The　intrinsic　broadcast　nature　of　wireless　communication　let　the　attackers　to　initiate　several　passive　attacks　such　as　eavesdropping.　In　this　attack,　the　attackers　do　not　disturb/stop　or　interrupt　the　communication　channel,　but　it　will　silently　steal　the　information　between　authentic　users.　For　this　purpose,　physical　layer　security　(PLS)　is　one　of　the　promising　methodologies　to　secure　wireless　transmissions　from　eavesdroppers.　However,　PLS　is　further　divided　into　keyless　security　and　secret　key-based　security.　The　keyless　security　is　not　practically　implemented　because　it　requires　full/part　of　instantaneous/statistical　channel　state　information　(CSI)　of　the　eavesdroppers.　Alternatively,　key-based　security　is　exploiting　the　randomness　and　reciprocity　of　wireless　channels　that　do　not　require　any　CSI　from　an　eavesdropper.　The　secret　key-based　security　is　due　to　the　unpredictability　of　wireless　channels　between　two　users.　However,　the　secret　key-based　security　mainly　on　two　basic　parameters,　i.e.　coherence　time　and　transmission　power.　Nevertheless,　the　wireless　channel　between　users　has　a　short　coherence　time,　and　it　will　provide　shorter　keys＇　length　due　to　which　eavesdropper　can　easily　extract　keys　between　communicating　parties.　To　overcome　this　limitation,　we　proposed　the　power　allocation　scheme　to　improve　the　secret　key　generation　rate　(SKGR)　to　strengthen　the　security　between　authentic　users.