Codebit parsers for adaptive bit loading over MIMO channels

Adaptive bit loading (ABL) can be employed to compensate for the signal strength variation across spatial channels in MIMO system that employs SVD beamforming. Due to the significant spread of singular values across the spatial streams, it is beneficial to load each stream with a different number of codebits. In the so called vertically encoded MIMO system, all spatial channels share one channel encoder, and a codebit parser distributes the contiguous codebits into multiple spatial channels, where the ABL scheme determines the load per channel. It is desirable that the codebits in each spatial channel are evenly spaced in the original codeword in order to maximize spatial diversity. The existing block codebit parser (2002) assigns the continuous blocks of codebits to each stream respectively. In the paper, we derive a few codebit parsers, including the optimal one. The simulation results over 802.11n convolutionally coded channels demonstrate the superiority.