IMAGE TRANSMISSION THROUGH MC-CDMA CHANNEL: AN IMAGE QUALITY EVALUATION

Abstract

The multicarrier code division multiple access (MC-CDMA) system is considered as an advancement in mobile communication system. Seen as the next generation communication technology after the 3G, signals can be easily transmitted and received using the Fast Fourier Transform (FFT) device without increasing the transmitter and receiver complexities. Besides, the MC-CDMA system provides good spectral efficiency. If the number of sub-carriers and the spacing between sub-carriers are chosen properly, it is unlikely that all the sub-carriers will be in deep fade. Thus, it provides frequency diversity. Frequency diversity means that frequencies separated by more than the coherence bandwidth of the channel will be uncorrelated and thus will not experience the same fades. Three types of MC-CDMA systems were proposed — MC-CDMA, multicarrier DS-CDMA and multitone CDMA. In MC-CDMA systems, the transmitter spreads the user data over different sub-carriers using spreading code (Hadamard Walsh code) in frequency domain. The multicarrier DS-CDMA system spreads the S/P converted data streams using spreading code in time domain. This scheme is proposed for uplink communication because this scheme can provide quasi-synchronization. In the MT-CDMA scheme, the S/P converted data stream is spread in time domain so that the spectrum of each sub-carrier prior to spreading operation can satisfy the orthogonality condition with minimum frequency separation. Thus, the spectrum of each sub-carrier no longer satisfies the orthogonality condition. MC-CDMA uses longer spreading code as compared to other schemes and thus accommodates more users. The JPEG2000 still image compression is a new image compression technique which is optimized not only for efficiency, but also for scalability and interoperability in network and mobile environment. This standard can provide superior low bit rate performance and continuous-tone and bi-level compression. Because of the robustness to bit errors, JPEG2000 is widely used in wireless communication channel.