Discrete Dynamics in Nature and Society

Research Article

A Hybrid Genetic Algorithm for Satellite Image Downlink Scheduling Problem

Algorithm 2

The hybrid genetic algorithm.
Input  : a set of downlink requests; : a set of visibility masks;
Output  : the best solution found so far;
; / Initialize a population of request permutations
by randomly sorting /
while stopping condition is not reached do
; / Select two individuals for reproduction /
; / Generate two new individuals by crossover /
; / Use SGA to calculate the utility of   /
; / Use SGA to calculate the utility of   /
; / Initialize improving flag /
;
while    do /  Neighborhood search continues until the utility is not improved /
;
for   to   do
for   to   do
; / Use the exchange operator /
; / Use SGA to calculate the utility of   /
if    then
; / Preserve the exchange which improves the utility /
; / Update the utility of   /
;
end if
end for
end for
end while
while    do /  Neighborhood search continues until the utility is not improved /
;
for   to   do
for   to   do
; / Use the exchange operator /
; / Use SGA to calculate the utility of   /
if    then
; / Preserve the exchange which improves the utility /
; / Update the utility of   /
;
end if
end for
end for
end while
; / Update the population by replacing two of the worst individuals /
end while
; / Select the request permutation with the highest utility in the population /
; / Use SGA to generate the final solution /
return  ;