摘要
As a complement of terrestrial networks,non-terrestrial networks(NTN)have ad⁃vantages of wide-area coverage and service continuity.The NTN is potential to play an impor⁃tant role in the 5G new radio(NR)and beyond.To enable the massive machine type communi⁃cations(mMTC),the low earth orbit(LEO)satellite is preferred due to its lower transmission delay and path loss.However,the LEO satellite may generate notable Doppler shifts to de⁃grade the system performance.Recently,orthogonal time frequency space(OTFS)modulation has been proposed.It provides the opportunity to allocate delay Doppler(DD)domain resourc⁃es,which is promising for mitigating the effect of high mobility.Besides,as the LEO satellite constellation systems such as Starlink are thriving,the space spectrum resources have become increasingly scarce.Therefore,non-orthogonal multiple access(NOMA)is considered as a candidate technology to realize mMTC with limited spectrum resources.In this paper,the ap⁃plication of OTFS enabled NOMA for mMTC over the LEO satellite is investigated.The LEO satellite based mMTC system and the OTFS-NOMA schemes are described.Subsequently,the challenges of applying OTFS and NOMA into LEO satellite mMTC systems are discussed.Fi⁃nally,the potential technologies for the systems are investigated.
基金
supported by the Fundamental Research Funds for the Cen⁃tral Universities under Grant Nos.2021YJS202,2020JBZD005 and 2021RC205
the National Key Research and Development Program under Grant Nos.2016YFE0200900 and 2016YFB1200102-04,NSFC under Grant Nos 61725101 and U1834210
the Royal Society Newton Advanced Fellow⁃ship under Grant Nos.61961130391 and NA191006
Beijing Natural Haidian Joint Fund under Grant No.L172020
Major Projects of Beijing Municipal Science and Technology Commission under Grant No.Z181100003218010
State Key Lab of Rail Traffic Control and Safety under Grant Nos.RCS2021ZQ002,RCS2018ZZ007 and RCS2020ZT010
Teaching Reform Project under Grant No.134496522
the Open Research Fund from Shen⁃zhen Research Institute of Big Data under Grant No.2019ORF01006
the PCL Future Greater-Bay Area Network Facilities for Large-scale Exper⁃iments and Applications Project under Grant No.LZ0019.
