Noise and Signal Power Reduction in Radio over Fiber Distributed Antenna System
Md Salik Parwez (1251128)
The radio over fiber (RoF) distributed antenna system (DAS) has been chosen as a potential candidate for future generation wireless communication systems. In RoF DAS, the signal after passing through wireless channel suffers from noise and multi path distortion. Moreover the optical components as well as the amplifiers in RoF along with additional circuitries involved, introduce extra noise and distortion to already noised signal. These noise and distortion causes problem to extract the signal at the receiver. Also it imposes limit on the applicable input power to the RoF components. It is therefore necessary to estimate the channel to accurately extract the exact information from the noised and distorted signal. In this research, we propose alternative method to reduce signal power before passing the signal to RoF system. This is achieved by modifying the conventional channel estimation methods i.e., LS and MMSE. This method, besides reducing the computation, also causes gain in signal to noise ratio (SNR) by 3-4 dB. Also in order to reduce the noise level, we propose wavelet decomposition based noise suppression. After performing computer simulation, it was found that the wavelet based method considerably reduced the noise which also resulted in gain of 3-5 dB at low SNR region while at higher SNR, it reaches near ideal performance.