In this paper, we present an extension of linear communication channels identification algorithms to non linear channels using higher order cumulants (HOC). In the one hand, we develop a theoretical analysis of non linear quadratic systems using second and third order cumulants. In the other hand, the relationship linking cumulants and the coefficients of non linear channels presented in the linear case is extended to the general case of the non linear quadratic systems identification. This theoretical development is used to develop three non linear algorithms based on third and fourth order cumulants respectively. Numerical simulation results example show that the proposed methods able to estimate the impulse response parameters with different precision.Keywords: Higher order cumulants, Blind identification, Non linear quadratic systems.
Copyright c 2016 Institute of Advanced Engineering and Science
IntroductionApplications of higher order cumulants theory in the blind identification domain are widely used in various works [1]-[3], [6,7]. Several models are identified in the literature such as the linear and non linear systems. In the part of the linear case, we have important results established that the blind identification is possible only from the second order cumulants (autocorrelation function) of the output stationary signal, but these methods is not able to identify correctly the channel models excited by non Gaussian signal and affected by Gaussian noise, because the additive Gaussian noise will be vanish in the higher order cumulants domain. The sensitivity of the second order cumulants to the additive Gaussian noise appealed to other blind identification methods exploiting the cumulants of order superieur than two [4,5]. There are several motivations behind this interest, first the methods based on HOC are blind to any kind of a Gaussian process, whereas autocorrelation function (second order cumulants) is not. Consequently, cumulants based methods boost signal to noise ratio (SNR) when signals are corrupted by Gaussian measurement noise. Second, the HOC methods are useful in identifying non minimum phase systems and in reconstructing non minimum phase signals when the signals are non Gaussian.The linear models are not efficient for representing and modeling all systems, because the majority of systems are represented by non linear models [7,8]. However, when linear modeling of the channel is not adequate, the non linear modeling appeared like an alternative efficient solution in most real cases. Moreover, quadratic non linear systems are widely used in various engineering fields such as signal processing, system filtering, predicting, identification and equalization [9,10].In this contribution, firstly we present a theoretical development of non linear quadratic systems using higher order cumulants. Indeed, we develop the relationship linking third order cumulants and the coefficients of non linear channels, then the method developed [11] for linear channels, is extended to the general case ...