Perhaps you should try some spelling variations:
"modified allocation optimization algorithm" » "modified allocation optimization algorithms", "modified allocation optimisation algorithm", "modified allocation estimation algorithms", "modified location optimization algorithm"
"modified channel estimation algorithm" » "modified channel excitation algorithm"

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

• If you are trying to use Boolean operators, they must be ALL CAPS: (("modified channel estimation algorithm") OR ("modified allocation optimization algorithm"))~.
• Removing quotes may allow a broader search: (( modified channel estimation algorithm ) or ( modified allocation optimization algorithm ))~.
• Adding a wildcard symbol may retrieve word variants: (("modified channel estimation algorithm") or ("modified allocation optimization algorithm"))*.