Abstract
In this paper, we investigate the effect of output quantization on the secrecy capacity of the
binary-input Gaussian wiretap channel. As a result, a closed-form expression with infinite summation
terms of the secrecy capacity of the binary-input Gaussian wiretap channel is derived for the case
when both the legitimate receiver and the eavesdropper have unquantized outputs. In particular,
computable tight upper and lower bounds on the secrecy capacity are obtained. Theoretically, we
prove that when the legitimate receiver has unquantized outputs while the eavesdropper has binary
quantized outputs, the secrecy capacity is larger than that when both the legitimate receiver and the
eavesdropper have unquantized outputs or both have binary quantized outputs. Further, numerical
results show that in the low signal-to-noise ratio (SNR) (of the main channel) region, the secrecy
capacity of the binary input Gaussian wiretap channel when both the legitimate receiver and the
eavesdropper have unquantized outputs is larger than the capacity when both the legitimate receiver
and the eavesdropper have binary quantized outputs; as the SNR increases, the secrecy capacity when
both the legitimate receiver and the eavesdropper have binary quantized outputs tends to overtake.