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Event Details

  • Wednesday, November 8, 2017
  • 15:30 - 16:00

Optical Wiretap Channel with Input-Dependent Gaussian Noise Under Peak and Average Intensity Constraints

This paper studies the optical wiretap channel with input-dependent Gaussian noise, in which the main distortion is caused by an additive Gaussian noise whose variance depends on the current signal strength. Subject to non-negativity and peak intensity constraints on the channel input, we first evaluate the conditions under which this wiretap channel is stochastically degraded. We then study the secrecy capacity-achieving input distribution of this wiretap channel and prove it to be discrete with a finite number of mass points, one of them located at the origin. Moreover, we show that the entire rate-equivocation region of this wiretap channel is also obtained by discrete input distributions with a finite support. Similar to the case for Gaussian wiretap channel under a peak power constraint, here too, we observe that under non-negativity and peak intensity constraints, there is a tradeoff between the secrecy capacity and the capacity in the sense that both may not be achieved simultaneously. Furthermore, we prove the optimality of discrete input distributions in the presence of an additional average intensity constraint. Finally, we shed light on the asymptotic behavior of the secrecy capacity in the low and high intensity regimes. In the low intensity regime, the secrecy capacity scales quadratically with the peak intensity constraint. On the contrary, in the high intensity regime, secrecy capacity does not scale with the constraint.