Secrecy Energy Efficient Beamforming for SatelliteTerrestrial Coordinated Communication Systems This paper investigates the secrecy energy efficiency maximization (SEEM) problem in a satelliteterrestrial coordinated communication systems. First, we formulate a coordinated transmission optimization problem by using the secrecy energy efficiency (SEE) as optimization criterion and meanwhile the transmission quality of the terrestrial link and the transmission power of the satellite and ground base station as constraints. Due to the fractional form of SEE, the formulated optimization problem is nonconvex and mathematically intractable. Then, we transform the original fractional problem into an equivalent subtractive problem, and employ the difference of twoconvex functions (D.C.) approximation method to arrive at an approximate convex problem. Finally, we propose a convergence proven iterative algorithm to solve the modified maximization problem. Simulation results are presented to illustrate the effectiveness of our proposed algorithm.

On the Ergodic Secrecy Rate of Massive MIMO Transmission with Partial Legitimate User CSI In this paper, we consider the downlink transmission over a singlecell massive multipleinputmultipleoutput (MIMO) system in the presence of multiple singleantenna eavesdroppers (massive MIMOME). We concentrate on the practical scenario where partial channel state information (CSI) of legitimate users and no CSI of eavesdroppers are available at the base station and consider both types of eavesdroppers including the noncolluding and colluding eavesdroppers. Random unitary beamforming (RUB) based scheme is used to describe the partial CSI of legitimate users. We derive the closedform expression of ergodic secrecy rate for RUB based massive MIMOME transmission, and its single legitimate user particular case. We also present numerical results to illustrate the performancecomplexity tradeoff among different massive MIMO transmission schemes. We show that RUB based scheme can enhance secrecy performance of massive MIMO transmission with lower implementation complexity.