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General Design Of Scma Codebook

Posted on:2020-07-19Degree:MasterType:Thesis
Country:ChinaCandidate:H Y HuangFull Text:PDF
GTID:2428330575956448Subject:Information and Communication Engineering
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Fifth generation(5G)wireless networks are expected to support massive connectivity with a great number of users and reliable service with low latency.Non-orthogonal multiple access(NOMA)effectlively improve the communication system resource utilization to support more users at the same time.Sparse code multiple access(SCMA)is a typical NOMA technology.The principle of SCMA is that multi-user binary data directly maps to mulltidimensional sparse sequence of SCMA codebook.So the SCMA multi-user codebook design is one of the keys deciding system performance.A Line-to-Plane idea of codebook design is proposed in this thesis.The criterion of this design method is maximizing the Euclidean distance of constellations.On single carrier,the basic constellation set is rotated to get other multi-user constellation sets.Elements of the basic constellation set are distributed in the real number axis,and elements of all sets are distributed in complex rectangular coordinate plane.Then,let constellation sets are same on each carrier to complete system codebook.This design method ensures the system performance to be non-destructive with low design complexity.It is a general design of SCMA codebook that can be applied to high overload and high-order modulation system.Considering services of users may be different in fact,a new multiple access technology named Multi-codeword SCMA(McSCMA)is proposed in the thesis.In McSCMA,single user is allowed to randomly select multiple codewords according to its service to do data modulation.Obviously,with same overload,McSCMA needs more codewords than SCMA.Because of that,the thesis further puts forward the design method of McSCMA codebook based on Line-to-Plane design.Besides,the number of polits is in direct proportion to the number of possible codeword combinations.So there are more potential polits in McSCMA system.The interference of too many potential pilots that are not completely orthogonal will impact Active User Detection(AUD)performance expressed by False Alarm Rate(FAR).The thesis raises Codeword Grouping(CG),which can reduce potential pilots,to lower FAR of AUD and the complexity of demodulation in the receiver.
Keywords/Search Tags:SCMA, codebook design, grant-free transmission, Codeword Grouping
PDF Full Text Request
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