Adaptive Ofdm System Resource Allocation Problem

As a representative of multi-carrier transmission technique, orthogonal frequency division multiplexing(OFDM) has won increasingly broad application for its high ability of anti-fading in the wireless multipath channel. Adaptive OFDM(AOFDM) technique can adaptively adjust resource allocation for each subcarrier, this will highly improve the robustness and efficiency of a OFDM transmission system. This dissertation has some work on this subject, represents an in-depth study on both theory and algorithm.First, this dissertation briefly introduces the development course of wireless communications and OFDM technique, and the concept of AOFDM is brought out.After giving a summary of current researches on this subject, the dissertation illuminate the background of its research and set out the whole article structure. Chapter 2 briefly introduces some AOFDM relevant techniques, including the basic characteristics of wireless channel, the fundamental OFDM and algorithm techniques, which will pave a way for the following further study.Chapter 3 and chapter 4 formulates the research achievements on single-user AOFDM system. The dissertation deduces or analyzes the ideal resource allocation results based on both channel capacity and concrete modulation types(MPSK MQAM), analysises and simulation comparisons are made for them. The dissertation re-proves the equality of all the three kind of optimization problems more systematicly by integrating and considering them together, and demonstrates its significance with a example. The dissertation proposes or improves three high-level algorithms, i.e., the greedy algorithm, the theory approach algorithm and the uniformly allocation algorithm, each of them can solve all the three problems, the dissertation then compares them thoroughly and makes some valuable conclusions.Chapter 5 formulates the research achievements on multi-user AOFDM system. The dissertation makes an in-depth study on the joint allocation theory, purposely investigates the Lagrange relaxation algorithm, points out its loopholes and proposes an optimized joint algorithm. On the aspect of step by step allocation method, the dissertation investigates the ACG algorithm, analyzes a improved algorithm and proposes a new algorithm which takes user QoS into account, finally a mend for the whole algorithm flow is analyzed. Simulations show that all these improvements and new algorithms are highly efficient.Finally, the dissertation summarizes the whole work and gives some directions for the further research.