Algorithm 2. The Local Neighbor-optimal Selecting Algorithm (LNSA)

INPUT: the position information of all nodes S = {S1, S2, …, Sn} in $D_i\left(P_i,2R\right)$. OUTPUT: the selected nodes Sb = {S′b1, S′b2, …, S′bi, …, S′bh}. 1: Divide ROI into many regular hexagons H1, H2, …, Hi, …, Ha with the virtual grid points as the center, build the polar coordinate system in Hi 2: Perform the following steps in each regular hexagon Hi 3: Refine the nodes in Hi with $\left|{\rho }_{S_i}-R\right|\le \delta$ and constitute S′c = {Sc1, Sc2, …, Sck} 4: for i = 1: k 5: If ${\alpha }_{{S^{\prime }}_{\mathrm{mod}(i+1,c)}}-{\alpha }_{{S^{\prime }}_i}>2\theta$ 6: Pick the spare nodes from $S-S_C^{\prime }$ to join S′c 7: i = i − 1 8: End 9: End 10: Choose nodes every $2\theta$ as the awakening nodes S′bi = {Sb1, Sb2, …, Sbm} in S′c.

11: End 12: Sb = {S′b1, S′b2, …, S′bi, …, S′bh}