The effect of Transmitter's Eavesdropper CSI on the Secure Degrees of Freedom of the MIMO MAC

We investigate the secure degrees of freedom (SDoF) of the two-transmitter multiple access channel (MAC) with multiple antennas transmitters and multiple antennas legitimate receiver in the vicinity of an eavesdropper that has N-E. antennas. The SDoF is derived for two cases of the legitimate nodes knowledge about eavesdroppers' channels, instantaneous CSI and statistical CSI. Comparing the SDoF of the two cases, the effect of eavesdropper CSI knowledge on the SDoF is developed. We derive the exact sum SDoF for both cases and provide matching respective upperbounds. We show that obtaining statistical CSI can achieve even more SDoF in some cases than obtaining the instantaneous eavesdropper's channels coefficients if some time slots were dedicated to channel estimation.