  Primordial Black Holes (PBHs) in the mass range $\sim 10^{17}- 10^{22}$g are
currently unconstrained, and can constitute the full Dark Matter (DM) density
of the universe. Motivated by this, in the current work, we aim to relate the
existence of PBHs in the said mass range to the production of observable
Gravitational Waves (GWs) in the upcoming GW detectors. We follow a relatively
model-independent approach assuming that the PBHs took birth in a radiation
dominated era from enhanced primordial curvature perturbation at small scales
produced by inflation. We show that the constraints from CMB and BAO data allow
for the possibility of PBHs being the whole of DM density of the universe.
Finally, we derive the GW spectrum induced by the enhanced curvature
perturbations and show that they are detectable in the future GW detectors like
eLISA, BBO and DECIGO.

High Energy Physics - Phenomenology;Cosmology and Nongalactic Astrophysics