Energy Efficiency in Fading Relay Channels under Secrecy and QoS Constraints

Transmission over a half-duplex relay channel with secrecy and quality-of-service (QoS) constraints is studied. It is assumed that data is stored in buffers prior to transmission and transmitters operate with a constraint on the buffer overflow probability. Using the effective capacity formulation, secrecy throughput is derived for the half duplex two-hop fading relay system operating in the presence of an eavesdropper. The scenario without security considerations is also addressed. For both scenarios, minimum energy per bit is obtained. The impact of QoS exponents and channel correlation on the throughput is investigated via numerical analysis. Taking into account the path loss effect, the effect of the relay and eavesdropper locations on the throughput and energy efficiency is studied in a simple linear network.