“…In an AF relay, the received signal from the source is amplified and then retransmitted [36]. For AF relays, the corresponding relay selection and power allocation problems have been discussed in the context of performance specifications such as maximum information secrecy [45], minimum mean-square transmission error [12], and minimum total transmission power [18]. On the other hand, a DF relay demodulates and then decodes the received signal before retransmission.…”