  The performance of energy detection (ED) for independent and identically
distribution (i.i.d.) signal models is analyzed over generalized composite
non-linear line-of-sight (LOS) and non-line-of-sight (NLOS) shadowed fading
scenarios. The novel expressions for {\alpha}-\k{appa}-{\mu}/Gamma and
{\alpha}-{\eta}-{\mu}/Gamma fading channels have been derived to approximate by
using the mixture gamma (MG) distribution under low instantaneous
signal-to-noise (SNR) condition. On the basis of the deduced fading
distributions, novel, exact and close-form detective models are derived to
evaluate the sensing performance with different key fading parameters over
generalized non-linear and shadowed composite fading channels.
