Reduced-Complexity Demodulation for MIMO-BICM-IDD using Modified Stack Algorithms

Bit-interleaved coded-modulation (BICM) with iterative demodulation and decoding (IDD) is a popular architecture for the development of practical communication schemes that operate at rates close to capacity. In multiple-input multiple-output (MIMO) BICM-IDD schemes, a key computational bottleneck is the demodulation step; that is, the extraction of "soft" information about the transmitted bits from the channel output. The concept of list-based demodulation provides a convenient framework for managing the trade-off between accuracy and computational cost in the extraction of this soft information, especially when tree-search techniques are used to construct the list. In this paper, we will propose several list-based demodulators based on modifications of the stack algorithm for searching a tree. The modifications partition the stack in ways that enable efficient and effective searching of the tree from the perspective of list-based demodulation. Simulation results show that the proposed demodulators achieve desirable trade-offs between complexity and performance.