【摘要】：無線通信系統(tǒng)中,信道的衰落特性仍然是影響系統(tǒng)性能的主要因素,采用多天線的空間分集技術(shù)是對抗信道衰落的主要手段。但在無線通信網(wǎng)絡(luò)中,設(shè)備終端由于多方面限制無法安裝多天線,這就使得多天線技術(shù)的應(yīng)用受到了極大限制。協(xié)作分集技術(shù)是利用無線通信網(wǎng)絡(luò)中具有單天線的無線通信終端進(jìn)行相互協(xié)作,共享彼此的天線,從而達(dá)到模擬多天線分集技術(shù)的效果。Hunter等人首先提出將信道編碼技術(shù)與協(xié)作分集技術(shù)相結(jié)合,使系統(tǒng)在能夠獲得分集增益的同時也能夠獲得編碼增益。在此之后,國內(nèi)外學(xué)者們相繼提出了采用RCPC碼、LDPC碼等不同信道編碼方式的協(xié)作通信方案,并證明了其性能的優(yōu)異性。但是這些信道編碼方案都是固定碼率的信道編碼方式,因而極大的限制了其在協(xié)作通信系統(tǒng)中的應(yīng)用。噴泉碼是一種無碼率信道編碼方案,能夠很好的適用于協(xié)作通信系統(tǒng)之中。基于此本文提出了基于噴泉碼的協(xié)作通信方案,首先對無線信道下噴泉碼的譯碼算法進(jìn)行了優(yōu)化,提出了基于外信息符號差的串行BP譯碼(ESD-SBP)算法;其次提出了基于噴泉碼的混合轉(zhuǎn)發(fā)協(xié)作方案,解決了在協(xié)作伙伴無法正確譯碼的情況下,系統(tǒng)無法獲得分集增益的問題,主要工作與研究成果如下:針對噴泉碼在無線信道中進(jìn)行傳輸,采用BP迭代譯碼算法進(jìn)行譯碼時,迭代次數(shù)往往很大而且缺少有效的迭代停止機(jī)制的問題。本文首先對BP迭代譯碼進(jìn)行改進(jìn),將串行BP譯碼算法應(yīng)用于噴泉碼譯碼,將噴泉碼的譯碼速度提高了一倍;其次通過對噴泉碼譯碼過程的外信息轉(zhuǎn)移曲線(EXIT)圖的分析,提出了采用一次完整迭代后節(jié)點(diǎn)的外信息符號差作為迭代停止的標(biāo)志,最終提出了 ESD-SBP譯碼算法,仿真結(jié)果表明,該算法能夠在保證噴泉碼優(yōu)異性能的前提下,有效的減少譯碼的迭代次數(shù),提高系統(tǒng)性能。針對協(xié)作通信中中繼節(jié)點(diǎn)無法對源節(jié)點(diǎn)信息進(jìn)行正確譯碼時,無法獲得分集增益的問題。本文首先提出了基于噴泉碼的編碼協(xié)作方案以及放大轉(zhuǎn)發(fā)方案,通過理論分析表明,在中繼節(jié)點(diǎn)能夠?qū)υ垂?jié)點(diǎn)的信息正確譯碼的情況下,協(xié)作通信系統(tǒng)能夠獲得度為二的滿分集增益,但譯碼失敗時就無法獲得任何分集增益;而放大轉(zhuǎn)發(fā)方式無論中繼節(jié)點(diǎn)能否對源節(jié)點(diǎn)的信息正確譯碼均能夠獲得一定的分集增益,但是效果有限,據(jù)此,本文提出了混合轉(zhuǎn)發(fā)(HF)方案。仿真結(jié)果表明,HF協(xié)作方案相較于其它協(xié)作方案具有更加優(yōu)異的誤碼率性能。
[Abstract]:In wireless communication systems, the fading characteristics of the channel are still the main factors affecting the performance of the system, and the spatial diversity technology with multiple antennas is the main means to combat the channel fading. However, in wireless communication networks, the application of multi-antenna technology is greatly limited because the terminal can not install multiple antennas because of various limitations. Cooperative diversity technology is to make use of wireless communication terminals with single antenna in wireless communication network to cooperate with each other and share each other's antennas. In order to achieve the effect of analog multi-antenna diversity, Hunter et al first proposed the combination of channel coding and cooperative diversity, so that the system can obtain diversity gain and coding gain at the same time. After this, scholars at home and abroad have put forward different channel coding schemes, such as RCPC code, LDPC code and so on, and proved their excellent performance. However, these channel coding schemes are fixed-rate channel coding schemes, which greatly limit their application in cooperative communication systems. Fountain code is a rate-free channel coding scheme, which can be used in cooperative communication system. Based on this, a cooperative communication scheme based on fountain code is proposed. Firstly, the decoding algorithm of fountain code in wireless channel is optimized, and the serial BP decoding (ESD-SBP) algorithm based on the symbol difference of external information is proposed. Secondly, a hybrid forwarding cooperation scheme based on fountain code is proposed, which solves the problem that the system can not obtain diversity gain when the cooperative partner can not decode correctly. The main work and research results are as follows: when using BP iterative decoding algorithm to transmit fountain code in wireless channel, the number of iterations is often large and the problem of effective iterative stopping mechanism is lacking. In this paper, the BP iterative decoding is improved, the serial BP decoding algorithm is applied to the fountain code decoding, and the decoding speed of the fountain code is doubled. Secondly, through the analysis of the (EXIT) diagram of the external information transfer curve in the decoding process of fountain code, this paper proposes that the symbol difference of external information of the node after a complete iteration is taken as the sign of the iteration stop, and finally proposes the ESD-SBP decoding algorithm. Simulation results show that the algorithm can effectively reduce the number of iterations of decoding and improve the performance of the system on the premise of ensuring the excellent performance of the fountain code. The diversity gain can not be obtained when the relay node of cooperative communication can not correctly decode the source node information. In this paper, the coding and cooperation scheme based on fountain code and the scheme of amplification and forwarding are proposed. The theoretical analysis shows that the relay node can decode the information of the source node correctly. The cooperative communication system can obtain the full diversity gain of degree 2, but it can not obtain any diversity gain when the decoding fails. However, no matter whether the relay node can correctly decode the information of the source node, the amplification and forwarding scheme can obtain a certain diversity gain, but the effect is limited. Therefore, a hybrid forwarding (HF) scheme is proposed in this paper. The simulation results show that the BER performance of the HF cooperative scheme is better than that of other cooperative schemes.
【學(xué)位授予單位】：哈爾濱工程大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TN911.22

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本文編號：2396795