Fountain Codes And Their Applications In 5G Mobile Communication System

In recent years,with the rapid development of some emerging services,such as ultra-clear video broadcast,virtual reality,augmented reality,driveless cars and so on,more and more services have penetrated into the mobile Internet,which is a challenge to mobile com-munication technologies.In 2015,the ITU formally defined three main usage scenarios for 5G mobile communication technologies:eMBB,mMTC and uRLLC.Different scenarios have different performance requirement:eMBB requires high transmission efficiency,high spectral efficiency and large communication capacity;mMTC requires massive connection and ultra-low power consumption;uRLLC requires ultra-high reliability and short delay.The existing channel coding and decoding scheme has been difficult to meet these requirements.Fountain code as an application layer error correction mechanism has great research value and application foreground under the new situation.The thesis focuses on the coding and decoding technology,implementation and application of fountain codes in 5G scenarios.Firstly,the thesis studies two major fountain codes,i.e.LT codes and Raptor codes.The thesis describes the encoding and decoding algorithms of LT codes,with some common de-gree distribution function.The computation complexity and performance of LT codes under differents lengths or decoding algorithms are analyzed.The coding and decoding scheme of system Raptor codes and the inactivation decoding algorithm based on GE are introduced.The R10 Raptor code accoding to IETF RFC 5053 and the RaptorQ code accoding to IETF RFC 6330 are studied in detail,and the influence of length and channel erasure probability on their performance are investigated.In addition,the thesis studies distributed LT(DLT)codes and LT codes with feedback in mMTC scenario.The system model of multiple-access relay networks and DLT codes apply on it are introduced,along with the degree distribution function,the coding method carried out by the sources and the operation adopted at the relay.Performance comparison between DLT codes and corresponding tranditional LT codes is given.The shift method of shifted LT(SLT)code's degree distribution are introduced,and the performance of SLT codes are mesured by feedback overhead.The thesis present a novel shifted distributed LT codes under partial information,which has significant advantages proved by simulations.Futhermore,the thesis studies the joint coding technology of physical layer and applica-tion layer.The thesis introduces the major technologies in channel coding module of mobile communication system,including CRC,code block segmentation,rate matching,HARQ,LTE Turbo encoder and 5G LDPC encoder.The thesis describes the joint coding schemes in detail and optimizes the code rate combination.Objective comparison of tranditional schemes and different joint coding schemes is given in the thesis.Finally,the thesis studies the applicaiton of Raptor codes on vsible light communication(VLC),which is an important supplement to 5G.The thesis designs and realizes an Raptor code software used in multi-color VLC system.The thesis gives the overview of DCO-OFDM VLC systems,then color mixing ratio optimization is made under consideration of the illumination requirement and power constraint.The thesis elaborates the core function design of software,including architecture,protocol,concurrency,Raptor code structure and so on.At last,the software is tested with a VLC hardware testbed.