scholarly journals Time Switching Based Wireless Powered Relay Transmission with Uplink NOMA

Sensors ◽  
2021 ◽  
Vol 21 (16) ◽  
pp. 5467
Author(s):  
Zhihua Lin ◽  
Shihua Cao ◽  
Jianqing Li
Keyword(s):  
Multiple Access ◽  
Relay Node ◽  
Base Station ◽  
Spectrum Efficiency ◽  
Transmission Model ◽  
System Throughput ◽  
Time Switching ◽  
Power Domain ◽  
End Node ◽  
Save Energy

Non-orthogonal multiple access (NOMA) utilizes power domain multiplexing to improve spectrum efficiency compared with orthogonal multiple access (OMA). In the Internet of Things (IoT) uplink NOMA networks, if the channel between the far-end node and the base station is in deep fading, allocating larger transmitting power for this node cannot achieve higher spectrum efficiency and overall system throughput. Relay cooperative communication reduces the transmitting power at the far-end node but leads to extra energy expenditure at the relay node. Fortunately, simultaneous wireless information and power transfer (SWIPT) is advocated in energy-constrained IoT networks to save energy consumption. However, early works all focus on energy harvesting (EH) from one source node or one dedicated power supply station. In this paper, we propose a time switching based wireless powered relay transmission model with uplink NOMA where our EH technique can harvest energy from two simultaneously transmitting nodes. More importantly, by optimizing relay position more energy is harvested from the near-end node at the relay and relay signal attenuation to the destination is reduced as well. Furthermore, the closed-form expressions of outage probability and overall system throughput are derived, and numerical results prove that NOMA in our EH scheme achieves better performance compared to the traditional EH scheme and OMA by optimizing the position of the relay node, time switching factor and so on.

A Novel User Grouping Algorithm for Downlink NOMA

2021 ◽  
Author(s):  
Navideh Ghafouri Jeshvaghani ◽  
Naser Movahhedinia ◽  
Mohammad Reza Khayyambashi
Keyword(s):  
Interference Cancellation ◽  
Multiple Access ◽  
Spectrum Efficiency ◽  
System Capacity ◽  
Substantial Impact ◽  
User Grouping ◽  
Radio Access ◽  
Power Domain ◽  
Rate Maximization ◽  
Sum Rate

Abstract Non-orthogonal multiple access (NOMA) is one of the promising radio access techniques for resource allocation improvement in the 5th generation of cellular networks. Compared to orthogonal multiple access techniques (OMA), NOMA offers extra benefits, including greater spectrum efficiency which is provided through multiplexing users in the transmission power domain while using the same spectrum resources non-orthogonally. Even though NOMA uses Successive Interference Cancellation (SIC) to repeal the interference among users, user grouping has shown to have a substantial impact on its performance. This prformance improvement can appear in different parameters such as system capacity, rate, or the power consumption. In this paper, we propose a novel user grouping scheme for sum-rate maximization which increases the sum-rate up to 25 percent in comparison with two authenticated recent works. In addition to being matrix-based and having a polynomial time complexity, the proposed method is also able to cope with users experiencing different channel gains and powers in different sub-bands.

scholarly journals Frequency Domain Backoff for Continuous Beamforming Space Division Multiple Access on Massive MIMO Wireless Backhaul Systems

2020 ◽  
Vol 16 (1) ◽  
pp. 1-10
Author(s):  
Kazuki Maruta
Keyword(s):  
Frequency Domain ◽  
Multiple Access ◽  
Random Access ◽  
Packet Delay ◽  
Base Station ◽  
Spatial Multiplexing ◽  
System Throughput ◽  
Space Division Multiple Access ◽  
Wireless Backhaul ◽  
Space Division

This paper newly proposes a frequency domain backoff scheme dedicated to continuous beamforming space division multiple access (CB-SDMA) on massive antenna systems for wireless entrance (MAS-WE). The entrance base station (EBS) has individual base band signal processing units for respective relay stations (RSs) to be accommodated. EBS then continuously applies beamforming weight to transmission/reception signals. CB-SDMA yields virtual point-to-point backhaul link where radio resource control messages and complicated multiuser scheduling are not required. This simplified structure allows RSs to work in a distributed manner. However, one issue remains to be resolved; overloaded multiple access resulting in collision due to its random access nature. The frequency domain backoff mechanism is introduced instead of the time domain one. It can flexibly avoid co-channel interference caused by excessive spatial multiplexing. Computer simulation verifies its superiority in terms of system throughput and packet delay.

scholarly journals A Power-Domain NOMA Inspired Overlay Spectrum Sharing Scheme

2018 ◽  
Author(s):  
Fazlul Kader
Keyword(s):  
Spectrum Sharing ◽  
Multiple Access ◽  
Spectrum Efficiency ◽  
User Needs ◽  
Sum Capacity ◽  
Closed Form Solutions ◽  
Sharing Scheme ◽  
Power Domain ◽  
Cooperative Spectrum Sharing ◽  
Capacity Gain

Non-orthogonal multiple access (NOMA) and cooperative spectrum sharing (CSS) are integrated into this work to enhance both spectrum efficiency and utilization. An overlay spectrum sharing is proposed by exploiting NOMA in coordinated direct and relay transmission (CDRT) (termed as CSS-NOMA-CDRT). In CSS-NOMA-CDRT, a primary strong NOMA user is directly served by primary transmitter (PT), whereas a primary NOMA weak user needs the assistance of a relay to communicate with PT. Instead of using a dedicated relay, a secondary transmitter (ST) acts as a relay to forward the primary symbol to NOMA weak user and ST transmits own symbol to its receiver at the same time. The performance of the proposed CSS-NOMA-CDRT is evaluated along with closed-form solutions, in terms of ergodic sum capacity and outage probability. Through the analytical and Monte Carlo simulation results, it is demonstrated that CSS-NOMA-CDRT can obtain remarkable capacity gain as compared to the conventional NOMA-based CDRT.

scholarly journals Benefiting wireless power transfer scheme in power domain based multiple access: ergodic rate performance evaluation

2021 ◽  
Vol 10 (2) ◽  
pp. 785-792
Author(s):  
Anh-Tu Le ◽  
Minh-Sang Van Nguyen ◽  
Dinh-Thuan Do
Keyword(s):  
Power Allocation ◽  
Multiple Access ◽  
Wireless Power Transfer ◽  
Ergodic Capacity ◽  
Base Station ◽  
Power Transfer ◽  
Wireless Power ◽  
Transfer Scheme ◽  
Power Domain ◽  
Fixed Power

Power domain based multiple access scheme is introduced in this paper, namely Non-orthogonal multiple-access (NOMA). We deploy a wireless network using NOMA together with a wireless power transfer (WPT) scheme for dedicated user over Nakagami-$m$ fading channel. When combined, these promising techniques (NOMA and WPT) improve the system performance in term of ergodic performance at reasonable coefficient of harvested power. However, fixed power allocation factors for each NOMA user can be adjusted at the base station and it further provide performance improvement. We design a new signal frame to deploy a NOMA scheme in WPT which adopts a linear energy harvesting model. The ergodic capacity in such a NOMA network and power allocation factors can be updated frequently in order to achieve a fair distribution among NOMA users. The exact expressions of ergodic capacity for each user is derived. The simulation results show that an agreement between analytic performance and Monte-Carlo simulation can be achieved. 

scholarly journals Exploiting outage performance in device-to-device for user grouping

2021 ◽  
Vol 24 (2) ◽  
pp. 904
Author(s):  
Dinh-Thuan Do ◽  
Chi-Bao Le
Keyword(s):  
System Performance ◽  
Multiple Access ◽  
Base Station ◽  
Spectrum Efficiency ◽  
Frame Structure ◽  
Outage Performance ◽  
User Grouping ◽  
Numerical Result ◽  
Device To Device ◽  
New Form

The spectrum efficiency and massive connections are joint designed in new form of device-to-device for user grouping. A pair of users is implemented with nonorthogonal multiple access (NOMA) systems. Although NOMA benefits to such system in term of the serving users, device to device (D2D) faces the interference from normal cellular users (CUE). In particular, we derive exact formulas of outage probability to show system performance. In this article, we compare two schemes to find relevant scheme to implement in practice. The frame structure is designed with two timeslot related to uplink and downlink between the base station and D2D users. We confirm the better scheme in numerical result by considering the impacts of many parameters on outage performance.

scholarly journals Energy-Efficient Resource Allocation for NOMA-based Backscatter Communications

2020 ◽  
Author(s):  
Yongjun Xu ◽  
Zhijin Qin ◽  
Guan Gui
Keyword(s):  
Resource Allocation ◽  
Energy Efficient ◽  
Power Efficiency ◽  
Multiple Access ◽  
Base Station ◽  
Spectrum Efficiency ◽  
Quadratic Transformation ◽  
Backscatter Communication ◽  
Efficient Resource ◽  
Energy Efficient Resource Allocation

Backscatter communication (BackCom) is a promising technique for achieving high spectrum efficiency and power efficiency in the future Internet of Things systems. The capacity of BackCom networks can be maximized by optimizing the backscatter time and the reflection coefficient (RC). However, system energy efficiency (EE) cannot be guaranteed usually. In this paper, we investigate the energy-efficient resource allocation problem of a non-orthogonal multiple access (NOMA)-based BackCom. Particularly, the base station (BS) transmits signals to two cellular users based on the NOMA protocol, meanwhile, a backscatter device backscatters the signals to users using the passive radio technology. The total EE of the considered system is maximized by jointly optimizing power allocation for each NOMA user and the RC of backscatter device where the decoding order and the quality of service (QoS) of each user are guaranteed. To solve such a non-convex problem, we develop an efficient iterative algorithm to obtain the optimal solutions by using Dinkelbach's method and the quadratic transformation approach. Numerical results show that the proposed algorithm can significantly improve the system EE compared with the orthogonal multiple access (OMA) scheme and the NOMA system without backscatter devices.

scholarly journals Hybrid Cognitive-Radio NOMA with Blind Transmission Mode Identification and BER Constraints

2021 ◽  
Author(s):  
Hamad Yahya ◽  
Emad Alsusa ◽  
Arafat Al-Dweik
Keyword(s):  
Cognitive Radio ◽  
Multiple Access ◽  
Side Information ◽  
Primary User ◽  
Base Station ◽  
Transmission Mode ◽  
Receiver Design ◽  
Spectrum Utilization ◽  
Power Domain ◽  
Mode Tm

<div>The synergy of nonorthogonal multiple access (NOMA) and cognitive radio (CR) can provide efficient spectrum utilization for future wireless networks and enable supporting heterogeneous quality of service (QoS) requirements. In this context, this article aims at evaluating the throughput of a downlink CR-NOMA network where the secondary user (SU) data is opportunistically multiplexed with the primary user (PU) data using power-domain NOMA. The data multiplexing process is constrained by the PU QoS requirements. The multiplexing process can be considered seamless with respect to the PU because its receiver design will generally remain unchanged. Moreover, we consider the case where the SU detects its own data by blindly identifying the adopted transmission mode (TM) at the base station, which can be PU orthogonal multiple access PU-OMA, SU-OMA, PU/SU-NOMA, and no transmission. Consequently, the network can be classified as a hybrid underlay-interweave. The detection process is considered blind because the SU does not receive side information about the adopted TM. The obtained analytical results corroborated by Monte Carlo simulation results show that the proposed CR-NOMA network can provide substantial throughput improvement over conventional NOMA networks, particularly at low signal-to-noise ratios (SNRs) because the unutilized PU spectrum can be used by the SU. Moreover, in good channel conditions the PU can tolerate some interference from the SU, which may improve the channel utilization significantly. </div><div><br></div>

scholarly journals Throughput and Outage Probability Analysis for Cognitive Radio-Non-Orthogonal Multiple Access in Uplink and Downlink Scenarios

2020 ◽  
Vol 7 (4) ◽  
pp. 659-666
Author(s):  
H.T. Madan ◽  
Prabhugoud I. Basarkod
Keyword(s):  
Cognitive Radio ◽  
Outage Probability ◽  
Power Allocation ◽  
Cognitive Radio Networks ◽  
Multiple Access ◽  
Radio Networks ◽  
Spectrum Efficiency ◽  
Secondary Users ◽  
Power Domain ◽  
The Impact

Non orthogonal multiple access (NOMA) in cognitive radio (CR) network has been recognized as potential solution to support the simultaneous transmission of both primary and secondary users. In addition, CR-NOMA can also be used to serve multiple secondary networks in overlay cognitive radio networks. The aim of our work is to increase the secondary user’s throughput without compromising in QoS requirements of the primary users. Our presented work analyses the performance of power domain NOMA in cognitive radio networks for both uplink and downlink scenarios. The primary aspect of the work is to investigate the impact of power allocation on spectrum efficiency and fairness performance of CR-NOMA. Objective function is to maximize the overall throughput under the QOS constraints of the users. We have derived closed form expressions for optimized power allocation coefficient(α) for CR-NOMA uplink and downlink communications. Parameters causing the channel outage, have been examined and conditions for outage probability is derived for CR-NOMA communication. Finally, we have presented the simulation results to validate the mathematical models that are developed for power allocation coefficient and outage probability.

scholarly journals Security performance analysis for power domain NOMA employing in cognitive radio networks

2020 ◽  
Vol 9 (3) ◽  
pp. 1046-1054
Author(s):  
Thi-Anh Hoang ◽  
Chi-Bao Le ◽  
Dinh-Thuan Do
Keyword(s):  
Cognitive Radio ◽  
Multiple Access ◽  
Base Station ◽  
Cognitive Networks ◽  
Secrecy Outage Probability ◽  
Security Threat ◽  
Performance Improvements ◽  
Legitimate User ◽  
Power Domain ◽  
Secrecy Outage

The power domain non-orthogonal multiple access (NOMA) technique introduces one of the fundamental characteristics and it exhibits the possibility of users to decode the messages of the other paired users on the same resources. In cognitive radio inspired NOMA (CR-NOMA), the base station (BS) has to serve untrusted users or users with different security clearance. This phenomenon raises a security threat particularly in such CR-NOMA. This paper develops a tractable analysis framework to evaluate the security performance of cooperative non-orthogonal multiple access (NOMA) in cognitive networks, where relay is able to serve two far NOMA users in the presence of external eavesdropper. In particular, we study the secrecy outage probability in a two-user NOMA system. This situation happens in practical the BS is pairing a legitimate user with another untrusted user. Main reason is that the non-uniform distribution in terms of trusted and untrusted users in the cell. By performing numerical results demonstrate the performance improvements of the proposed NOMA scheme in comparison to that of several situations in terms of different parameters. Furthermore, the security performance of NOMA is shown to verify the derived expressions.

scholarly journals ARQ: The Gateway from NOMA to NOM

2020 ◽  
Author(s):  
Arafat Al-Dweik ◽  
Youssef Iraqi
Keyword(s):  
Multiple Access ◽  
System Throughput ◽  
High Signal ◽  
Signal To Noise ◽  
System Complexity ◽  
Power Domain ◽  
Single User ◽  
Point To Point ◽  
Adaptation Scheme ◽  
New Framework

<div>This work presents a new framework that utilizes</div><div>power-domain (PD) nonorthogonal multiple access (NOMA) as a multiplexing scheme to improve the throughput of point-to-point (P2P), or single user, communications. The proposed framework synergizes PD-NOMA and automatic repeat request (ARQ) to enable multiplexing and transmitting multiple packets that belong to the same user simultaneously. To overcome channel estimation and feedback limitations, and to reduce the system complexity, a simple adaptation scheme is proposed select the</div><div>appropriate number packets to be transmitted within a given</div><div>transmission slot. Moreover, the number of transmitted packets</div><div>is limited to a maximum of two to allow the receiver to blindly</div><div>identify the number of transmitted packets in a particular</div><div>transmission slot. The obtained results show that the proposed</div><div>NOM scheme can eventually double the system throughput at</div><div>high signal-to-noise ratios (SNRs), and hence, reduce the delay</div><div>by 50%. The system complexity and overhead are generally</div><div>comparable to conventional ARQ systems.</div>

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