In this work, reliable and secure transmission over generic-Gaussian wiretap channel model is investigated. An Adaptive Granular Hybrid Automatic Repeat reQuest (AG-HARQ) protocol is proposed which tries to minimize the required rate for successful decoding by the legitimate parties while amplifying the privacy by minimizing the information leakage to a wiretapper. In the case of LDPC decoding failure at the legitimate receiver (Bob), a retransmission is requested until correct decoding or until the maximum number of transmitted packets is reached. As soon as Bob is able to correctly decode the LDPC codeword, the retransmissions are stopped to avoid any additional bits leakage to the eavesdropper (Eve). In our proposed method, to minimize the leakage, a confidence level index, Cj, for correct decoding is defined as the mean of absolute value of the Log-Likelihood Ratio (LLR). In the case of failure, only the sub-packets with the smallest Cj values will be retransmitted since they represent the most unreliable information sub-packets. Frame Error Rate (FER) is used as a metric to show the effectiveness of the proposed method.
['Ahmadreza Amirzadeh', 'Mohamed Haj Taieb', 'Jean-Yves Chouinard']
Adaptive granular HARQ LDPC-based coding for secrecy enhancement in wiretap channels