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Research Of Grant-free Random Access Scheme Of Large-scale Terminal Based On MIMO

Posted on:2024-09-18Degree:MasterType:Thesis
Country:ChinaCandidate:J W WangFull Text:PDF
GTID:2568307136992759Subject:Electronic information
Abstract/Summary:PDF Full Text Request
As one of the three scenarios of 5G,massive machine type communication(mMTC)features a large number of devices with device types,random data bursts,and short uplink data packets.The traditional grant-based access approach incurs too much signaling overhead,making the system too difficult to cope with.Developing lightweight grant-free random access schemes to facilitate the transmission of massive terminal multi random access and improve system capacity is a challenging task for mobile communication networks.To address this,this thesis investigates the use of multiple input multiple output(MIMO)technology for large-scale grant-free random access in terminals and explores an efficient competitive access scheme.By effectively reusing resources across multiple domains,the goal is to improve the random access success rate of terminals and enhance wireless resource utilization efficiency.The main research objectives and achievements of this thesis are as follows.(1)To address the issue of limited preamble resources in grant-free random access of mMTC terminals,we study a code-domain and power-domain resource joint reuse strategy,and propose a scheme called grant-free random access scheme for mMTC based on multi-power level and multipreamble.This scheme enables terminals to transmit multiple preambles with a selected power level in multiple uplink random access slots,in order to make full use of multiple combined preambles to expand the preamble set space and combined with non-orthogonal multiple access(NOMA)to further improve the efficiency of multiple access.The simulation results demonstrate that compared to the distributed layered grant-free NOMA scheme and the multi-preamble grant-free random access scheme,the proposed scheme effectively improves the access success probability for users and exhibits better adaptability to large-scale random access scenarios.(2)To address the challenging issue of grant-free random access conflicts in mMTC terminals,we proposes a conflict resolution-based random access scheme.In this scheme,the terminal randomly selects a preamble and forms a data frame in the uplink.The selected data frame is simultaneously transmitted over multiple uplink time-frequency resource blocks.The base station prioritizes the detection of data frames on non-conflict time-frequency resource blocks and employs successive interference cancellation techniques to eliminate their replicas from other time-frequency resource blocks.It then recovers data from other terminals using preamble detection,iteratively repeating this process to resolve access conflicts.Simulation results demonstrate that the proposed scheme outperforms traditional single orthogonal preamble schemes,contention resolution diversity slot Aloha schemes,and improved multi-slot preamble allocation schemes.It effectively resolves access conflicts and fully utilizes the preamble space,achieving a more efficient random access with higher throughput.This thesis investigates the problem of multi-terminal overload access with limited preamble resources,aiming to reduce random access conflicts in large-scale terminals and enhance the multiaccess capability of cellular networks.
Keywords/Search Tags:massive grant-free random access, non-orthogonal multiple access, successive interference cancellation, access conflict resolution, access success probability
PDF Full Text Request
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