Document Type : Research Articles
Authors
1 Qom University of Technology
2 Faculty member of Qom University of Technology, Qom, Iran
3 ICT Research Institute, Iran Telecommunication Research Center (ITRC), Tehran, Iran
Abstract
In this study, the authors investigate the impact of residual additive hardware impairments (HWIs) on the energy efficiency of a cooperative secure communication system. Within the framework of physical layer security and from the viewpoint of green communications, an energy efficient (EE) optimization technique is proposed for an amplify and forward (AF) relay network under the assumption that HWIs are present at the relay. Specifically, the authors derive the optimal transmit power at the base station (BS) to minimize the relay’s transmit power. The system employs the destination based cooperative jamming (DBCJ) scheme, in which the BS securely transmits information to the user equipment (UE) via an untrusted relay.
First, the case where HWIs exist only at the relay’s receiving side is considered. Assuming a fixed power for the cooperative jamming (CJ) signal, a closed form expression for the optimal transmit power is obtained, showing that it is inversely proportional to the first hop channel gain. Subsequently, when HWIs are present only on the transmitting side of the relay, a similar closed form expression is derived under the same CJ power assumption. These results effectively characterize the influence of residual HWIs on system performance and demonstrate that higher first hop channel quality leads to a lower required transmit power, thereby improving overall energy efficiency.
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