Adaptive OFDMA for downlink underwater acoustic communications

Multiuser communication has been an important research area of underwater acoustic communications and networking. This paper studies the use of adaptive OFDMA in a multiuser downlink scenario, where a central node sends data to multiple distributed nodes simultaneously. The reduction of channel feedback via clustering and quantization is considered, and an interleaved power-bit loading algorithm is presented to jointly assign the data subcarriers to different users and allocate the power and bits on each subcarrier. Simulation results show the performance improvement due to subcarrier allocation with and without additional power and bit loading. An experiment conducted in a swimming pool illustrates potential benefits and challenges of harvesting the multiuser diversity through adaptive subcarrier allocation.