Full-Duplex Device-to-Device Relays in a Novel Hybrid and Adaptive Joint Relaying Network: Symbol Error Analysis and Optimum Power Allocation

This paper proposes a new relaying protocol for transmitting from a cellular user to the base station with the joint cooperation of a Full-Duplex (FD)-enabled Device-to-Device (D۲D) pair. In the proposed scheme, the receiver of the D۲D acts as a relay, with the cooperation of its transmitter pair via D۲D communication between them. The cooperation approach of the D۲D receiver is chosen as Adaptive Decode-and-Forward (ADF), while the cooperation strategy of the D۲D transmitter is chosen as either ADF, Amplify-and-Forward (AF), or Hybrid relaying protocol. These scenarios are named "Decode and Joint Cooperation," "Amplify and Joint Cooperation," and "Hybrid and Adaptive Joint Cooperation," respectively. The Average Symbol Error Probability (ASEP) of the system is studied over independent and identically distributed (i.i.d) complex Gaussian (Rayleigh envelope) channels, with perfect Channel State Information (CSI) in the presence of Residual Self-Interference (RSI) at the FD relays, as well as Co-Channel Interference (CCI). Moreover, closed-form and high Signal-to-Interference-plus-Noise Ratio (SINR) tight ASEP approximations are established. The optimum power allocation is formulated based on the approximate relations, and the optimal solutions and their characteristics are discussed in detail. Analytical comparisons and simulations confirm the theoretical results and demonstrate significant performance improvements.