基于LDPC码的MIMO分集系统的理论研究
发布时间：2019-05-08 15:14
【摘要】：低密度奇偶校验码(Low-density parity-check code,LDPC)纠错能力强,简单易实现,已经被确定为下一代移动通信中长码的编码方案。在时频资源有限的情况下,多输入多输出(Multiple Input Multiple Output,MIMO)技术可以大幅提高系统的有效性和可靠性。实际中经常采用分集技术来减小信道衰落对通信系统造成的影响。将LDPC码与MIMO技术相结合,可以同时利用分集增益和编码增益以改善系统传输可靠性,本文主要对基于LDPC码的MIMO分集系统的实现方案及性能进行了深入研究。首先,本文对不同调制方式在高斯信道、非频选快衰落信道和非频选慢衰落信道下的Shannon限进行了分析和计算。对Shannon限的求解思路是先获得信道容量的计算公式,然后利用数值积分和插值来求解不同条件下的Shannon限,其核心是对信道容量的求解。对于高斯信道,本文给出了适用于不同调制方式的信道容量的通用表达式;对于非频选快衰落信道,假设可以实现完美交织,且接收端完全已知信道状态信息,那么信道容量就是遍历容量;对于非频选慢衰落信道,借鉴中断概率的概念,本文给出了非频选慢衰落信道的数学模型,并且对其信道容量进行了推导和求解。接着,本文对时间选择性衰落信道下基于LDPC码的MIMO分集系统进行了研究。由于本文使用的是码速率为1/2的LDPC码,其信息位和校验位长度相等,在此基础上提出一种基于信号处理和信息传递的软译码算法,这种软译码算法充分利用信道信息对信息位和校验位的初始似然比进行了修正,进一步改善了系统性能。最后,针对频率选择性衰落信道,本文对基于LDPC码的MIMO分集系统的实现方案和性能做了进一步研究。与时间选择性衰落信道相比,频选信道中存在多条可分辨径,接收端相当于增加了额外的频率分集增益,将基于LDPC码的MIMO分集系统应用到频选信道中,以期达到更好的误码率性能;其次,对时选信道下基于信号处理和信息传递的软译码算法进行了修改,使其适用于频率选择性衰落信道,进一步提高系统可靠性。
[Abstract]:Low density parity check (Low-density parity-check code,LDPC) code has strong error correcting ability and is easy to implement. It has been identified as the coding scheme of long code in next generation mobile communication. In the case of limited time-frequency resources, multi-input multiple-output (Multiple Input Multiple Output,MIMO) technology can greatly improve the effectiveness and reliability of the system. In practice, diversity technology is often used to reduce the impact of channel fading on communication systems. Combining LDPC code with MIMO technology, both diversity gain and coding gain can be used to improve the transmission reliability of the system. In this paper, the implementation scheme and performance of MIMO diversity system based on LDPC code are studied in depth. Firstly, the Shannon limits of different modulation modes in Gao Si channel, non-frequency selective fast fading channel and non-frequency selective slow fading channel are analyzed and calculated. The solution of Shannon limit is to obtain the calculation formula of channel capacity first, and then use numerical integration and interpolation to solve the Shannon limit under different conditions, the core of which is to solve the channel capacity. For Gao Si channel, the general expression of channel capacity suitable for different modulation modes is given in this paper. For non-frequency selective fast fading channels, assuming that perfect interleaving can be achieved and the receiver knows the channel state information completely, then the channel capacity is ergodic capacity. For non-frequency selective slow fading channels, using the concept of interrupt probability for reference, this paper presents a mathematical model of non-frequency selective slow fading channels, and deduces and solves its channel capacity. Secondly, the MIMO diversity system based on LDPC codes in time-selective fading channels is studied. In this paper, a soft decoding algorithm based on signal processing and information transmission is proposed, which is based on the same length of the information bit and the check bit, because the LDPC code with the code rate of 1 ~ 2 is used. The soft decoding algorithm makes full use of the channel information to modify the initial likelihood ratio of the information bit and the check bit, which further improves the performance of the system. Finally, for frequency selective fading channels, the implementation scheme and performance of MIMO diversity system based on LDPC codes are further studied in this paper. Compared with the time-selective fading channel, there are several separable paths in the frequency-selective channel, and the receiver increases the additional frequency diversity gain. The MIMO diversity system based on LDPC code is applied to the frequency-selective channel. In order to achieve better bit error rate performance; Secondly, the soft decoding algorithm based on signal processing and information transmission in time-selective channel is modified to make it suitable for frequency-selective fading channel and further improve the reliability of the system.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN919.3
本文编号：2472008
[Abstract]:Low density parity check (Low-density parity-check code,LDPC) code has strong error correcting ability and is easy to implement. It has been identified as the coding scheme of long code in next generation mobile communication. In the case of limited time-frequency resources, multi-input multiple-output (Multiple Input Multiple Output,MIMO) technology can greatly improve the effectiveness and reliability of the system. In practice, diversity technology is often used to reduce the impact of channel fading on communication systems. Combining LDPC code with MIMO technology, both diversity gain and coding gain can be used to improve the transmission reliability of the system. In this paper, the implementation scheme and performance of MIMO diversity system based on LDPC code are studied in depth. Firstly, the Shannon limits of different modulation modes in Gao Si channel, non-frequency selective fast fading channel and non-frequency selective slow fading channel are analyzed and calculated. The solution of Shannon limit is to obtain the calculation formula of channel capacity first, and then use numerical integration and interpolation to solve the Shannon limit under different conditions, the core of which is to solve the channel capacity. For Gao Si channel, the general expression of channel capacity suitable for different modulation modes is given in this paper. For non-frequency selective fast fading channels, assuming that perfect interleaving can be achieved and the receiver knows the channel state information completely, then the channel capacity is ergodic capacity. For non-frequency selective slow fading channels, using the concept of interrupt probability for reference, this paper presents a mathematical model of non-frequency selective slow fading channels, and deduces and solves its channel capacity. Secondly, the MIMO diversity system based on LDPC codes in time-selective fading channels is studied. In this paper, a soft decoding algorithm based on signal processing and information transmission is proposed, which is based on the same length of the information bit and the check bit, because the LDPC code with the code rate of 1 ~ 2 is used. The soft decoding algorithm makes full use of the channel information to modify the initial likelihood ratio of the information bit and the check bit, which further improves the performance of the system. Finally, for frequency selective fading channels, the implementation scheme and performance of MIMO diversity system based on LDPC codes are further studied in this paper. Compared with the time-selective fading channel, there are several separable paths in the frequency-selective channel, and the receiver increases the additional frequency diversity gain. The MIMO diversity system based on LDPC code is applied to the frequency-selective channel. In order to achieve better bit error rate performance; Secondly, the soft decoding algorithm based on signal processing and information transmission in time-selective channel is modified to make it suitable for frequency-selective fading channel and further improve the reliability of the system.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN919.3
【参考文献】
相关期刊论文 前1条
1 余来妹;;MIMO系统和无线信道容量研究[J];中国新通信;2014年04期
，本文编号：2472008
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