Multiple Input and Multiple Output (MIMO) systems have shown a tremendous potential to increase the spectral efficiency and the reliability of wireless communication. These aspects are quantified in terms of the spatial multiplexing gain and the diversity gain respectively. There is a trade-off between diversity and multiplexing gains. Bit Interlevead Coded Modulation with Iterative Decoding (BICM-ID) for MIMO channels has been addressed as an effective mean to achieve high data rates while maintaining high diversity. It has been discussed that when signal constellation, interleaver and error control code are fixed, signal mapping has a crucial influence on the error performance of a BICM-ID system. The role of signal mapping applies to the error performance of MIMO-BICM-ID system. In this book, the design of multi-dimensional constellation mapping for MIMO-BICM-ID system is studied. Based on minimizing pair-wise error probability, a design criterion is proposed to find the optimal constellation mapping for MIMO-BICM-ID. Some 2-D and 3-D constellation mappings are presented. Simulation results show significant improvement of Bit Error Rate at high signal to noise ratio.