Abstract
Non-orthogonal multiple-access (NOMA) has recently been proposed to improve throughput and spectrum-efficiency of 5G cellular networks and beyond. It is also a key enabler for ultra-reliable and low-latency (URLL) communications. Moreover, the Internet-of-Things (IoT) paradigm has emerged to practically provide massive connectivity for smart devices and systems, which entails spectrum- and energy-efficient transmission schemes. To this aim, NOMA and energy-harvesting (EH) solutions have been put forth to address such demands, making the combination of such technologies inevitable in NOMA-based URLL-EH-IoT networks. On the other hand, random-access (RA) techniques are the key solution to enable massive URLL-EH-IoT networks, since they reduce signaling overhead, packet latency, and energy consumption when massive numbers of clustered IoT devices with sporadic traffic behavior are considered. In this paper, uplink RA-NOMA in URLL-EH-IoT networks with short packet and diversity transmissions is studied and analyzed. Network metrics—such as average packet latency, reliability, and GoodPut—are derived for the RA-NOMA scenario and compared with its RA-OMA counterpart to explore the advantages of RA-NOMA over RA-OMA. Moreover, the analytical derivations have been validated and shown to coincide with the simulation results. Furthermore, the effect of the transmission diversity and number of data bits per blocklength on the different network metrics are extensively evaluated. Lastly, the analytical derivations are utilized to find the optimum values of the IoT nodes’ transmit power, number of packet replicas, and number of transmitted data bits per blocklength, such that the maximum sum-GoodPut of a RA-NOMA IoT cluster is achieved, subject to URLL constraints.
Highlights
The explosive and exponential growth in the number of smart mobile devices, applications, and services in the current 5G cellular and emerging Internet-of-Things (IoT) networks calls for intelligent spectrum- and energy-efficient transmission techniques to meet the demands for massive connectivity, high data rates, and low-latency [1], [2]
NUMERICAL RESULTS This section numerically evaluates the effect of the number of replicas K of an IoT node’s packet, number of data bits nd in each packet per blocklength, and the transmit power of the IoT nodes on the GoodPut, reliability, and packet latency for the RA-non-orthogonal multiple access (NOMA) and RA-OMA scenarios
This paper has considered UL RA-NOMA EH-IoT networks with ultra-reliable and low-latency (URLL) requirements
Summary
The explosive and exponential growth in the number of smart mobile devices, applications, and services in the current 5G cellular and emerging Internet-of-Things (IoT) networks calls for intelligent spectrum- and energy-efficient transmission techniques to meet the demands for massive connectivity, high data rates, and low-latency [1], [2]. Closed-form expressions for the block error rates of a two-users NOMA network have been derived, while demonstrating the superior performance of NOMA over OMA in reducing transmission latency. To achieve the target ultra-reliability and realize low-latency, short packet and diversity transmissions are adopted Network metrics such as average packet latency, reliability, and GoodPut are mathematically derived, while accounting for IoT nodes’ sporadic traffic behavior and energy arrival rate. Derived analytical expressions for critical IoT network performance metrics (i.e. average packet latency, reliability, and GoodPut), where energy- and data-causality are considered simultaneously in deriving the network metrics. Utilized the analytical derivations to maximize the sumGoodPut of a RA-NOMA cluster, subject to constraints on reliability, average packet latency, SIC decoding order, and transmit power.
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