无线通信系统中编码协作技术的研究
发布时间：2018-12-31 15:49
【摘要】：无线通信系统中,信道的衰落特性仍然是影响系统性能的主要因素,采用多天线的空间分集技术是对抗信道衰落的主要手段。但在无线通信网络中,设备终端由于多方面限制无法安装多天线,这就使得多天线技术的应用受到了极大限制。协作分集技术是利用无线通信网络中具有单天线的无线通信终端进行相互协作,共享彼此的天线,从而达到模拟多天线分集技术的效果。Hunter等人首先提出将信道编码技术与协作分集技术相结合,使系统在能够获得分集增益的同时也能够获得编码增益。在此之后,国内外学者们相继提出了采用RCPC码、LDPC码等不同信道编码方式的协作通信方案,并证明了其性能的优异性。但是这些信道编码方案都是固定码率的信道编码方式,因而极大的限制了其在协作通信系统中的应用。喷泉码是一种无码率信道编码方案,能够很好的适用于协作通信系统之中。基于此本文提出了基于喷泉码的协作通信方案,首先对无线信道下喷泉码的译码算法进行了优化,提出了基于外信息符号差的串行BP译码(ESD-SBP)算法;其次提出了基于喷泉码的混合转发协作方案,解决了在协作伙伴无法正确译码的情况下,系统无法获得分集增益的问题,主要工作与研究成果如下:针对喷泉码在无线信道中进行传输,采用BP迭代译码算法进行译码时,迭代次数往往很大而且缺少有效的迭代停止机制的问题。本文首先对BP迭代译码进行改进,将串行BP译码算法应用于喷泉码译码,将喷泉码的译码速度提高了一倍;其次通过对喷泉码译码过程的外信息转移曲线(EXIT)图的分析,提出了采用一次完整迭代后节点的外信息符号差作为迭代停止的标志,最终提出了 ESD-SBP译码算法,仿真结果表明,该算法能够在保证喷泉码优异性能的前提下,有效的减少译码的迭代次数,提高系统性能。针对协作通信中中继节点无法对源节点信息进行正确译码时,无法获得分集增益的问题。本文首先提出了基于喷泉码的编码协作方案以及放大转发方案,通过理论分析表明,在中继节点能够对源节点的信息正确译码的情况下,协作通信系统能够获得度为二的满分集增益,但译码失败时就无法获得任何分集增益;而放大转发方式无论中继节点能否对源节点的信息正确译码均能够获得一定的分集增益,但是效果有限,据此,本文提出了混合转发(HF)方案。仿真结果表明,HF协作方案相较于其它协作方案具有更加优异的误码率性能。
[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.
【学位授予单位】：哈尔滨工程大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN911.22
本文编号：2396795
[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.
【学位授予单位】：哈尔滨工程大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN911.22
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