En Cheng

A simulation based on Gilbert-Elliot packet loss model is developed to simulate an image transmitting system in underwater acoustic channel. This developed system is applied as a platform to study the relation between image quality assessment parameter PSNR, image activity measure (IAM) and channel's packet loss rate. A group of sample images were transmitted in this communication system and a formula of PSNR, the initial value of IAM, and packet loss rate was fitted by the data from the degraded sample images. With the help of the fitted formula, then we are able to predict the possible quality of image transmission, and beforehand choices of channel or source processing techniques in the communication system becomes possible, too. Experimental results indicate that the predicting method of underwater image transmitting quality based on Gilbert-Elliot model can provide certain references for establishing strategies of underwater image transmission. © 2013 ACADEMY PUBLISHER.

SNR (Signal to Noise Ratio) estimation is a very important parameter for channel estimation of the communication system. In this paper, some SNR estimation methods of digital modulation system are applied and improved in FM modulation system. Then we summarize several SNR estimation methods (EHM (Envelope High order Moment method), SE (Spectrum Estimation method), FD (Frequency Domain method), EMV (Envelope Mean Variance method), M2M4 (Second order and Fourth order Moment method)). Furthermore, according to the characteristics of FM modulation system, we put forward the improvement of M2M4 and also discuss the optimal algorithm for underwater acoustic Rayleigh channel, Rician channel and Bellhop channel by comparing these methods.