共查询到20条相似文献,搜索用时 0 毫秒
1.
A new class of gradient adaptive step-size LMS algorithms 总被引:2,自引:0,他引:2
The gradient adaptive step-size least-mean-square (LMS) algorithms [an important family of variable step-size LMS (VSLMS) algorithms] are revisited. We propose a simplification to a class of the studied algorithms and show that this leads to a new class of VSLMS algorithms with reduced complexity but with no observable loss in performance 相似文献
2.
A new class of dithering algorithms for black and white (B/W) images is presented. The basic idea behind the technique is to divide the image into small blocks and minimize the distortion between the original continuous-tone image and its low-pass-filtered halftone. This corresponds to a quadratic programming problem with linear constraints, which is solved via standard optimization techniques. Examples of B/W halftone images obtained by this technique are compared to halftones obtained via existing dithering algorithms. 相似文献
3.
We introduce a novel framework for soft-input, soft-output (SISO) equalization in frequency selective multipleinput multiple-output (MIMO) channels based on the well-known belief propagation (BP) algorithm. As in the BP equalizer, we model the multipath channels using factor graphs (FGs) where the transmitted and received signals are represented by the function and variable nodes respectively. The edges connecting the function and variable nodes illustrate the dependencies of the multipath channel and soft decisions are developed by exchanging information on these edges iteratively. We incorporate powerful techniques such as groupwise iterative multiuser detection (IMUD), probabilistic data association (PDA) and sphere decoding (SD) in order to reduce the computational complexity of BP equalizer with relatively small degradation in performance. The computational complexity of this new reduced-complexity BP (RCBP) equalizer grows linearly with block size and memory length of the channel. The proposed framework has a flexible structure that allows for parallel as well as serial detection. We will illustrate through simulations that the RCBP equalizer can even handle overloaded scenarios where the channel matrix is rank deficient, and it can achieve excellent performance by applying iterative equalization using the low-density parity check codes (LDPC). 相似文献
4.
In the letter a new technique for increasing the efficiency of an automatic-repeat-request communication system is described. This technique uses all the received versions of a codeword, and also those versions containing errors. Such a strategy, together with a soft demodulation of each received symbol, is particularly efficient when applied to ARQ schemes in which each block erroneously received is retransmitted many times. 相似文献
5.
Jungwon Lee Ji-Woong Choi Hui-Ling Lou Jongsun Park 《Communications Letters, IEEE》2009,13(10):736-738
In this letter, we propose a soft-decoding ML MIMO demodulation method that lowers the complexity of the existing ML method. The proposed method finds the nearest point without calculating the Euclidean distance by exploiting the regular structure of bit-to-symbol mapping. It enables significant reduction of the number of distance calculations which is a major complexity burden. 相似文献
6.
《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1985,73(8):1336-1338
This letter features the derivation of a new recursive maximum-likelihood (RML) algorithm. A simplified version of this algorithm is the same as the RML algorithm proposed in [1]. The relative performance of these algorithms is studied with the help of an example in spectral estimation. 相似文献
7.
Two different methods of soft-decision demodulation for channels with finite intersymbol interference (ISI) in the presence of additive white Gaussian noise (AWGN) are analyzed. In both schemes, the cutoff rate R 0 of the discrete channel created by the demodulator output quantization is chosen as the design criterion. Expressions for the optimal thresholds of the quantizer associated with the demodulation of binary signals are derived. Results for the channel with memory equal to one symbol duration are presented. As a special case, the (1-D) channel with soft decision demodulation is analyzed. Closed-form solutions show that a 4-b quantizer improves performance substantially in this case 相似文献
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干涉图象相位解调是信息光学处理的重要内容,其解调算法的复杂性、鲁棒性以及精度直接影响干涉法测量参数的实用性与精度。本文对三种相位解调算法1)基于傅立叶变换的分析算法(FTA)、2 )干涉图象分块多项式拟合迭代算法以及3 )基于小波变换的相位梯度解调算法的原理及性能进行了研究和比较。仿真实验表明,基于小波变换的相位梯度解调算法具有较高的精度和较好的鲁棒性。 相似文献
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一种新的FBG传感信号解调技术研究 总被引:1,自引:0,他引:1
在基于当前FBG传感信号解调技术的基础上,提出了基于可调谐法布里一珀罗(F-P)滤波法和非平衡马赫一曾德尔(M-z)滤波法的FBG解调方法,并进行了系统仿真模型的设计,对其仿真结果与单独的可调谐F-P滤波法和非平衡M-z滤波法的仿真结果进行了比较.结果表明这种方法的性能得到了明显的提高,适用于FBG传感信号的静态和动态解调. 相似文献
12.
Conventional gradient-based adaptive filters, as typified by the well-known LMS algorithm, use an instantaneous estimate of the error-surface gradient to update the filter coefficients. Such a strategy leaves the algorithm extremely vulnerable to impulsive interference. A class of adaptive algorithms employing order statistic filtering of the sampled gradient estimates is presented. These algorithms, dubbed order statistic least mean squares (OSLMS), are designed to facilitate adaptive filter performance close to the least squares optimum across a wide range of input environments from Gaussian to highly impulsive. Three specific OSLMS filters are defined: the median LMS, the average LMS, and the trimmed-mean LMS. The properties of these algorithms are investigated and the potential for improvement demonstrated. Finally, a general adaptive OSLMS scheme in which the nature of the order-statistic operator is also adapted in response to the statistics of the input signal is presented. It is shown that this can facilitate performance gains over a wide range of input data types 相似文献
13.
提出了一种以PC机声卡作为采集卡,以PC机的CPU代替DSP器件的QPSK信号的数字化实时解调方法。详细介绍了适合于PC机实时处理的载波频率恢复、符号定时恢复、自适应信道均衡等QPSK信号实时解调的核心算法。最后,结合PSK31的QPSK信号给出了整个系统的测试结果。 相似文献
14.
V. A. Bogdanovich A. G. Vostretsov 《Journal of Communications Technology and Electronics》2010,55(8):893-899
Multiuser demodulation algorithms oriented to application under the conditions of a priori uncertainty of the noise distribution
and the energy parameters of noise and signals are proposed. The principles of asymptotic robustness and invariance are used
for construction of such algorithms. The a priori uncertainty of the noise distribution is overcome based on the principle
of asymptotic robustness. The invariance principle provides for suppression of multiple access noise with a priori uncertain
characteristics. The asymptotic (with respect to the size of an observed sampling) approach to algorithm construction is due
to a large signature base. 相似文献
15.
相比于传统多输入多输出(MIMO)系统,大规模MIMO的天线数量大幅增加,使得系统的容量提升、误比特率下降,但也造成预编码矩阵维度升高,算法复杂度、系统成本及实现难度增大。将大规模MIMO系统主要采用的预编码技术分为线性和非线性两个部分,对两者进行了归纳和对比,并着重介绍了几种经过简化的线性预编码算法和几种比较典型的非线性预编码算法,指出因为非线性算法的复杂度很高,故未来大规模MIMO系统的预编码应当以线性算法为主。 相似文献
16.
This paper addresses the issue of advanced equalization methods for space-time communications over multiple-input multiple-output block fading channel with intersymbol interference. Instead of resorting to conventional multiuser detection techniques (based on the straightforward analogy between antennas and users), we adopt a different point of view, and separate time equalization from space equalization, thus introducing a higher degree of freedom in the overall space-time equalizer design. Time-domain equalization relies on minimum mean-square error criterion and operates on multidimensional modulation symbols, whose individual components can be detected in accordance with another criterion. In particular, when the optimum maximum a posteriori criterion is chosen, substantial performance gains over conventional space-time turbo equalization have been observed for different transmission scenarios, at the price of an increased, albeit manageable, computational complexity. 相似文献
17.
A new class or adaptive infinite impulse response ( IIR) or recursive filter algorithms is obtained by incorporating a simple modification in the correction vectors of some existing algorithms. The resulting class of algorithms explores the inherent parallelism present in their coefficient update equations, and hence the possibility of faster initial convergence. Two IIR filter algorithms are considered for discussion and simulation. 相似文献
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本文提出采用DSP和软件解调技术实现NAVTEX接收机的方法,应用基于短时快速傅立叶变换的方法实现了NAVTEX信号软件解调,克服了传统NAVTEX接收机硬件相干解调所具有的受环境、温度等外界因素影响而导致误码率升高等问题,有效地提高了NAVTEX接收机的环境适应性和工作可靠性。 相似文献
20.
Locally optimal soft handoff algorithms 总被引:5,自引:0,他引:5
The design of soft handoff algorithms for cellular radio systems is considered. The design problem is posed as a tradeoff between three metrics: the rate of handoffs, the mean size of the active set, and the link quality. It is argued that the algorithm that optimizes the tradeoff among these metrics is impractical. Hence, a locally optimal (LO) handoff algorithm is derived as a practical approximation to the optimal handoff algorithm. The LO algorithm is shown to yield a significantly better tradeoff than the static threshold handoff algorithm used in second-generation code-division multiple-access (CDMA) systems. It is also shown that the dynamic threshold algorithm, which is an ad hoc algorithm proposed for third-generation CDMA systems, achieves nearly the same performance as the LO algorithm. Thus, an analytical justification is developed for the dynamic threshold algorithm. Further, the handoff algorithm design is separated into independent design problems on the forward and reverse links. The forward link LO algorithm is shown to be computationally intensive but is also shown to be closely approximated by the simpler reverse link LO algorithm. 相似文献