The Study Of Adaptive Equalization And Spitial Diversity Technology Applied To UWA Communication

Nowadays, digital communication through band-limited underwater acoustic channel (UWAC) is of general interest in the field of underwater communication. In order to achieve high data rates on the severely band-limited underwater acoustic channels, bandwidth-efficient modulation techniques must be employed, together with some sophisticated signal processing algorithms, such as adaptive equalization technique for the intersymbol interference caused by channel multipath propagation.To attain reliable data transmission over UWA channels, spatial diversity technology and adaptive equalization technology are selected as major research issue. The main content in this paper are as follows:All kinds of linear and nonlinear adaptive equalization and typical algorithms are studied elaborately. And their performances are compared by simulation. On the base of above algorithms, corresponding derive algorithms are simulated and analyzed. To decrease operation of the equalization algorithm, the block equalization, sparse algorithm and the algorithm based on channel estimated are deduced in detail, also these algorithms simulation and comparison have been done. Several general methods of signal diversity process are described, and the principle of the joint equalization combiner and MMSE equalization combiner are deduced in detail to test computation complexity of the structure. The principles of the linearity diversity equalizer and decision feedback diversity equalizer are presented, and the MMSE of the latter is proved to be better than the former. Multi-channel adaptive algorithms are presented and comparison, and the performance difference between the spatial diversity equalizer and general equalizer are testified by simulation. On the base of spatial diversity equalization the artificial neural network technique is combined. The recursion neural network diversity equalizer ispresented, also the corresponding improved adaptive update algorithm, and the validity of the structure and algorithm are testified. To track the Doppler shift, the second order digital phase lock loop is combined with the spatial diversity equalizer. The simulation and test results show that the method can compensate the fast change of the carrier wave phase caused by the time-vary of UWAC.To improve the efficiency of UWAC, the multi input and multi output (MEMO) system is studied, and the computer simulation is done for the performance. The acoustic communication test is completed in Songhua Lake in Jilin province. Using these data, we demonstrate the efficiency of several equalization algorithms, including compassion study and evaluation of their performance.