Research On 60GHz Unlicensed Spectrum Wireless Access

With the rapid development of Internet,the demand for mobile data traffic has exploded,constantly challenging the limit of wireless network capacity.However,the licensed spectrum resources below 6GHz are very scarce.Some network services are considered to be extended to the unlicensed frequency band.Therefore,the fourth generation mobile communication system introduces.licensed assisted access to offload the data traffic of the licensed spectrum.In the fifth generation mobile communication system,the NR unlicensed frequency band technology is proposed,and the related access technologies in the low unlicensed frequency bands have been widely studied.In order to further expand the spectrum,60GHz millimeter-wave high-band unlicensed access technology has gradually become a hot spot,and it is considered to further increase system capacity by using 60GHz large bandwidth resources.This thesis mainly considers the 60GHz unlicensed band application scenario,aiming to reduce the data transmission delay introduced by the Listen Before Talk(LBT)channel detection mechanism and provide higher saturation throughput.At present,there are three challenges in this scenario:1)When the channel competition is fierce,the original channel access mechanism has a large access delay and a low access success rate;2)The problem of hidden nodes on 60GHz is serious,resulting in excessive random access delay;3)When the channel competition is fierce,the feedback delay of wireless data transmission is large,and there is a problem of semi-static codebooks overlapping.In view of the above problems,the work of this thesis is as follows:(1)Aiming at the problem that the access delay of NR-U is large when the channel competition is fierce,this thesis designs an enhanced channel access mechanism,which dynamically selects whether to perform LBT handover,and designs the public and private DCI comprehensive indication and configuration.Corresponding timers are used to reduce the delay of switching between different service requirements.The system transmission delay and saturated throughput are derived by establishing a Markov chain model.The simulation results show that when the channel collision probability is greater than 0.55,using the enhanced mechanism can effectively reduce the average transmission delay.(2)Aiming at the problems of hidden nodes and large random access delay on 60GHz,a semi-static configuration transmission resource distribution scheme based on LBT failure rate is proposed,which reduces the delay of LBT detection before channel access.At the same time,two monitoring window mechanisms based on dynamic climbing and scaling factor are proposed to dynamically reduce the length of the monitoring window,which can avoid unnecessary power waste.The simulation results show that the proposed scheme can significantly reduce the access delay.(3)Aiming at the problems of large data feedback delay and semistatic codebooks overlapping in NR-U,a group indicator is proposed to indicate that UE receives the PDSCH group and the value of the group indicator is used to decide whether to enable auxiliary resources.Configure multiple PUCCH resources and automatically delay to the next feedback point.Aiming at the problem of semi-static codebooks overlapping,a scheme of assisting BS and UE to calculate the new feedback set is proposed.The simulation results show that the proposed scheme can improve the effective feedback rate and reduce the feedback delay,and the maximum optimized delay of the scheme is 2.56ms.