Abstract
Sparse code multiple access (SCMA) is one of the Non-Orthogonal Multiple Access (NOMA) that attracts many researchers for its promising future uses in 5G systems. In this paper, a Computer Generated-Sparse Code Multiple Access (CG-SCMA) is proposed. CG-SCMA generates a complex SCMA codebook that maximizes the Minimum Euclidian Distance (MinED) of 16-point star-QAM. This codebook is generated using computer program to specify the most appropriate values for this constellation. Then Trellis Coded Modulation (TCM) is used to divide the constellation into four sub constellations to maximize MinED. The new codebook reaches MinED for four sub constellations {3.46, 2.16, 2.16, 3.46} and achieves increment over SCMA codebook based 16-point star-QAM by 10.1%. The multiplexer and de-multiplexer for proposed codebook and traditional SCAM codebook is implemented using netFPGA-1G-CML Kintex-7. it can speed up the process by 597.6 times over MATLAB simulator and decreasing BER compared to open literature codebooks.
Highlights
The massive number of users produces a large-scale of heterogeneous traffic
Due to Orthogonal Multiple Access schemes (OMA) inability to combat with intercell interference, Non- Orthogonal Multiple Access (NOMA) has been adopted in second and third generation cellular systems and has been introduced as a solution to be used in cellular generations [4], [5]
Sparse Code Multiple Access (SCMA) features the advantages of Code Division Multiple Access (CDMA) and Low Density Signature (LDS)
Summary
The massive number of users produces a large-scale of heterogeneous traffic This will require the development of new modulation and multiple access (MA) scheme. MA technique can improve the frequency efficiency and system’s capacity by allowing multiple users to make use of available resource at the base station [1]. SCMA features the advantages of Code Division Multiple Access (CDMA) and Low Density Signature (LDS). Low complexity MPA is used in detection of multiuser at the receiver side, taking advantage of the sparse structure of the signature in LDS- CDMA [3]. The design of codebook allows the reduction of the number of constellation points used This reduction leads to reduction in complexity, MPA can be used for decoding at the receiver side [3], [10]. Bitwise output LLRs are calculated according to the bit- to codeword mapping
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