检索结果-内蒙古大学图书馆

Complete characterization of the equivalent MIMO channel for quasi-orthogonal space-time codes

IEEE TRANSACTIONS ON INFORMATION THEORY 2008年第7期54卷 3315-3327页

作者： Sezgin, Aydin Oechtering, Tobias Josef Stanford Univ Dept Elect Engn Stanford CA 94305 USA Fraunhofer Inst Telecommun D-10587 Berlin Germany Tech Univ Berlin Heinrich Hertz Chair Mobile Commun Technol D-10587 Berlin Germany

Recently, a quasi-orthogonal space-time block code (QSTBC) capable of achieving a significant fraction of the outage mutual information of a multiple-input-multiple-output (MIMO) wireless communication system for the case of n(T) = 4 transmit and n(R) = 1 receive antennas was proposed. We generalize these results to n(T) = 2(n) transmit and an arbitrary number of receive antennas. Furthermore, we completely characterize the structure of the equivalent channel for the general case and show that for all n(T) = 2(n) and n(R) the eigenvectors of the equivalent channel are fixed and independent from the channel realization. Furthermore, the eigenvalues of the equivalent channel are independent identically distributed random variables each following a noncentral chi-square distribution with 4n(R) degrees of freedom. Based on these important insights into the structure of the QSTBC, we derive tight lower and upper bounds for the outage probability achieved with QSTBC. Finally, by utilizing the special structure of the QSTBC, we propose a new transmit strategy, which decouples the signals transmitted from different antennas in order to detect the symbols separately with a linear ML-detector rather than joint detection, an up to now only known advantage of orthogonal space-time block codes (OSTBC).

关键词： equivalent channel multiple-input-multiple-output (MIMO) quadratic forms quasi-orthogonal design space-time coding

来源：评论

学校读者我要写书评

暂无评论

Iterative EM receiver for space-time coded systems in MIMO frequency-selective fading channels with channel gain and order estimation

引用

IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2004年第6期3卷 1928-1935页

作者： So, DKC Cheng, RS Univ Manchester Sch Elect & Elect Engn Manchester M60 1QD Lancs England Hong Kong Univ Sci & Technol Dept Elect & Elect Engn Hong Kong Hong Kong Peoples R China

An iterative receiver for a space-time trellis coded system in frequency-selective fading channel is proposed. It performs channel gain estimation and sequence detection by using the expectation-maximization (EM) algorithm. Channel order estimation is included in the receiver to avoid unnecessary trellis computations by using the conditional model order estimator (CME). In addition, three modifications to the original CME criterion are proposed to improve the estimation accuracy. Simulation results show that the proposed receiver has a slight degradation in frame error rate performance to the known channel maximum likelihood receiver. Moreover, it outperforms the conventional fixed long-tap length EM receiver with a lesser complexity. Furthermore, the proposed modifications to the CME criterion improve the channel order estimation accuracy, thus minimizing unnecessary computations.

关键词： complexity expectation-maximization (EM) algorithm intersymbol interference modeling space-time coding

来源：评论

学校读者我要写书评

暂无评论

Transmit diversity scheme with power control for wireless communications

引用

IEICE TRANSACTIONS ON COMMUNICATIONS 2001年第7期E84B卷 1720-1726页

作者： Fan, PY Li, JJ Cao, ZG Tsinghua Univ Dept Elect Engn State Key Lab Microwave & Digital Commun Beijing 100084 Peoples R China

In this paper, we present a new transmit diversity scheme with power control by using two transmit antennas in which the power control unit is added to adaptively suit the channel fading variation. Compared to the transmit diversity scheme (STD, one space time coding scheme) proposed by Alamouti and the traditional maximal ratio combining (MRC) diversity scheme employed at the receiver, simulation results indicate that the new scheme has considerable performance gain. We also discuss the effects of the imperfect channel parameter Estimation on the performance of the system. Simulation results show that the new system is more robust to the estimation error of channel fading parameters than the STD. As the signal to noise ratio is relatively high, the diversity scheme with power control is more sensitive to the channel estimation error compared to the NRC. But when the channel estimation accuracy is relatively high, the diversity scheme with power control still has better performance than the ideal MRC as the BER is about 1 x 10(-3).

关键词： antenna arrays differential detection space-time coding transmit diversity

来源：评论

学校读者我要写书评

暂无评论

Design of linear dispersion codes: Asymptotic guidelines and their implementation

引用

IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2005年第6期4卷 2892-2906页

作者： Gohary, RH Davidson, TN McMaster Univ Dept Elect & Comp Engn Hamilton ON L8S 4K1 Canada

In this paper, a design method is developed for the class of linear-dispersion (LD) codes-a diverse set of space-time codes that subsumes several standard designs. The development begins by showing that for systems that employ a large number of transmit antennas, LD codes constructed from unitary coding matrices are asymptotically optimum from different design perspectives, viz., minimum mean square error (MMSE), mutual information, and average pairwise error probability (PEP). Those measures have a direct impact on the detection complexity, data rate, and error performance that a spice-time code can achieve. Using the insight generated by the asymptotic result, a structured design technique for the LD coding matrices, that suits a broad class of configurations is provided. The resulting codes can support high data rates and provide performance advantages over current designs when decoded with a standard detector. Based on the asymptotic results, a row interleaving scheme is proposed, and it is shown to result in significant performance enhancement.

关键词： efficient detection ergodic capacity multiple-input-multiple-output (MIMO) communication systems space-time coding Stiefel manifold

来源：评论

学校读者我要写书评

暂无评论

MIMO capacity with interference

引用

IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS 2003年第5期21卷 793-801页

作者： Blum, RS Lehigh Univ Dept Elect & Comp Engn Bethlehem PA 18015 USA

System capacity is considered for a group. of interfering users employing single-user detection and multiple transmit and receive antennas for flat Rayleigh-fading channels with independent fading coefficients for each path. The focus is on the case where there is no channel state information at the transmitter, but channel state information is assumed it the receiver. It, is shown that the optimum signaling is sometimes different from cases where the users do not interfere with each other. In particular, the optimum. signaling will sometimes put all power into a single transmitting antenna, rather than divide power equally between independent streams from the different antennas. If the interference is either sufficiently weak or sufficiently strong, We show that either the optimum interference-free approach, which puts equal power into each antenna, or the approach that puts,all power into a single Antenna is optimum and we show how to find the regions where each Approach is best.

关键词： antenna arrays capacity interference multiple-input multiple-output (MIMO) space-time coding

来源：评论

学校读者我要写书评

暂无评论

Joint Data Detection and Channel Estimation for Fading Unknown time-Varying Doppler Environments

引用

IEEE TRANSACTIONS ON COMMUNICATIONS 2010年第8期58卷 2277-2291页

作者： Vilaipornsawai, Usa Leib, Harry McGill Univ Dept Elect & Comp Engn Montreal PQ H3A 2A7 Canada

This work considers a joint channel estimation and data detection technique for Multiple space-time Trellis Codes (MSTTCs) operating over unknown time-varying channels with large Doppler spread. We propose an algorithm, called Doppler Adaptive Smoothed Data Detection and Kalman Estimation (DA-SDD-KE), that jointly detects data and estimates the channel as well as the time-varying Doppler. In this scheme, an Adaptive Kalman Predictor (AKP) consisting of a KP and a covariance-based Doppler estimator is incorporated into a Per-Survivor Processing (PSP)-based algorithm that utilizes the past, present and future received symbols for smoothed data detection. For comparison purposes, we also develop a Doppler Adaptive version of the Delayed Mixture Kalman Filtering (DMKF) technique, referred to as DA-DMKF, where the adaptive estimations of the channel and the Doppler shift are based on sequences of importance samples. Moreover, we propose a model for generating a Rayleigh fading process with time-varying Doppler using the sum of sinusoids method. The performance of the DA-SDD-KE and DA-DMKF algorithms over channels with constant, linear and quadratic Doppler functions is evaluated using computer simulations, revealing that the DA-SDD-KE algorithm performs well for all considered Doppler functions, and provides a considerably gain over the DA-DMKF algorithm.

关键词： Per-survivor processing Kalman estimation decoding channel estimation Doppler estimation space-time coding

来源：评论

学校读者我要写书评

暂无评论

Multi-User Downlink System Design with Bright Transmitters and Blind Receivers

引用

IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2012年第11期11卷 4074-4084页

作者： Li, Liangbin Jafarkhani, Hamid Univ Calif Irvine Ctr Pervas Commun & Comp Irvine CA 92717 USA Univ Calif Irvine Dept Elect Engn & Comp Sci Irvine CA USA

This paper considers a scenario for multi-user multi-input multi-output (MIMO) communication systems when perfect channel state information at the transmitter (CSIT) is given while the equivalent channel state information at the receiver (CSIR) is not available. Such an assumption is valid for the downlink multi-user MIMO systems with linear precoders that depend on channels to all receivers. We propose a concept called dual systems with zero-forcing design based on the duality principle, originally proposed to relate the Gaussian multi-access channel (MAC) and the Gaussian broadcast channel (BC). For the K-user N x 2 MIMO BC with N antennas at the transmitter and two antennas at each of the K receivers, we design a downlink interference cancellation (IC) transmission scheme by obtaining the dual of uplink MAC systems employing IC methods. The transmitter simultaneously sends K precoded Alamouti codes, one for each user. Each receiver zero-forces the unintended user's Alamouti codes and decouples its own data streams using two simple linear operations independent of CSIR. Analysis shows that the proposed scheme achieves a diversity gain of 2(N - K + 1) for equal energy constellations with short-term power and rate constraints. Power allocation among K users can also be performed to improve the array gain but not the diversity gain. Numerical results demonstrate that the bit error rate of the downlink IC scheme has a diversity gain improvement compared to the block diagonalization (BD) method, which requires global channel information at each node.

关键词： Multi-antenna precoding systems broadcast channels duality block diagonalization interference cancellation space-time coding orthogonal designs

来源：评论

学校读者我要写书评

暂无评论

Low-Complexity Multi-Stream space-time Codes-Part II: Unitary-Transform Codes

引用

IEEE TRANSACTIONS ON COMMUNICATIONS 2012年第2期60卷 375-383页

作者： Hochwald, Bertrand Stauffer, Erik Univ Notre Dame Dept Elect Engn Notre Dame IN 46556 USA Broadcom Corp Sunnyvale CA USA

We examine the design of space-time codes that allow simple encoding and decoding of high and low-priority streams of data. This paper comprises two parts. In the first part we introduce the system model, establish performance and complexity criteria, and introduce "direct-sum" codes that combine existing space-time codes with hierarchical modulation. In this second part, we show that the direct-sum codes of the first part can be greatly improved upon by non-direct-sum designs. We demonstrate unitary-transform codes for two and four antennas. In particular, one such code performs 4 dB better than the direct-sum Alamouti code, with per-bit decoding complexity on one stream that is a bounded function of the rate of the other stream.

关键词： space-time coding broadcast hierarchical coding multi-stream

来源：评论

学校读者我要写书评

暂无评论

Application of transmit diversity for improved robust watermarking

引用

Journal of Systems Engineering and Electronics 2004年第2期15卷 163-170页

作者： SunRui SunHong YaoTianren DepartmentofElectronicandInformationEngineering HuazhongUniversityofScienceandTechnologyWuhan430074P.R.China DepartmentofCommunicationEngineering WuhanUniversityWuhan430072P.R.China

Many common multimedia signal processing, including cropping, filtering, and perceptual coding, make watermark signal fading-like modification. A scheme that applies transmit diversity technique to improve robustness of digital watermarking is presented. First, the scheme decomposes the original image using wavelet pyramid algorithm and chooses the middle-frequency band for transmission channel that the watermark will be embedded into. Then the watermark is pseudo-randomly permuted. The scheme makes use of space-time coding and differential detection technique to embed and extract watermark. The extracting process has access to neither the original image nor channel state information. Experimental results demonstrate that the scheme improves the performance of robust watermarking.

关键词： digital watermark transmit diversity space-time coding differential detection wavelet transform.

来源：评论

学校读者我要写书评

暂无评论

A Refined Channel Estimation Method for STBC/OFDM Systems in High-Mobility Wireless Channels

引用

IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2008年第11期7卷 4312-4320页

作者： Ku, Meng-Lin Huang, Chia-Chi Natl Chiao Tung Univ Dept Commun Engn Hsinchu 300 Taiwan

In this paper, we investigate channel estimation for orthogonal frequency division multiplexing (OFDM) systems with space-time block code (STBC) in mobile wireless channels. Our proposed method consists of two-stage processing and is developed on the basis of the classical discrete Fourier transform (DFT)-based channel estimation method. In the initialization stage, we employ a multipath interference cancellation technique to estimate multipath delays and multipath complex gains. In the tracking stage, we develop a refined decision-feedback (DF) DFT-based channel estimation method in which a few pilot tones inserted in OFDM data symbols are applied to form an optimal gradient vector at the first iteration such that the error propagation effect is mitigated. In order to reduce computational complexity, an approximate weighting matrix is adopted to avoid matrix inversion. We demonstrate the proposed method through computer simulation of an STBC/OFDM system with two transmit antennas and a single receive antenna. The results show that our method outperforms the classical DFT-based method, the STBC-based minimum mean square error (MMSE) method, and the Kalman filtering method as well, and that significant signal-to-noise ratio (SNR) performance improvement can be achieved, especially when a high-level modulation scheme, e.g. 16QAM, is adopted in high-mobility environments.

关键词： Multiple-input multiple-output systems space-time coding orthogonal frequency division multiplexing channel estimation IEEE 802.16e

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：