Algorithm 1 PCH Election

$m$ ← the M code of the CH

Level i ← the level of the PCH

d ← the depth of the quadtree

sink ← the location of Sink node

Get PCH ($m$, level i, d, sink)

{

begin

[CHs] = [NW, NE, SW, SE]// Get the 4 CHs of the i-th level whose M code are $m$

[Xc,Yc] = (M,i)// Get the center coordinate of the area where the M code is $m$

[Xs,Ys] = sink //Get the coordinates of the sink node

If(Xs>Xc)&(Ys>Yc)

PCH =SE

Else if(Xs<Xc)&(Ys>Yc)

PCH = SW

Else if(Xs<Xc)&(Ys>Yc)

PCH = NW

Else (Xs>Xc)&(Ys<Yc)

PCH = NE

end

end

Return PCH// Return the calculated PCH node

}