Simple Semi-Grant-Free Transmission Strategies Assisted by Non-Orthogonal Multiple Access

Zhiguo Ding, Robert Schober, Pingzhi Fan, H. Vincent Poor

Research output: Contribution to journalArticlepeer-review

92 Scopus citations


Grant-free transmission is an important feature to be supported by future wireless networks since it reduces the signaling overhead caused by conventional grant-based schemes. However, for grant-free transmission, the number of users admitted to the same channel is not capped, which can lead to a failure of multi-user detection. This paper proposes non-orthogonal multiple-access (NOMA) assisted semi-grant-free (SGF) transmission, which is a compromise between grant-free and grant-based schemes. In particular, instead of reserving channels either for grant-based users or grant-free users, the focus here is on an SGF communication scenario, where users are admitted to the same channel via a combination of grant-based and grant-free protocols. As a result, a channel reserved by a grant-based user can be shared by grant-free users, which improves both connectivity and spectral efficiency. Two NOMA assisted SGF contention control mechanisms are developed to ensure that, with a small amount of signaling overhead, the number of admitted grant-free users is carefully controlled and the interference from the grant-free users to the grant-based users is effectively suppressed. Analytical results are provided to demonstrate that the two proposed SGF mechanisms employing different successive interference cancelation decoding orders are applicable to different practical network scenarios.

Original languageEnglish (US)
Article number8662677
Pages (from-to)4464-4478
Number of pages15
JournalIEEE Transactions on Communications
Issue number6
StatePublished - Jun 2019
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Electrical and Electronic Engineering


  • Non-orthogonal multiple access (NOMA)
  • cognitive radio NOMA
  • grant free transmission
  • massive connectivity


Dive into the research topics of 'Simple Semi-Grant-Free Transmission Strategies Assisted by Non-Orthogonal Multiple Access'. Together they form a unique fingerprint.

Cite this