信道进行迭代更新,同时根据信道估计结果重建各用户对当前用户的多址干扰(MAI),并使用干扰抵消器予以抵消,通过在均衡器、译码器和干扰抵消器之间的迭代逐次提高当前用户信息的输出信噪比,最终实现正确解调。其中,信道估计算法采用LMMSE初始化的分簇OMP稀疏信道估计算法,多普勒估计采用时频二维搜索结合自相关相位估计的方法,计算机仿真结果表明该接收机具有与已知信道时接近或相当的性能。进行了多用户水声通信海上试验,在4.5km、6km和7km三个距离实现了对2个用户、3个用户和4个用户的同时通信,每个用户的通信净速率约为500bps,证明了本文所提出的方法能够有效应用在多用户水声通信中,为水声通信网络的发展提供了一种重要的物理层通信技术手段。 相似文献
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《Communications, IEEE Transactions on》2005,53(2):269-277
A novel split soft-decision equalizer (SSE) with near-optimum performance is proposed for wireless multipath channels with large delay spread. The concept of SSE is significantly different from the traditional notions of the Viterbi algorithm and decision-feedback equalizer. Instead of dealing with received sequence as a combined sequence, it splits the received sequence into its constituent paths. Using an iterative soft-decision algorithm, reliability of the soft decisions on each decomposed element is improved iteratively. The major advantage of SSE is the independence of computation complexity on channel time dispersion. Joint design of SSE with a soft-decision decoder is also considered in this paper. Performance analysis and simulation results show that performance of the proposed algorithm comes very close to that of the logarithmic maximum a posteriori decoder. 相似文献
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This paper considers properties of the extrinsic information transfer (EXIT) functions of turbo equalized intersymbol interference channels and finite-impulse response precoders. An analytic expression is derived for the maximum value of the EXIT function of the equalizer. Using this parameter, a design strategy is proposed for allocating redundancy between the equalizer and the decoder. The key quantities are pilot-symbol rate and code puncturing, for fixed overall data and symbol rates. 相似文献
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An importance sampling simulation technique is used to estimate the bit-error rate (BER) of a symbol-by-symbol trellis-coded modulation (TCM) decoder/equalizer proposed for digital microwave radio applications. To evaluate the performance at a BER smaller than 10-6, we investigate a randomized bias technique previously developed by the authors. To properly select the bias vectors, the asymptotic (infinite signal-to-noise ratio) decision boundary is first determined. The simulation technique is then extended to the one-shot symbol-by-symbol TCM decoding/equalization algorithm which is equivalent to the recursive symbol-by-symbol detection algorithm of Abend and Fritchman (1970). By using this novel importance sampling technique, we can speed up the simulation and efficiently evaluate the BER performance of the TCM decoder/equalizer 相似文献
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In this letter, the performance of the HIPERLAN system in an indoor multipath fading channel is considered. Due to the high carrier frequency and high data rate, a simple noncoherent demodulator followed by a nonlinear equalizer, which includes a RAM and a Viterbi decoder, is proposed to cope with intersymbol interference. The novelty of the proposed equalizer is that a complex noncoherent signal is used. Although the complexity of the receiver is doubled, performance is greatly improved with respect to real receivers 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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The performance of the proposed radial basis function (RBF) assisted turbo-coded adaptive modulation scheme is characterized in a wideband channel scenario. We commence by introducing the novel concept of the Jacobian RBF equalizer, which is a reduced-complexity version of the conventional RBF equalizer. Specifically, the Jacobian logarithmic RBF equalizer generates its output in the logarithmic domain and hence it can be used to provide soft outputs for the turbo-channel decoder. We propose using the average magnitude of the log-likelihood ratio (LLR) of the bits in the received transmission burst before channel decoding as the channel quality measure for controlling the mode-switching regime of our adaptive scheme 相似文献
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水声信道均衡中基于信道估计的均衡方法理论上具有更优的均衡性能,但较高的计算复杂度限制了算法的实际应用。针对这一问题,该文首先基于Kalman滤波和Turbo均衡提出一种迭代Kalman均衡器,实现了基于软符号的迭代信道估计与迭代Kalman均衡,且复杂度较常规方法降低约1个数量级。其次,针对单一均衡算法和单一方向Turbo均衡器存在的误差传递现象,设计了基于迭代Kalman均衡器与改进成比例归一化LMS (IPNLMS)自适应均衡器相结合的混合双向Turbo均衡器,提高了自适应均衡器的收敛速度和均衡性能,并通过双向均衡结构带来的增益改善了符号估计误差传递的现象。理论分析与仿真实验验证了该文算法的有效性。 相似文献
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A simple structure of a per-channel automatic equalizer for an orthogonally multiplexed QAM system is proposed and the performance is analyzed. It is shown that a dual automatic equalizer withT/2 -long tapped delay lines, whereT is a period of individual baseband baud, can equalize not only the transmission channel distortions, but the timing deviations and demodulating carrier phase deviations. Despite its high efficiency, the orthogonally multiplexed QAM system has been regarded as overly costly. However, by using the dual automatic equalizer with fairly simple structure, the system is competitive with conventional single channel data transmission systems. 相似文献
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A method of joint equalization and decoding for block transmission with coding across blocks is presented. It is well suited for bandwidth efficient QAM transmission using large transmit symbol alphabets, whereby the blocking structure can be arbitrary in principle. The method consists in multiple iterations of equalization and decoding, whereby information is exchanged back and forth between the decoder and the equalizer. The equalizer is based on Cholesky factorization of the equivalent discrete-time channel matrix (Eur. Trans. Telecommun 10 (1999) 351; Grundlagen der Kommunikationstechnik, Springer, Berlin, 2004). The convergence behavior of the iterative equalization and decoding method is analyzed by means of an upper bound on the extrinsic information transfer. It is shown that the method has improved bit error performance versus separate equalization and decoding without decoder feedback and, thus, yields superior power efficiency. 相似文献
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A novel multiuser separation and equalization scheme is proposed for single carrier wireless communication systems integrating frequency-domain (FD) multiuser turbo equalization (MUTE) and successive interference cancellation (SIC). The proposed iterative structure consists of multiple layers of detection, and at each layer the user with strongest power is processed by a frequency-domain multiuser equalizer to yield the soft extrinsic information on the coded bits of that user, which is delivered to a channel decoder after deinterleaving. The extrinsic information gleaned by the decoder is fed back to both the current and previous multiuser equalizers for the next iteration as a-priori information. The soft symbols of the current user are evaluated by the a-posteriori information of coded bits provided by the multiuser equalizer, and the interference reconstructed by the current user’s soft symbols is canceled out from the received signals in frequency domain. The interference-canceled signals are fed forward to subsequent layers for detection of other users. The proposed scheme effectively mitigates multiple access interference and intersymbol interference by an iterative (turbo) detection method. Numerical simulation examples demonstrate that the proposed FD MUTE with SIC outperforms the traditional MMSE multiuser equalizer over the severely doubly-selective channels, and the bit-error-rate performance tends to be better with the increase of iterations. 相似文献
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New upper bounds for the performance of the optimum combined symbol-by-symbol (SbS) Abend-Fritchman-like equalizer and decoder are presented, and a related criterion for the actual design of good trellis-coded-modulated (TCM) schemes effectively matched to the distortion introduced by the intersymbol interference (ISI)-corrupted transmission channel is developed. The actual application of the proposed design criterion is also addressed 相似文献
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After a recall concerning the structures of wide band transmission systems equalizers and their adjustment procedure, this article presents the realization of a programmable automatic equalizer for the band 4.60 MHz. The authors successively describe: the network, the solid state variable component used for control, optimisation algorithms for the adjustment of the equalizer, and finally the experimental results achieved with a eight echos equalizer. 相似文献