Iterative Receiver Design for FTN Signaling Aided Sparse Code Multiple Access

Weijie Yuan, Nan Wu*, Andrew Zhang, Xiaojing Huang, Yonghui Li, Lajos Hanzo

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

61 Citations (Scopus)

Abstract

The sparse code multiple access (SCMA) is a promising candidate for bandwidth-efficient next generation wireless communications, since it can support more users than the number of resource elements. On the same note, faster-than-Nyquist (FTN) signaling can also be used to improve the spectral efficiency. Hence in this paper, we consider a combined uplink FTN-SCMA system in which the data symbols corresponding to a user are further packed using FTN signaling. As a result, a higher spectral efficiency is achieved at the cost of introducing intentional inter-symbol interference (ISI). To perform joint channel estimation and detection, we design a low complexity iterative receiver based on the factor graph framework. In addition, to reduce the signaling overhead and transmission latency of our SCMA system, we intrinsically amalgamate it with grant-free scheme. Consequently, the active and inactive users should be distinguished. To address this problem, we extend the aforementioned receiver and develop a new algorithm for jointly estimating the channel state information, detecting the user activity and for performs data detection. In order to further reduce the complexity, an energy minimization based approximation is employed for restricting the user state to Gaussian. Finally, a hybrid message passing algorithm is conceived. Our Simulation results show that the FTN-SCMA system relying on the proposed receiver design has a higher throughput than conventional SCMA scheme at a negligible performance loss.

Original languageEnglish
Article number8891911
Pages (from-to)915-928
Number of pages14
JournalIEEE Transactions on Wireless Communications
Volume19
Issue number2
DOIs
Publication statusPublished - Feb 2020

Keywords

  • Sparse code multiple access
  • channel estimation
  • faster-than-Nyquist signaling
  • grant-free
  • high spectral efficiency
  • hybrid message passing

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