New Image Transmission Schemes for DST-Based MC-CDMA System

In recent years, one important research area for multimedia broadcasting is how to encrypt images over communication systems. However, wireless transmission is usually under many constraints and limitations like multipath fading, InterSymbol Interference and jitter especially for such applications require relatively high data rates compared to voice transmissions. Interleaving techniques with multicarrier code division multiple access system are used to combat multi-path fading environment. This paper proposes three new transmission schemes of encrypted images for downlink discrete sine transform-based multi-carrier code division multiple access (DST-MC-CDMA) system. For each one of them, two or three stages are added to the DST-MC-CDMA system to combat the wireless transmission problems. The three stages are called Randomization stage, Interleaving stage, and PIC stage. The randomization stage encrypts the image using a two dimensional chaotic map before the DST-MC-CDMA modulation. The interleaving stage interleaves the DST-MC-CDMA signal before the transmission. The stage of parallel interference cancellation is used to cancel the multiple access interference from the received image. The main aim is to clarify the received image by combating the wireless channel weaknesses. The results of the experiments reveal that the proposed schemes are superior to conventional one that uses only equalization. Moreover, a significant performance improvement in terms of the mean square error and peak to signal and noise ratio values when applying the proposed schemes is shown in the results.