Orthogonal Frequency Division Multiplexing (OFDM) is a promising candidate for Multi-Carrier (MC) transmission. The combination of OFDM and Code Division Multiple Access (CDMA) referred to as OFDM-CDMA has drawn much interest in wireless communication systems. Inspite of its various beneficial qualities, the drawback includes the requirement of Cyclic Prefix (CP) to avoid interference between OFDM symbols. In this paper, we address the effect of CP length by evaluating the performance of two OFDM-CDMA systems 1)MC-CDMA 2) MC-Direct Sequence(DS)-CDMA. Simulation results shows that MC-CDMA outperforms MC-DS-CDMA with reduced cyclic prefix length. Moreover, it was also found that spreading factor have significant effect on the performance after CP reduction.Key words: MC-direct sequence (DS)-CDMA,multicarriercode-division multiple access (MC-CDMA), orthogonal frequency division multiplexing (OFDM), cyclic prefix (CP).

In last decade the transmission of image over wireless network has become challenging. Compressed bit stream of image/video need less storage and bandwidth but highly sensitive to propagation of errors. So error control is an important technique in image/video transmission. This paper proposed multilayered bit stream of JPEG coded image transmission through wireless channel (SUI) using Unequal Error Protection (UEP). The Protection level will be decided based on the importance of layer in retrieval of image. The JPEG image data stream is partitioned into three layers: 1) DC coefficients 2) High informative AC coefficients 3) Low informative AC coefficients. Even with strong error protection applied, in higher noisy environment undetected block error still exists in transmission stream which degrades the image quality. So it requires repairing of block errors. For repairing of block errors first the damaged blocks are detected then repaired using linear interpolation. The simulation results shows quality of recovered image can be improved using different error controlling techniques like UEP and error concealment.

In this paper an image transmission system has been proposed where Joint Photographic Experts Group (JPEG) algorithm is used as an image coder and Rate Compatible Punctured Convolution (RCPC) channel coder is used for transmission of coded image over wireless channels (AWGN and Rayleigh fading). JPEG bit stream is partitioned into DC and AC bit streams. AC bit stream further classified using edge density property of block. Priorities based Unequal error Protection (UEP) applied to bit stream. Distortion analysis (MSE) is given for proposed image transmission scheme. The simulation results shows reduction in distortion compared to conventional Equal Error Protection (EEP). This proposed algorithm can be applied for low frequency as well as high frequency images.