【作者】 张大鹏；

【导师】 刘琚；

【作者基本信息】 山东大学 ， 通信与信息系统， 2009， 博士

【摘要】 中国第3代移动通信系统（3G）已投入商用,超3代（B3G）或第4代（4G）移动通信系统的关键技术也趋于成熟。通信技术的发展使人们之间的距离变短,对整个社会的发展起到变革性作用。作为通信技术的一个重要分支,无线通信已经成为当今世界发展最快的技术之一,并已成为社会发展的重要标志。更快的传输速率、更优的传输质量和更广的适用范围永远是无线通信的追求目标。然而,实际的通信系统面临着诸多复杂的问题,多径、频移、噪声、多址干扰、符号间干扰以及带宽的限制都严重影响通信链路的质量和系统容量,并已成为制约通信发展的关键因素。九十年代提出的多输入多输出（MIMO）无线通信技术为无线通信系统引入了又一维可利用的空间,并以其能够充分挖掘空间资源,最大限度地提高频谱利用率和功率效率而受到广泛重视。空时信号处理理论提供了解决问题的有效途径,该理论属于信息科学的一个新的分支,涉及时域信号处理、空域信号处理、信道编码等诸多学科。其中,酉空时调制技术因发、收两端均无需信道信息而十分适合高速移动的通信环境,但是它在低信噪比条件下存在差错性能较差的问题。本论文主要就酉空时调制的差错性能、符号设计以及与信道编码的级联和综合设计等方面进行了研究,分析了目前的研究难点并提出了合理的解决方案。本文的学术贡献主要在于:1)对现有的空时码提出一种新的分类标准;利用矩生成函数独立推导了酉空时调制的成对差错概率,避免了对复数构成本身的讨论,给出被积分式的收敛域,并根据二元检测的一般原理推导出了Chernoff上界,此方法可扩展到其它类型的空时码。2)提出了简化搜索和星座降维方案,可适用于不同的实际设计准则中,在不降低实际差错性能的前提下可使计算量分别降至原先的10^-6和10^-20以下。3)提出酉空时符号及差分酉空时符号级的Turbo码方案,包括分量码的并行级联和串行级联,相对于比特级处理方案,可在不降低差错性能的前提下减少计算量;提出酉空时符号级的多进制MAP、Log-MAP、Max-Log-MAP及SOVA迭代译码算法;并且首次分析了发射分集在酉空时调制和Turbo码级联方案中的实际作用。4)受网格编码调制星座集分割理论的启发,提出比特交织编码酉空时调制方案,该技术的信道编码和酉空时调制各自独立,利用硬判决反馈实现迭代解调—译码,可在不降低数据速率的前提下大大降低系统的误比特率。相比网格编码酉空时调制有更好的差错性能,且计算复杂度不高,是一种实用的编码调制相结合的方案。5)分别提出Cayley差分酉空时调制和多级空时调制与并行Turbo码的级联方案,并给出与之适应的译码算法。其中,Cayley差分酉空时调制与Turbo码的级联可以在准静态或连续性衰落信道中提供可靠的高数据率;而多级空时调制与Turbo码的级联经过迭代译码后可在短相干时间和低信噪比条件下实现可靠的无线通信。综上所述,本论文针对目前MIMO空时系统存在的问题,以提高非相干空时调制的有效性和可靠性为核心进行了研究,包括酉空时调制本身的理论以及与信道编码相结合的技术。论文最后总结了该研究领域亟待解决的一些问题和下一步的研究重点,同时对该领域的发展趋势进行了展望。更多还原

【Abstract】 The 3rd generation mobile communication system has been put into commercial uses in China,and the key technologies of the beyond 3rd generation or 4th generation mobile communication systems are developing as time goes by.The development of communication technology makes the distance between people shorter and has a revolutionary effect on the whole society.As an important branch of communication technology,wireless communication is now becoming an important sign of the social development.Higher data rate,better quality and wider application are the goals of wireless communication forever.However,in reality,wireless communication system meets with many complicated problems,such as multi-path,frequency shifting,noise, multi-access influence,inter-symbol interference(ISI) and the limitation of bandwidth, which greatly affect the quality of communication links and system capacity and also become the key factors obstructing the development of wireless communications.Multi-input-multi-output(MIMO) technologies,proposed in the 1990’s,have introduced another useful dimension and have received wide attention because it can make full use of space resources,increase the data rate and improve the power efficiency.The theory of space-time signal processing provides an effective tool for solving the communication problems and is a new branch of information theory, relating to temporal domain signal processing,spatial domain signal processing, channel coding and so on.Unitary space-time modulation(USTM) is ideally suited for communication with high speed mobility as it needs no channel state information for both the transmitter and the receiver,but its error performance is not good at low signal-to-noise ratio(SNR).This dissertation mainly discussed the error performance of USTM,signal design and the combination with channel coding,analyzed the problems and proposed some reasonable solutions.The academic contributions of this dissertation are mainly as follows.1) We proposed a new classification method for the existing space-time codes. Using the moment generating function,we independently derive the pair-wise error probability(PEP) of USTM and give the region of convergence for the integrant. Using the basic binary detection theory,we get the Chernoff upper bound(CUB) for USTM.The method for deriving the PEP and CUB can be utilized to other kind of space-time codes.2) We gave simplified search and size-reduced algorithms for unitary space-time (UST) constellations,which can be used in different design rules.It can decrease the computation complexity to one millionth and even much less.3) We proposed(differential) unitary space-time symbol-based Turbo codes, including both the parallel and serial concatenation of the component codes. Compared with the bit-wise processing scheme,it can decrease the calculation amount without lowering the error performance.Corresponding to the multi-ary Turbo coding,we also present the UST symbol-based MAP,Log-MAP, Max-Log-MAP and SOVA iterative decoding algorithms.We discussed the effect of transmit diversity in the concatenation scheme of USTM and Turbo code for the first time.4) Based on the set partitioning theory of trellis coded modulation,we brought out the bit interleaved coded(BIC) USTM,where the channel coding and unitary space-time modulation are mutually independent.The iterative decoding is realized by the hard decision feed back,which can greatly increase the error performance and do not decrease the data rate.Compared with the trellis coded USTM scheme, BIC-USTM can perform better while its complexity is not too high,which makes it a practical combination scheme for coding and USTM.5) We concatenated Cayley differential unitary space-time modulation and multilevel space-time modulation with parallel Turbo coding respectively,and derived the corresponding decoding algorithms.The concatenation of Turbo code with Cayley DUSTM can bring a high reliable data rate in continuous fading channels,while the Turbo coded multilevel space-time modulation can give a reliable communication in short coherence interval and low SNR with iterative decoding.In short,we investigate to increase the reliability and effectivity of noncoherent space-time modulation,including the theory of USTM itself and the combination with channel coding.Finally,the problems to be solved related to this domain and future research topics are summarized,furthermore,the prospect of the developing tendency is analyzed as well.更多还原