PERFORMANCE EVALUATION OF RATE ADAPTIVE MODULATION AND CODING TECHNIQUES THROUGH FADING CHANNELS

Realistic channels affect the transmission greatly in mobile wireless systems. They result in various data impairments. The channel state varies with geographical conditions and timings. The integration of appropriate channel coding and modulation techniques can reduce this effect. However, utilizing fixed parameters under varying channel conditions leads to an inefficient utilization of resources. To avoid any conflicts and to acquire better spectral efficiency, link adaptation is the technique followed now days in emerging standards. Underlying concept of link adaptation is to choose specific parameters according to realistic channel conditions. In this paper, parameters which are measured, monitored and dynamically adapted incorporate modulation scheme, coding rate, pre-coder matrix indices and transmission modes/layers. Turbo coding and STBC (Space Time Block Code) are the channel coding techniques utilized in the proposed model. Paper explains how the occurrence of irreducible errors makes it strenuous for systems using restricted parameters to lessen the manipulative effects in the absence of adaptations. It also represents the effect of adaptations on average data rate and BER exploiting three parameters which are channel quality indicator, pre-coder matrix indicator and rank identification. Matlab software is used for obtaining simulative results.