Secure Degrees-of-Freedom of the MIMO X Channel with Delayed CSIT
This research addresses the problem of secure communication capacity for MIMO X channels with delayed channel state information at the transmitter, which is important for wireless communication system designers.
This paper investigates the secure degrees-of-freedom (SDoF) for the MIMO X channel with confidential messages and delayed CSIT. It proposes a transmission scheme that generalizes existing methods and derives a sum-SDoF lower bound. The study reveals that for a fixed number of receive antennas N, the minimum number of transmit antennas to achieve the maximum lower bound is approximately 1.56N.
In this paper, we study the secure degrees-of-freedom (SDoF) characterization for the multiple-input multiple-output (MIMO) X channel with confidential messages and delayed CSIT. In particular, we propose a transmission scheme, which can be regarded as a generalization of the state-of-the-art scheme without security and with delayed CSIT. The key of this generalization is performing the security analysis, by which we derive the optimal duration of the artificial noise transmission phase. As a result, we derive the sum-SDoF lower bound. Furthermore, we reveal that if the number of receive antennas, denoted by N, is fixed, the minimum number of transmit antennas achieving the maximum of the lower bound is $\frac{7+\sqrt{33}}{8}N$.