DFT provides coherent integration?
@ecook: Your time-domain notion of coherent integration is correct. (Where multiple periodic sequences must be time-synchronized before the averaging operation.)

The only way I could justify the remark that "coherent integration can be provided by DFT" is in the following scenario: let's say your DFT's input is an $x1(n)$ sinusoidal sequence and your DFT result is the complex valued $X1(m)$ sequence. Then some moments later you collect a new $x2(n)$ time sequence of the same sinusoidal signal and produce a new complex-valued DFT result of $X2(m)$. To average (integrate) those $X1(m)$ and $X2(m)$ sequences you would add their magnitudes. That's a form of incoherent averaging (incoherent integration), also called "scalar averaging." (Averaging $X1(m)$'s and $X2(m)$'s real and imaginary parts individually may lead to spectral energy cancellation and you don't want that to happen.)  

If, on the other hand, your $x2(n)$ time sequence was time-synchronized with the previous $x1(n)$ time sequence you can add $X1(m)$'s and $X2(m)$'s real and imaginary parts individually. That's a form of coherent averaging (coherent integration), also called "time-synchronous averaging."

Know this however, as Peter Kootsookos points out, averaging phase angles is tricky. Have a look at Peter's explanation at:
http://www.dsprelated.com/showarticle/57.php