节点文献
千兆速率同轴电缆接入编码调制技术研究
【作者】 颜丹丹；
【导师】 唐友喜；
【作者基本信息】 电子科技大学 ， 通信与信息系统， 2012， 硕士
【摘要】 电信网、互联网和广播电视网的三网融合是未来家庭网络发展的方向，广播电视网在三网融合中占有一定的资源优势，我国广播电视部门选用混合光纤同轴接入作为下一代广播电视网的接入技术，进行网络宽带化和双向化改造。然而，现有的同轴电缆接入系统频带利用率不超过7bps/Hz，物理层速率只有百兆，已很难满足用户对高速数据传输的需求，为此，人们提出了多种进一步提升接入速率的方案。其中，千兆速率同轴电缆接入系统的频带利用率超过8bps/Hz，通过多通道聚合，在128MHz信号带宽上，物理层传输速率超过1000Mbps，误比特率为107以下。本文研究千兆速率同轴电缆接入系统物理层的编码调制技术。为达到优异的译码性能和高效的传输速率，物理层采用了LDPC编码技术与高阶QAM调制技术，本文对这两种关键技术的理论算法、仿真及实现作了详细阐述。首先，本文回顾了同轴电缆接入技术和编码调制技术的发展历程和研究现状，对千兆速率同轴电缆接入系统和物理层作综述说明。较详细描述了物理层的LDPC编译码和高阶QAM调制解调两种关键技术。全文主要对LDPC编译码与高阶QAM调制解调技术进行了研究。对LDPC编译码进行算法设计和实现，分析现有的算法的优缺点，总结出适合的编译码算法，对算法进行仿真验证，在FPGA上实现了自适应高速LDPC编译码器。推导了高阶QAM调制解调中的LLR快速计算公式，在性能不损失的情况下，计算复杂度显著降低，并在FPGA上实现了自适应LLR计算器。最后，对比特级信号处理进行联合仿真和模块集成，搭建测试平台，对同轴电缆接入系统进行测试与分析。测试结果表明，系统物理层的各项指标达到了设计需求。本文所设计的LDPC编码器、译码器和LLR计算器的工作时钟速率达到384MHz，译码器的数据吞吐量达到380Mbps，译码性能与理论设计一致。以上结论验证了本文设计的LDPC编译码器和LLR计算器在同轴接入系统中的有效性，对高速信号处理中的编码与调制技术研究也有重要的参考价值。
【Abstract】 The convergence of telecommunication, Internet and broadcasting television net isthe direction of future home network development. Broadcasting television net plays inpossession of certain advantages in resources in the triple, The cable televisiondepartment of China chose Hybrid fiber coaxial access network as the next generationof radio and television network access technology, using this technology to complete thetransformation of network broad band and bidirectional.However, the existing coaxial cable access system’bandwidth utilization rate is notmore than7bps/Hz and physical layer rate is only100Mbps. As the requirements oftransmission rate increase, the existing coaxial cable access technology has beendifficult to meet user demand for high speed data transmission. Therefore, people hasput forward a variety of plan to enhance access rate, including Gigabit rate coaxial cableaccess system. It is capable of providing7bps/Hz of system’bandwidth utilization rateand1000Mbps of physical layer downlink rate iIn the128MHz signal bandwidth.In this paper, the modulation and coding technology of Gigabit rate coaxial cableaccess system’s physical layer are researched. To achieve efficient transmission rate, theLDPC coding and high order QAM modulation technologies are key technologies ofphysical layer. In this paper, the algorithm, simulation and realization of the two keytechnologies are elaborated.This paper first reviews the development course and the present research situation ofthe coaxial cable access technology and coding modulation technology. Gigabit ratecoaxial cable access systems and physical layer are made a summary description. Partsof the physical layer’s key technologies, including LDPC coding and high order QAMmodulation and demodulation, are also presented.This paper mainly research on the LDPC codec and high order QAM modulation anddemodulation technology. Design and implement the LDPC codec’s algorithm. Startingwith an analysis of the existing algorithms, find suitable algorithm for this system, andsimulate the algorithm. Finally, design the high speed adaptive LDPC codec. In view ofthe high order QAM modulation, derivate the fast calculation formula of LLR.Compared with the general calculating formula, the complexity of computation isreduced a lot. Complete the realization of the adaptive LLR calculator on FPGA.Finally, complete simulation and module integration of bit grade signal processing.Build the test platform, test and analysis the coaxial access system. The test results showthat, the design of the LDPC encoder, decoder and LLR calculator’s working clock rateis up to384MHz. Decoder throughput reached380Mbps. The indicators of basebandsignal processing have reached the design requirements.The above conclusion verifies that the design of the LDPC encoder and LDPCdecoder and LLR calculator in coaxial access system is feasible and effective. It also has important reference value for the high speed signal processing in the coding andmodulation technology research.