In the popular bit-interleaved coded modulation (BICM) the output of the channel encoder and the input of the modulator are separated by a bit-level interleaver. From the decoder's point of view, the modulator, the transmission channel, and the demodulator (calculating bits' reliability metrics) become a memoryless BICM channel with binary inputs and real outputs. In unfaded channels, the BICM channel's outputs (reliability metrics) are known to be Gaussian for binary- or quaternary phase shift keying but their probability density function (PDF) is not known for higher-order modulation. We fill this gap by presenting an algorithmic method to calculate closed-form expressions for the PDF of reliability metrics in BICM with arbitrary modulation and bits-to-symbol mapping when the so-called max-log approximation is applied. Such probabilistic description of BICM channel is useful to analyze, from an information- theoretic point of view, any BICM constellation/mapping design.

We present a numerically efficient method to evaluate uncoded bit-error rate for arbitrary two-dimensional constellation and nonuniform signaling in fading channels. Compared to the bounding techniques, treating the problem at the same level of generality, the proposed method is shown to be more accurate (by construction) and numerically more efficient: for moderate constellation size, the complexity reduction may reach two orders of magnitude. The operation of the proposed method is illustrated with numerical examples obtained in Nakagami-m fading.

An analytical method to predict accurately the performance of iterative demapping in bit-interleaved coded modulation (BICM-ID) is presented. It is based on the analytical evaluation of the bit error rate at the output of the demapper and, in comparison with previously known methods (e.g., those based on EXIT charts), considerably reduces the need for simulations. The results obtained with the proposed method are compared with those obtained by EXIT analysis and through simulations.

In the popular bit-interleaved coded modulation (BICM) the output of the channel encoder and the input of the modulator are separated by a bit-level interleaver. From the decoder's point of view, the modulator, the transmission channel, and the demodulator (calculating bits' reliability metrics) become a memoryless BICM channel with binary inputs and real outputs. The BICM channel's outputs (reliability metrics) are known to be Gaussian for binary- or quaternary phase shift keying but no expression for their probability density function (PDF) is known for higher-order modulation. We fill this gap presenting an algorithmic method to calculate closed-form expressions for the PDF of reliability metrics in BICM with arbitrary modulation and bits-to-symbol mapping. Such probabilistic description of BICM channel provides a useful tool to analyze, from an information- theoretic point of view, any BICM constellation/mapping design.

We present a numerically efficient method to evaluate exactly uncoded bit error rate for transmission in fading channels. The presented method deals with arbitrary two-dimensional constellation, arbitrary bits-to-symbols mapping, and with non-uniform signaling. Compared to the bounding techniques, treating the problem at the same level of generality, the proposed method offers not only accuracy but also is numerically much more efficient: for moderate constellation size, the complexity reduction may reach two orders of magnitude. The operation of the proposed method is illustrated with numerical examples considering non-uniform signaling in transmission over Nakagami-mfading channel.