Blind Identification of LDPC Codes in Multipath Fading Channel via Expectation Maximization
Yu Liu, Fanggang Wang, Jingwen Zhang, Bo Ai, Zhangdui D. Zhong · 2018
As the advent of cognitive radios, blind encoder identification has attracted increasingly attentions since it plays an important role in blind signal processing. The existing works mainly focus on additive white Gaussian noise (AWGN) channel, while the blind identification in multipath scenarios has not been sufficiently investigated. In this paper, we consider the blind low-density parity-check (LDPC) codes identification in the presence of unknown multipath fading channel. Then, a likelihood-based classifier is proposed using the expectation maximization (EM) algorithm to obtain the maximum likelihood estimates of the unknown parameters, including multipath fading channel and modulated symbols. Then, we adopt an average log-likelihood ratio (LLR) estimator to classify the unknown encoder. Numerical results show that the proposed algorithm provides promising identification performance in multipath channels, especially in the low signal- to-noise ratio region.