ALAMOUTI SPACE-TIME CODING SCHEME ASSISTED BY METAMATERIAL-ENHANCED MAGNETIC INDUCTION(M2I) FOR UNDERWATER ACOUSTIC COMMUNICATION

Abstract

The acoustic distributed Multi-Input-Multi-Output(MIMO) systems implementedas Alamouti Space-time coding is equipped in the Underwater Robot Swarms(URSs)used to enable a long range and high throughput communication system. However,the acoustic transducers cannot provide real-time and accurate synchronization for the distributed transmitters due to the large delay of acoustic channels in the underwater environment. In addition, the narrow bandwidth of the acoustic transducers leads to an increase in synchronization time and errors. To overcome the aforementioned drawbacks, an M2I assisted acoustic distributed MIMO system is implemented. Since the M2I antenna has high propagation speed, there is a reduction in the time taken for synchronization. To quantitatively analyze the improvement of the system, we deduce the synchronization errors, Signal-to-NoiseRation (SNR) and the Bit error rate (BER) of the system. The Alamouti encoded system is finally implemented on an indoor tank test bed setup to validate the results.To make computations more feasible, Out-Of-Tree(OOT) modules are created on GNU-Radio to implement the Alamouti encoding and decoding blocks.