摘要
下一代移动通信的主要目标之一是在时变,频率选择性和带宽受限的无线信道上提供高速有效的多媒体服务。结合动态资源分配的正交频分多址(OFDM,Orthogonal Frequency Division Multiplexing)技术是最有潜力增进系统频谱利用率,提高数据传输率的技术之一。
本文着重讨论了已知信道状态信息(CSI,Channel State Information)条件下,多用户OFDM系统的子载波,比特和功率的动态分配算法及其硬件验证方案。首先就固定速率功率动态分配算法(MA,Margin Adaptive)进行了研究,讨论了MA分配算法的优化模型及其经典算法,进而提出的基于需求度次优MA资源分配算法,在本文所述的业务模型下,性能非常接近最优算法,而且计算复杂度也有大幅度的降低。
然后,对于功率固定速率动态分配算法(RA,Rate Adaptive),本文建立了下行OFDM系统在发射总功率一定且在保证用户之间比例公平的前提下,最大化系统总容量的子载波、功率和比特分配优化模型,提出了一种在保证一定用户公平性条件下提升系统容量的次优算法。该算法将子载波分配和比特分配分为两个独立的步骤进行,每个步骤都能保证用户一定程度的比例公平性,并且结合多用户分集调度以及贪婪比特分配的思想进行资源优化分配,从而具有较高的系统吞吐量。通过系统仿真,我们验证了该算法在满足一定公平性条件下比最优公平性算法具有更高的系统容量性能。
最后,本文还给出了基于picoArray技术的HDP102平台和PC8520系统的算法验证方案和结果。经过初步的硬件实现和检测,得出本文所提出的次优动态资源分配算法能在系统中正常工作,并保证较高的下行链路的数据传输速率。
One of the main objectives in future wireless networks is to provide high-rate data services with satisfying QoS (Quality of Service) and fairness over time-varying, frequency selective fading and band-limited wireless channels. Orthogonal Frequency Division Multiplexing (OFDM) combined with dynamic resource allocation method is one of the most potential techniques to satisfy this need.
This thesis focuses on the dynamic resource allocation algorithms in multiuser OFDM system and their hardware verification with multicore DSP platform. Firstly, the optimizing model of multiuser OFDM systems has been established, and the dynamic power allocation algorithms with fixed transmission rate, namely Margin Adaptive (MA) algorithms, have been analyzed. Furthermore, a novel suboptimal MA Greedy algorithm based on demand function has been proposed to reduce the computing complexity with subscribers' fairness and QoS guaranteed. Utilizing the simulation of real-time services, we have proved that compared to static allocation algorithms, the proposed MA Greedy algorithm could enhance the system performance by 5-6dB with low computing complexity, which is very close to the optimal MA algorithm.
Subsequently, the mathematic model of rate adaptive (RA) algorithms which aims for maximizing the overall system capacity under the constraint of fixed total transmitting power has been built. Then, a suboptimal fairness algorithm based on demand function has been put forward to improve the system capacity. In this algorithm, the allocation process is divided into two separate steps, resource calculation and subcarrier allocation. With the employment of multiuser diversity scheduling and the Greedy bit allocation algorithm, this algorithm could implement high system throughput and proportional fairness with low computing complexity. Through the simulation with non-real-time services, we proved that with the fairness of subscribers guaranteed, the proposed suboptimal fairness algorithm could provide a higher overall performance to OFDM systems than the optimal fairness algorithm.
Finally, a preliminary scheme has been provided to verify the feasibility and validity of proposed RA algorithm. The result showed that the algorithm operate well on the selected multicore DSP platform.
引文
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