One of the biggest challenges for the next generation wireless systems is to accommodate the increasing user demand and to achieve a ubiquitous high-data-rate coverage. To overcome these challenges, many resources are needed. Therefore, intelligent radio resource management schemes are required to combat these challenges. The problem of the power allocation in OFDM-based DF relaying systems is addressed in this thesis. The power of each subcarrier is computed exactly with a low complexity solution to maximize the total transmission rate. For this purpose, the problem is solved in two steps, where i n the first step, the rate on each subcarrier is maximized with the assumption that each subcarrier has a limited power. As a result, the capacity function is simplified and the source and relay power related to the limited power of each subcarrier are identified. In the next step, using the results of the previous step , the total power of subcarriers that maximizes the total sum rate is obtained. To evaluate the accuracy of the proposed method, through simulations its accuracy is compared with the traditional solutions, i.e., bisection method. Simulation result indicate that the proposed method provides accurate solution through less iterations compared to bisection method. Moreover, the proposed method can find the exact value for subcarriers power. Moreover, the proposed method is generalized to the selection relaying strategy. Numerical results show as the distance between source and relay increases, selection relaying strategy works better than fixed relaying strategy.
