MIMO-NOMA-Aided Healthcare IoT Networking: Automated Massive Connectivity Protocol

This paper addresses the design of multiple access protocol for healthcare Internet of things (HIoT) networking, where devices are massively deployed to facilitate ubiquitous service provision. While non-orthogonal multiple access (NOMA) has been considered a major breakthrough for next generation smart healthcare network and beyond, automated random access enabled massive connectivity remains a challenge. To this end, automated massive connectivity protocol is developed, where multiple devices compete for a power level to gain access whenever needed. The power level is selected randomly from a predetermined set derived using large dimensional analysis presuming user-load $K$ significantly outnumbers the antennas equipped at access point (AP). As a contention-based random access protocol, the contention is resolved using ALOHA protocol. Moreover, simple forward error corrections (FECs) are introduced to enable massive connectivity in finite blocklength regime as well as to mitigate severe interference. In contrast to existing multiple-input multiple-output NOMA (MIMO-NOMA), the proposed scheme avoids spectral efficiency penalty due to preamble and the potentially long latency due to infinite blocklength as a result of density evolution method. The simulated results demonstrate that quality of service (QoS) in terms of enhanced random access, improved spectral efficiency and reduced power consumption, which justify the proposed MIMO-NOMA design evidently.