Research On Group-assisted Communication Mechanism In SL-U

In recent years,the rapid development of mobile Internet has brought great changes to people’s lives,and the data flow of wireless networks has increased dramatically.However,the spectrum resources of authorized bands are expensive and scarce,which will make it difficult to meet the needs of data traffic in the future.In the Fourth Generation Mobile Communication System(4G),Licensed Assisted Access(LAA)technology alleviates the problem of authorized bands by offloading data traffic from dedicated bands to unauthorized bands.NR-based access to unlicensed spectrum(NR-U)technology has also evolved in the Fifth Generation Mobile Communication System New Radio(5G NR)communication system as an extension of 5G NR in unlicensed spectrum.Faced with the challenges of scarce authorized spectrum resources and increasing performance requirements,SL-U(Sidelink-based access to unlicensed spectrum)technology can not only make the network structure lightweight,but also offload data traffic for 5G NR authorized spectrum.The resource selection and channel access mechanism for SL-U users is key issues for efficient use of resources on unauthorized spectrum.Based on the standard technology related to SL-U,this paper focuses on the resource allocation mechanism and group-assisted channel access mechanism for SL-U users when they coexist with existing Wi-Fi users in unlicensed spectrum.In this paper,the research content is simulated and validated by the system-level simulation of the coexistence of SL-U users and Wi-Fi users.First,this paper studies the resource selection mechanism in SL-U technology,aiming at the centralized resource selection mode of user terminals.User terminals need time-frequency domain resources before transmitting data in the SL-U resource pool.This paper considers the possible negative impact of resource collision on communication system performance caused by resource selection of user terminals not coordinated by the base station,and proposes a SL-U Mode 1 centralized resource selection scheme.Then,in the system-level simulation,the proposed scheme is analyzed to verify the feasibility of the proposed scheme.Second,in this paper,the SL-U user access mechanism is studied for the scenario of data packet unsaturated communication.By analyzing the independent access and group-assisted methods used by the side-link users to access the channel,we find that the LBT(Listen Before Talk)detection problem caused by the independent channel access schemeis severe.Therefore,we consider introducing a group-assisted channel access scheme into the SL-U system.In this paper,based on the principle that the group members use COT(Channel Occupy Time)to access the channel in a cyclic manner,a group-assisted scheme with fixed time slot allocation pattern is proposed.Subsequently,in order to speed up the intra-group cycle,a SL-U user grouping scheme based on WK-means algorithm is proposed.Finally,in order to balance the packet waiting time in the user cache,we consider associating the number of group members with the channel access priority,and propose a SL-U group-assisted LBT parameter dynamic setting mechanism.In the system-level simulation,the utility and performance of the three schemes are analyzed and compared,which verifies the performance advantages and features of the three schemes.