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This paper studies the secondary network relying relay selection to transmit signal from the secondary source (base station) to two destinations. Especially, two destinations are required non-orthogonal multiple access (NOMA) scheme and it benefits to implementation of the Internet of Things (IoT) systems. However, eavesdropper over-hears signal related link from selected relay to destination. This paper measure secure performance via metric, namely secure outage probability (SOP). In particular, signal to noise ratio (SNR) criterion is used to evalute SOP to provide reliable transmission to the terminal node. Main results indicates that the considered scheme provides performance gap among two signals at destination. The exactness of derived expressions is confirmed via numerical simulation.

In a wireless system, dual-hop transmission requires Full-Duplex (FD) to transmit signals from the base station too far users. It is more beneficial if we deploy non-orthogonal multiple access to serve specific users, i.e. normal users (near and far users) and device-to-device users. The fairness and outage performance of these users can be studied. We particularly focus on mathematical analysis of outage performance which is computed based on Signal to Noise Ratio (SNR) of received signals at each kind of user. We derive a closed-form formula of such outage probability along with throughput. To realize both the FD NOMA, this paper performs system performance metrics and considers how self-interference make influences system performance. The simulation results validate the theoretical analysis and show that our scheme can obtain a better outage probability and throughput performance with high transmit SNR at the base station and lower required target rates.

In this paper, a hybrid satellite-terrestrial spectrum sharing system allows terrestrial secondary network to cooperate with a primary satellite network and to further provide higher spectrum efficiency. For massive connections design, we implement non-orthogonal multiple access (NOMA) technique to form cognitive radio based satellite-terrestrial (CR-NSHT) system relying on NOMA and further achieve more benefits compared with traditional schemes. The secondary network only remains its stable operation when the outage probability of such system is guaranteed, and thereby, to explore advantages of spectrum sharing opportunities. Considering Shadowed-Rician fading for satellite links, and Nakagami- $m$ as well as Rician fading for terrestrial links, we derive the closed-form expressions of the outage probability to evaluate the performance of secondary network. We consider further system performance metrics including ergodic capacity, energy efficiency and multi-user scenarios. We also demonstrate the impacts of power allocation factors, transmit signal-to-noise ratio (SNR) at the source, parameters of satellite links, target rates, and fading severity parameters on the system performance. Numerical and simulation results validate our analysis and highlight the performance gains of the proposed schemes for CR-NSHT with relay link serving secondary network and direct link serving the primary network.

This paper considers ergodic capacity of energy harvesting (EH) based cellular networks. Such a network employs non-orthogonal multiple access (NOMA) together with relaying scheme to serve two far users. In this system model, relay is facilitated power splitting (PS) protocol to implement energy harvesting (EH). To examine capacity, expressions of signal to noise ratio (SNR) need be computed to achieve capacity. Power allocation factors are different for two users in such system and hence performance gap happens to distinguish requirements for separated users. It can be confirmed that the proposed paradigm exhibits maximal achievable capacity in some scenarios of setting parameters. To confirm exactness of the analytical expressions and show advantages of the proposed EH-NOMA, simulation results are performed in terms of ergodic capacity.

This paper studies the two-hop transmission relying unmanned aerial vehicle (UAV) relays which is suitable to implement in the internet of things (IoT) systems. To enhance system performance in order to overcome the large scale fading between the base station (BS) and destination as well as achieve the higher spectrum efficiency, where non-orthogonal multiple access (NOMA) strategies were typically applied for UAV relays to implement massive connections transmission. In particular, outage probability is evaluated via signal to noise ratio (SNR) criterion so that the terminal node can obtain reasonable performance. The derivations and analysis results showed that the considered fixed power allocation scheme provides performance gap among two signals at destination.The numerical simulation confirmed the exactness of derived expressions in the UAV assisted system.

We consider spectrum-sharing scenario where coexist two communication networks including primary network and secondary network using the same spectrum. While the primary network includes directional multi-transceivers, the secondary network consists of relaying-based transceiver forwarding signals by energy harvesting assisted relay node. In cognitive radio, signals transmitted from secondary network are sufficiently small so that all of primary network receivers have signal to noise ratio (SNR) greater than a given threshold. In contrast, the transmitted signals from primary network cause increasing noise which is difficult to demodulate at secondary network nodes and hence it leads to the peak power constraint. In this paper, we focus on the influence of random location of transceivers at primary network using decode-and-forward protocol. Specifically, we derive closed-form outage probability expression of the secondary network under random location of transceivers and peak power constraint of primary network. This investigation shows the relationship between the fraction of energy harvesting time $$\alpha $$ of time switching-based relaying protocol on outage probability of secondary network and throughput. In addition, we analyse the influence of the number of primary network transceivers as well as primary network’s SNR threshold on secondary network. Furthermore, the trade-off between increasing energy harvesting and rate was investigated under the effect of energy conversion efficiency. The accuracy of the expressions is validated via Monte-Carlo simulations. Numerical results highlight the trade-offs associated with the various energy harvesting time allocations as a function of outage performance.

In this paper, the performance of overlay cognitive radio (CR) in secondary networks as utilizing non-orthogonal multiple access (NOMA) is examined. We consider transmission quality from the relay to the far NOMA users who expect to multiple access to core network. In this system model, weak users who have weak signal and weak channel condition are focused on. Our proposal analysis contributes to improve the outage performance of far NOMA end-users. We first identify signal to noise ratio (SNR) to discover separated signal for each user, and exact expressions of outage probability is examined in assumption that receiver can delete the interference with successive interference elimination completely.. Then, we determine outage and throughput performance based on the noise ratio signal (SNR) achiveved. Theoretical and simulation results prove that the both proposed models can attain the outstanding performance enhancement in secondary network for far NOMA users.

This paper examines non-orthogonal multiple access (NOMA) and explores the effect of multiple antenna equipped at base station to serve many users who expect to multiple access to core network. This system model using multiple input single output (MISO) contributes enhancement on the outage performance of two NOMA end-users. We first introduce a simple model of power distribution to NOMA users who use both direct link and relay link to improve quality of transmission. Inspired by NOMA strategy, we then identify signal to noise ratio to discover separated signal for each user, and exact expressions of outage probability are developed in assumption that receiver can eliminate the interference completely with successive interference cancellation. Theoretical and simulation results show that the both suggested models can achieve the remarkable performance improvement of two NOMA users.

Non-orthogonal multiple access (NOMA) and energy harvesting (EH) are combined to introduce a dual-hop wireless sensor system. In particular, this paper considers a novel EH protocol based on time power switching-based relaying (TPSR) architecture for amplify-and-forward (AF) mode. We introduce a novel system model presenting wireless network with impacts of energy harvesting fractions and derive analytical expressions for outage probability and ergodic rate for the information transmission link. It confirmed that the right selection of power allocation for NOMA users can be performed to obtain optimal outage and ergodic capacity performance. Theoretical results show that, in comparison with the conventional solutions, the proposed model can achieve acceptable outage performance for sufficiently small threshold signal to noise ratio (SNR) with condition of controlling time switching fractions and power splitting fractions appropriately in considered TPSR protocol. We also examine the impacts of transmitting power at source, transmission rate, the other key parameters of TPSR to outage, and ergodic performance. Simulation results are presented to corroborate the proposed system.

Power domain-based non-orthogonal multiple access (PDMA) is one emerging technology thanks to higher system capacity, lower latency, and massive connectivity. Such PDMA is proposed to address several challenges in the fifth-generation wireless systems. In this paper, we first reveal that the non-orthogonal multiple access (NOMA) techniques have evolved from fairness assurance under impact of co-channel interference (CCI). Then, we comprehensively investigate on signal to noise ratio (SNR) to detect two separated signals, then outage performance evaluations of the two users are conduced. Monte Carlo simulations are deployed to verify exactness of outage probabilities.

It can be studied in this paper that a cooperative non-orthogonal multiple access (NOMA) helps device-to-device (D2D) communication system through base station (BS). In particular, we investigate BS selection scheme as a best channel condition for dedicated devices where a different data transmission demand on each device is resolved. The analysis on amplifying-and forward (AF) relay is proposed to evaluate system performance of the conventional cooperative NOMA scheme. Under the realistic assumption of perfect channel estimation, the achievable outage probability of both devices is investigated, and several impacts on system performance are presented. The mathematical formula in closed form related to probability has also been found. By implementing Monte-Carlo simulation, the simulation results confirm the accuracy of the derived analytical results. Also, the proposed D2D cooperative NOMA system introduces expected performance on reasonable selected parameters in the moderate signal to noise ratio (SNR) regime.

Relay network have received considerable attention, especially when limited size of terminals and power resources constraints in wireless sensor network. In this paper, we investigate the performance of two-way three-node amplify-and-forward relaying networks in the presence of channel estimation errors. Such problem is considered as the main cause of performance degradation in wireless communications. We analyze signal to noise ratio (SNR) under channel estimation error of two kinds of AF-based relaying networks. Finally, we simulate the outage probability in different manners for performance comparison.

The hybrid schemes for channel estimation are considered as the flexible structure satisfying demand of high data rate transmission in the multiple-input multiple-output (MIMO) technique. Generally, the training-based least square (LS) algorithm is chosen in wide applications from the first generation wireless network to the newest one of MIMO. For resolving the bandwidth efficiency problem, we can combine the LS estimation with the pure blind techniques such as second-order statistics (SOS). In this paper, we attempt to find the hybrid scheme which is so-called semi-blind channel estimation and outperforms than the conventional LS based approaches. Simulation results confirm our modified scheme and illustrate that the subspace based new semi-blind channel estimation is capable of improving the performance of the overall system.

This paper presents a least square based semi-blind channel estimation using the new orthogonal pilot scheme for multiple-input multiple-output (MIMO) wireless communications. In practice, knowledge of the wireless unknown channel is often estimated by sending known training symbols to the receiver. We determine the optimal training sequence aiming to minimize the mean square error (MSE) of the channel estimator under a total transmit power constraint. In order to reduce the training overhead, this semi-blind algorithm only use fewer number of training symbols for decomposed channel matrices. Combining the advantage of semi-blind approach with designed pilot scheme addresses the improvement of the total bandwidth efficiency. In addition, the problem of power allocation between the pure data and the training symbols is also calculated. Experimental studies are carried out to study and validate the optimal performance of the proposed scheme.