Optimal Power Allocation Strategies in Full-duplex Relay Networks

In this work, we consider a dual-hop, decode-and-forward network where the relay can operate in full-duplex (FD) or half-duplex (HD) mode. We model the residual self-interference as an additive Gaussian noisewith variance proportional to the relay transmit power, and we assume a Gaussian input distribution at the source.Unlike previous work, we assume that the source is only aware of the transmit power distribution adopted by therelay over a given time horizon, but not of the symbols that the relay is currently transmitting. This assumptionbetter reflects the practical situation where the relay node also forwards signaling traffic, or data originated byother sources. Under these conditions, we identify the optimal power allocation strategy at the source and relay,which in some cases coincides with the half duplex transmission mode. In particular, we prove that such strategyimplies either FD transmissions over an entire frame, or FD/HD transmissions over a variable fraction of theframe. We determine the optimal transmit power level at the source and relay for each frame, or fraction thereof.We compare the performance of the proposed scheme against reference FD and HD techniques, which assumethat the source is aware of the symbols instantaneously transmitted by the relay. Our results highlight that ourscheme closely approaches or outperforms such reference strategies.