Adaptive multilevel code selection and MUI cancellation for DS/CDMA over fading channel

For transmission of speech or multimedia information in a time-varying mobi le channel, fixed rate codes are normally used designed for average or wors t channel conditions. However, fixed rate codes fail to explore the time-va rying nature of the mobile channel. In their previous work the authors have shown that a multilevel code, when used in conjunction with multiuser inte rference (MUI) cancellation in cascade, yields better performance than a co nventional coded modulation scheme applied to CDMA. They show that, when mu ltilevel codes are changed with varying channel conditions (i.e. are chosen adaptively according to the channel state information (CSI)), throughput ( average number of information bits per symbol duration) can be increased wi thout too much performance degradation. Code selection criteria as well as some codes with appropriate thresholds are also presented.