Perhaps you should try some spelling variations:
channel modulation » channel regulation
channel formation » channel estimation, channel function, channel forming
processing dsp » processing data, processing design

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: ((channel formation) OR (channel modulation)) processing dsp.
• Adding a wildcard symbol may retrieve word variants: ((channel formation) or (channel modulation)) processing dsp*.