Algorithm 1 A framework of data transmission

1:A normal sensor senses an event, it broadcasts a localization request message towards the neighbor anchor nodes over a period. 2:Surface anchor nodes receive the packet, they associate their locations with the message and forward to the BS 3:When the anchor’s message reaches the BS, the distance $\overline{d}$ is calculated according to (12) and is stored at the BS. 4:The BS updates M entries of $\overline{d}$ in the localization table and uses them for obtaining sensor location according to Section 3.2 and adjusting the distance value according to Section 3.4.