System capacity of CDMA, TDMA and FDMA in cluster type underwater acoustic networks

It is well acknowledged that CDMA scheme could achieve higher system capacity in cellular type Radio Frequency networks (RFN) than either TDMA or FDMA, since the system capacity of TDMA or FDMA is resource (bandwidth) restricted, while the one of CDMA is interference restricted; and the interference level can be reduced by lowering the user activity ratio and controlling of transmission power. However, this conclusion could not be applied to underwater acoustic networks (UANs) due to the significant differences between propagation environment of RFNs and that of UANs. Using sonar equation and with the Thorp's water absorption formula, this paper analyzes the capacity of CDMA, TDMA and FDMA schemes in a cluster type underwater acoustic network. In the following analysis, all the power symbols, e.g., Pts, Pintracluster, etc., represent time average value instead of instantaneous value.