Image Transmission in Hierarchically Modulated Signals over Fading and Shadowing Channels

In order to have a higher throughput, it is essential to apply a higher order M-ary QAM modulation to yield more data on each carrier. This can be considered as the basis for adaptive transmission rate control where more parameters and signal information are available. In this thesis, M-ary modulation techniques are simulated over AWGN channel, Rayleigh fading channel and Log-Normal shadowing channel. To achieve the purpose of achieving higher throughput, it is necessary to recognize the performance indicators and investigate the criteria which are used for good performance. The five scenarios presented in this thesis are as follows: 1) Comparing the effect of Log-Normal Shadowing on different Hierarchical Modulations such as (64-QAM, 16-QAM, 4-QAM and 2-QAM). 2) The evaluation of BER of QAM system over AWGN and Rayleigh fading channels and considering the effect of shadowing. 3) Determine the important factors on the lognormal shadowing phenomena and how the factors affect this process. 4) Studying the relationship between the BER and variance in shadowing and fading channel. 5) The random input has been replaced by an image to investigate the effect of shadowing on quality of image. It is found that depth of shadowing influences the received signal quality and causes to have poor performance and throughput. Depth of shadowing is varied by the mean and variance of shadowing distribution function. Therefore, the Bit Error Rate (BER) of the system has been analyzed from low to high Eb/No through MATLAB/R2012a Simulink application in order to find out the effective factors on depth of fading phenomenon. It is observed that the system desirably works at high Eb/No. One of the significant parts of this research consists of the effects of Log-Normal Shadowing phenomenon on systems BER performance. Based on the results of the simulation, it is obvious that shadowing has a negative effect on the systems BER performance. In this study, 2-QAM system has received more attention because of having less sensitivity to shadowing phenomenon in comparison with 4, 16 and 64-QAM. Then the effective factors of shadowing have been studied and the results show that variance of Log-Normal distribution can be controlled as the only factor to control shadowing. This effect can be easily seen in the images, obtained. Keywords: Hierarchical Modulation, QAM Modulation, Multipath Fading Channel, AWGN Channel, Rayleigh Fading, Depth of Shadowing, Log-normal Shadowing ,Small Scale Fading and Large Scale Fading.