A TDD-CDMA system with pre-phase subcarrier equalizer using asymmetric modulation scheme in duplex channel

A multicarrier (MC) signal has a large peak to mean envelope power ratio, so that the MC signal suffers from a high level of intermodulation distortion due to the non-linearity of the power amplifier stage. For portable terminals, it is difficult to adopt a linear amplifier because high power efficiency is needed. To solve the problem mentioned above, we propose a time division duplex (TDD) code division multiple access (CDMA) communication system which uses an asymmetric modulation between the forward and the reverse link. The system consists of multicarrier modulation for the forward link and single carrier modulation for the reverse link. A pre-equalization method for the forward link transmission is also presented in this paper. In frequency selective fading, the system achieves the frequency diversity effect without any channel estimation unit at the mobile station by using the pre-subcarrier equalizer