Adaptive Modulation Coding Scheme in Amplify and Forward Relay Networks

Abstract: Wireless communications have become an essential part of our daily life. Despite the fact that wireless networks are simple to set up and deploy, the channel conditionsin wireless networks are susceptible to fading and attenuation, thereby reducing the transmission efficiency and reliability. The influence of unstable wireless channels, fading and attenuation is a significant limitation of wireless networks. The persistent and exponential increase in the usage of wireless communication services demands for enhanced reliability, transmission range and efficiency. This can be achieved byexploring and proposing different propagation techniques and models. This thesis evaluates a network model which makes use of an adaptive modulation coding scheme in the presence of an Amplify-and-Forward relaying environment. We deploy adaptive modulation technique in combination with Amplify-and-Forward relaying transmission mechanism to select the best suitable transmission path and obtain better transmission efficiency for a wireless communication system. The network model thus designed comprises of two links, one considering the relay transmission path that travels from the source-to-relay-to-destination, and the other link considering the direct transmission path traveling from the source to the destination, while both the links undergo Nakagami-m fading. In addition, the system ensures better performance in different conditions by making use of adaptive modulation and coding scheme and deploying distinct modulation and coding schemes based on the condition of the communication channel. The performance of this system model is analysed through mathematical analysis and the results are validated and depicted through simulation in MATLAB under different conditions. We have thereby derived the closed-form expressions for the Signal to Noise Ratio (SNR), Outage Probability, and the Packet Error Rate (PER) for the considered network model in the Nakagami-m fading environment. Different fading parameters that affect the system performance are considered and varied while obtaining the required results through MATLAB simulations. The system model proposed significantly reduces the outage probability and packet error rate and aids in achieving better system performance and reliability.