Noise improvement of SNR gain in parallel array of bistable dynamic   systems by array stochastic resonance
  We report the regions where a signal-to-noise ratio (SNR) gain exceeding unity exists in a parallel uncoupled array of identical bistable systems, for both subthreshold and suprathreshold sinusoids buried in broadband Gaussian white input noise. Due to independent noise in each element of the parallel array, the SNR gain of the collective array response approaches its local maximum exhibiting a stochastic resonant behavior. Moreover, the local maximum SNR gain, at a non-zero optimal array noise intensity, increases as the array size rises. This leads to the conclusion of the global maximum SNR gain being obtained by an infinite array. We suggest that the performance of infinite arrays can be closely approached by an array of two bistable oscillators operating in different noisy conditions, which indicates a simple but effective realization of arrays for improving the SNR gain. For a given input SNR, the optimization of maximum SNR gains is touched upon in infinite arrays by tuning both array noise levels and an array parameter. The nonlinear collective phenomenon of SNR gain amplification in parallel uncoupled dynamical arrays, i.e. array stochastic resonance, together with the possibility of the SNR gain exceeding unity, represent a promising application in array signal processing. 
Fabing Duan, Francois Chapeau-Blondeau, Derek Abbott