Blind equalizers with simulated annealing optimization for digital communication systems

New batch-type methods and their recursive extensions are introduced for blind equalization of digital communication channels. Based on the underlying cost function of the existing Bussgang and cumulantfitting algorithms, simulated annealing (SA) optimization is successfully employed to identify and equalize the communication channels. Many of the existing blind equalization algorithms utilize a stochastic gradient approach to minimize non-linear cost functions. Owing to the multimodal nature of these functions, the gradient algorithms might converge to the wrong solution. In contrast, the proposed methods are based on a global optimization algorithm. the SA algorithm tends to avoid the local minima encountered. The feasibility and convergence behaviour of the proposed algorithms are examined by means of computer simulations. Computational complexity issues in the implementation of the algorithms are discussed.     

Influence of bioflavonoids from the radix extract of Scutellaria baicalensis on the level of serum lipids, and the development of laboratory rats fed with fresh and oxidized fats

The aim of this study was to assess the influence of bioflavonoids from the radix of Scurellaria baicalensis on the level of lipids, via the determination of the concentrations of triglycerides, total cholesterol and high-density lipoprotein (HDL) cholesterol in the plasma of laboratory rats fed high-fat and high-cholesterol diets, and via the calculation of their atherogenic index. We also studied the influence of bioflavonoids on their physical development by measuring the increase in their body mass and liver mass. The rats were fed a diet with a 15% content of fresh or oxidized lard or sunflower oil, along with 0.5% added cholesterol. 0.05% S. baicalensis radix extract was added to the diet of half of the rats as the source of bioflavonoids. In the group of rats fed a diet containing oxidized oil we observed a significantly lower increase in body mass (15.5 +/- 7.6 g/4 weeks/rat) than that observed for the control rats (77.0 +/- 15.7 g/4 weeks/rat). The addition of S. baicalensis radix extract to the diet raised the increase in body mass in the groups receiving oil as the source of fat; those receiving fresh oil had a 40% increase, and those receiving oxidized oil showed a 300% increase relative to the appropriate controls. In all the groups of rats fed a diet with bioflavonoids added, a beneficial decrease in the plasma triglyceride content was observed relative to the appropriate controls. In the plasma of rats on a diet containing the extract and fresh or oxidized oil or fresh lard, we observed a beneficial reduction in the total cholesterol level relative to the appropriate controls. The atherogenic index was higher for the group of animals fed with fresh lard than for those fed with fresh oil, and higher for those fed with oxidized oil than for those fed with oxidized lard. The addition of bioflavonoids to the diet beneficially reduced the atherogenic index value in the group fed with fresh oil, and increased its value in the group fed with oxidized lard.     

Comparison of the effects of microwave cooking and conventional cooking methods on the composition of fatty acids and fat quality indicators in herring

The aim of this study was to examine the changes which occur under the influence of different heating methods in the compositions of fatty acids and selected fat quality indicators in fillets of herring. The results that are compared herein were obtained via conventional culinary techniques and using microwave radiation. Culinary processes like boiling, grilling and frying, whether done conventionally or with a microwave oven, did not lead to a reduction in the n-3 polyunsaturated fatty acids (PUFAs) fraction of the total fatty acids, indicating that these fatty acids have a high durability and a low susceptibility to thermal oxidative processes. The culinary processes used in this study also had an insignificant influence on the fat quality indicators--the peroxide and anisidine value. The fat quality indicators in herring, both after conventional and microwave heating, differ little, and indicate a low content of primary and secondary products of oxidation.     

Analytic alpha-stable noise modeling in a Poisson field ofinterferers or scatterers

This paper addresses non-Gaussian statistical modeling of interference as a superposition of a large number of small effects from terminals/scatterers distributed in the plane/volume according to a Poisson point process. This problem is relevant to multiple access communication systems without power control and radar. Assuming that the signal strength is attenuated over distance r as 1/r/m, we show that the interference/clutter could be modeled as a spherically symmetric α-stable noise. A novel approach to stable noise modeling is introduced based on the LePage series representation. This establishes grounds to investigate practical constraints in the system model adopted, such as the finite number of interferers and nonhomogeneous Poisson fields of interferers. In addition, the formulas derived allow us to predict noise statistics in environments with lognormal shadowing and Rayleigh fading. The results obtained are useful for the prediction of noise statistics in a wide range of environments with deterministic and stochastic power propagation laws. Computer simulations are provided to demonstrate the efficiency of the α-stable noise model in multiuser communication systems. The analysis presented will be important in the performance evaluation of complex communication systems and in the design of efficient interference suppression techniques     

Detection in alpha-stable noise environments based on prediction

In this paper we consider detection of baseband signals in partial response signalling (PRS) systems in the presence of additive, coloured noise. The additive noise in the system is a mixture of Gaussian noise and impulsive noise modelled as an alpha-stable process. The dependence in observation samples results from the excess bandwidth in the matched filters of the receivers. The detectors proposed are based on a noise estimation–cancellation technique. In particular, by exploiting past decisions as well as past received samples, we estimate the noise and subsequently cancel it. We adopt two approaches for designing predictors: in the first we use a minimum mean square error (MMSE) criterion and we employ Volterra filters as predictors; in the second we use the minimum dispersion (MD) criterion and we limit our attention to linear predictors. The effects of the predictor order, the number of exploited samples and the filtering allocation on the system performance are examined through Monte Carlo simulations. It is demonstrated that the proposed detectors, while having simple structures, offer substantial performance improvements over conventional detectors. © 1997 John Wiley & Sons, Ltd.     

Performance of FH SS radio networks with interference modeled as amixture of Gaussian and alpha-stable noise

We consider the performance of frequency-hopping spread spectrum (FH SS) radio networks in a Poisson field of interfering terminals using the same modulation and power. The problem is relevant to wireless random-access communication systems where little information about transmitters requires stochastic modeling of their positions. Assuming that the signal strength is attenuated over distance r on average as 1/r ^m, we show that the interference in the network could be modeled as a mixture of Gaussian and α-stable noise. Based on this modeling, we derive expressions for the probability of error (P_e ) for systems with M-ary frequency shift keying (FSK) which use conventional envelope detectors. Because conventional envelope detectors are optimum only in Gaussian noise and are suboptimum in the noise considered, we also investigate noncoherent detectors which offer improved performance. We examine receivers with limiting nonlinearities and detectors which are optimal in Cauchy noise. Numerical calculations and Monte Carlo simulations are provided to confirm the accuracy of the analysis presented. The results obtained are useful in the performance evaluation of multiple-access radio networks in environments varying from urban settings to office buildings with deterministic and stochastic propagation laws such as lognormal shadowing and Rayleigh fading     

QoE‐ and energy‐efficient resource optimization in OFDMA networks with bidirectional relaying

Because of the surging demands of multimedia services, quality‐of‐experience (QoE) is becoming an important metric to evaluate network quality from users' perspective. In this paper, resource optimisation to achieve optimal tradeoff between QoE and energy consumption in bidirectional orthogonal frequency‐division multiple‐access relaying networks is addressed so as to provide satisfactory multimedia delivery quality and support green communications. We first formulate a QoE‐energy efficiency tradeoff optimisation where QoE requirements and relaying traffic balance are considered and prove that QoE‐energy efficiency is quasiconcave on QoE, which suggests the existence of a unique global optimal tradeoff point. We then propose an optimisation framework to achieve the optimal tradeoff efficiently. With the framework, we develop resource allocation approaches for two specific relaying strategies, that is, two‐phase decode‐and‐forward relaying with dynamic XOR network coding and compute‐and‐forward relaying with physical network coding via structured codes. Numerical results validate theoretical findings and demonstrate the effectiveness of the proposed optimisation solution for achieving the tradeoff between QoE and energy consumption. Copyright © 2015 John Wiley & Sons, Ltd.