Acoustic channel modeling and simulation

The simulator generates a series of channel impulse responses for a given time-varying underwater acoustic channel geometry. It addresses the effects of multipath, rough surface scattering, motion-induced Doppler, and large-scale channel variation.

Acoustic channel simulator 

Multi-FFT detection of OFDM signals in time-varying channels

Multi-FFT demodulation techniques include partial FFT (P-FFT), shaped FFT (S-FFT), fractional FFT (F-FFT), and Taylor series FFT (F-FFT). These techniques are beneficial on channels where residual Doppler shifting and time-variation are not negligible over the duration of an OFDM block.


Packet coding for fading channels with long delays

Random linear packet coding improves the reliability and throughput efficiency on channels with long propagation delays, such as the underwater acoustic channels. Adaptive power and rate control are combined with packet coding to counteract large-scale fading.

Joint power and rate control 

Acoustic multicarrier ICI-mitigating receiver

In mobile acoustic systems, Doppler effect can be severe enough that the received OFDM signal experiences non-negligible frequency offsets even after initial resampling. In situations with high mobility, however, OFDM systems are challenged by thetime-variability of the channel, as the relative motion between transmitter and receiver creates carrier-dependent Doppler shifts, thus introducing inter-carrier interference (ICI) which has a detrimental impact on data detection performance. Reliable coherent data detection requires the channel state information at the receiver. Pilot-assisted channel estimation based on physical propagation model is used to obtain the necessary channel state information for reliable coherent communications. When multiple receive elements are available, correlation between the elements, if exists, can be exploited to reduce the signal processing complexity without compromising the performance.

Acoustic multicarrier ICI-mitigating receiver 

Exploitation and exploration in actuated communication networks

This NSF-supported project aims to design mobile underwater acoustic networks in which navigation mechanisms for communication-constrained autonomous underwater vehicles is integrated with sensing and classification to provide solutions for the exploration-exploitation tradeoff. The project is a collaboration between Northeastern University, University of Southern California and Massachusetts Institute of Technology. An MIT news article that describes some of our work is here. More about our project, along with relevant publications, can be found here.