Dear Prateek Verma ,

The probability of detection depends on signal to noise ratio: S/N.

Namely as the S/N increases the the detection probability increases.

The noise threshold is set by the detector itself.

When you increase the number of sensing points or sensing instants then we we have N signals instead of one as the power sums up.

Then one has SUM Si from i =1 to N instead of only one signal.

Then the signal to noise ratio will be multiplied as the number of signals increases. This will be pronounced at weaker signals and fading channels.

Best wishes