Mambu-RAM: a mud-aided random access MAC for underwater networks

The following report considers a multi-beam directional network where nodes have linear arrays capable of performing digital beamforming. Digital beamforming has greatly advanced the feasibility of uncoordinated random access in directional networks. Unlike its analog counterpart, digital beamforming alleviates the need for complex beam scheduling algorithms. A key tradeoff in such systems is the number of transducers and the network throughput. In many practical scenarios of interest, the addition of many transducers is not possible due to size weight and power (SWaP) constraints. In this work, we show for SWaP constrained nodes, the addition of a linear multiuser detector (MUD) can be utilized to further increase the throughput. It is also discussed how the varying number of chips could be used in an adaptive fashion to achieve the maximum possible throughput. Lastly, considerations of other MUD receivers are introduced along with possible further improvements such as power control.