Max Grade, Daifeng Wang, Diptendu Ghosh et al. · 2012
The objective of Lab 4 is to study and implement a decision-directed timing-recovery algorithm at receiver in the baseband communication system. Timing recovery guarantees that the receiver samples the received signals correctly. Normally, the received signal y[k] can be seen as a function of the timing offset τ; i.e., y [ k] = y ( kT / M + τ), where T is the symbol period and M is the over-sampling factor. We aim to sample the received signals at time kT / M + τ, so it is crucial to obtain the timing offset τ. Figure 1 shows the conceptual diagram of the timing recovery system.
Cited by 0
Wei Zeng-ju, Ye Zhang · 2011
Estimation technology is one of the key technologies in the Orthogonal Frequency Division Multiplexing(OFDM) system, and the Decision-Directed channel estimation algorithm is paid close attention because of the superiority of decreasing means square error(MSE) and bit error rate(BER). In this paper, a Decision-Directed channel estimation algorithm based on linear minimum mean square error(LMMSE) was proposed, and it is simulated in the white Gaussian noise channel and multipath Rayleigh channel. The result shows that this algorithm has obvious superiority comparing to the other Decision-Directed algorithm in terms of decreasing MSE and BER.
Cited by 1
Wynn C. Stirling, M. Morf · IEEE Transactions on Automatic Control · 1984
A decision-directed receiver uses the estimate of the rate of the discrete-time point process (DTPP) output of the (0-1) detector as the unknown prior probability of the Bernoulli input sequence. This correspondence applies the results of Segall [5] to permit the estimation of a time-varying rate.
Cited by 4
Wynn C. Stirling, M. Morf · 1982
A new decision-directed (DD) procedure is introduced to address the binary detection problem for nonstationary priors. Using a martingale approach, an explicit, recursive finite-dimensional filter is applied to the problem of computing the conditional expectation of the stochastic rate of the discrete-time point process (DTPP) representing the output of the detector. Conventional DD techniques strictly apply only when the rate is constant. The approach described herein allows the rate to be modeled as a finite-state Markov chain, and allows a further extension to address the situation where the Markov transition matrix possesses an observation-dependent component.
Cited by 2
Wei Rao, Jianbing Liu, Yuan-yuan Liu et al. · 2009
A new series equalizer based on constant modulus algorithm (CMA) and decision-directed (DD) algorithm is proposed to overcome inter-symbol interference (ISI) much better in the communication system without the aid of training sequences. The proposed equalizer uses the CMA as the forward filter and DD algorithm as the back filter. These two filters are series and operate concurrently. It makes full use of the advantages of the CMApsilas "eye-opened" ability and DDpsilas superior convergence performance. Therefore the proposed equalizer obtains not only the faster convergence and lower residual error but also the ability of phase rotation-compensated. Computer simulations with underwater acoustic channels are presented and the simulation results are shown to prove the efficiency of the proposed equalizer.
Cited by 2
Diogo C. Soriano, Everton Z. Nadalin, Ricardo Suyama et al. · Communications in Nonlinear Science and Numerical Simulation · 2012
Cited by 2
Jinbiao Xu, Yumin Wang · 2002
A new decision-directed (NDD) algorithm based on a new cost function is proposed for equalization of QAM channels. It can be seen as a variable step-size algorithm of the conventional DD algorithm, whose adaption step-size is changed according to the region in which the equalized signal lies in the constellation plane. The reasonableness of the new decision-directed algorithm is illustrated from the DD algorithm. The new algorithm can accomplish blind equalization and carrier phase recovery simultaneously and can achieve faster convergence speed and small residual ISI. Simulation results confirm the effectiveness of the proposed algorithm.
Cited by 4
Steven J. Nowlan, Geoffrey E. Hinton · IEEE Transactions on Communications · 1993
An adaptation algorithm for equalizers operating on very distorted channels is presented. The algorithm is based on the idea of adjusting the equalizer tap gains to maximize the likelihood that the equalizer outputs would be generated by a mixture of two Gaussians with known means. The decision-directed least-mean-square algorithm is shown to be an approximation to maximizing the likelihood that the equalizer outputs come from such an independently and identically distributed source. The algorithm is developed in the context of a binary pulse-amplitude-modulation channel, and simulations demonstrate that the algorithm converges in channels for which the decision-directed LMS algorithms does not converge.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Cited by 72
Ebrahim Karami · International Journal of Communication Systems · 2012
SUMMARY In this paper, the performance of decision directed (DD) maximum likelihood (ML) channel tracking algorithm is analyzed. The ML channel tracking algorithm presents efficient performance especially in the decision directed mode of the operation. In this paper, after introducing the method for analysis of DD algorithms, the performance of ML MIMO channel tracking algorithm in the DD mode of operation is analyzed. In this method channel tracking error is evaluated for a given decision error rate. Then, the decision error rate is approximated for a given channel tracking error. By solving these two derived equations jointly, both the decision error rate and the channel tracking error are computed. The presented analysis is compared with simulation results for different channel ranks, Doppler frequency shifts, and signal‐to‐noise ratios, and it is shown that the analysis is a good match for simulation results especially in high rank MIMO channels and high Doppler shifts. Copyright © 2012 John Wiley & Sons, Ltd.
Cited by 14Open access
Woo-Jin Oh · The Journal of the Korean Institute of Information and Communication Engineering · 2011
MB-OFDM(Multi-Band Orthogonal Frequency Division Multiplexing)은 ISM(Industrial, Scientific and Medical) 대역을 사용하는 초 광대역 통신으로 기존 통신 시스템과 공존하기 위해서 검출 및 회피 기법인 DAA(Detect-And-Avoid)을 사용하는 것이 요구되고 있다. 본 논문에서는 DAA를 위한 간섭신호 검출 방식으로 결정궤환 방식을 제안하여 기존의 방법에 비하여 수렴 속도가 빠르고 간단히 구현할 수 있는 특징을 갖고 있다. 제안된 방식은 AWGN(Additive White Gaussian Noise), 및 LOS(Line-Of-Sight)채널에서는 -20dB의 간섭까지 검출하는 우수한 성능을 보이고 있다. 또한 비 LOS 채널에서는 적절한 채널 클리핑을 통하여 AWGN 채널에 근사한 성능을 제시하였다. Since the MB-OFDM(Multi-Band Orthogonal Frequency Division Multiplexing) is an ultra wideband communication system operated on ISM(Industrial, Scientific and Medical) band, DAA(Detect-And-Avoid) is required for co-existence with the other communication service. In this paper we propose the new detection algorithm based on decision-feedback, which shows faster convergence time and less complexity than previous works. The proposed algorithm detects interference above -20dB in AWGN(Additive White Gaussian Noise) and LOS(Line-Of-Sight) channel, and close to AWGN in non-LOS channel under appropriate channel clipping.
Cited by 0Open access
Le Wang, Xucen Wu, Chenglin Zhang · 2023
With the increasing demand for wideband transmission for telemetry systems, multipath fading causes the performance degradation of synchronization. The commonly-used algorithms are least square (LS) and linear minimum mean square error (LMMSE) channel estimation instead of the conventional phase and timing synchronization. The carrier frequency offset (CFO) is also estimated considering the multipath interference, which is different from conventional CFO estimation methods. The mentioned channel and CFO estimation reduce the synchronization performance degradation under multipath channels compared to the traditional synchronization methods used in narrow systems. The higher accuracy channel and CFO estimation means the better performance of the receiver. In this paper, we propose a decision-directed channel and CFO estimation algorithm for SOQPSK-TG to improve the synchronization performance. It uses the detected symbols to refine the estimated channel impulse response and CFO iteratively. The SOQPSK-TG signal has the detected symbol error propagation when reconstructing the modulated signal. We also present a simple method to avoid error propagation. The numerical results demonstrate the performance improvement of our proposed methods compared to the conventional estimation methods.
Cited by 1
Guangliang Ren, Jiangtao Xing, Huining Zhang · IEEE Transactions on Vehicular Technology · 2008
An effect of decision errors on the decision-directed (DD) algorithm for residual carrier frequency offset (RCFO) estimation is analyzed, and a new signal-to-noise ratio (SNR)-assisted DD algorithm is proposed to estimate the RCFO in wireless orthogonal frequency-division multiplexing (OFDM) systems. In the algorithm, the received data on the subchannels with high SNRs are employed in the cross-correlation operation between the adjacent OFDM symbols, and the data of the cross correlation on the subchannels are hard decided. With these decisions and the SNR-weighted factors on the subchannels, the new algorithm estimates the RCFO in high accuracy. The simulation results indicate that the proposed scheme achieves a much better performance than the conventional DD schemes.
Cited by 4
Wei Rao · Procedia Environmental Sciences · 2011
The Constant Modulus Algorithm (CMA) is recognized as the most widely used algorithm in blind channel equalization practice. However, the CMA cost function exhibits local minima, which often leads to ill-convergence. This paper proposes a concurrent equalizer, in which a Soft Decision Directed (SDD) equalizer operates cooperatively with a CMA equalizer, controlled through a non-linear link that depends on the system a priory state. The simulation results show that the proposed equalizer has faster convergence rate and lower steady-state mean square error than the CMA equalizer.
Cited by 3Open access
Ming Liu, Tong Zhao, Bo Wang et al. · 2021
The rapid development of electronic technology and weapons and equipment has promoted the transformation of the war situation. Electronic warfare has become more and more important in modern warfare. Reasonable interference decision-making according to the battlefield environment can achieve better combat results. Therefore, the interference decision-making link is in a very critical position in combat. For different confrontation environments, obtaining appropriate interference allocation schemes can improve the interference effect and overall revenue, and to some extent, reduce the loss of interference resources and equipment. In terms of the static multi-jammer cooperative interference decision algorithm, this paper aims at the current common optimization algorithms that are greatly affected by human factors and the search method is inefficient, and proposes an improved artificial bee colony algorithm based on directed mutation to solve static multi-interference machine coordination interferes decision-making issues. Simulation shows that the optimization ability and convergence speed of the artificial bee colony algorithm based on directed mutation have been improved to a certain extent.
Cited by 1
Wang, B-S, Zhang, C-Y, Lin, B · The HKU Scholars Hub (University of Hong Kong) · 2010
The blind algorithm based on Parzen windows method probability density function (PDF) has a better performance then constant modulus algorithm (CMA). Similarly to CMA, this algorithm has a stochastic phase rotation phenomena. Through the phase information of the maximum a posteriori (MAP) criterion, a concurrent soft decision-directed blind equalization algorithm based on Parzen window method PDF (PPDF (Posterior Probability Density Function) + SDD (Soft Decision Decoding)) was studied. Simulation for high-order quadrature amplitude modulation (QAM) shows that the proposed algorithm improves the equalizer performance by offering faster convergence and smaller misadjustment. Furthermore, the proposed algorithm overcomes the stochastic phase rotation phenomena.
Cited by 0
Shafayat Abrar, Azzedine Zerguine, Maâmar Bettayeb · IEEE Transactions on Neural Networks · 2002
Stop-and-go decision-directed (S-and-G-DD) equalization is the most primitive blind equalization (BE) method for the cancelling of intersymbol-interference in data communication systems. Recently, this scheme has been applied to complex-valued multilayer feedforward neural network, giving robust results with a lower mean-square error at the expense of slow convergence. To overcome this problem, in this work, a fast converging recursive least squares (RLS)-based complex-valued backpropagation learning algorithm is derived for S-and-G-DD blind equalization. Simulation results show the effectiveness of the proposed algorithm in terms of initial convergence.
Cited by 14
Vikesh Agrawal, Hemant Namdeo, Santosh Kumar Singh et al. · Indian Journal of Surgery · 2020
Cited by 4
Fatima Lounoughi, Mohamed Djendi · 2023
This paper presents a new adaptive decision directed equalizer (DDE) for the receivers of Advanced Wireless communication systems. The proposed approach is based on the use of a recursive non quadratic (RNQ) adaptive algorithm in a DDE system with a training sequence, the new algorithm is denoted DDE-RNQ. The proposed DDE-RNQ equalizer achieves better performances in different situations even when strong noise components are present in the channel. In the proposed DDERNQ, the non quadratic distance criterion between the equalizer output and the decision circuit is used rather than the squared mean square error (MSE) distance for the computation of the branch metrics. Compared to the conventional DDE based normalized least mean square (DDE-NLMS) equalizer, the proposed DDE-RNQ shows superior performances of speed convergence and residual error versus the original DDE-NLMS equalizer in terms of MSE.
Cited by 1
Tongtong Xu, Zheng Xiang, Hua Yang et al. · Frontiers in Neurorobotics · 2021
At present, in robot technology, remote control of robot is realized by wireless communication technology, and data anti-interference in wireless channel becomes a very important part. Any wireless communication system has an inherent multi-path propagation problem, which leads to the expansion of generated symbols on a time scale, resulting in symbol overlap and Inter-symbol Interference (ISI). ISI in the signal must be removed and the signal restores to its original state at the time of transmission or becomes as close to it as possible. Blind equalization is a popular equalization method for recovering transmitted symbols of superimposed noise without any pilot signal. In this work, we propose a concurrent modified constant modulus algorithm (MCMA) and the decision-directed scheme (DDS) with the Barzilai-Borwein (BB) method for the purpose of blind equalization of wireless communications systems (WCS). The BB method, which is two-step gradient method, has been widely employed to solve multidimensional unconstrained optimization problems. Considering the similarity of equalization process and optimization process, the proposed algorithm combines existing blind equalization algorithm and Barzilai-Borwein method, and concurrently operates a MCMA equalizer and a DD equalizer. After that, it modifies the DD equalizer's step size (SS) by the BB method. Theoretical investigation was involved and it demonstrated rapid convergence and improved equalization performance of the proposed algorithm compared with the original one. Additionally, the simulation results were consistent with the proposed technique.
Cited by 1Open access
Tongtong Xu, Zheng Xiang · Research Square · 2020
Abstract In this work, concurrent modified constant modulus algorithm and decision-directed scheme with the Barzilai-Borwein method is proposed for blind equalization of wireless communications systems. The Barzilai-Borwein method, the two-step gradient method, is usually used to solve multidimensional unconstrained optimization problems. The proposed algorithm concurrently operates a modified constant modulus algorithm equalizer and a decision directed equalizer, it then adaptively adjusts the step size of the decision directed equalizer using Barzilai-Borwein method. Theoretical analysis is provided to illustrate that the proposed algorithm has a faster convergence speed, and better equalization performance than the original one. Simulation results support the new proposed technique.
Cited by 0Open access