Algorithm 2 DV-HOP localization scheme with RSSI based on ELM-RCC (RHOP-ELM-RCC).

Input: the distance between anchor l and unknown node j: $d_{jl}(l=1,2,\cdots ,q)$.   (1) Obtain the hop count and RSSI distance by broadcasting the beacon messages and RSSI packets of each anchor nodes;   (2) Average hop size and calculate the mean value of RSSI distance per hop based on Equation (25);   (3) Compute the distances between anchor nodes and unknown nodes with the correction factor γ on the basis of Equation (26);   (4) Use the distances obtained in Equation (26) as the input of ELM-RCC, and then, calculate the coordinate $(x_j,y_j)$ for unknown node j using ELM-RCC. Output: the coordinate of unknown node j.