Nowadays, marine scientists have a growing interest to know what happens in the ocean water column. One potential technology is to use underwater acoustic sensor networks that providing continuous sea environmental data. Although a number of MAC techniques can be used in thesenetworks, Spatial-TDMA is one of the most efficient in terms of energy, which is a critical parameter in underwater networks. In addition to, the high propagation delay of acoustic waves in the water makes the reliability of the transmissions an important dare to overcome.
In this article, we consider both concepts applying to a multi-hop network topology (many-to-one network). Spatial TDMA is the slot planning used for scheduled the node transmissions, and this is done with a fair bandwidth assignation. We propose an algorithm to find the shortest frame in a transmission cycle using graph cliques. Finally, we evaluate the capabilities of using the CRC-32 detecting code adopted in 802.3 standard to estimate a suitable length for payload field in the data transmissions.