Sepahdar Falsafi - Faculty of Electrical and Computer Engineering Imam Hossain Comprehensive University Tehran, Iran
HamidReza Khodadadi - Faculty of Electrical and Computer Engineering Imam Hossain Comprehensive University Tehran, Iran

In Non-orthogonal multiple access, a user with a weaker channel gain is assigned more power than a user with a stronger channel. This type of power allocation allows the strong user (SU) to apply the successive interference cancellation (SIC) method that first detects the symbols of the weak user (WU) before detecting its data. The SIC method makes the WU data vulnerable to eavesdropping at the SU and so increases the detection complexity. This paper studies the physical layer security of the data against eavesdropping. The proposed scheme uses directional modulation that distorts the symbols transmitted in an undesired direction therefore the external eavesdroppers receive different symbols. It becomes complicated for an external eavesdropper to track and detect the signal of legitimate users. This scheme eliminates the WU data on the location of the SU so the strong user does not need the SIC. We analyze the impacts of various factors on security, such as the number of antennas and the secrecy rate.

component, NOMA, directional modulation, DM-RFDA, eavesdropper, secrecy