Owing to the exponential proliferation of the Internet of Things (IoT), it is anticipated that the number of small IoT devices will grow expeditiously over the next few years. These billions of small IoT sensor and devices will consume a huge power for data transmission. In this fashion, Radio frequency (RF) energy harvesting has been contemplated as an appealing solution to the architecture of long-term and self-sustainable nextgeneration wireless systems such as IoT network. However, in the practical environment, such IoT network or systems are subjected to external interference factors which often results in the loss of the system rate. Different from generic RF EH system in the literature where only a source node data is relayed through intermediate EH relaying node, in this paper, we have considered to transmit the data of IoT relay node along with source node data using Non-orthogonal multiple access (NOMA) protocol in the presence of an interfering signal to their respective destinations. Specifically, in the presence on interfering signal, we study the combination of two popular energy harvesting relaying architectures-time switching (TS) relaying and power splitting (PS) relaying with NOMA protocol for IoT relay systems. Considering the interference from the external entity, we have mathematically derived the outage probability, throughput and sum-throughput for our proposed system. Extensive simulations are carried out to find out the optimal TS and PS factor that maximizes the sum-throughput of the considered system in the presence of an interfering signal. The analytical results of our system model under consideration are validated by the simulation results, and representative performance comparisons are presented.

In this paper, a bidirectional relaying (BR) non-orthogonal multiple access (NOMA) with simultaneous wireless information and power transfer (SWIPT) termed as BR NOMA-SWIPT is proposed and investigated for the Internet of Things (IoT) relay networks. Here, multiple NOMA users in one group can communicate or exchange information with multiple NOMA users in another group through a common energy harvesting (EH) based relay. The EH based relay exploits the radio frequency (RF) energy supplied by the two NOMA user groups to recharge itself, and then it exchanges the information between them. Specifically, the two groups of NOMA users transmit the information intended for the exchange to the relay node using the uplink NOMA protocol. The relay node first harvests the RF energy through the signals of the two group of NOMA users, and then it carries out the exchange of information between two NOMA user groups by using the downlink NOMA protocol. To the best of our knowledge, there is no existing study or research on BR NOMA with SWIPT. Therefore, in this paper, we examine in detail, the performance of BR NOMA-SWIPT enabled IoT relay networks. Specifically, we study a popular EH time switching (TS) relaying architecture with BR and NOMA. We also study the effect of both perfect successive interference cancellation (pSIC) and imperfect SIC (ipSIC) on the proposed BR NOMA-SWIPT system. Analytical expressions for the outage probability and ergodic capacity are mathematically derived. The analytical results of our proposed system model are validated by the simulation results, and representative performance comparisons are presented thoroughly, which not only provides practical insights into the effect of different system parameters on the overall network performance, but it also demonstrates that our proposed BR NOMA-SWIPT can attain significant throughput and capacity gains as compared to conventional BR multiple access schemes.

Amidst the rapid development of the fifth generation (5G) networks, Internet of Things (IoT) is considered as one of the most important part of 5G next generation networks as it can support massive object communications. These massive object communications in the context of IoT is expected to consume a huge power. Furthermore, IoT sensors or devices are rather power constrained and are mostly battery operated. Therefore, energy efficiency of such network of IoT devices is a major concern. On the other hand, energy harvesting (EH) is an emerging paradigm that allows the wireless nodes to recharge themselves through radio frequency (RF) signals directed to them from the source node and then relaying or transmitting the information. Although a myriad of works have been carried out in the literature for EH, the vast majority of those works only consider RF EH at the relay node and successfully transmitting the source node data. Those approaches do not consider the data transmission of the relay node that may be an energy deprived IoT node which needs to transmit its own data along with the source node data to their respective destination nodes. Therefore, in this paper, we envisioned a RF EH and information transmission system based on time switching (TS) relaying, power splitting (PS) relaying and non-orthogonal multiple access (NOMA) which is suitable for wireless powered IoT relay systems. A source node information data is relayed through power constrained IoT relay node $Io{T}_R$ that first harvests the energy from source node RF signal using either TS and PS relaying protocol and then transmits the source node information along with its information using NOMA protocol to the respective destination nodes. Considering NOMA as a transmission protocol, we have mathematically derived analytical expressions for TS and PS relaying protocol for our proposed system. We have also formulated an algorithm to find out optimal TS and PS factor that maximizes the sum-throughput for our proposed system. Our proposed system analytical results for TS and PS protocol are validated by the simulation results.

Differentsystemmodels utilizing nonorthogonal multiple access (NOMA) have been successfully studied to meet the growing capacity demands of the Internet of Things IoT) devices for the next-generation networks. However, analyzing the antieavesdropping for NOMA systems under different scenarios and settings still needs further exploration before it can be practically deployed. Therefore, in this article, we study the secrecy performance of a cooperative NOMA system in the IoT networks where two source nodes communicate with their respective destination nodes via a common relay in the presence of an eavesdropper. Specifically, two source nodes send their data in parallel over the same frequency band to the common relay node using uplink NOMA. Then, the relay node forwards the decoded symbols to the respective destination nodes using downlink NOMA in the presence of an eavesdropper. To enhance the security performance of the considered system, we study and propose an artificial noise (AN)-aided scheme in which the two destination nodes emit a jamming signal to confuse the eavesdropper while receiving the signal from the common relay node. We also study the effect of NOMA power allocation, perfect successive interference cancellation (pSIC), and imperfect successive interference cancellation (ipSIC) on the considered system. Analytical expressions for the ergodic capacity (EC), ergodic secrecy sum rate (ESSR), and secrecy outage probability (SOP) are mathematically derived and verified with the simulation results. Our results demonstrate that a significantly higher ESSR and lower SOP of the system can be attained compared to a conventional NOMA system without a destination-assisted jamming signal scheme.

We propose and investigate a bidirectional device-to-device (D2D) transmission scheme that exploits cooperative downlink non-orthogonal multiple access (NOMA) (termed as BCD-NOMA). In BCD-NOMA, two source nodes communicate with their corresponding destination nodes via a relaying node while exchanging bidirectional D2D messages simultaneously. BCD-NOMA is designed for improved outage probability (OP) performance, high ergodic capacity (EC) and high energy efficiency by allowing two sources to share the same relaying node for data transmission to their corresponding destination nodes while also facilitating bidirectional D2D communications exploiting downlink NOMA. Simulation and analytical expressions of the OP, EC and ergodic sum capacity (ESC) under both perfect and imperfect successive interference cancellation (SIC) are used to demonstrate the effectiveness of BCD-NOMA compared to conventional schemes.

A number of analytical models have been proposed to describe the priority schemes of the enhanced distributed channel access (EDCA) mechanism of the IEEE 802.11e standard. EDCA provides a class-based differentiated quality of service (QoS) to IEEE 802.11 WLANs. Many have used a multiple number of nodes to study the differentiation behaviour of the model. However, in many real-life usage scenarios Internet traffic is often asymmetric with much downlink traffic from the access point to the stations and little traffic in the reverse direction. Hence, most of the overall traffic differentiation will happen in the virtual collision handler (VCH) of the access point. If the access point uses EDCA, it should know the characteristics of the VCH to be able to control the differentiation of the downlink traffic. The main contribution of this paper opposed to other works is that it demonstrates how a generic channel model of 802.11e can be modified to predict the performance behaviour of the VCH with a remarkably good accuracy. In doing so, we first introduce virtual collision handling into the generic model. We also show how to derive a closed-form solution for the performance. We observe good match between the analytical model and simulations