The Performance Comparisons between the Unconstrained and Constrained Equalization Algorithms

This paper proposes two unconstrained algorithms, the Steepest Decent (SD)algorithm and the Conjugate Gradient (CG) algorithm, based on a superexcellent cost function. At thesame time, two constrained algorithms which include the Constrained Steepest Decent (CSD) algorithmand the Constrained Conjugate Gradient algorithm (CCG) are deduced subject to a new constraincondition. They are both implemented in unitary transform domain. The computational complexities ofthe constrained algorithms are compared to those of the unconstrained algorithms. Resultingsimulations show their performance comparisons.

Joint receiving mechanism based on blind equalization with variable step size for M-QAM modulation

The problem of inter symbol interference（ ISI） in wireless communication systems caused by multipath propagation when using high order modulation like M-Q AMis solved. Since the wireless receiver doesn＇t require a training sequence,a blind equalization channel is implemented in the receiver to increase the throughput of the system. To improve the performances of both the blind equalizer and the system,a joint receiving mechanismincluding variable step size（ VSS） modified constant modulus algorithms（ MC-MA） and modified decision directed modulus algorithms（ MD DMA） is proposed to ameliorate the convergence speed and mean square error（ MSE） performance and combat the phase error when using high order QAM modulation. The VSS scheme is based on the selection of step size according to the distance between the output of the equalizer and the desired output in the constellation plane. Analysis and simulations showthat the performance of the proposed VSS-MCMA-MD DMA mechanismis better than that of algorithms with a fixed step size. In addition,the MCMA-MDDMA with VSS can performthe phase recovery by itself.

Self-adjusting decision feedback equalizer for variational underwater acoustic channel environments

Aimed at the abominable influences to blind equaliza-tion algorithms caused by complex time-space variability existing in underwater acoustic channels, a new self-adjusting decision feedback equalization （DFE） algorithm adapting to different under-water acoustic channel environments is proposed by changing its central tap position. Besides, this new algorithm behaves faster convergence speed based on the analysis of equalizers’ working rules, which is more suitable to implement communications in dif-ferent unknown channels. Corresponding results and conclusions are validated by simulations and spot experiments.

A new algorithm of background equalization in digtal sonar

Background equalization technique has been extensively studied in the field of fre quency spectrum analysis. It has been proved an effective method to improve line spectrum extraction. In a multi-beam digital sonar system, the time/bearing display is the most im portant interface between signal processing module and console module. It has been proved that the system gain is often lost in the illterface between these two modules. Background equalization technique can improv the overall performance of the time/bearing display win dow. The result of post processing of multi-beam data is filtered each time before displayed in screen. It is shown that the algorithm of median value filtering combined with OTA (Order Truncate Average) method is an efficient technique to equalize the non-uniform, non-stationary background data. A variable length of window is adopted to match the different width of main lobe of beam patterns. The results of system simulation show that the algorithm described in this paper is efficient in the case that the background of multi-beam data is not uniform

Blind equalization of underwater acoustic channel using a combined constant modulus algorithm

A kind of Combined Constant Modulus Algorithm (CCMA) is presented to compensate the defects of the Constant Modulus Algorithm (CMA) and the Sign Error CMA (SECMA). And CCMA is applied to the equalization of the underwater acoustic channel (UWAC). Based on the decision of the equalizer’s output, its iteration process switches between

Evolving ADSL Channel Equalizer

The time domain equalizer of ADSL Channel plays an important role in whole receiving process to high speed bit streams. In this paper, a novel ADSL channel equalization method based on evolutionary algorithm is proposed, in which we establish the equalizer through the method of channel identification.The proposed method is capable of simultaneously evolving both coefficients and the ranks of the equalizer and therefore it can be applied to different characteristics of loops. Experimental results show our method has better performance (short search time and high modeling precision).