【作者】 张蓝星；

【导师】 仇润鹤；

【作者基本信息】 东华大学 ， 通信与信息系统， 2008， 硕士

【摘要】 高速率、高可靠性的数据传输以及端到端的服务质量是下一代移动通信系统的首要目标,多入多出(MIMO,Multi-InputMulti-Output)技术、正交频分复用(OFDM,Orthogonal FrequencyDivision Multiplexing)技术和自适应传输已经被广泛认为是未来移动通信系统中的主要候选技术。MIMO技术通过采用多个发射天线和接收天线可以显著提高无线通信系统的信道容量,增强数据传输的可靠性。OFDM技术可以把频率选择性衰落的信道转化成一组正交的平坦衰落的信道,因此将MIMO技术与OFDM技术相结合的多入多出—正交频分复用(MIMO-OFDM)技术成为未来移动通信系统设计的主选架构。本文首先对无线信道进行了分析,对其参数多径效应和多普勒效应进行了研究,并引入MIMO-OFDM的系统概念,并重点介绍和分析波束成型技术,以及自适应调制的三大关键技术。其次,通过对波束成型技术的介绍,引入并推出多用户情况下的子载波分配方案,分别对基于正确信道信息和非精确信道信息的情况进行了讨论。其中,在正确信道信息的系统模型下,推出以最大特征值为分配准则的子载波分配方案,通过仿真结果表明,这种分配方案可以有效获取多用户的分集效果。接着对非精确信道信息的实际系统进行了讨论,并提出了信道预测模型,该模型通过各个用户信道的相关系数来均衡信道时延的影响,仿真结果表面该模型能够有效减小信道信息时延所造成的性能损失。本文最后对注水分配法基本原理进行了研究,讨论了最常用的比特数和误码率上限不变时发射功率最小化算法,然后提出了基于变步长的比特功率分配算法,该算法对于步长选择进行优化,和比特数和误码率上限不变时发射功率最小化算法相比,在系统复杂度方面有了明显的降低,同时两者性能非常接近,而且通过仿真可知其多用户时性能将更好,因此可以很好的应用于多用户的MIMO-OFDM系统。更多还原

【Abstract】 High data-rate, high reliable transmission and guarantee end-to-end Qos are required to be provided for the next generation mobile communication. MIMO, OFDM, and adaptive transmission have been comprehensively considered as the major candidate techniques for future radio communication systems. MIMO technology can increase the channel capability notably and enhance reliability of data-transmission with the help of multi-send antenna and multi-receive antenna. OFDM has the ability of transforming the frequency-selective channel into a collection of parallel flat-fading sub channels. Therefore combination of MIMO and OFDM is regarded as the potential architecture for the future communication system.In this paper, wireless channel, the parameters of multi-path effect and Doppler Effect were analyzed firstly, and then mainly focus on introduction and analysis of Beam-Forming, and 3 key technology of adaptive modulation.Based on the Beam-Forming technology, multi-carrier allocation programs was introduced, and it was discussed based on the correct channel information and non-accurate information of channel. Among two different circumstance, in the correct channel information system model, the greatest eigenvalue distribution criteria for the subcarrier allocation program was introduced, and the simulation results show that the distribution program can be effective multi-user access to the diversity effect. Then channel for non-precision actual information systems were discussed and a channel prediction model was proposed, the model balance the channel Delay through multi-users’ correlation coefficient, and the simulation result shows that this model effectively reduce the loss caused by channel information Delay.Finally, the basic principles of water-filling method was studied, and then discussed the most commonly used unchanged-bit number and bit error rate when minimize the transmitting power method. Then the power allocation algorithm which is based on the variable step-bit was proposed, the algorithm optimize the choice of step, and compared with the former algorithm, this power allocation algorithm based on the variable step-bit can decrease the complexity of the system while the performance are quite close to each other. Through simulation, the performance of the multi-user will be better, so it can be good for the multi-user MIMO-OFDM system.更多还原