Font Size: a A A

Research On Multiple Access Techniques For Massive Machine-Type Communications

Posted on:2020-10-16Degree:DoctorType:Dissertation
Country:ChinaCandidate:G Y MaFull Text:PDF
GTID:1368330578476883Subject:Communication and Information System
Abstract/Summary:PDF Full Text Request
As the key technical support for the 4th industrial revolution in the future,the booming development of the internet of things has aroused the industry's enthusiasm for machine-type communications.Unlike traditional human-type communications,machine-type communications in the internet of things focuses on the requirements of high connectivity and high reliability.To this end,two new scenarios have been proposed in the 5th generation mobile communications system,which are massive machine-type communications and ultra-reliable low latency communications.Among them,the massive machine-type communications system mainly provides communication services for a large number of micro sensors and actuators in the future intelligent sensing and control systems.Since the served micro-devices tend to have low power consumption requirements,the industry introduces the grant-free random access procedure to reduce the signaling overhead.At the same time,due to the scarce spectrum in the low frequency band,how to use the limited radio resources to realize the grant-free random access of massive devices becomes the main challenge of massive machine-type communications.The key to coping with this challenge is the effective multiple access techniques.There-fore,it is important to study novel multiple access techniques for massive machine-type communications to achieve efficient connections of massive low-power user equipment.Based on the problems of limited radio resources and limited energy supply in mas-sive machine-type communications,this thesis adopts the theory of coding theory,com-binatorial mathematics,signal detection and estimation for the requirements of high connectivity,high reliability and low complexity of massive machine-type communications system.With the research methods of model establishment,algorithm design,performance evaluation and simulation verification,this thesis proposes a novel multiple access technique for massive machine-type communications,called tandem spreading multiple access.Around this technique,this thesis studies the corresponding transceiver design,asynchronous solutions and multi-slot design.The research points of the thesis mainly include the following aspects:1)For the grantfree random access procedure,considering the sporadic transmission characteristics of massive machine-type communications,this point proposes a novel multiple access scheme,named tandem spreading network-division multiple ac-cess.This scheme is based on the limitations of the iterative algorithm in the existing multiple access techniques.The tandem spreading network-division multiple access scheme initially determines the transceiver design of tandem spreading multiple access,which provides a basis for subsequent improvements.The scheme divides user data packets into segments and generates redundancy segments using physical layer network coding.At the same time,the scheme introduces a new type of spreading method,called tandem spreading,which uses multiple spreading sequences to spread the symbols on different segments of a single user.Based on physical layer network coding and tandem spreading,the receiver can implement user identification and data detection without relying on the iterative algorithm,which can effectively support sporadic random access of massive user devices.2)Considering the potential internet of things applications that require both high connectivity and high reliability in the future,as well as the limitations of existing research on the trade-off of various system performance requirements,this point proposes coded tandem spreading multiple access schemes based on tandem spreading network-division multiple access to improve the transceiver of tandem spreading multiple access technique.This scheme introduces segment coding and improves the codebook design of tandem spreading,which not only can support more user devices,but also achieve high reliable access.For the coded tandem spreading multiple access,this point explores the trade-off between connectivity,reliability and user rate,and concludes that coded tandem spreading multiple access is able to flexibly achieve high connectivity and high reliability at the expense of user data rate.3)Considering the asynchronous arrival of uplink access signals due to different user equipment locations in massive machine-type communications,this point proposes the corresponding asynchronous solution for tandem spreading multiple access technique.The scheme adopts a new spreading sequence,and interleaves the spreading chips on the transmitter side to effectively alleviate the influence of asynchronicity on user identification and data detection.At the same time,the scheme introduces the corresponding uplink channel estimation,which makes it feasible to implement tandem spreading multiple access in practical grant-free random access system.4)For the collision resolution limitations of the physical layer multiple access techniques in massive machine-type communications,this point combines tandem spreading multiple access with the medium access control layer multiple access techniques to introduce a multi-slot design scheme.The scheme can complement the collision resolution capability of tandem spreading multiple access and the medium access control layer technique coded slot ALOHA to achieve a higher connectivity and reliability.Based on the scheme,this point analyzes the collision resolution capability and deduces the corresponding average user collision resolution probability.Numerical simulation verifies the corresponding theoretical analysis and shows that the multislot design can improve the reliability by further sacrificing the user data rate.
Keywords/Search Tags:Massive Machine-Type Communications, Grant-free Random Access, Multiple Access, Tandem Spreading, Segment Coding, Asynchronous Transmission, Multi-Slot Design
PDF Full Text Request
Related items