Two-step wireless positioning technique by exploitation of extended reference nodes

Wireless positioning systems rely on a minimum number of transmitters with known locations as reference nodes to locate a target device. However, in harsh environments where the number of available reference nodes is inadequate, wireless positioning systems may suffer from significant performance degradation. In this paper, we propose a wireless positioning technique utilizing transmitting nodes from other co-existing networks to improve the locationing performance in terms of accuracy and coverage. The procedure of the proposed location technique can be divided into two steps. During the first step, locations of extended reference nodes from other co-existing networks - i.e. additional active transmitters external to the original positioning network - are collaboratively estimated by the original reference nodes. The positioning of the target node can then be improved by a combined use of the original and newly discovered extended reference nodes. Maximum likelihood (ML) principle is applied in both estimation steps. The position estimation performance is analyzed and compared with the Cramer-Rao Lower Bound (CRLB). Computer simulations show that the accuracy of the position estimation using this approach can be improved by the joint effort of the extended and original reference nodes.