Maximizing Secrecy Rate of an OFDM-based Multi-hop Underwater Acoustic Sensor Network

Abstract

Consider an OFDM based, multi-hop underwater acoustic sensor network with M + 1 underwater sensing nodes that report their sensed data to a sink node (on water surface). A malicious node Eve attempts to eavesdrop the ongoing communication between a sensor node and the sink node. To this end, this work performs joint optimal node selection for data forwarding and sub-carrier power allocation (across OFDM sub-carriers) to maximize the secrecy capacity on each hop. Specifically, the optimization problem formulated is a mixed binary-integer program, which is solved via dual decomposition method. Since this is the first work on secure routing, we compare the performance of the proposed scheme with the classical depthbased routing (DBR) scheme in simulations. The simulation results show that: i) the proposed scheme outperforms the DBR scheme (i.e., the performance gap between the two schemes increases) with increase in the transmit power budget of the sensor nodes, ii) the proposed scheme benefits from the increase in the density of sensor nodes (while the DBR scheme fails in such situation).