The Orthogonal Frequency Division Multiplexing (OFDM) and Code Division Multiple Access (CDMA) techniques, has drawn a lot of attention to be a candidate to support multimedia services in mobile communications. In this book, Space Time Block Coding (STBC-OFDM) block has been studied extensively, and a new structures for STBC-OFDM were proposed based on Discrete Multiwavelets Transform Critically-Sampled (DMWTCS). The purpose of proposed system is to achieve better BER performance than the conventional STBC-OFDM using FFT and DWT under different channel models. After that several structures of STBC-MC-DS-CDMA systems based on FFT, DWT and DMWTCS were proposed and examined. Then proposed Finite Radon Transform (FRAT) as a data mapper in (OFDM and MC-DS-CDMA) instead of the conventional data mapping techniques. This technique will increase the orthogonality significantly and keeps bandwidth efficiency and Bit per Hertz due to the use of IFFT twice in FRAT and multicarrier modulation. The FRAT structures will modify by using DWT and DMWTCS instead of FFT and examined also under different channel models.