Low SNR design of space-time block codes based on union bound and indecomposable error patterns

Space-time block codes have attracted recent interest due to their ability to take advantage of available diversity to transmit data over a wireless fading channel. Since they were first introduced, several strategies have been proposed for their design. In most cases, these designs were optimized for high SNR through a worst case pairwise error probability analysis and either placed strict constraints on the structure of codewords or were limited to codesets of low cardinality. This work addresses the issue of code design specifically for low SNR environments using union bound-based performance criteria which are SNR dependent. A more accurate union bound-based measure for performance evaluation of codes is developed and a variation of a locally optimum algorithm used to systematically construct good codeword sets is presented. New found codes are compared via simulation with other existing codes and are shown to exhibit improved performance.