The received signal strength (RSS) based target localization problem in underwater\nacoustic wireless sensor networks (UWSNs) is considered. Two cases with respect to target transmit\npower are considered. For the first case, under the assumption that the reference of the target\ntransmit power is known, we derive a novel weighted least squares (WLS) estimator by using\nan approximation to the RSS expressions, and then transform the originally non-convex problem\ninto a mixed semi-definite programming/second-order cone programming (SD/SOCP) problem for\nreaching an efficient solution. For the second case, there is no knowledge on the target transmit power,\nand we treat the reference power as an additional unknown parameter. In this case, we formulate a\nWLS estimator by using a further approximation, and present an iterative ML and mixed SD/SOCP\nalgorithm for solving the derived WLS problem. For both cases, we also derive the closed form\nexpressions of the Cramer-Rao Lower Bounds (CRLBs) on root mean square error (RMSE). Computer\nsimulation results show the superior performance of the proposed methods over the existing ones in\nthe underwater acoustic environment.
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