A factor-graph approach to joint OFDM channel estimation and decoding in impulsive noise channels
We propose a factor-graph-based approach to joint channel, impulse, symbol and bit estimation (JCISB) of LDPC-coded orthogonal frequency division multiplexing (OFDM) systems in impulsive noise environments. Impulsive noise arises in many modern wireless and wireline communication systems, such as cellular LTE and powerline communications, due to uncoordinated interference that is much stronger than thermal noise. Our receiver merges prior knowledge of the impulsive noise models with the recently proposed “generalized approximate message passing” (GAMP) algorithm, and soft-input soft-output decoding through the sum-product framework. Unlike the prior work, we explicitly consider channel estimation in the problem formulation. For N subcarriers, the resulting receiver has a complexity of O(N logN), comparable to a typical DFT receiver. Numerical results indicate that the proposed receiver outperforms all prior impulsive noise OFDM decoders with improvements that reach 13dB when compared to the commonly used DFT receiver.