| With the promotion of the triple play and Broadband Chinese strategy,the demand for cable television network transmission technology research is increasing.At the same time,the need of consumers for cable television networks is changing,consumers are no longer satisfied with traditional television broadcasting services,higher quality,faster speed and more personalized services have become the basic needs for them.Changes in user requirements have imposed higher requirements on the performance of cable television networks.How to improve network bandwidth and spectrum efficiency has become an urgent problem for cable television network technology to solve.At present,cable access network technologies in China include C-HPAV,C-DOCSIS,HINOC which is a new access scheme independently designed and developed in China.Cable access network technologies abroad mainly include DOCSIS and FTTH.The DOCSIS series of international standards are formulated by the cable standards organization Cable Labs,and is based on the cable television system HFC network.DOCSIS is a classic specification for cable network access technology.The DOCSIS series of specifications include 1.0,1.1,2.0,3.0,and 3.1 generations of technologies.DOCSIS 3.1,released in October 2013,through the introduction of new technologies and improvement of existing technologies,has increased data transmission rate by an order of magnitude compared to previous version 3.0,which is up to 10 Gbps downstream and 1 Gbps upstream.Besides,full duplex DOCSIS 3.1,released in Septemper 2017,futher rectified the disadvantage of asymmetric upstream and downstream transmission rates,providing up to 10 Gbps downstream and 2.5 Gbps upstream transmission rates,which is the ultra-high-speed standards for cable television networks.This thesis mainly focuses on the design of the simulation system for DOCSIS3.1 MAC layer protocol,and then the mechanism performance is evaluated.Based on the analysis of DOCSIS3.1 MULPI specification,the simulation system is designed on the existing simulation platform to test and analyse the performance of DOCSIS 3.1 MAC layer protocol maechanisms under different scenarioos.Besides,in order to solove the network performance optimization problem under the multi-profile management framework,one optimization model is proposed,and an aloorithm is applied to work out it,and its effectiveness is verified by simulation.First of all,a deep study of mechanisms of DOCSIS3.1 protocol is made in this thesis,including network topology,protocol stack,physical layer spectrum planning and bandwidth requirements,LDPC coding,channel planning mechanism,channel access mechanism,channel bonding technology,variable bit-loading and multi-profile management mechanisms and data transmission.Secondly,the dedicated simulation system for the DOCSIS 3.1 MAC layer protocol is designed on the existing simulation platform and some critical technologies are simulated,mainly including data transmission,channel planning,dynamic bandwidth allocation,priority support.Then,a variety of scenarios are designed and throughput,delay,and delay jitter are selected as the main performance metrics to evaluate the simulation results as well as the performance of DOCSIS3.1 MAC layer protocol,and further researches are made on the problems found in the simulation.For the multi-profile management mechanism which has a large impact on system performance,an optimization model is established with the aim of optimizing the network throughput,the CM grouping scheme as an optimization variable,under the conditions of CM number,profile number,and channel SNR conditions.To solove the model,the genetic algorithm is choosed.The validity of this optimization model and this algorithm is proved helpful for network performance by simulation later.The findings of this thesis not only provide experience and ideas for the follow-up study of the DOCSIS 3.1 MAC protocol,but also provide positive references for our laboratory to independently design the new 10 G coaxial technology. |
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