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Author: Kah Ping Lee Publisher: ISBN: Category : Coding theory Languages : en Pages :
Book Description
Intersymbol interference (ISI) is a major impairment in wireless communication and hence equalization is applied to combat such interference. In addition to maximum likelihood sequence estimation equalizer and filtering equalizer, turbo equalization associates with trellis-based channel equalizer and channel decoder was proposed to overcome the ISI more efficiently. Such "turbo principle" stems from the concept of turbo coding which obtains the coding gain approaches to Shannon limit prediction. Turbo code is a refinement of the concatenated encoding structure plus an iterative and soft-input/soft output algorithm such as maximum a-posteriori (MAP) algorithm for decoding the code sequence. Similar to turbo code, turbo equalizer performs the equalization and decoding iteratively until the convergence is achieved. However, for a system with high-level modulation, the optimal MAP equalizer is prohibited due to its computational complexity. Thus, the sub-optimum equalizers such as decision feedback equalizer (DFE) have to be considered. Due to the improvement of the system performance based on the conventional DFE algorithm is limited by the error propagation, a novel low complexity DFE algorithm is proposed. The new method detects the symbols using the extra metric and the feedback symbol from previous iteration The simulation results show that the performance of the proposed DFE algorithm improves dramatically compared with the conventional DFE algorithm.
Author: Kah Ping Lee Publisher: ISBN: Category : Coding theory Languages : en Pages :
Book Description
Intersymbol interference (ISI) is a major impairment in wireless communication and hence equalization is applied to combat such interference. In addition to maximum likelihood sequence estimation equalizer and filtering equalizer, turbo equalization associates with trellis-based channel equalizer and channel decoder was proposed to overcome the ISI more efficiently. Such "turbo principle" stems from the concept of turbo coding which obtains the coding gain approaches to Shannon limit prediction. Turbo code is a refinement of the concatenated encoding structure plus an iterative and soft-input/soft output algorithm such as maximum a-posteriori (MAP) algorithm for decoding the code sequence. Similar to turbo code, turbo equalizer performs the equalization and decoding iteratively until the convergence is achieved. However, for a system with high-level modulation, the optimal MAP equalizer is prohibited due to its computational complexity. Thus, the sub-optimum equalizers such as decision feedback equalizer (DFE) have to be considered. Due to the improvement of the system performance based on the conventional DFE algorithm is limited by the error propagation, a novel low complexity DFE algorithm is proposed. The new method detects the symbols using the extra metric and the feedback symbol from previous iteration The simulation results show that the performance of the proposed DFE algorithm improves dramatically compared with the conventional DFE algorithm.
Author: Longbao Wang Publisher: ISBN: Category : Feedback control systems Languages : en Pages : 142
Book Description
"This dissertation investigates both of the frequency domain and time domain turbo equalization with multiple-input multiple-output (MIMO) fading channels for radio frequency and underwater acoustic communications. First, a low complexity frequency domain turbo equalization (FDTE) is proposed for the MIMO systems with zero padding (ZP) or cyclic prefix (CP) inserted between the transmitted data blocks and its performance is tested on the real-world UWA communications experiments. Second, as high speed communication system requires efficient bandwidth usage and power consumption, CP or ZP is not transmitted as auxiliary information. An inter-block interference cancelation and CP reconstruction algorithm is developed to re-arrange the channel matrix into a block diagonal one. This improvement makes the FDTE effectively detects the continuous data stream from the high speed UWA communications and its performance has been verified by processing data collected from the UWA communications experiment. Finally, a low complexity soft interference cancelation (SIC) time domain turbo equalizer for MIMO systems with high level modulation is proposed. Compared with the conventional linear or nonlinear turbo equalizers, the proposed SIC turbo equalizer can theoretically reach the bound set up by the ideal match filter and its bit error rate (BER) performance from Monte Carlo simulation achieves a lower error floor as well as a more rapid convergence speed."--Abstract, page iv.
Author: Amirhossein Rafati Publisher: ISBN: Category : Equalizers (Electronics) Languages : en Pages : 202
Book Description
"Multiple-input multiple-output (MIMO) wireless communication systems have attracted a lot of interest in the past decade due to their capability in delivering high spectral efficiency as well as their robust performance against fading. In MIMO inter-symbol interference (lSI) channels, a severe interference problem occurs due to the lSI and co-channel interference. Thus, the error propagation problem becomes more serious, and its mitigation has to be considered when designing the receiver. In this regard, a turbo equalizer which exchanges soft information between the equalizer and the decoder has been shown to be an effective method to combat the lSI caused by frequency-selective channels. By iteratively exchanging soft extrinsic information between a soft-input soft-output equalizer and a decoder, turbo equalizer can achieve large performance gains over a separated equalizer and decoder structure. In its original form, Douillard employed maximum a posteriori probability (MAP) equalization and decoding methods in an iterative fashion. However, the computational complexity required to derive the a posteriori log likelihood ratio (LLR) for the MAP decoder is prohibitive. Therefore, the design of low-complexity turbo equalizers based on minimum mean square error (MMSE) criterion has attracted considerable attention in the past few years. In this work, a new soft decision feedback equalizer (SDFE) is proposed for MIMO Communication systems. The computational complexity of the proposed algorithm only linearly grows with the number of equalizer coefficients, compared with the quadratic complexity of minimum mean square error (MMSE)-based linear turbo equalizer with time-varying coefficients. The performance of our proposed algorithm is tested by extensive undersea trial data collected in two medium-range undersea experiments"--Abstract, Leaf iv.
Author: Gregory E. Bottomley Publisher: John Wiley & Sons ISBN: 1118105273 Category : Technology & Engineering Languages : en Pages : 192
Book Description
The most thorough, up-to-date reference on channel equalization—from basic concepts to complex modeling techniques In today's instant-access society, a high premium is placed on information that can be stored and communicated effectively. As a result, storage densities and communications rates are being pushed to capacity, causing information symbols to interfere with one another. To help unclog pathways for the clearer conveyance of information, this book offers in-depth discussion of the significant contributions and future adaptability of channel equalization and a set of approaches for solving the problem of intersymbol interference (ISI). Chapter explorations in Channel Equalization include: Channel equalization topics presented with incremental learning methodology—from the very fundamental concept to more advanced mathematical knowledge Coverage of technology used in second-, third- and fourth-generation cellular communication systems A set of homework problems that reinforce concepts discussed in the book Tutorial explanations of recent developments currently captured in IEEE technical journals Unlike existing digital communications books that devote cursory attention to channel equalization, this invaluable guide addresses a crucial need by focusing solely on the background, current state, and future direction of this increasingly important technology. A unique mix of basic concepts and complex frameworks for delivering digitized data make Channel Equalization a valuable reference for all practicing wireless communication engineers and students dealing with the pressing demands of the information age.
Author: Giorgio A. Vitetta Publisher: John Wiley & Sons ISBN: 1118576608 Category : Technology & Engineering Languages : en Pages : 849
Book Description
This book introduces the theoretical elements at the basis of various classes of algorithms commonly employed in the physical layer (and, in part, in MAC layer) of wireless communications systems. It focuses on single user systems, so ignoring multiple access techniques. Moreover, emphasis is put on single-input single-output (SISO) systems, although some relevant topics about multiple-input multiple-output (MIMO) systems are also illustrated. Comprehensive wireless specific guide to algorithmic techniques Provides a detailed analysis of channel equalization and channel coding for wireless applications Unique conceptual approach focusing in single user systems Covers algebraic decoding, modulation techniques, channel coding and channel equalisation
Author: Sang-Yick Leong Publisher: ISBN: Category : Electronic dissertations Languages : en Pages :
Book Description
Channel modeling, estimation and equalization are discussed throughout this dissertation. Relevant research topics are first studied at the beginning of each chapter and the new methods are proposed to improve the system performance. MLSE is an optimum equalizer for all the case. However, due to its computational complexity, it is impractical for today technologies in third generation wireless communication. Thus, a suboptimum equalizer so-called perturbation equalizer is proposed, which outperforms the RSSE equalizer in the sense of bit error rate or computational complexity. In order to improve the system performance dramatically, the iterative equalization algorithm is implemented. It has been shown that the turbo equalization using the trellis based Maximum A Posteriori equalizer is a powerful receiver that yielding the optimum system performance. Unfortunately, due to its exhausted computational complexity, a suboptimal equalizer is required. An improved DFE algorithm, which only requires low computational complexity, is proposed for turbo equalization. The promising simulation results indicate that the proposed equalizer provides significant improvement in bit error rate while compared to the conventional DFE algorithm. Prior to channel equalization, channel estimation enable us to extract the necessary channel information from the pilot symbols for equalizers. Least-squares algorithm is a promising estimation algorithm providing the channel is time-invariant in a given period. Based on the derivations, we show that the channel is no longer constant and a new least-squares based algorithm is proposed to estimate the channel accurately. Simulation results convince us that the new algorithm provides the equalizer more reliable information. Besides, antenna diversity is another promising technique implemented practically to improve the system performance provided that the channels of antennas are not correlated. A new three dimensional multiple-input multiple-output abstract model is proposed for the investigation and understanding of the correlation of fading channel. The new model allows us to consider the channel correlation of which the mobile stations receive the incoming waves from any directions and angle spreads. Based on this abstract model, the closed form and mathematical tractable formula is derived for space-time correlation function. The new function can be further simplified other known special cases.
Author: Jian Zhang Publisher: ISBN: Category : Equalizers (Electronics) Languages : en Pages : 252
Book Description
"This dissertation investigates single carrier frequency-domain equalization (SC-FDE) with multiple-input multiple-output (MIMO) channels for radio frequency (RF) and underwater acoustic (UWA) wireless communications. It consists of five papers, selected from a total of 13 publications. Each paper focuses on a specific technical challenge of the SC-FDE MIMO system. The first paper proposes an improved frequency-domain channel estimation method based on interpolation to track fast time-varying fading channels using a small amount of training symbols in a large data block. The second paper addresses the carrier frequency offset (CFO) problem using a new group-wise phase estimation and compensation algorithm to combat phase distortion caused by CFOs, rather than to explicitly estimate the CFOs. The third paper incorporates layered frequency-domain equalization with the phase correction algorithm to combat the fast phase rotation in coherent communications. In the fourth paper, the frequency-domain equalization combined with the turbo principle and soft successive interference cancelation [sic] (SSIC) is proposed to further improve the bit error rate (BER) performance of UWA communications. In the fifth paper, a bandwidth-efficient SC-FDE scheme incorporating decision-directed channel estimation is proposed for UWA MIMO communication systems. The proposed algorithms are tested by extensive computer simulations and real ocean experiment data. The results demonstrate significant performance improvements in four aspects: improved channel tracking, reduced BER, reduced computational complexity, and enhanced data efficiency"--Abstract, leaf iv.
Author: Kah Ping Lee
Author: Kah Ping Lee
Author: Longbao Wang
Author: Hermanus Carel Myburgh
Author: Grace Ogheneruonano Oletu
Author: Amirhossein Rafati
Author: Gregory E. Bottomley
Author: Giorgio A. Vitetta
Author: Xiangguo Tang
Author: Sang-Yick Leong
Author: Jian Zhang