This letter proposes a new sparse code multiple access (SCMA) system for handling the coexistence of active user equipments (UEs) and inactive UEs, which share the same frequency/time resources for an uplink grant-free scenario. SCMA systems use a message passing algorithm, which considers all UEs to be active UEs. Therefore, inactive UEs cause significant decoding problem in SCMA systems. In order to solve the coexistence problem, we propose code words and a novel SCMA receiver which can distinguish the signal of active/inactive UEs. The numerical results show that the proposed SCMA receiver achieves a remarkable enhancement in false alarm probability, miss detection probability, and bit-error rate.
Bibliographical noteFunding Information:
Manuscript received July 29, 2017; accepted August 27, 2017. Date of publication September 5, 2017; date of current version December 8, 2017. This work was supported in part by the National Research Foundation of Korea(NRF) grant funded by the Korea government (NRF-2015R1A2A1A01006162) and in part by Institute for Information & communications Technology Promotion (IITP) grant funded by the Korea government (MSIP) (No. R0101-16-244, Development of 5G Mobile Communication Technologies for Hyper-connected smart services) and grant funded by the Korea government (MSIT) (2016-0-00181-002, Development on the core technologies of transmission, modulation and coding with low-power and lowcomplexity for massive connectivity in the IoT environment). The associate editor coordinating the review of this letter and approving it for publication was A. Lioumpas. (Corresponding author: Daesik Hong.) J. Kim, K. Lee, J. Kim, and D. Hong are with ITL, Yonsei University, Seoul 03722, South Korea (e-mail: firstname.lastname@example.org; email@example.com; firstname.lastname@example.org; email@example.com).
All Science Journal Classification (ASJC) codes
- Modelling and Simulation
- Computer Science Applications
- Electrical and Electronic Engineering