A Cross Layer Approach with CSMA/CA based Protocol and CDMA Transmission for Underwater Acoustic Networks

In this paper, we propose a cross layer design which combines the PHYsical and the MAC layers for a distributed wireless underwater acoustic networks. The PHYsical layer is based on a CDMA transmission as used in UMTS systems, reception is done using a RAKE receiver. The MAC layer is a based on the CSMA/CA protocol. As we work in the case of underwater acoustic networks, the propagation delay is much more significant compared to radio channel. Therefore, the use of RTS/CTS used in the CSMA/CA protocol induces an increase in delay. The use of CSMA techniques allows to several nodes to transmit simultaneously through the common channel and without using control sequences RTS/CTS to reserve the medium. We show in this paper that our proposition solves the problem of collision present in the case of CSMA/CA. The comparison between our cross layer approach and the CSMA/CA is done in term of available throughput of nodes and average delay of transmission.