Perhaps you should try some spelling variations:
optimization algorithm » optimization algorithms, optimisation algorithm, estimation algorithm
time approximation » _ approximation
one approximation » _ approximation, rough approximations
qoe optimization » game optimization, _ optimization, stage optimization

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (( ((one approximation) OR (time approximation)) algorithm ) or ( qoe optimization algorithm ))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (( ((one approximation) OR (time approximation)) algorithm ) OR ( qoe optimization algorithm )).
• The words AND, OR and NOT may confuse the search; try adding quotes: "(( ((one approximation) OR (time approximation)) algorithm ) or ( qoe optimization algorithm ))".
• Adding a wildcard symbol may retrieve word variants: (( ((one approximation) OR (time approximation)) algorithm ) or ( qoe optimization algorithm ))*.