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Multiscale Wireless Communications Using Compactly-Parametrized Wavelets 基于紧凑参数化小波的多尺度无线通信
G. Mandyam
Wireless communications has traditionally involved single-scale modulation, usually involving either time or frequency conditioning of the transmitted signal. In this paper multiscale modulation, wherein time-frequency conditioning of the transmitted signal is used, is considered with respect to typical wireless communications systems. Multipath channels require equalization, which can be complex in the time-frequency domain. In this work, a different approach in which the modulating wavelet is matched to a specific channel condition is proposed. Specifically, compactly supported wavelet bases are employed, and based on their parameterization a wavelet is selected that best characterizes the wireless channel conditions
无线通信传统上涉及单尺度调制,通常涉及传输信号的时间或频率调节。本文考虑了典型无线通信系统的多尺度调制,其中使用了传输信号的时频调节。多径信道需要均衡,这在时频域中是复杂的。在这项工作中,提出了一种不同的方法,其中调制小波与特定的信道条件相匹配。具体来说,采用紧凑支持的小波基,并基于它们的参数化选择最能表征无线信道条件的小波
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引用次数: 0
Blind Equalization in OFDM Systems Exploiting Guard Interval Redundancy 利用保护间隔冗余的OFDM系统中的盲均衡
F. O. Alayyan, K. Abed-Meraim, A. Zoubir
We introduce a new low-complexity equalizer for OFDM systems, which in the presence of a guard interval, utilizes existing redundancy in the time domain to completely eliminate inter-symbol-interference. We prove that the usage of this guard interval redundancy is sufficient to obtain a zero-forcing time domain equalizer of the channel. The main advantage of this approach resides in its simplicity as the equalizer coefficients are estimated using a second-order least square fitting (LSF). In addition, to fully exploit the data information, we propose to use the previous LSF based equalizer in conjunction with a constant modulus algorithm (CMA). This would help to refine the equalizer estimation, especially for short data lengths, and to improve the system performance. Several implementations are proposed and compared through simulation experiments
本文提出了一种新的低复杂度的OFDM均衡器,该均衡器在存在保护间隔的情况下,利用时域已有的冗余来完全消除符号间干扰。我们证明使用这种保护间隔冗余足以获得信道的强制零时域均衡器。这种方法的主要优点在于它的简单性,因为均衡器系数是使用二阶最小二乘拟合(LSF)估计的。此外,为了充分利用数据信息,我们建议将先前基于LSF的均衡器与常模算法(CMA)结合使用。这将有助于改进均衡器估计,特别是对于短数据长度,并提高系统性能。提出了几种实现方案,并通过仿真实验进行了比较
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引用次数: 5
A Multi-user SC-FDE-MIMO System for Frequency-Selective Channels 频率选择信道的多用户SC-FDE-MIMO系统
Li Guo, Yih-Fang Huang
This paper proposes a multi-user multiple input-multiple output (MIMO) system based on a singlecarrier frequency-domain equalization (SC-FDE) technique for frequency-dispersive multipath environments, where the signals are corrupted by both co-channel interference (CCI) and intersymbol interference (ISI). The proposed scheme effectively suppresses both CCI and ISI simultaneously with relatively low complexity. Furthermore, it does not impose any restriction on the number of available antennas. Simulation results show that the proposed scheme offers improved bit error rate and throughput performance and is superior to multi-carrier systems. The proposed scheme will make the multi-user MIMO system for frequency-selective channels more practically feasible.
本文提出了一种基于单载波频域均衡(SC-FDE)技术的多用户多输入多输出(MIMO)系统,用于频率色散多径环境下信号受同信道干扰(CCI)和码间干扰(ISI)的干扰。该方案能有效地同时抑制CCI和ISI,且复杂度较低。此外,它对可用天线的数量没有任何限制。仿真结果表明,该方案提高了误码率和吞吐量,优于多载波系统。该方案将使多用户选频MIMO系统更具实际可行性。
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引用次数: 5
On Subspace-based Blind Channel Estimation Algorithms for SFBC MC-CDMA systems 基于子空间的SFBC MC-CDMA盲信道估计算法研究
S. N. Nazar, I. Psaromiligkos
The issue of blind channel estimation for the downlink of Space-Frequency Block Coded Multi-Carrier Code Division Multiple Access (SFBC MC-CDMA) systems is ad- dressed. Specifically, we consider an intuitive subspace-based channel estimation method and we investigate the corresponding necessary and sufficient conditions under which the channel estimate is unique (within a complex scalar). The derived identifiability conditions are used to highlight two interesting properties of SFBC MC-CDMA systems: (i) there is no antenna order ambiguity even when only one spreading code is assigned to each user, (ii) channel identifiablility is guaranteed, regardless of the channel zeros location. We also establish the unbiasedness of the channel estimates and we derive closed-form expressions for the mean-square-error (MSE) of the estimates as well as the corresponding Cramer-Rao bound (CRB). For the derivation of the CRB, we follow a novel approach which assumes the knowledge of only the spreading code of the desired user and results in a much tighter bound than the CRB derived based on the knowledge of all users' signatures. I. INTRODUCTION Transmit diversity techniques, and particularly Space- Time/Frequency Block Codes (STBC/SFBC) (1), are known to be very effective for combating multipath fading in broad- band wireless communications. These schemes are even more attractive when applied to a robust multiple access technique such as Multi-Carrier Code Division Multiple Access (MC- CDMA). However, the diversity and coding gains that are possible in such systems can only be realized if the underlying channels are accurately acquired at the receiver (4). The issue of blind channel estimation for STBC MC-CDMA systems has been addressed in the past (2), (3); however, to the authors best knowledge, no channel estimation method has been proposed or analyzed for SFBC MC-CDMA. In this work, as a first step in filling that void, we investigate the problem of blind channel estimation for SFBC MC-CDMA systems. We begin by presenting a system model for complex modulation schemes that enables us to treat the links between the multiple transmit antennas and the single receive antenna as a single channel and, thus, reduces the multichannel estima- tion problem to a single-input single-output (SISO) problem. This allows us to develop a simple, intuitive, subspace-based
研究了空频分组编码多载波码分多址(SFBC MC-CDMA)系统下行链路的信道盲估计问题。具体来说,我们考虑了一种直观的基于子空间的信道估计方法,并研究了信道估计是唯一的(在复标量内)的必要和充分条件。导出的可识别条件用于突出SFBC MC-CDMA系统的两个有趣特性:(i)即使只给每个用户分配一个扩展码,也没有天线顺序模糊;(ii)无论信道零点位置如何,信道可识别性都得到保证。我们还建立了信道估计的无偏性,并推导了估计的均方误差(MSE)的封闭表达式以及相应的Cramer-Rao界(CRB)。对于CRB的推导,我们采用了一种新颖的方法,该方法只假设期望用户的传播码的知识,并且比基于所有用户签名的知识推导的CRB的约束要严格得多。发射分集技术,特别是空时/频块码(STBC/SFBC)(1),被认为是对抗宽带无线通信中的多径衰落非常有效的技术。当这些方案应用于多载波码分多址(MC- CDMA)等鲁棒多址技术时,就更有吸引力了。然而,只有在接收器准确获取底层信道的情况下,才能实现这种系统中的分集和编码增益(4)。过去已经解决了STBC MC-CDMA系统的盲信道估计问题(2),(3);然而,据笔者所知,目前还没有针对SFBC MC-CDMA的信道估计方法被提出或分析。在这项工作中,作为填补这一空白的第一步,我们研究了SFBC MC-CDMA系统的盲信道估计问题。我们首先提出了一个复杂调制方案的系统模型,使我们能够将多个发射天线和单个接收天线之间的链接视为单个通道,从而将多通道估计问题减少到单输入单输出(SISO)问题。这允许我们开发一个简单的,直观的,基于子空间的
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引用次数: 5
Common and Dedicated Pilot-Based Channel Estimates Combining and Kalman Filtering for WCDMA Terminals WCDMA终端的公共和专用导频信道估计组合和卡尔曼滤波
A. Bastug, G. Montalbano, D. Slock
We consider a family of user dedicated downlink channel estimation methods in WCDMA receivers which are particularly suited for the presence of dedicated channel transmit beamforming and which assume no a priori knowledge of the path delays and the beamforming parameters. They exploit all the transmitted pilot sequences as well as the structured dynamics of the channel. First we build slot-wise least squares (LS) estimates of the channels associated with dedicated and common pilots. Then we optimally improve the dedicated channel estimate quality by jointly Kalman filtering the two LS estimates or alternatively (suboptimally) Kalman filtering them separately and combining via weighted LS. In the suboptimal case, the order of Kalman filtering and weighted LS combining results in differing performance and complexity in different conditions
我们考虑了WCDMA接收机中一系列用户专用下行信道估计方法,这些方法特别适用于存在专用信道发射波束形成的情况,并且不假设路径延迟和波束形成参数的先验知识。它们利用了所有传输的导频序列以及信道的结构动态。首先,我们建立了与专用导频和普通导频相关的信道的时隙最小二乘(LS)估计。然后通过联合卡尔曼滤波两个LS估计或交替(次优)卡尔曼滤波它们并通过加权LS组合来最优地提高专用信道估计质量。在次优情况下,卡尔曼滤波和加权LS组合的顺序导致不同条件下的性能和复杂度不同
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引用次数: 4
Efficient Demodulation in Cooperative Schemes Using Decode-and-Forward Relays 使用译码转发中继的合作方案的有效解调
Tairan Wang, A. Cano, G. Giannakis
Cooperative communication systems using various relay strategies can achieve spatial diversity gains, enhance coverage and potentially increase capacity. For the practically attractive decode-and-forward (DF) relay strategy, we derive an efficient demodulator at the destination in the form of a weighted combiner. The weights are selected adaptively to account for the quality of both source-relay-destination and source-destination links. Analysis proves that the novel demodulator can achieve the maximum possible diversity, regardless of the underlying constellation. Its error performance tightly bounds that of maximumlikelihood (ML) demodulation which provably quantifies the diversity gain of ML detection with DF relaying. Simulations corroborate our theoretical analyses and compare performance of the novel decoder with existing diversity-achieving strategies including analog amplify-and-forward and selective-relaying.
使用各种中继策略的协作通信系统可以实现空间多样性增益,增强覆盖范围并可能增加容量。对于实际有吸引力的解码和转发(DF)中继策略,我们在目标处以加权组合器的形式导出了有效的解调器。自适应地选择权重以考虑源-中继-目的链路和源-目的链路的质量。分析证明,无论底层星座如何,该解调器都能实现最大可能的分集。它的误差性能严格限制了最大似然解调的误差性能,证明了用DF中继量化最大似然检测的分集增益。仿真验证了我们的理论分析,并将新型解码器的性能与现有的分集实现策略(包括模拟放大转发和选择性中继)进行了比较。
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引用次数: 28
FPGA Implementation of Viterbi Decoders for MIMO-BICM MIMO-BICM Viterbi解码器的FPGA实现
S. Haene, A. Burg, D. Perels, P. Luethi, N. Felber, W. Fichtner
The FPGA implementation of Viterbi decoders for multiple-input multiple-output (MIMO) wireless communication systems with bit-interleaved coded modulation (BICM) and per-antenna coding is considered. The paper describes how the recursive add-compare-select (ACS) unit, which constitutes the performance bottleneck of the circuit, can be pipelined to increase the throughput. As opposed to employing multiple parallel decoders, silicon area (resource utilization on the FPGA) is significantly reduced. The proposed optimizations lead to an implementation that achieves a throughput of 216 Mbps in a 4 times 4 MIMO-WLAN system prototype based on IEEE 802.11a
研究了多输入多输出(MIMO)无线通信系统中比特交织编码调制(BICM)和单天线编码的Viterbi解码器的FPGA实现。本文介绍了如何将构成电路性能瓶颈的递归添加比较选择(ACS)单元流水线化以提高吞吐量。与采用多个并行解码器相反,硅面积(FPGA上的资源利用率)显着减少。所提出的优化导致在基于IEEE 802.11a的4 × 4 MIMO-WLAN系统原型中实现216 Mbps的吞吐量
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引用次数: 17
Representation of unit range numbers 单位范围数字的表示
T. Lang, J. Bruguera
Floating–point representation has a large dynamic range but can be inefficient for computations with values that have a limited range. This issue is explored here for values in the range −1 to 1, which, for instance, is the range of some trigonometric functions and exponentials. Examples are shown in which the results are inaccurate, because of the small density of the representation close to 1. Although a fractional fixedpoint representation seems suitable for these computations, its uniform density does not allow the representation of values close to zero and close to one, resulting in similar inaccuracies. To improve the accuracy, we propose a more suitable representation, that we call unity representation. This representation is able to represent very small values with high accuracy, as in floating point, as well as values very close to 1. We show the advantages of this representation providing several computation examples. Moreover, we list the architectural support that is needed to use this representation in a floating-point processor.
浮点表示具有很大的动态范围,但对于具有有限范围的值的计算可能效率低下。这个问题是在- 1到1的范围内探讨的,例如,这是一些三角函数和指数的范围。示例显示的结果是不准确的,因为接近1的表示密度很小。尽管分数不动点表示似乎适合于这些计算,但它的均匀密度不允许表示接近于0和接近于1的值,从而导致类似的不准确性。为了提高准确率,我们提出了一种更合适的表示,我们称之为统一表示。这种表示法能够以高精度表示非常小的值,如浮点数,以及非常接近1的值。我们通过几个计算实例来说明这种表示的优点。此外,我们还列出了在浮点处理器中使用这种表示所需的体系结构支持。
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引用次数: 0
Rao-Blackwellized Gauss-Hermite Filter for Joint Frequency Offset and Channel Estimation for the MIMO-OFDM System 用于MIMO-OFDM系统联合频偏和信道估计的rao - blackwelzed高斯-赫米特滤波器
Kyeong Jin Kim, R. Iltis
We propose a new frequency offset and channel estimation algorithm for a MIMO-OFDM system. To estimate offset parameters which enter the observation function in a nonlinear manner, we propose a Gauss-Hermite Filter which incorporates the Kalman filter (KF) conditioned on a random offset sample. To reduce the complexity, the Rao-Blackwellization is employed. In the MIMO-OFDM system, the initial estimate for the offsets and channels are obtained using one training symbol. In the remaining OFDM symbol intervals, the MIMO data detector is employed to detect the transmitted data symbols. The used data detector and Gauss-Hermite filter based channel/offset estimator are finally combined in a joint decision-directed algorithm
针对MIMO-OFDM系统,提出了一种新的频偏和信道估计算法。为了估计以非线性方式进入观测函数的偏移参数,我们提出了一种基于随机偏移样本的卡尔曼滤波器(KF)的高斯-赫米特滤波器。为了降低复杂度,采用了rao - blackwell化方法。在MIMO-OFDM系统中,用一个训练符号来获得偏移量和信道的初始估计。在剩余的OFDM符号间隔内,使用MIMO数据检测器检测传输的数据符号。最后将所使用的数据检测器和基于高斯-埃尔米特滤波器的信道/偏移估计器结合在一个联合决策导向算法中
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引用次数: 3
Hidden Markov Modeling of Noise Periodograms Using Rayleigh Mixture Models 基于瑞利混合模型的噪声周期图隐马尔可夫建模
K. Sørensen, S. Andersen
In this paper, we derive an Expectation-Maximization algorithm for hidden Markov models (HMMs) with a multivariate Rayleigh mixture model (RMM) in each state. We compare the use of multivariate RMMs to multivariate Gaussian mixture models in the general case where the HMM is a dynamic model and for the special case where it has a single state and reduces to a static model. We evaluate the proposed method when used to model probability density of periodpgrams from real-life noise sources and white Gaussian noise, which we include for reference purposes.
本文推导了一种具有多元瑞利混合模型的隐马尔可夫模型的期望最大化算法。在HMM是动态模型的一般情况下,我们比较了多元rmm和多元高斯混合模型的使用,而在HMM具有单一状态并减少为静态模型的特殊情况下。我们评估了所提出的方法,当用于模拟来自现实噪声源和高斯白噪声的周期图的概率密度时,我们包括了参考目的。
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引用次数: 1
期刊
Conference Record of the Thirty-Ninth Asilomar Conference onSignals, Systems and Computers, 2005.
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