【作者】 陈佳锐；

【导师】 唐碧华；

【作者基本信息】 北京邮电大学 ， 应用数学， 2007， 硕士

【摘要】 多载波系统具有抗多径干扰能力强、频谱利用率高的优点，非常适合未来的高速无线传输应用。在多载波系统中，不同的子载波经受不同的信道衰落，具有不同的传输能力。通过研究有效的无线资源分配策略，可以提高多载波系统的传输性能。因此自适应分配算法得到广泛关注，是当前多载波系统研究的热点问题之一。本文在对多载波系统自适应分配算法进行认真研究的基础上，主要完成以下的工作：本文首先介绍了几种典型的自适应比特和功率分配算法，并对Fischer算法进行了改进，提出了Fischer-Evo算法。然后分析了它们对于OFDM系统性能的改善情况和计算复杂度。仿真结果表明，Fischer-Evo算法无论是在性能上还是在效率上都比其他算法有更好的表现，适合在实际系统中使用。本文为固定速率的OFDM系统提出了一种追踪-可控自适应分配算法。该算法利用前一次的分配信息作为无线资源的预分配，通过局部调整来实现系统的最优或次优分配。并且可以通过设置调整门限来控制计算的次数，在牺牲一定性能的情况下降低复杂度，达到性能和效率的平衡。仿真结果表明，该算法的计算复杂度小，运算效率很高。本文为变速率的OFDM系统提出了一种高效变速率自适应分配算法，利用仙农公式和拉格朗日公式把系统的优化目标和限制条件结合起来，解出最优的理论分配结果。接着通过比特取整过程以及部分子载波功率和比特调整过程，实现系统资源的合理分配。仿真结果表明，该算法性能优良，运算速度快。MC-CDMA是OFDM技术和CDMA技术的有效结合。为了把自适应分配算法应用到MC-CDMA中，本文提出一种高效MC-CDMA自适应分配算法。该算法借鉴OFDM系统中自适应分配算法的思想，为各个扩频支路确定合适的比特数目和发射功率。仿真结果表明，该算法能够大大降低发射功率，优化系统的性能。更多还原

【Abstract】 Multi-carrier system is very suitable for future high-rate wireless communication, due to its robust to multi-path interference and high frequency efficiency. The sub-channels in multi-carrier system suffer different wireless fading, so they have different channel capacity. Through the study of efficient allocation strategy, the performance of multi-carrier system can be improved. Therefore adaptive allocation algorithms have been widespread concerned and become one of the focuses in multi-carrier system research. Basing on the in-depth study of adaptive allocation algorithm, the main research work in this thesis includes:In this thesis, some typical adaptive bit and power allocation algorithm are first introduced. At the same time, we improved the Fischer algorithm and proposed Fischer-Evo algorithm. Then, we analyze these algorithms’ performance and complexity. Simulation results show that Fischer-Evo algorithm performs better than others both in performance and efficiency, so it is more applicable for practical implementations.In this thesis, a Track-Control algorithm is proposed for constant-rate OFDM systems. This algorithm uses the former allocation information as system resource pre-distribution, and finishes the optimal or hypo-optimal allocation with partial adjusting. Meanwhile, the iteration can be controlled by setting the adjusting threshold and the complexity can be reduced by sacrificing some performance. So it can come to the balance of algorithm’s performance and efficiency. Simulation results show that the proposed algorithm has small algorithmic complexity and high efficiency. In this thesis, An Efficient Variability Rate algorithm is proposed for variable-rate OFDM systems. This algorithm can get the theoretic optimal allocation by using Shannon and Lagrange formula to combine system’s optimizing object and limitation condition. Finally, with the bit integer conversion process and the partial sub-channel’s power and bit adjusting process, the system resource allocation is finished. Simulation results show that the proposed algorithm has excellent performance and fast operation ability.MC-CDMA is an effective combination of OFDM and CDMA technology. To apply adaptive allocation algorithm to MC-CDMA, a high efficiency MC-CDMA adaptive allocation algorithm is proposed in this thesis. We distribute proper bit and power for each spread branch by using adaptive allocation ideas in OFDM for reference. Simulation results show that the proposed algorithm can remarkably reduce transmission power and improve system performance.更多还原