Adaptive Resource Allocation For Multi-Carrier Systems

Adaptive resource allocation for multi-carrier systems is studied in this thesis.Several adaptive resource allocation algorithms are proposed for OFDM systems with continuous bits, OFDM systems with discrete bits,and MIMO-OFDM systems with imperfect feedback.Multicast Rate Adaptive(MRA) problem is studied for OFDM systems with continuous bits.The objective is to maximize the spectrum efficiency while guaranteeing each multicast group's QoS.Firstly,we point out that the optimal resource allocation is NP-hard,and exhausted search is needed to obtain the optimal solution.Given subcarrier allocation results, the optimal power allocation with guaranteed QoS is proved to be a minimum power limited multilevel water-filling,and a low-complexity method based on bi-section search is given to find the water levels.Secondly,Dual decomposition theory is used to obtain an upper bound to the performance of MRA problem,and a near-optimal resource allocation is proposed. Simulation results show that the performance of the proposed algorithm is very close to the bound,and the bound is very tight,so the duality gap for MRA problem is neglectable.Lastly, to reduce the complexity of solving the MRA problem based on dual decomposition theory, five heuristic resource allocation algorithms are proposed.Analysis and simulations are given to demonstrate the effectiveness of the proposed heuristic algorithms,and their low computational complexity makes them very suitable for implementation in practical systems.Adaptive resource allocation for OFDM systems with discrete bits is also considered in this thesis.The objective is to maximize the spectrum efficiency while guaranteeing the BER requirement of each multicast service.We first extend the resource allocation algorithm from continuous bit scenes to discrete bit cases,which results in performance loss.To improve the system performance,a multiple description coding based resource allocation algorithm is proposed.The decoding flexibility of multiple description coding is well exploited,and the resource allocation is performed more effectively.Simulation results show that the proposed algorithm can improve the system performance under different scenarios.Adaptive resource allocation based on imperfect feedback is studied for MIMO-OFDM systems with VBLAST architecture.The definitions of confidence coefficient and equivalent variance are introduced to indicate the feedback quality,and their closed expressions are derived under the practical environment with both feedback delay and feedback error.Based on these closed expressions,an adaptive subcarrier allocation algorithm based on imperfect feedback is proposed.Not only the feedback channel information,but also the feedback quality is considered in the algorithm.Simulation results show that the proposed algorithm can improve system performance in various imperfect feedback scenarios.Adaptive resource allocation can utilize the limited system power and scarce spectrum resource effectively,and provide significant performance gain.The research results and contributions in this thesis are important references for resource allocation in multi-carrier systems.Some of the proposed algorithms with low computational complexity are also very meaningful for practice.