Design and Evaluation of Buffer-Aided Cooperative NOMA With Direct Transmission in IoT

• Published in: IEEE internet of things journal Vol. 8; no. 10; pp. 8145 - 8158
• Main Authors: Xu, Peng, Wang, Yunwu, Chen, Gaojie, Pan, Gaofeng, Ding, Zhiguo
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 15.05.2021; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Average delay; Buffer storage; buffer-aided cooperation; Buffers; cooperative nonorthogonal multiple access (C-NOMA); Delays; diversity order; Downlink; Internet of Things; NOMA; Nonorthogonal multiple access; outage probability; Relays; Signal to noise ratio
• DOI: 10.1109/JIOT.2020.3042505
• ISSN: 2327-4662

The high spectrum efficiency of nonorthogonal multiple access (NOMA) is attractive to solve the massive number of connections in the Internet of Things (IoT). This article investigates a buffer-aided cooperative NOMA (C-NOMA) system in the IoT, where the intended users are equipped with buffers for cooperation. The direct transmission from the access point to the users and the buffer-aided cooperative transmission between the intended users are coordinated. In particular, a novel buffer-aided C-NOMA scheme is proposed to adaptively select a direct or cooperative transmission mode, based on the instantaneous channel state information and the buffer state. Then, the performance of the proposed scheme, in terms of the system outage probability and average delay, is theoretically derived with closed-form expressions. Furthermore, the full diversity order of three is demonstrated to be achieved for each user pair if the buffer size is not less than three, which is larger than conventional nonbuffer-aided C-NOMA schemes whose diversity order is only two in the considered C-NOMA system in the IoT.