What is the difference between upsampling and up conversion (done during signal transmission)? Also is upconversion different from modulation?
Your first sentence is not correct.  The terminology of 'sample rate conversion' operations is often misused.  I suggest you replace your first sentence with, "Interpolation is when you increase the sample rate of a DISCRETE signal sequence."  I'd also replace your second sentence with, "Modulation is when you, by multiplying with a carrier frequency, shift a signal's spectral components up in frequency by a fixed amount." (The term "modulation" is typically used when talking about continuous signals.)  As far as I understand the terminology, "up-conversion" is when you shift the spectral components of a discrete sequence up in frequency by a fixed amount. [-Rick Lyons-]