Modelling and Simulation of IDMA-OFDM for Underwater Acoustic Communication

The Ocean exhibits phenomenon of changing acoustic signal transmission due to its non-stationary nature. Water columns in between transmitter and receiver are not fixed at any point of time. Thus, designing of a wireless communication systems for underwater applications becomes significantly challenging. The speed of sound in water is 1500 m/s which introduces large delay spread in acoustic signal due to multipath phenomenon. The large time delay causes Inter-symbol Interference; this ISI degrades the performance of many receivers. However orthogonal frequency division multiplexing is multi-tone modulation reduces long time delay spreads of acoustic channels. The interleave division multiple access distinguishes each user with the unique random interleaver code. The IDMA-OFDM is superior design for reducing error bursts in multi-access underwater applications. A Simulink based simulation modell of IDMA-OFDM system has been discussed in this paper. Satisfactory performance of the implementation was observed through analysis of BER with respect to SNR. The results have been concluded by comparing simulated data in BER tool of Simulink.Defence Science Journal, Vol. 65, No. 4, July 2015, pp. 307-311, DOI: http://dx.doi.org/10.14429/dsj.65.860

MIMO-OFDM AND IDMA SCHEME IN UNDERWATER COMMUNICATION

Under water acoustic communication has been growing rapidly from last few decades due to its application i.e. in oceanography, marine research and defense. There is big need of underwater communication technique to explore oceans but it is not as simple as in air. It is quite different from air communication. Electromagnetic waves, optical fiber or coaxial wire cannot be used in underwater because of its limitation. However it is still challenging to communicate in underwater because of the different parameters of channels such as fading, bandwidth limitations, multi-paths or refractive properties of sound channel. That’s why there is only one reason to use acoustics waves but the bandwidth of its signal is very low. Due to low speed of acoustic waves, fading problem occurs. We require high spectral efficiency for superior communication i.e. data rate is high and fading is low. For minimizing this problem we have been used MIMO-OFDM scheme with IDMA. MIMO is the technique in which we use multiple antennas at the transmitter and the receiver side. We use same channel for sending and receiving more than one data signal. Thus by using this technique the data rate is increased and OFDM save the bandwidth and avoids fading