scholarly journals Optimal UAV's Deployment and Transmit Power Design for Two Users Uplink NOMA Systems

2021 ◽  
Vol 14 ◽  
Author(s):  
Fayong Zhao
Keyword(s):  
Multiple Access ◽  
Optimization Problem ◽  
Transmission Rate ◽  
Initial Study ◽  
Power Constraint ◽  
Transmit Power ◽  
Access Technology ◽  
Aerial Vehicle ◽  
Simulation Results ◽  
Rate Requirement

In order to fully utilize the spectrum resources, this work considers a unmanned aerial vehicle (UAV) uplink communication system based on non-orthogonal multiple access technology (NOMA), in which the UAV receives information from the ground users with a certain flying altitude. As an initial study, we consider a simplified setup with two ground users to draw some insightful results. Explicitly, we first formulate an optimization problem that maximizes the sum throughput subject to each user's transmit power constraint and their corresponding minimum transmission rate requirement. Then, both the optimal transmit power and UAV's deployment location are derived with the aid of employing the Karush-Kuhn-Tucher (KKT) conditions. Simulation results show that the proposed UAV's deployment scheme with the users' power allocation can achieve a higher sum throughput compared with two existing benchmark schemes.

scholarly journals Clustering and Auction-Based Power Allocation Algorithm for Energy Efficiency Maximization in Multi-Cell Multi-Carrier NOMA Networks

2019 ◽  
Vol 9 (23) ◽  
pp. 5034 ◽  
Author(s):  
Abuzar B. M. Adam ◽  
Xiaoyu Wan ◽  
Zhengqiang Wang
Keyword(s):  
Energy Efficiency ◽  
Power Allocation ◽  
Cooperative Game ◽  
Multiple Access ◽  
Optimization Problem ◽  
Interference Mitigation ◽  
Base Stations ◽  
Frequency Division ◽  
Simulation Results ◽  
Inter Cell Interference

In this paper, we investigate the energy efficiency (EE) maximization in multi-cell multi-carrier non-orthogonal multiple access (MCMC-NOMA) networks. To achieve this goal, an optimization problem is formulated then the solution is divided into two parts. First, we investigate the inter-cell interference mitigation and then we propose an auction-based non-cooperative game for power allocation for base stations. Finally, to guarantee the rate requirements for users, power is allocated fairly to users. The simulation results show that the proposed scheme has the best performance compared with the existing NOMA-based fractional transmit power allocation (FTPA) and the conventional orthogonal frequency division multiple access (OFDMA).

scholarly journals Max–Min Fairness Optimization for D2D Communications Coexisting with Cellular Networks

Electronics ◽  
2020 ◽  
Vol 9 (9) ◽  
pp. 1422
Author(s):  
Hoai Giang Nguyen ◽  
Xuan Tung Nguyen ◽  
Van Son Nguyen ◽  
Trinh Van Chien ◽  
Tien Hoa Nguyen ◽  
...  
Keyword(s):  
Spectral Efficiency ◽  
Multiple Access ◽  
Optimization Problem ◽  
Mutual Interference ◽  
D2d Communications ◽  
Power Budget ◽  
Good Service ◽  
Coverage Area ◽  
Channel Condition ◽  
Simulation Results

This paper considers a system consisting of a nonorthogonal multiple access (NOMA)-based device-to-device (D2D) communication system within a cellular network, in which the time and frequency resources are shared by everyone. In particular, D2D groups that constitute different pairs are assigned to the subchannels that the cellular users occupy. A max–min fairness optimization problem with power budget constraints is formulated and solved in this paper to reduce the mutual interference between the cellular users and D2D devices that substantially impacts that with the worst channel condition. For a low computational complexity solution, we propose the use of the bisection method together with the solution of a system of linear equalities. The proposed algorithm can provide uniformly good service to all of the cellular users and D2D devices in the coverage area by utilizing the minimal total transmit power. The simulation results indicate the effectiveness of the proposed algorithm in the improvement of the spectral efficiency of the worst user under the different widely used subchannel assignments and pairing techniques.

A New SLNR-Based Precoding for Multiuser MIMO Downlinks

2014 ◽  
Vol 644-650 ◽  
pp. 4066-4071
Author(s):  
Xin Min Li
Keyword(s):  
Bit Error Rate ◽  
Error Rate ◽  
Base Station ◽  
Semidefinite Relaxation ◽  
Constraint Condition ◽  
Multiuser Mimo ◽  
Power Constraint ◽  
Transmit Power ◽  
Simulation Results

A new SLNR-based precoding is proposed for multiuser MIMO downlinks, which pursues the goal that minimizes total transmit power under each user’s SLNR constraint. The goal problems can be successfully solved by using semidefinite relaxation (SDR) techniques, and power constraint condition added in goal problems can efficiently reduce total transmit power of the base station. Simulation results show that our proposed scheme is almost feasible for users with one antenna, and it has better bit error rate (BER) and lower total transmit power than the maximal-SLNR based precoding method, when it satisfies large SLNR thretholds.

scholarly journals Specific Quality of Service Constrained Optimal Allocation of Transmit Power in Uplink Cognitive OFDMA System

2020 ◽  
Vol 9 (3) ◽  
pp. 105-121
Author(s):  
Lutfa Akter ◽  
◽  
Normin Nahar
Keyword(s):  
Resource Allocation ◽  
Quality Of Service ◽  
Optimal Allocation ◽  
Power Budget ◽  
Transmit Power ◽  
Ofdma System ◽  
Capacity Maximization ◽  
Simulation Results ◽  
Rate Requirement

This paper investigates an optimal allocation of transmit power for uplink cognitive OFDMA system. The aim is to construct two optimization frameworks namely, framework-I and II for uplink cognitive OFDMA system that minimizes it’s transmit power while maintaining Quality of Service (QoS). The measures for QoS include SNR threshold for framework-I whereas, for framework-II, it is measured by minimum rate requirement (bits/sec/Hz) to obtain a certain bit error rate (BER). Simulation results reveal the effectiveness of the proposed frameworks. Additionally, for framework-I, effects of different SNR threshold and users’ power budget are observed on the allocation of transmit power. Whereas, for framework-II, effects of different target BER, users’ power budget and minimum rate requirement are observed on the allocation of transmit power. Results are also compared with the results obtained from conventional capacity maximization based resource allocation approaches in terms of allocated transmit power, energy efficiency (EE) and spectral efficiency (SE). Simulation results reveal that, the proposed frameworks are incredibly successful in terms of utilization of power budget of users and EE compared to conventional capacity maximization based resource allocation approaches.

scholarly journals Power Allocation for Energy-Harvesting-based Fading Cognitive Multiple Access Channels: with or without Successive Interference Cancellation

2017 ◽  
Vol 63 (1) ◽  
pp. 65-72
Author(s):  
Qun Li ◽  
Ding Xu
Keyword(s):  
Power Allocation ◽  
Interference Cancellation ◽  
Multiple Access ◽  
Base Station ◽  
Successive Interference Cancellation ◽  
Multiple Access Channel ◽  
Power Constraint ◽  
Transmit Power ◽  
Sum Rate ◽  
Power Limit

Abstract This paper considers a fading cognitive multiple access channel (CMAC), where multiple secondary users (SUs), who share the spectrum with a primary user (PU), transmit to a cognitive base station (CBS). A power station is assumed to harvest energy from the nature and then provide power to the SUs. We investigate the power allocation problems for such a CMAC to maximize the SU sum rate under the interference power constraint, the sum transmit power constraint and the peak transmit power constraint of each individual SU. In particular, two scenarios are considered: with successive interference cancellation (SIC) and without SIC. For the first scenario, the optimal power allocation algorithm is derived. For the second scenario, a heuristic algorithm is proposed. We show that the proposed algorithm with SIC outperforms the algorithm without SIC in terms of the SU sum rate, while the algorithm without SIC outperforms the algorithm with SIC in terms of the number of admitted SUs for a high sum transmit power limit and a low peak transmit power limit of each individual SU.

scholarly journals Joint Resource Allocation for Multiuser Opportunistic Beamforming Systems with OFDM-NOMA

Entropy ◽  
2021 ◽  
Vol 23 (7) ◽  
pp. 809
Author(s):  
Wen-Bin Sun ◽  
Ming-Liang Tao ◽  
Ling Wang ◽  
Xin Yang ◽  
Rui-Zhe Zhou ◽  
...  
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Multiple Access ◽  
Optimization Problem ◽  
Spectrum Efficiency ◽  
Computation Complexity ◽  
Transmit Power ◽  
Feedback Information ◽  
Joint Resource Allocation ◽  
Multiple Access Schemes ◽  
Opportunistic Beamforming

Opportunistic beamforming (OBF) is an effective technique to improve the spectrum efficiencies (SEs) of multiple-input-multiple-output (MIMO) systems, which can obtain multiuser diversity gains with both low computation complexity and feedback information. To serve multiple users simultaneously, many multiple-access schemes have been researched in OBF. However, for most of the multiple-access schemes, the SEs are not satisfactory. To further improve the SE, this paper proposes a downlink multiuser OBF system, where both orthogonal frequency division multiplexing (OFDM) and non-orthogonal multiple-access (NOMA) methods are applied. The closed-form expressions of the equivalent channels and SE are derived in frequency selective fading channels. Then, an optimization problem is formulated to maximize the SE, although the optimization problem is non-convex and hard to solve. To obtain the solution, we divide the optimization problem into two suboptimal issues, and then a joint iterative algorithm is applied. In the proposed optimization scheme, the subcarrier mapping ϑ, user pairing knc and allocated power Pknc are determined to maximize spectrum efficiency (SE) and reduce bit error ratio (BER). According to numerical results, the proposed method achieves approximately 5 dB gain on both SE and BER, compared to the existing beamforming methods with low feedback information. Moreover, the SE of the proposed method is approximately 2 (bps/Hz) higher than sparse code multiple-access (SCMA), when the number of waiting users and the ratio of transmit power to noise variance are respectively 10 and 20 dB. It is indicated that the proposed scheme can achieve high and low BER with the limited feedback and computation complexity, regardless of the transmit power and the number of waiting users.

scholarly journals Cache-enabled physical-layer secure game against smart uAV-assisted attacks in b5G NOMA networks

2020 ◽  
Vol 2020 (1) ◽  
Author(s):  
Chao Li ◽  
Zihe Gao ◽  
Junjuan Xia ◽  
Dan Deng ◽  
Liseng Fan
Keyword(s):  
Power Allocation ◽  
Secure Communication ◽  
Multiple Access ◽  
Dynamic Game ◽  
Physical Layer ◽  
Allocation Strategy ◽  
Aerial Vehicle ◽  
Simulation Results ◽  
Multiple Attack ◽  
Allocation Factor

AbstractThis paper investigates cache-enabled physical-layer secure communication in a no-orthogonal multiple access (NOMA) network with two users, where an intelligent unmanned aerial vehicle (UAV) is equipped with attack module which can perform as multiple attack modes. We present a power allocation strategy to enhance the transmission security. To this end, we propose an algorithm which can adaptively control the power allocation factor for the source station in NOMA network based on reinforcement learning. The interaction between the source station and UAV is regarded as a dynamic game. In the process of the game, the source station adjusts the power allocation factor appropriately according to the current work mode of the attack module on UAV. To maximize the benefit value, the source station keeps exploring the changing radio environment until the Nash equilibrium (NE) is reached. Moreover, the proof of the NE is given to verify the strategy we proposed is optimal. Simulation results prove the effectiveness of the strategy.

Multiple Access using Time Modulated Array with Single RF Chain

2019 ◽  
Vol 12 (5) ◽  
pp. 395-401
Author(s):  
Xu He ◽  
Yuan Ding ◽  
Gaojian Huang
Keyword(s):  
Power Efficiency ◽  
Multiple Access ◽  
Narrow Band ◽  
Average Power ◽  
Access Technology ◽  
Signal Peak ◽  
Single Radio ◽  
Rf Chain ◽  
Synthesis Approach ◽  
Single Rf Chain

Background: A new wireless multiple access technology enabled by using Time Modulated Arrays (TMAs) is proposed in this paper. Methods: It benefits due to the requirement of only a single Radio Frequency (RF) chain, compared with other multiple-RF-chain schemes. Results: As a result, it is able to greatly reduce the system cost, energy consumption, and complexity. Conclusion: In addition, the signal through the single RF chain is narrow-band modulated, reducing the signal Peak-to-Average-Power-Ratio (PAPR), thus, further enhancing the power efficiency of the RF chain, especially for power amplifiers. The operation principle and synthesis approach are elaborated in this paper, and are demonstrated with two examples.

scholarly journals Autonomous Power Decision for the Grant Free Access MUSA Scheme in the mMTC Scenario

Sensors ◽  
2020 ◽  
Vol 21 (1) ◽  
pp. 116
Author(s):  
Wissal Ben Ameur ◽  
Philippe Mary ◽  
Jean-François Hélard ◽  
Marion Dumay ◽  
Jean Schwoerer
Keyword(s):  
Interference Cancellation ◽  
Error Propagation ◽  
Multiple Access ◽  
Transmission Rate ◽  
Free Access ◽  
Decoding Complexity ◽  
Machine Type ◽  
Machine Type Communications ◽  
Multiple Access Schemes ◽  
Lower Complexity

Non-orthogonal multiple access schemes with grant free access have been recently highlighted as a prominent solution to meet the stringent requirements of massive machine-type communications (mMTCs). In particular, the multi-user shared access (MUSA) scheme has shown great potential to grant free access to the available resources. For the sake of simplicity, MUSA is generally conducted with the successive interference cancellation (SIC) receiver, which offers a low decoding complexity. However, this family of receivers requires sufficiently diversified received user powers in order to ensure the best performance and avoid the error propagation phenomenon. The power allocation has been considered as a complicated issue especially for a decentralized decision with a minimum signaling overhead. In this paper, we propose a novel algorithm for an autonomous power decision with a minimal overhead based on a tight approximation of the bit error probability (BEP) while considering the error propagation phenomenon. We investigate the efficiency of multi-armed bandit (MAB) approaches for this problem in two different reward scenarios: (i) in Scenario 1, each user reward only informs about whether its own packet was successfully transmitted or not; (ii) in Scenario 2, each user reward may carry information about the other interfering user packets. The performances of the proposed algorithm and the MAB techniques are compared in terms of the successful transmission rate. The simulation results prove that the MAB algorithms show a better performance in the second scenario compared to the first one. However, in both scenarios, the proposed algorithm outperforms the MAB techniques with a lower complexity at user equipment.

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