Analyzing Uplink Grant-Free Sparse Code Multiple Access System in Massive IoT Networks

Ke Lai, Jing Lei, Yansha Deng, Lei Wen, Gaojie Chen, Wei Liu

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)


Grant-free sparse code multiple access (GF-SCMA) is considered to be a promising multiple access candidate for future wireless networks. In this article, we focus on characterizing the performance of uplink GF-SCMA schemes in a network with ubiquitous connections, such as the Internet-of-Things (IoT) networks. To provide a tractable approach to evaluate the performance of GF-SCMA, we first develop a theoretical model taking into account the property of multiuser detection (MUD) in the SCMA system. Then, the error rate performance of GF-SCMA in the case of codebook collision is analyzed to investigate the reliability of GF-SCMA when reusing codebook in massive IoT networks. For performance evaluation, accurate approximations for both success probability and average symbol error probability (ASEP) are derived. To elaborate further, the analytical results are utilized to discuss the impact of codeword sparse degree in GF-SCMA. After that, we conduct a comparative study between SCMA and its variant, dense code multiple access (DCMA), with GF transmission to offer insights into the effectiveness of these two schemes. This facilitates the GF-SCMA system design in practical implementation. Simulation results show that denser codebooks can help to support more user equipments (UEs) and increase the reliability of data transmission in a GF-SCMA network. Moreover, a higher success probability can be achieved by GF-SCMA with denser UE deployment at low detection thresholds since SCMA can achieve overloading gain.

Original languageEnglish
Pages (from-to)5561-5577
Number of pages17
JournalIEEE Internet of Things Journal
Issue number7
Early online date3 Sept 2021
Publication statusPublished - 1 Apr 2022


  • NOMA
  • Power control
  • Uplink
  • Internet of Things
  • Reliability
  • Analytical models
  • Geometry
  • Grant-free (GF) transmission
  • random access (RA)
  • SCMA
  • stochastic geometry


Dive into the research topics of 'Analyzing Uplink Grant-Free Sparse Code Multiple Access System in Massive IoT Networks'. Together they form a unique fingerprint.

Cite this