Energy Efficiency of FullDuplex TwoWay Channels This paper studies the energy efficiency (EE) of twoway channels operating in the fullduplex (FD) mode. The residual selfinterference (RSI) and selfinterference cancellation (SIC) power are modeled as linear functions over the transmission power. The EE maximization problem for the considered FD mode with individual spectral efficiency (SE) constraint is formulated, and the corresponding optimal power allocation is derived by using fractional programming. Then, we further maximize the EE with sum SE constraint and the closedform expression of this maximum EE is derived. Somehow surprisingly, numerical results show that the FD mode beats the halfduplex (HD) mode when the distance between the two transceivers is relatively large.

Energy and SpectralEfficiency Tradeoff in Beam Domain Massive MIMO Downlink with Statistical CSIT We investigate energy and spectralefficiency tradeoff by optimizing resource efficiency (RE) for singlecell massive multipleinput multipleoutput (MIMO) downlink transmission with only statistical channel state information available at the transmitter (CSIT). We first show that beam domain transmission is favorable for RE optimization in massive MIMO downlink, by deriving a closedform solution for the eigenvectors of the optimal transmit covariance matrices. With this conclusion, the RE optimization precoding design is reduced to a realvalued power allocation problem. Exploiting sequential optimization and random matrix theory, we further propose a lowcomplexity twolayer waterfillingstructured power allocation algorithm. Numerical results demonstrate the effectiveness of our proposed statistical CSI aided RE optimization approach.