基于LDPC碼的MIMO分集系統(tǒng)的理論研究
發(fā)布時(shí)間：2019-05-08 15:14
【摘要】：低密度奇偶校驗(yàn)碼(Low-density parity-check code,LDPC)糾錯(cuò)能力強(qiáng),簡單易實(shí)現(xiàn),已經(jīng)被確定為下一代移動通信中長碼的編碼方案。在時(shí)頻資源有限的情況下,多輸入多輸出(Multiple Input Multiple Output,MIMO)技術(shù)可以大幅提高系統(tǒng)的有效性和可靠性。實(shí)際中經(jīng)常采用分集技術(shù)來減小信道衰落對通信系統(tǒng)造成的影響。將LDPC碼與MIMO技術(shù)相結(jié)合,可以同時(shí)利用分集增益和編碼增益以改善系統(tǒng)傳輸可靠性,本文主要對基于LDPC碼的MIMO分集系統(tǒng)的實(shí)現(xiàn)方案及性能進(jìn)行了深入研究。首先,本文對不同調(diào)制方式在高斯信道、非頻選快衰落信道和非頻選慢衰落信道下的Shannon限進(jìn)行了分析和計(jì)算。對Shannon限的求解思路是先獲得信道容量的計(jì)算公式,然后利用數(shù)值積分和插值來求解不同條件下的Shannon限,其核心是對信道容量的求解。對于高斯信道,本文給出了適用于不同調(diào)制方式的信道容量的通用表達(dá)式;對于非頻選快衰落信道,假設(shè)可以實(shí)現(xiàn)完美交織,且接收端完全已知信道狀態(tài)信息,那么信道容量就是遍歷容量;對于非頻選慢衰落信道,借鑒中斷概率的概念,本文給出了非頻選慢衰落信道的數(shù)學(xué)模型,并且對其信道容量進(jìn)行了推導(dǎo)和求解。接著,本文對時(shí)間選擇性衰落信道下基于LDPC碼的MIMO分集系統(tǒng)進(jìn)行了研究。由于本文使用的是碼速率為1/2的LDPC碼,其信息位和校驗(yàn)位長度相等,在此基礎(chǔ)上提出一種基于信號處理和信息傳遞的軟譯碼算法,這種軟譯碼算法充分利用信道信息對信息位和校驗(yàn)位的初始似然比進(jìn)行了修正,進(jìn)一步改善了系統(tǒng)性能。最后,針對頻率選擇性衰落信道,本文對基于LDPC碼的MIMO分集系統(tǒng)的實(shí)現(xiàn)方案和性能做了進(jìn)一步研究。與時(shí)間選擇性衰落信道相比,頻選信道中存在多條可分辨徑,接收端相當(dāng)于增加了額外的頻率分集增益,將基于LDPC碼的MIMO分集系統(tǒng)應(yīng)用到頻選信道中,以期達(dá)到更好的誤碼率性能;其次,對時(shí)選信道下基于信號處理和信息傳遞的軟譯碼算法進(jìn)行了修改,使其適用于頻率選擇性衰落信道,進(jìn)一步提高系統(tǒng)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.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TN919.3
本文編號：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.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TN919.3
【參考文獻(xiàn)】
相關(guān)期刊論文 前1條
1 余來妹;;MIMO系統(tǒng)和無線信道容量研究[J];中國新通信;2014年04期
，本文編號：2472008
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