基于无速率码与Vector OFDM的编码调制技术研究
发布时间：2018-09-03 14:32
【摘要】：高速移动的宽带无线通信系统是未来无线通信发展的明显趋势,其中移动性是现有和未来无线通信、车辆网络、高速铁路等系统所具有的重要属性。更高的通信带宽和移动速度使得信号经历的通信信道更为复杂多变,信道表现出明显的时间色散和频率色散双选择性衰落特性。如何适应双选择性衰落信道快速多变的复杂特性,保证通信的可靠传输,提高通信传输效率是未来移动通信需要解决的关键技术之一。本文围绕无速率编译码技术和Vector OFDM调制技术开展研究,主要研究内容概括如下。本文分析了双选择性衰落信道的BEM模型,提出双选择性衰落信道下的自适应Vector OFDM系统。与传统固定调制方式和循环前缀的Vector OFDM系统不同,自适应Vector OFDM系统在给定误码差错阈值的条件下,通过估计信道条件信息(CSI)自适应变换域信号的调制方式和二维循环前缀长度。采用自适应机制,在信道条件好的情况下可以大幅度提高每符号承载消息比特数目。由于双选择信道的分集受到信道自由度、码率、向量长度等诸多因素影响,自适应Vector OFDM在改交码率,提高传输效率的同时,能够提高联合多径-多普勒分集增益,降低比特差错概率。本文研究了无速率码的度数分布特征,提出了基于信号空间分集的无速率码联合度数译码规划设计。与一般编码映射机制不同,该方法受至Underboeck提出的信号空间分集思想启发,通过信号空间分集逐层增大信号空间子层相邻星座点的欧氏距离,映射符号的比特具有不同的置信度期望。潜在的比特不等差错保护使得接收端可以不用比较接收端符号置信度大小,更加迅速地迭代更新接收消息的对数似然信息LLR。文章分析了16QAM和64QAM信号空间分集的误比特率以及来自信道的对数似然信息,并给出了一般高阶调制无速率码译码规划详细的方案设计。该方案可以在不需要额外的带宽开销和降低码率的前提下,提高译码性能,显著降低误码率。本文最后结合无速率码和Vector OFDM调制,设计了联合编码调制方法以对抗双选择性衰落信道。基于广义无速率码分组码,文章理论分析了度数分布对译码复杂度和译码差错概率的影响,得出两点结论,即当分组无速率码的平均度数相等时译码复杂度最低,同时译码成功概率最大。根据两点结论以及双选择信道分集理论,提出了两种编码调制方案,一种是基于度数均匀分布的联合编码调制,另一种基于遍历双选择信道子信道以获取联合多径-多普勒分集增益的编码调制机制。与普通的无速率码串联Vector OFDM系统相比,两种编码调制方案均可以提高系统性能,降低误比特率。
[Abstract]:High speed mobile broadband wireless communication system is an obvious trend of wireless communication in the future, in which mobility is an important attribute of existing and future wireless communication, vehicle network, high-speed railway and other systems. The higher communication bandwidth and moving speed make the communication channel more complex and changeable. The channel shows obvious dual selective fading characteristics of time dispersion and frequency dispersion. How to adapt to the complex characteristics of double-selective fading channels, ensure reliable transmission of communication and improve the transmission efficiency are the key technologies to be solved in future mobile communications. This paper focuses on the rate-free coding and decoding technology and Vector OFDM modulation technology, the main research content is summarized as follows. In this paper, the BEM model of dual selective fading channel is analyzed, and an adaptive Vector OFDM system is proposed for dual selective fading channel. Different from the conventional Vector OFDM system with fixed modulation mode and cyclic prefix, the adaptive Vector OFDM system estimates the modulation mode of the (CSI) adaptive transform domain signal and the 2-D cyclic prefix length by estimating the channel condition information under the given error threshold. The adaptive mechanism can greatly increase the number of message bits per symbol under good channel conditions. Due to the influence of channel freedom, bit rate, vector length and so on, the adaptive Vector OFDM can improve the joint multipath Doppler diversity gain while improving the transmission efficiency. Reduce bit error probability. In this paper, the degree distribution characteristics of rate free codes are studied, and the joint degree decoding planning design of rate free codes based on signal space diversity is proposed. Different from the general coding mapping mechanism, this method is inspired by the idea of signal space diversity proposed by Underboeck, and increases the Euclidean distance of adjacent constellation points in signal space sublayer by signal space diversity layer by layer. The bits of the mapping symbols have different confidence expectations. Potential bit unequal error protection makes it possible for the receiver to iterate over and update the logarithmic likelihood information (LLR.) of the received message more quickly without comparing the magnitude of the received symbol confidence. In this paper, the bit error rate (BER) of spatial diversity of 16QAM and 64QAM signals and the logarithmic likelihood information from the channel are analyzed, and the detailed scheme of decoding planning for general high-order modulation rate-free codes is given. The proposed scheme can improve the decoding performance and significantly reduce the bit error rate without additional bandwidth overhead and bit rate reduction. Finally, combining rate free code and Vector OFDM modulation, a joint coded modulation method is designed to counteract the dual selective fading channel. Based on the block codes of generalized rateless codes, the influence of degree distribution on decoding complexity and decoding error probability is analyzed theoretically, and two conclusions are drawn: the decoding complexity is the lowest when the average degree of block codes is equal. At the same time, the probability of successful decoding is the highest. Based on the two-point conclusion and the theory of dual-selection channel diversity, two coding modulation schemes are proposed, one is joint coded modulation based on uniform distribution of degrees. Another coding modulation mechanism is based on traversing dual selective channel subchannels to obtain joint multipath Doppler diversity gain. Compared with the conventional rate-free series Vector OFDM system, both coding and modulation schemes can improve the performance of the system and reduce the bit error rate (BER).
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN929.53
本文编号：2220249
[Abstract]:High speed mobile broadband wireless communication system is an obvious trend of wireless communication in the future, in which mobility is an important attribute of existing and future wireless communication, vehicle network, high-speed railway and other systems. The higher communication bandwidth and moving speed make the communication channel more complex and changeable. The channel shows obvious dual selective fading characteristics of time dispersion and frequency dispersion. How to adapt to the complex characteristics of double-selective fading channels, ensure reliable transmission of communication and improve the transmission efficiency are the key technologies to be solved in future mobile communications. This paper focuses on the rate-free coding and decoding technology and Vector OFDM modulation technology, the main research content is summarized as follows. In this paper, the BEM model of dual selective fading channel is analyzed, and an adaptive Vector OFDM system is proposed for dual selective fading channel. Different from the conventional Vector OFDM system with fixed modulation mode and cyclic prefix, the adaptive Vector OFDM system estimates the modulation mode of the (CSI) adaptive transform domain signal and the 2-D cyclic prefix length by estimating the channel condition information under the given error threshold. The adaptive mechanism can greatly increase the number of message bits per symbol under good channel conditions. Due to the influence of channel freedom, bit rate, vector length and so on, the adaptive Vector OFDM can improve the joint multipath Doppler diversity gain while improving the transmission efficiency. Reduce bit error probability. In this paper, the degree distribution characteristics of rate free codes are studied, and the joint degree decoding planning design of rate free codes based on signal space diversity is proposed. Different from the general coding mapping mechanism, this method is inspired by the idea of signal space diversity proposed by Underboeck, and increases the Euclidean distance of adjacent constellation points in signal space sublayer by signal space diversity layer by layer. The bits of the mapping symbols have different confidence expectations. Potential bit unequal error protection makes it possible for the receiver to iterate over and update the logarithmic likelihood information (LLR.) of the received message more quickly without comparing the magnitude of the received symbol confidence. In this paper, the bit error rate (BER) of spatial diversity of 16QAM and 64QAM signals and the logarithmic likelihood information from the channel are analyzed, and the detailed scheme of decoding planning for general high-order modulation rate-free codes is given. The proposed scheme can improve the decoding performance and significantly reduce the bit error rate without additional bandwidth overhead and bit rate reduction. Finally, combining rate free code and Vector OFDM modulation, a joint coded modulation method is designed to counteract the dual selective fading channel. Based on the block codes of generalized rateless codes, the influence of degree distribution on decoding complexity and decoding error probability is analyzed theoretically, and two conclusions are drawn: the decoding complexity is the lowest when the average degree of block codes is equal. At the same time, the probability of successful decoding is the highest. Based on the two-point conclusion and the theory of dual-selection channel diversity, two coding modulation schemes are proposed, one is joint coded modulation based on uniform distribution of degrees. Another coding modulation mechanism is based on traversing dual selective channel subchannels to obtain joint multipath Doppler diversity gain. Compared with the conventional rate-free series Vector OFDM system, both coding and modulation schemes can improve the performance of the system and reduce the bit error rate (BER).
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN929.53
【参考文献】
相关期刊论文 前1条
1 Xiqian Luo;Zhaoyang Zhang;Caijun Zhong;Xinyu Jin;;Exploiting cooperative multipath Doppler diversity in relay-assisted high-speed train communications[J];Chinese Science Bulletin;2014年35期
，本文编号：2220249
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