Investigation of Channel Modeling and Simulation of OFDM Based Communication Near Northern Regions of Arabian Sea

摘要

Wideband nature of oceanic channel when dealing with multicarrier acoustic subcarriers introduces severe Doppler shifts, little variations may cause overlapping of subcarriers such that entire signal can get completely distorted. Therefore, one of the major problems in OFDM based underwater acoustic communication is the sensitive nature of wideband acoustic subcarriers. In this study, Bellhop beam tracing is used to model two regions in the north of Arabian Sea and the two-step receiver algorithm is used over these channel models. Multipath with delay channel model is obtained using the Bellhop ray tracing algorithm while random Doppler shift is induced in MATLAB on each block and also in the complete OFDM packet. In the first step, resembling converts a wideband problem in to narrowband problem and in the second step; high resolution Carrier Offset Frequency (CFO) tracking compensates the residual Doppler. Cyclic Prefix (CP) OFDM scheme based on block-by-block processing is deliberated here for fast varying channel. In the proposed algorithm, null subcarriers are facilitated for Doppler removal while pilot bits are used for Least Square (LS) channel estimation. Simulation on MATLAB is carried out on both channels, i.e., near Gawadar Coast and Karachi Harbor; satisfactory results are achieved in terms Low Bit Error Rates (BER) even in high relative speed between transmitter and receiver. These results further suggested and make convinced for the experimental test/ trials, specifically in the region of north Arabian Sea.