Underwater Acoustic Network Simulation With Lookup Tables From Physical-Layer Replay

Abstract

An underwater acoustic network simulation methodology is presented that is based on lookup tables (LUTs) with physical-layer error ratios. These LUTs are prepared with a validated replay channel simulator, which is here driven by channel measurements from the Kauai Acomms MURI 2011 (KAM11) experiment. Three physical-layer candidates are considered: a coherent single-carrier scheme, a coherent multicarrier scheme, and an incoherent scheme. The three modulation schemes are operated at a fixed message size and at four different data rates. Low rates are more robust to noise, interference, and channel dispersion, but also more prone to collisions in a network with busy traffic, because the packets are longer. Error statistics for colliding packets have been measured and are incorporated in the network simulator as collision LUTs. Example simulations are presented for a reduced flooding protocol with or without retransmissions. The results demonstrate how retransmissions pose a tradeoff between performance at high and low traffic load. The best network performance is obtained if the highest data rate is selected that yields a reasonably well-connected network. Collision avoidance is more important than the extended connectivity offered by low-rate signaling. On the other hand, at a given bit rate, a physical-layer scheme with extended connectivity but relatively weak links is shown to outperform a scheme with stronger links over fewer connections.