【作者】 张海刚；

【导师】 袁东风；

【作者基本信息】 山东大学 ， 通信与信息系统， 2010， 博士

【摘要】 信道编码和调制是利用信道进行信息有效传输的重要手段,这里所谓有效传输是指在保证一定通信速率情况下实现无差错的传输(或传输质量满足一定差错要求)。信道编码是实现传输抗干扰的核心技术,而调制技术则将信号转变成适合信道传输的形式,并对信道容量和传输效率有着及其重要的影响。信道编码和调制技术一直是移动通信领域重要的研究课题。尽管随着Turbo、LDPC等高级信道编码的成熟和各种高阶调制的应用日益普及,目前无线通信系统已经达到了很高的水平,但从信息论的角度看,目前的通信系统距离理论极限还有很大距离,特别是目前的编码调制技术对于信道容量利用的程度在多用户条件下还不是很理想,所以编码调制还有待进一步深入的研究,为下一代无线通信系统做好技术储备。本文首先将着眼点集中于高级信道编码的一种：LDPC码,在对LDPC码深入分析的基础上,重点针对LDPC两类译码算法进行了研究,BP算法和WBF算法,并分别提出了两种能够实现性能和复杂度更好折中的新的译码算法。然后将LDPC码应用于MIMO系统中,基于本实验室搭建的MIMO平台在真实信道环境中验证了LDPC码的优异性能。同时,将LDPC和星座旋转结合用于基于OFDM的CR系统中,在保持高保护度的情况下将控制信息和可用信息一起传递,并对星座旋转的实质进行了分析,找到了星座旋转和调制集分割的关系,给出了高阶星座的分解原则。最后,还对李道本教授提出的OvCDM技术进行了分析和研究,从理论上阐述了OvCDM的原理,说明了这一技术对于调制编码理论的突破性贡献,并对Turbo-OvCDM方案进行了性能验证,在验证过程中,提出了新的归一化译码算法,提高了Turbo-OvCDM的性能。1、阐述了LDPC的基本原理,包括LDPC相关的关键概念,LDPC码的主要构造方法,LDPC的两类主要译码算法。针对BP算法提出了新的改进UMP-BP算法,对随机构造的码在不增加复杂度的情况下可以获得与BP算法相当的性能。针对WBF算法提出了新的改进WBF算法,对于FG-LDPC码可获得超过其他WBF并接近BP算法的性能。将LDPC码应用与MIMO平台,通过真实的信道环境验证了LDPC码的性能。2、通过对认知无线电(CR)系统的介绍,引入基于OFDM的CR系统,利用LDPC码和星座旋转将控制信息和可用信息一起传递,保证控制信息的可靠传递,并可有效提高传输效率。给出了星座旋转的方式和旋转检测方法,分析了星座旋转和调制编码集分割的关系,给出了高阶星座图分解的原则。3、阐明了OvCDM的基本原理,与现有编码、调制、(多址)复用方案的关系,对Turbo-OvCDM进行了验证分析,并在AWGN信道和Rayleigh信道分别得到可靠的性能结果。针对Turbo-OvCDM提出了改进的译码算法,利用初始信息的归一化,提高了译码性能,同时避免了高信噪比时的运算溢出。更多还原

【Abstract】 Channel coding and modulation are key technologies for efficient information transmission over wireless channel. Channel coding can offer error-correcting ability through redundancy and modulation changes the signal to the shape which is adapted to channel transmission. There are great improvements on channel coding and modulation in recent years especially Turbo code and LDPC codes have exhibited excellent performance. But in the view of information theory, there are still long road to approach the goal especially in multi-user and broadband conditions. This thesis first focuses on the decoding of LDPC codes and the application in MIMO and CR system of LDPC codes. Then OvCDM is investigated since it is a great break in coding and modulation theory. The coding is done on signal directly and without the limitation of finity field. The coding rate can exceed 1. The Turbo idea which can also been applied to OvCDM. A novel decoding method for Turbo-OvCDM is proposed in this thesis.The contents and major contributions of this thesis are as the following:1. Explain the principles of LDPC codes. Two novel decoding methods are proposed based on BP and WBF decoding methods respectively. The new methods both can acquire better tradeoff between performance and complexity. The new UMP-BP mothod has nearly the same performance as BP method for random constructed LDPC codes at high SNR. And the new WBF mothod defeats all the other WBF methods for FG LDPC codes. LDPC codes are also been applied to MIMO system. The excellent performance of LDPC codes is proved in real MIMO wireless channel.2. The CR model based on OFDM is explained. Then LDPC codes together with constellation rotation are applied to the CR system. The signaling message is transmited with jinformation message imultaneously. The relationship between constellation rotation and set partitioning in coded modulation is analyzed. 3. The relationship between OvCDM and common multiplexing and multiaddress tenologies is exlained theoretically. Turbo-OvCDM is applied in AWGN and Rayleigh fading channel. The identity analysis of OvCDM and the performance of Turbo-OvCDM are presented. Novel decoding method for Turbo-OvCDM is proposed for better performance.更多还原