A method includes communicating data in a channel. Received symbols for the data correspond to points of a received symbol space respectively. First and second dimensions of the received symbol space correspond to a real part and an imaginary part of the received symbols respectively. A first received symbol for the data is obtained. A first region of the received symbol space for the first received symbol is determined. A first regression model associated with the first region and a first bit of the first received symbol is retrieved from a storage. The first regression model includes a plurality of regressors. A first log-likelihood ratio (LLR) for the first bit of the first received symbol is estimated using the first regression model.