Dynamic network coded cooperative OFDM for underwater data collection

In this paper, we consider an underwater data collection problem, where multiple underwater nodes need to send data to one common destination. With the conventional ARQ protocol, the destination requests retransmission from each node individually without any node cooperation. We propose two protocols, selective relay cooperation and dynamic network coded cooperation, utilizing the fact that underwater nodes can overhear the transmission of others. In the selective relay cooperation, one node can be selected as a relay to transmit the data from another undecoded node in the retransmission round. In the network coded cooperation, the selected relay nodes transmit network coded packets, combining the packets from several undecoded nodes to the destination. The relay nodes participating the cooperation are selected by the destination based on the measured pilot signal to noise ratio of the underlying OFDM modulation. Simulation results based on one specific underwater topology show that the proposed schemes can achieve significant gains compared with the conventional ARQ scheme.