Optimizing CDMA Networks for Multimedia Applications Through Adaptive Modulation

With the emergence of multimedia applications in the mobile communication systems the data rate requirements have increased significantly to meet the demands. There are several possibilities for achieving higher data rates like using sophisticated receiver structures, powerful error correction codes and multi antenna systems for multi user detection. All these possibilities have been explored but the most promising solution to meet the growing demand resulting from multimedia applications is adaptive modulation. It tracks the time varying characteristics of wireless channels to increase the data rate and spectral efficiency. It will make use of higher order modulation schemes to meet data rate requirements. Adpative Modulation is now widely recognized as a key solution to increase the spectral efficiency of wireless systems. CDMA uses lower order modulation schemes such as BPSK and QPSK. In future data rate will strongly rise due to the multimedia applications. Therefore constellations with high order such as 16-QAM and up to 64-QAM have to be considered, which are to increase the spectral efficiency and thus the total data rate. In this paper an adaptive modulation architecture for CDMA is proposed and an algorithm to implement the adaptive modulation based on the signal to noise ratio is presented in this paper.