Research On Dynamic Resource Allocation Algorithms For Single-User OFDM Systems

With the development of economy and the improvement of people's living conditions, the requirement for the communications is becoming more and more high, the majority of users are not satisfied with mere voice, data and video transmission speed, now what we need is a new communication service with higher speed, higher quality of service, and supporting more business kind. Therefore, in order to meet these needs, the future of wireless mobile communication technology must seek the technology advancement from many aspects.OFDM has been considered as one of the key techniques in the forth generation mobile communication systems due to its high spectrum efficiency and strong immunity to interference. An important characteristic of OFDM systems is that a broadband wireless channel is divided into a number of parallel orthogonal narrow-band sub-channels, so that adaptive modulation can be applied to each sub-channel, and we can allocate bit and power dynamically according to the current status of the sub-channel, this greatly improves the efficiency of spectrum and alleviates the growing tension in the limited spectrum resource, while increases the system capacity. Therefore, the study on dynamic resource allocation has a certain theoretical value and practical significance.Nowadays there are many essays about dynamic resource allocation algorithms for single-user OFDM systems, and sub-channel allocation among multi-users also is a hot topic. This thesis is mainly focused on resource allocation algorithms in single-user OFDM systems. Aiming at the drawbacks on performance and complexity of the existing algorithms, several improved algorithms are proposed, and the simulation results show that the improved algorithms have better performance and lower complexity.The main work in this thesis is as follows. Firstly, the theoretical basis and optimization criteria commonly used in dynamic resource allocation are introduced. The classical algorithms for single-user OFDM systems, such as Leke's, Chow's and Jang's algorithm, are summarized. Their procedures and existing problems are analyzed in details. Secondly, in order to solve the problem of divergence in sub-optimal iterative algorithms in the actual channel, a dynamic boundary constraint iterative method which can avoid vibration is proposed and applied to iteration-based suboptimal allocation algorithms(such as Chow's, Jang's algorithm), The complexity of these algorithms are reduced dramatically. Finally, aiming to reduce the extremely high complexity problem of Greedy algorithm, we analyze the distribution property of the optimal allocation result obtained by greedy algorithm, and then propose a new optimal allocation algorithm. Simulation results show that the proposed optimal allocation algorithm in this thesis can converge to the optimal result rapidly, while the complexity is very low in all channel status.