【作者】 聂华；

【导师】 刘开华；

【作者基本信息】 天津大学 ， 通信与信息系统， 2007， 硕士

【摘要】 随着半导体工艺的不断进步和通信技术的不断发展,通信承载业务正在从传统的语音、文本向图像、视频等大流量的多媒体业务转变并由此促使宽带通信系统标准陆续提出并演进升级。对于宽带通信系统,从设计角度看,物理层的设计是提高系统容量的关键;从应用角度看,发射功率和频谱的有效性是制约标准应用的瓶颈,通常上述问题可以通过改变调制方式和编码方式改善。在众多技术中,Turbo码和LDPC码是两类译码性能接近香农极限的信道编码技术,在保证纠错性能的条件下能使得编码增益最大化,从而极大地降低发射功率。OFDM多载波传输技术不仅能极好地对抗高速传输下由信道引起的符号间串扰和频率选择性衰落,还能通过正交化信道最大程度的提高频谱有效性。上述优点使这两类技术不断纳入到新的宽带通信系统标准当中。Homeplug AV和802.11n是应用于数字家庭局域网的两个宽带接入标准。Homeplug AV是以电力线作为媒介传输音频和视频数据的标准;802.11n将是IEEE制定的无线局域网提高传输速率和传输距离的最终标准,本文采用其草案开展研究。论文的主要工作是:建立了Homeplug AV标准中电力线信道的仿真环境;详细描述了OFDM基本原理及两个标准的OFDM参数,并根据已有OFDM信道估计理论的三种算法进行严格的数学推导,给出其在实际系统设计中的应用;阐述了turbo乘积码、LDPC码和Turbo卷积码及二进制卷积码在以上两个标准中的编码过程;详细地介绍了二进制卷积码和Turbo卷积码的译码算法。在上述工作的基础上,根据传统的二进制Turbo卷积码的最佳译码算法,通过增加一个循环状态迭代估计过程,提出改进Homeplug AV中双重二进制Turbo卷积码译码过程的新算法。严格推导出高阶调制下比特对数似然比的软信息计算公式,丰富了Turbo码在不同调制方式下的译码性能分析,保证译码的最优性能。上述工作已获得初步成果,经仿真验证了算法的有效性,并将用于电力线通信专用集成电路芯片设计中。更多还原

【Abstract】 Many specifications of bandwidth communication systems have been gradually proposed and revoluted, because of the progress of semiconductor techniques, the developed communication technology, and the communication bearing services changed from traditional voice and text to high bit-rate photos and multimedia data. For the bandwidth communication, in the point of designing, physical layer is the key of increasing the capacity of communication systems; in the point of application, transmitted power and the efficiency of frequency are the bottleneck. These conditions could be solved by changing the type of channel coding and modulating. Turbo codes and LDPC codes are error-correcting codes which approchs to Shannon’s capacity limit. These two codes can maximize the coding gain in the same error bit rate, thus minimize the transmitted power. OFDM multi-carriers transmission technique not only decreases or cancels the Inter-Symbol Interference and frequency selective fading both caused by the physical channel, but also by orthogonalizing the transmission channel maximizes the efficiency of frequency. These two are employed in many recent specifications of bandwidth communication systems.Homeplug AV and 802.11n are the bandwidth access standards in digital home local area network.Homeplug AV is used to transmit the audio and video through the powerline. Proposed by IEEE(Institute of Electric and Electronic Engineering), the standard wireless local area network(WLAN) 802.11n will be the final edition for the maximum transmission rate and maximum transmission distance.This paper employs the draft edition of 802.11n.The main work lists below: setting the simulation platform of powerline channel in Homeplug AV; descripting the principle of OFDM and the parameter of OFDM in Homeplug AV and 802.11n in detail and the channel estimation algorithm of OFDM and in Homeplug AV; presenting the encoding process of turbo product code, LDPC code, binary convolutional code (BCC) and Turbo convolutional code (TCC); doing the decoding algorithm of BCC and TCC. The innovative point of this work is adding a progress of iterative estimation of circular state based on the traditional binary TCC optimal decoding algorithm obtaining good performance, then giving many simulation results in different modulation types.The work above has got a startling achievement. The algorithms have tested by simulation and its performance is better than other algorithms, and have employed in ASIC chip design of Homeplug AV.更多还原