Research On Radio Resource Management In OFDM Systems

As a multi-carrier modulation technique, OFDM (Orthogonal Frequency Division Multiplexing) has very good anti-multipath capability, anti-noise performance and a high spectral efficiency. It is considered to be the key technology in next generation mobile communication system, and attracts more and more attention.In an OFDM system, the allocation of resources (including sub-carrier, transmission bit and power allocation) has a very important impact on the system performance. Feasible allocation of subcarrier and power can reduce the bit error rate, transmit power and increase the bandwidth efficiency, the capacity of the system and the total data rate. Hence the research on principles of resources allocation is emphasized in this thesis, and an improved algorithm for proportional resource allocation was proposed, through the study of some classic algorithms. The simulation results show that the algorithm ensures the fairness among users and improves the system capacity effectively at the same time.In addition, more and more people choose to take the high-speed rail. Researchers also look forward to using advanced communications technology and reliable data transmission in the application environment of high-speed railway, such as train control and communication of passengers. Therefore, integrating with the practical application of OFDM, we analyzed the interference in the case of high-speed railway, and used a feasible power allocation algorithm to reduce the error rate in the practical scene and to improve the quality of the users' communication.In this paper, we simulated the interference in the case of fast-moving using WINNER II channel model. The simulation results show that the BER of the users in the train is affected by the interference of roadside base station, and the error rate will increase as the interference becomes larger. In addition, as a result of Doppler shift and other factors, the users in the train receive different BER at different speeds. And the error rate will increase as the train speed becomes higher. Considering the above, we used a power allocation algorithm which can minimize the bit error rate to reduce the error rate of the receiver in the high-speed scenario. The simulation results show that this method can effectively reduce the bit error rate of the receiver and improve the quality of the users' communication.