On the Optimality of Secure Communication Without Using Cooperative Jamming

Abstract: We consider secure communication over a two-user Gaussian interference channel, where each transmitter sends a confidential message to its legitimate receiver. For this setting, we identify a regime where the simple scheme of using Gaussian wiretap codebook at each transmitter (without cooperative jamming) and treating interference as noise at each intended receiver (in short, GWC-TIN scheme) achieves the optimal secure sum capacity to within a constant gap. The results are proved by first considering the deterministic interference channel model and identifying a regime in which a simple scheme without using cooperative jamming is optimal in terms of secure sum capacity. For the symmetric case of the deterministic model, this simple scheme is optimal if and only if the interference-to-signal ratio (in channel strengths) is no more than 2/3.