Algorithm 4. On-Demand Route Validation and Loop Avoidance

Function RecomputeRoute(Node C)     If C can directly reach the base station within range Rc2        Set C.Upstream = BS        Set C.HOP level = 1        Set Sup(C) = 1        Propagate local route-update information to direct downstream child CHs        Exit     Else        C broadcasts a Route-Request using range Rc2        Initialize CandidateSet = empty        For each candidate node U within Rc2            If U is alive               Initialize CurrentUpstream = U               Initialize VisitedSet = empty               Initialize Steps = 0               Initialize IsValid = false               While Steps < Dmax                  If CurrentUpstream = BS                      Set IsValid = true                      Break                  End if                  If CurrentUpstream is undefined OR CurrentUpstream is not alive                      Mark U as invalid                      Break                  End if                  If CurrentUpstream is already in VisitedSet                      Loop detected; mark U as invalid                      Break                  End if                  Add CurrentUpstream to VisitedSet                  Let NextUpstream = CurrentUpstream.Upstream                  If NextUpstream is undefined                      Mark U as invalid                      Break                  End if                  If distance(CurrentUpstream, NextUpstream) > Rc2                      Mark U as invalid                      Break                  End if                  Set CurrentUpstream = NextUpstream                  Set Steps = Steps + 1              End while              If Steps reaches Dmax before reaching a base station, mark U as invalid.              If IsValid = true                  Calculate Score(C, U)                  Add U to CandidateSet              End if            End if          End for          If CandidateSet is not empty              Select Ubest with the maximum score              Set C.Upstream = Ubest              Set C.HOP level = Ubest.HOP level + 1              Set Sup(C) = 1              Propagate local route-update information to direct downstream child CHs          Else              Set C.Upstream = undefined              Set Sup(C) = 0              Recovery failed; mark C as Disconnected          End if    End if End Function