共查询到20条相似文献,搜索用时 718 毫秒
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We propose a direct blind zeroforcing approach to cancel intersymbol interference (ISI) in multiple user finite impulse response (FIR) channels. By selectively anchoring columns of the channel convolution matrix, we present two column-anchored zeroforcing equalizers (CAZE), one without output delay and one with a chosen delay. Unlike many known blind identification algorithms, these equalizers do not need an accurate estimate of the channel orders. Exploiting second-order statistics (SOS) of the received signals, they can retain preselected d columns in the channel convolution matrix (d is the number of users) and force the remaining columns to zero. CAZE can effectively equalize single-input-multiple-output (SIMO) systems and can reduce dynamic multiple-input-multiple-output (MIMO) systems into a memoryless signal mixing system for source separation. Simulation results show that the CAZE is not only effective for blind equalization of linear quadrature amplitude modulation (QAM) systems, but it is also applicable to the nonlinear GMSK modulation in the popular wireless GSM systems when computational cost severely limits the use of nonlinear methods such as the Viterbi algorithm 相似文献
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本文针对正交幅度调制(QAM)信号的盲均衡与载波相位恢复问题,首先在对现有的基于功率最大化盲均衡算法分析的基础上,依据向量范数间的关系,给出了一种QAM信号盲均衡与载波相位恢复的无约束代价函数;然后对代价函数的收敛性和解的唯一性进行严格论证,证明代价函数在取得最优解时能够同时实现盲均衡与载波相位恢复;之后将其转化为采用随机梯度法实现的自适应算法。相对CMA、MMA等其他自适应算法,新算法可获得更好的性能,通过对高阶QAM信号的均衡仿真,进一步验证了算法的有效性。 相似文献
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Kuan-Hung Chen Chun-Nan Chen Tzi-Dar Chiueh 《Circuits and Systems II: Express Briefs, IEEE Transactions on》2005,52(12):816-820
With increasing demand for higher data rate, modern communication systems have grown more complex. Equalization has become more and more important as it is effective in mitigating the multipath fading often occurred in high-data-rate communication systems. However, the implementation complexity of adaptive equalizers is usually too high for mobile communication applications. In this paper, a novel adaptive equalization algorithm and its low-complexity architecture are proposed. This algorithm employs a new grouped signed power-of-two (GSPT) number representation. The GSPT algorithm and several enhanced versions are simulated as adaptive equalizers in a phase-shift keying communication receiver for several practical channels and the GSPT-based equalizers perform as well as the least mean square (LMS) equalizer. Moreover, for comparison, two GSPT-based equalizers and two other equalizers are implemented in field-programmable gate arrays. The GSPT-based equalizers require only about 25%-30% of the hardware resources needed in the LMS equalizer. Also the GSPT-based equalizers are more than twice as fast as the LMS equalizer. 相似文献
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This paper presents results of computer simulations and laboratory tests to investigate various digital techniques (i.e., trellis coded QAM, vestigial sideband (VSB) modulation, orthogonal frequency division multiplexing (OFDM), and adaptive equalization) proposed for Advanced Television (ATV) terrestrial broadcasting. The performance of these channel coding and modulation techniques, in the presence of various interferences (i.e., Gaussian noise, ATV and NTSC co-channel interference) and in a multipath distortion environment, is evaluated and compared. The effects of ATV interference into NTSC systems are also investigated 相似文献
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用于多电平QAM调制的新型的自恢复均衡技术的研究 总被引:7,自引:0,他引:7
本文对一种新的代阶函作了研究,提出一种适用于多民平QAM(MQAM)信号的自恢复的均衡算法,克服了CMA算法对相位不敏感的缺点,并在此基础上提出了两种改进的均衡算法,概率算法和混合算法,理论分析和计算机模拟表明这两种算法的收敛性能优越,而且误码性能与传统的LMS均衡算法一致,是两种很实用的均衡算法。 相似文献
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Gollamudi S. Kapoor S. Nagaraj S. Yih-Fang Huang 《Signal Processing, IEEE Transactions on》1998,46(9):2372-2385
This paper considers the problems of channel estimation and adaptive equalization in the novel framework of set-membership parameter estimation. Channel estimation using a class of set-membership identification algorithms known as optimal bounding ellipsoid (OBE) algorithms and their extension to tracking time-varying channels are described. Simulation results show that the OBE channel estimators outperform the least-mean-square (LMS) algorithm and perform comparably with the RLS and the Kalman filter. The concept of set-membership equalization is introduced along with the notion of a feasible equalizer. Necessary and sufficient conditions are derived for the existence of feasible equalizers in the case of linear equalization for a linear FIR additive noise channel. An adaptive OBE algorithm is shown to provide a set of estimated feasible equalizers. The selective update feature of the OBE algorithms is exploited to devise an updator-shared scheme in a multiple channel environment, referred to as updator-shared parallel adaptive equalization (USHAPE). U-SHAPE is shown to reduce the hardware complexity significantly. Procedures to compute the minimum number of updating processors required for a specified quality of service are presented 相似文献
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针对传输正交幅度调制信号的多输入多输出频率选择性衰落无线通信系统中的信号间干扰与信号内部的码间干扰问题, 提出了一种改进的软决策算法.该方法精确地利用了正交振幅调制(Quadrature Amplitude Modulation, QAM)信号星座图信息, 避免了经典恒模算法、多模算法中存在的误调问题, 提高了均衡性能.对代价函数采用梯度牛顿法进行优化, 与常用的梯度类算法相比, 其具有更快的收敛速度.通过均方误差和最大信道扭曲分析和验证了该算法的可靠性和有效性. 相似文献
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High-speed modems typically employ quadrature amplitude modulation (QAM) so that two signal paths, in-phase and quadrature, are simultaneously being used. The standard receiver structure has, in effect, four adaptive equalizers, one for each of the two signal paths and two to correct for cross coupling between signal paths. As a result, equalization normally requires8N multiplications per baud interval, whereN is the number of taps, to perform the needed signal processing including adaptive updating of the weights., In this correspondence, we present a new signal processing algorithm which requires only6N multiplications per baud interval. For fractionally spaced equalization and adaptive cancellation,N is quite large so that this saving can be of practical value in improwng throughput capability of custom chips, or depending on the architecture, with programmable signal processor chips. Specifically, the algorithm is advantageous for implementations where multiplications require a longer execution time than additions. 相似文献
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含软方向判决的修正CMA盲均衡新算法 总被引:2,自引:0,他引:2
提出了一种新颖的盲均衡算法MCMA SDD,它一方面在代价函数中同时包含了幅度和相位的信息,另一方面,增加了并行的软方向判决(SDD)盲均衡算法,使得MCMA SDD算法无需载波跟踪环就能够纠正相位的失真;在低信噪比条件下具有较快的收敛速度和较低的稳态均方误差。 相似文献
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《Signal Processing, IEEE Transactions on》2009,57(12):4788-4799
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There are two competing transmission systems for downstream digital transmission on hybrid fiber/coax cable networks: quadrature amplitude modulation (QAM), and vestigial sideband modulation (VSB). Both QAM and VSB are bandwidth efficient, and have the same bandwidth efficiency. Detailed calculations and simulations of QAM and VSB transmission on hybrid fiber/coax are reported here. It is shown that, since VSB has a higher symbol rate, it has at most 1/2 dB less received SNR than QAM at low frequencies because of dispersion and symbol timing jitter. This difference is negligible. Vendors proposing VSB recover the carrier with a pilot tone and a PLL, and vendors proposing QAM use all-digital data-directed carrier recovery. Simulations reported here show that QAM and VSB have very similar carrier recovery performance. It is concluded that for hybrid fiber/coax, VSB and QAM have practically the same overall performance, and the choice between these transmission systems should be based on considerations other than performance 相似文献
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A hybrid adaptive blind equalization algorithm for QAM signals in wireless communications 总被引:8,自引:0,他引:8
Lin He Amin M.G. Reed C. Jr. Malkemes R.C. 《Signal Processing, IEEE Transactions on》2004,52(7):2058-2069
A hybrid adaptive channel equalization technique for quadrature amplitude modulation (QAM) signals is proposed. The proposed algorithm, which is referred to as the modified constant modulus algorithm (MCMA), minimizes an error cost function that includes both amplitude and phase of the equalizer output. In addition to the amplitude-dependent term that is provided by the conventional constant modulus algorithm (CMA), the cost function includes an additive signal constellation matched error (CME) term. This term can be designed to satisfy a set of desirable properties. The MCMA is compared with the CMA for blind equalization. The performance is measured for wireless channels using both transient and steady-state behavior of the mean square error (MSE). It is shown that MCMA is superior and more robust in low signal-to-noise ratio (SNR) environments. Simulation results demonstrate that using MCMA improves adaptive channel equalization by increasing the convergence rate and decreasing the steady-state mean square error. 相似文献
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By minimizing a deterministic criterion of the constant modulus (CM) type or of the decision-directed (DD) type, we derive normalized stochastic gradient algorithms for blind linear equalization (BE) of QAM systems. These algorithms allow us to formulate CM and DD separation principles, which help obtain a whole family of CM or DD BE algorithms from classical adaptive filtering algorithms. We focus on the algorithms obtained by using the affine projection adaptive filtering algorithm (APA). Their increased convergence speed and ability to escape from local minima of their cost function make these algorithms very promising for BE applications 相似文献
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Motivated by increasing interest in energy efficient modulations, we provide the first look at adaptive equalization of biorthogonal signaling. While this modulation has historically been considered only for use in narrowband systems without intersymbol interference (ISI), recent attention has been given to its use in ISI channels. Due to the fact that biorthogonal modulation (BOM) results in a source that is not i.i.d., however, classical blind adaptive equalization techniques cannot be directly applied to equalization of BOM signals. We first examine minimum mean-squared error (MMSE) and least mean squares (LMS)-based equalizers, and identify some peculiarities that arise in equalization of BOM signals when compared to more traditional modulations like binary phase shift keying (BPSK). Next, we present two novel blind algorithms for the adaptive equalization of BOM signals: LTBOMB and TROMBONE. We discuss the convergence properties of these algorithms, and demonstrate their performance with numerical simulations 相似文献
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The polycepstra and prediction equalization algorithm (POPREA) is proposed for blind equalization of nonminimum phase channels. The algorithm equalizes the amplitude and phase of the channel independently by employing linear prediction and tricepstrum principles, respectively. It guarantees convergence to a global solution. The tracking and cancellation of phase due to carrier frequency offset is carried out independently of equalization. It is demonstrated, by means of computer simulations, that the proposed POPREA is able to open the eye pattern of QAM signal constellations faster than existing polyspectra-based equalizers. The complexity of the algorithm is high but comparable to that of polyspectra equalizers 相似文献
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In this paper, we study the blind equalization problem of time-varying (TV) systems where the channel variations are too rapid to be tracked with conventional adaptive equalizers. We show that using a finite Fourier basis expansion, a TV antenna array system can be cast into a time-invariant multi-input, multi-output (MIMO) framework. The multiple inputs are related through the bases, thereby allowing blind equalization to be accomplished without the use of higher order statistics. Two deterministic blind equalization approaches are presented: one determines the channels first and then the equalizers, whereas the other estimates the equalizers directly. Related issues such as order determination are addressed briefly. The proposed algorithms are illustrated using simulations 相似文献
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