Ricerc@Sapienza

Bidirectional underwater acoustic communications usually request the transmission of some control information among nodes to govern the data flow. Control signaling, employed as frame reception validation, is also a peculiarity of the Automatic Repeat on reQuest (ARQ) schemes. An alternative solution to the error control problem is using forward error correction, even though high redundancy is needed to obtain the low error rate, hence leading to a sensible throughput reduction. Furthermore, no control on data integrity is allowed. For the above reasons, we explore the possibility of implementing three different ARQ schemes by considering only the use of an explicit negative acknowledgment (NACK) for requiring frames retransmission. Specifically, the NACK frame index is related to a frequency-dependent message and the information frame(s) to be retransmitted are recognized, owing to a frequency-domain detection mechanism. Moreover, the proposed solution is very efficient when applied in a broadcast environment since it overcomes the necessity of performing a multiuser detection at the centralized broadcaster. In this context, we report both simulations and experimental tests results to show the effectiveness of the proposed scheme.