In this paper, the performance of a  two-hop cooperative network is analyzed assuming the use of a channel-aware dynamic time-switching (TS) energy harvesting (EH) protocol at the battery-assisted EH full-duplex relay node. In such networks, node-level energy considerations are important for efficient battery utilization but have not attracted research attention. Two battery management schemes are considered. In the first scheme, fixed  battery energy (FBE) is added to the harvested energy.  To further improve performance, a new dynamic battery energy (DBE) scheme is considered in which the amount of battery energy drawn is channel dependent. The performance of the network is analyzed with both FBE and DBE schemes for static and dynamic TS schemes assuming a practical nonlinear EH model. Expressions are also presented for the average battery energy consumption in each case. It is demonstrated that joint optimization of  the average battery energy consumption and the TS parameter is important. It is also demonstrated that the proposed dynamic TS protocol provides substantial gains in throughput and average energy savings compared to the static TS protocol with both FBE and DBE.  The derived insights can aid a system designer. Computer simulations validate the derived expressions.

This paper investigates a cooperative non-orthogonal multiple access (Co-NM) based network consisting of a multiantenna source, a full-duplex energy harvesting (EH) near user (NU) internet-of-things (IoT) node and multiple distant user (DU) IoT nodes. The source shares a direct link to the NU, while the NU augments the harvested energy by a limited amount of its battery energy to relay the information to the selected DU. Considering time-switching (TS) or power-splitting (PS) protocol, practical nonlinear EH, successive interference cancellation error, and opportunistic Co-NM/OMA (OM) switching, closed-form expressions are derived for the outage probability and throughput of both DU and NU. We demonstrate that the proposed opportunistic Co-NM/OM switching can ensure a performance similar to OM at the NU without loss in DU throughput. Also, a joint optimal choice of battery energy and PS/TS parameter helps in attaining a  maximum energy efficiency (EE). Moreover, Co-NM/OM switching ensures higher EE compared to Co-NM and OM.

The performance of an underlay coordinated direct and relay transmission (CDRT) based non-orthogonal multiple access (NOMA) network is limited by the random nature of the transmit powers due to the interference temperature limit (ITL) imposed by the primary network. In this paper, we show that combining the signals at both near and far users can significantly enhance throughput. Considering the practical scenario of imperfect successive interference cancellation, the performance of near and far user nodes is analyzed in terms of throughput and outage probability. The traditional case of static ITL is considered first. Then, analysis is presented for the case when the ITL depends on the primary channel state information, and it is shown that the gain in performance can be very large over static ITL. Closed-form expressions for NOMA power pportioning are presented for a special case. Further, it is shown that how optimum parameters can be chosen to maximize the performance. Simulations validate the derived analytical expressions.

This paper investigates the performance of a non-orthogonal multiple access (NOMA) enabled full-duplex (FD) device-to-device (D2D) communication network that is underlaid in the cellular uplink. The uplink cellular user is licensed to serve the BS. For improving spectrum utilization efficiency, it also concurrently relays D2D information in FD mode. The transmit powers of D2D nodes are chosen such that the cumulative interference at the BS is below the Interference Temperature Limit (ITL). Using the statistical channel knowledge and successive interference cancellation at the D2D nodes, an expression for the D2D throughput is derived in closed-form. Thereafter, using the approximate throughput expressions, a closed-form expression of ITL apportioning parameter is derived in closed form that maximizes the D2D throughput while ensuring desired quality of service at the BS. Computer simulations demonstrate accuracy of the derived expressions.

This paper investigates a cooperative non-orthogonal multiple access network where a near user (NU) harvests energy using time-switching (TS) or power-splitting (PS) protocol to assist information transmission to the far user (FU). Considering nonlinear energy harvesting and opportunistic cooperative mode (CM) to non-cooperative mode (NCM) switching, expressions are derived for FU and NU outage probabilities and throughput. We demonstrate that CM/NCM switching can guarantee NU’s performance similar to OMA without any degradation in FU throughput. Also, the choice of optimum PS/TS parameter is essential to maximize FU throughput while ensuring desired NU throughput. CM/NCM switching ensures higher energy efficiency.

This paper investigates the performance of a framework for low-outage downlink non-orthogonal multiple access (NOMA) signalling using a coordinated direct and relay transmission (CDRT) scheme with direct links to both the near-user (NU) and the far-user (FU). Both amplify-and-forward (AF) and decode-and-forward (DF) relaying are considered. In this framework, NU and FU combine the signals from BS and R to attain good outage performance and harness a diversity of two without any need for feedback. For the NU, this serves as an incentive to participate in NOMA signalling. For both NU and FU, expressions for outage probability and throughput are derived in closed form. High-SNR approximations to the outage probability are also presented. We demonstrate that the choice of power allocation coefficient and target rate is crucial to maximize the NU performance while ensuring a desired FU performance. We demonstrate performance gain of the proposed scheme over selective decode-and-forward (SDF) CDRT-NOMA in terms of three metrics: outage probability, sum throughput and energy efficiency. Further, we demonstrate that by choosing the target rate intelligently, the proposed CDRT NOMA scheme ensures higher energy efficiency (EE) in comparison to its orthogonal multiple access counterpart. Monte Carlo simulations validate the derived expressions.