A study on bi-orthogonal modulation for W-CDMA higher bit rate transmission

This paper studies a modulation method for a wideband code division multiple access (W-CDMA) system in order to enhance its performance. The modulation method studied here introduce bi-orthogonal modulation instead of multicode transmission in order to suppress the envelope variation which comes from code division multiplexing in multicode transmission. Bi-orthogonal modulation studied here selects a single code in both in-phase and quadrature components, and leads to relaxation of the requirement of HPA linearity. This relaxation enhances the implementation of the mobile station (MS) with smaller size or lower power consumption. Computer simulation results show that the power level of spurious emission in the adjacent channel is reduced by approximately 8 dB with use of bi-orthogonal modulation, while keeping the required E _b/I_o almost the same as multicode transmission