Research On Beaforming Of CDMA Based On Stochastic Resonance

As a key technology in smart antenna array, beamforming can effectively deal with the scarce problem of spectrum resource. Smart antenna array obtains the degree of freedom of the space-time in communications system, and makes use of the different direction of user’s signal. Adopting SDMA can seperate the signals of the same time, same frequency and same code, thus can significantly improve spectrum efficiency and enlarge system capacity. However, the accuracy of beamforming will be disturbed by noise, espcially in low signal-to-noise ratio, array performance and output signal-tonoise ratio will greatly decrease. The beam formation of array antenna can not accurately align the direction of users. Then beamforming will be useless in separating users in airspace and cancelling interference. Therefore, the improvement of the accuracy of beamforming in low SNR is a worth researching topic.Aiming at above problems, this paper will study the stochastic resonance and beamforming structure and algorithm. In the proposed structure, the received signal will be treated by stochastic resonance system, the weak signal submerged in the strong noise will be extracted, and then the adaptive array signal processing will work. In view of the high sampling rate requirements of stochastic resonance system, this paper mainly studies in the high frequency band(3~30M) beamforming.The main content of this paper is as follows:1.This paper detailedly introduces stochastic resonance model system based on Langevin equation, such as emulate the detection of weak communication signal.2.The general nonlinear stochastic resonance system(parameter, a=1 b=1) will be constraint by low frequency parameters in the detection of weak signal, which will cause great difficulties to practical application. In view of this situation, the author of this paper puts forward the double sampling method and the adjustment coefficient method to detect high frequency weak signal.3. Based on bistable system with tunable parameters, this paper studies the mutual relationship between input signal frequency and parameter. For the submerged input signal with different frequency in strong noise, this paper puts forward an adaptive adjustment of parameter, which will promote input signal frequency and bistable system to achieve the best effect of resonance.4.On the basis of the above research, this paper puts forward a kind of adaptive array antenna signal processing structure, applies the adaptive stochastic resonance to multi-target adaptive array algorithms, and promotes the performance of the algorithm greatly increases through the emulation in the very low SNR.