SPECTRUM-AWARE UNDERWATER NETWORKS Cognitive Acoustic Communications

Communication capacity in underwater acoustic networks is severely limited by the uniquely challenging characteristics of underwater acoustic communications (UACs). In this article, dynamic spectrum sharing inspired from cognitive radio (CR) is applied to UAC networks, and spectrum-aware underwater networks (SUNs), i.e., cognitive acoustic communications (CACs), are proposed. First, the problem of spectrum scarcity in SUN is elaborately discussed by investigating the variation in acoustic channel capacity with respect to communication frequency and bandwidth. Then, the analysis of capacity gain via spectrum sharing in SUN is presented. To uncover the capacity gain via CAC, simulation experiments are performed, considering the effects of depth, distance, shipping, waves, spectrum management delay, and spectrum accessibility. The results of simulation experiments revealed a tradeoff between capacity gain and spectrum management delay. Furthermore, the tradeoff for capacity gain and spectrum accessibility period is also discussed. Here, our goal is to envision the potentials of CAC for mitigating spectrum scarcity in UAC. © 2012 IEEE.