Abstract
The next generation Internet of Things (IoT) exhibits a unique feature that IoT devices have different energy profiles and quality of service (QoS) requirements. In this paper, two energy and spectrally efficient transmission strategies, namely wireless power transfer assisted non-orthogonal multiple access (WPT-NOMA) and backscatter communication (Back-Com) assisted NOMA (BAC-NOMA), are proposed by utilizing this feature of IoT and employing spectrum and energy cooperation among the devices. In particular, the use of NOMA ensures that the devices with different QoS requirements can share the same spectrum, and WPT and Back-Com are employed to utilize the cooperation among the devices with different energy profiles, which avoids the use of a dedicated power beacon. Furthermore, for the proposed WPT-NOMA scheme, the application of hybrid successive interference cancelation (SIC) decoding order is also considered, and analytical results are developed to demonstrate that WPT-NOMA can avoid outage probability error floors and realize the full diversity gain. Unlike WPT-NOMA, BAC-NOMA suffers from an outage probability error floor, and the asymptotic behavior of this error floor is analyzed in the paper by applying the extreme value theory. In addition, the effect of a unique feature of BAC-NOMA, i.e., employing one device's signal as the carrier signal for another device, is studied, and its impact on the diversity gain is revealed. Simulation results are also provided to compare the performance of the proposed strategies and verify the developed analytical results.
Highlights
The aim of this paper is to consider a Non-orthogonal multiple access (NOMA) uplink scenario, where a delay-sensitive non-energy-constrained Internet of Things (IoT) device and multiple delay-tolerant energy-constrained devices communicate with the same access point, and the use of NOMA ensures that the devices with different quality of service (QoS) requirements can share the same spectrum
Because some IoT devices are energy constrained, wireless power transfer (WPT) and Back-Com are employed to utilize the cooperation among the devices with different energy profiles, which avoids the use of a dedicated power beacon
As indicated in Theorem 1, if0 ̄s < 1 holds, WPT-NOMA can avoid outage probability error floors, which is consistent to the observations made from Fig. 1(a)
Summary
A. Motivations and the Related Existing Works. The generation Internet of Things (IoT) is envisioned to support various important applications, including smart home, intelligent transportation, wireless health-care, environment monitoring, etc [1]. The key step to implement the IoT is to ensure that a massive number of IoT devices with heterogeneous energy profiles and quality of service (QoS) requirements can be connected in a spectrally efficient manner, Manuscript received July 27, 2020; revised October 16, 2020 and December 11, 2020; accepted January 14, 2021. Date of publication January 19, 2021; date of current version May 18, 2021. The associate editor coordinating the review of this article and approving it for publication was N.
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