Gain Ratio Power Allocation Research Articles

Enhancing Performance of Power Allocation for VLC Networks by Non-Orthogonal Multiple Access-MIMO

Visible light communication, or VLC, networks emerged as a viable option for data access, particularly indoors. Their cost-effectiveness, protection to radio frequency (RF) intrusion, and extraordinarily high data speeds make them a desirable option for the upcoming generation of indoor networking technologies. In this paper, we propose the Exponential Gain Ratio Power Allocation (EGRPA), an effective and low-complex power splitting method, to increase the attainable sum amount in Multiple Input Multiple Output (MIMO) VLC downlink networks. Using numerical simulations, we assess the enactment of an indoor 2x2 MIMO VLC downlink model for several users. We also use Non-Orthogonal Multiple Access (NOMA) for enhancing spectrum efficacy. The usefulness and resilience of the suggested power splitting approach are established by the simulation outcomes, especially in scenarios with a high user count. In particular, the EGRPA power allocation algorithm shows a sum rate enhancement of more than 38.7%, 7.86%, and 7.04% for a system with three users when compared to the GRPA method, Normalized Gain Difference Power Allocation (NGDPA) method, and Logarithmic GRPA (NLGRPA) method, correspondingly.

Improved physical layer secrecy fairness in a realistic indoor NOMA VLC network under users’ mobility

This paper investigates the improvement of the secrecy rate fairness in a cellular non-orthogonal multiple access (NOMA) visible light communication (VLC) network. We formulate the users’ secrecy rate by taking into account the users (legitimate and illegitimate) mobility according to the random way-point (RWP) model. We propose an optimization problem to maximize the minimum secrecy rate for two legitimate users per cell, and then we generalize it for an arbitrary number of users. Moreover, utilizing secrecy considerations, we customize two well-known power allocation methods of fixed power allocation (FPA) and gain ratio power allocation (GRPA) as benchmarks for comparison of the proposed maximization power allocation method. Our numerical results demonstrate the superiority of the proposed power allocation algorithm compared with FPA and GRPA methods. Moreover, for the higher number of users, our results indicate the advantages of the proposed algorithm over modified FPA and GRPA methods. Finally, we investigate the effect of the optical receiver’s field of view fluctuations on the performance of the VLC network.

Machine-Learning-Based Indoor Localization under Shadowing Condition for P-NOMA VLC Systems.

The localization of agents for collaborative tasks is crucial to maintain the quality of the communication link for successful data transmission between the base station and agents. Power-domain Non-Orthogonal Multiple Access (P-NOMA) is an emerging multiplexing technique that enables the base station to accumulate signals for different agents using the same time-frequency channel. The environment information such as distance from the base station is required at the base station to calculate communication channel gains and allocate suitable signal power to each agent. The accurate estimate of the position for power allocation of P-NOMA in a dynamic environment is challenging due to the changing location of the end-agent and shadowing. In this paper, we take advantage of the two-way Visible Light Communication (VLC) link to (1) estimate the position of the end-agent in a real-time indoor environment based on the signal power received at the base station using machine learning algorithms and (2) allocate resources using the Simplified Gain Ratio Power Allocation (S-GRPA) scheme with the look-up table method. In addition, we use the Euclidean Distance Matrix (EDM) to estimate the location of the end-agent whose signal was lost due to shadowing. The simulation results show that the machine learning algorithm is able to provide an accuracy of 0.19 m and allocate power to the agent.

Performance Evaluation of Successive Interference Cancellation on Gain Ratio Power Allocation using Underwater Visible Light Communication Channel

Underwater Visible light communication (UVLC) is a network communication wirelessly where information is transmitted employing light through visible waves; in this case, the light source comes from a light-emitting diode (LED) as a transmitter underwater. VLC has several advantages over radio frequency technology, such as safer communication because light propagation cannot penetrate the wall, so it is difficult to do hacking, easy to get a license, relatively build cheap cost, and has no side effects on health. However, VLC has several limitations, one of which is the narrow bandwidth modulation. VLC undergoes a distribution of modulated bandwidth to allocate against each user. This bandwidth sharing has an impact on reduced system capacity. This study applied non-orthogonal multiple access (NOMA) to increase system capacity. This research analyzes the performance of the two best power allocation methods in a water medium, including gain ratio power allocation (GRPA) and static power allocation (SPA). In the results obtained in the NOMA-UVLC power allocation value, GRPA is more stable than SPA power allocation. Then applying residue in the successive interference cancellation (SIC) process will result in a decrease in system capacity compared to no residue in the SIC process. This study found that the GRPA power allocation is more stable in capacity performance compared to the application of SPA power allocation. Average capacity increase of 48.5% in GRPA power allocation

The Performance of Visible Light Communication Bit Error Rate with Power Allocation Strategy

Visible Light Communication (VLC) is a communication system that uses visible light as its transmission medium to transmit information signals with Light Emitting Diode (LED) and LASER light sources using visible light between 400 THz (375 nm) to 800 THz (780 nm). VLC has several advantages over the use of radio frequencies in a system. Performance analysis is needed to prove these advantages. Performance analysis was carried out using a mathematical computational simulation using google colab with the python programming language. By taking into account the power allocation (?) strategy in the form of gain ratio power allocation (GRPA) and static power allocation (SPA). The interesting thing from this research is that the power allocation in the VLC system greatly influences the resulting performance. So, it can be locked that the SPA power allocation strategy can be adjusted by producing ?? = 1 and finding the optimal BER value in the range of 10-6 to 10^-3.

Improved joint subcarrier and power allocation to enhance the throughputs and user fairness in indoor OFDM-NOMA VLC systems.

Orthogonal frequency division multiplexing non-orthogonal multiple access (OFDM-NOMA) is a promising multi-user access scheme in indoor visible light communication (VLC) systems. In this paper, we propose three novel joint subcarrier and power allocation algorithms in OFDM-NOMA-VLC to improve the throughputs and/or user fairness. These three proposed algorithms address the requirements in fairness-throughput-balanced (FTB), fairness-first (FF), and throughput-first (TF) scenarios, respectively. All of them improve the objective function in the previous joint allocation algorithm and ensure the fairness of users in terms of their overall throughput, rather than that in every subcarrier that is tight and redundant. The designs using the proposed algorithms also exhibit reduced peak-to-average power ratios (PAPRs) and so the average signal power can be better used to further enhance the throughput when the system is limited by the signal peak power. Simulations verify that the proposed algorithms are superior to the previous joint subcarrier and power allocation algorithm as well as the conventional fixed power allocation (FPA) and gain ratio power allocation (GRPA) algorithms. The performance improvement of the proposed algorithms is particularly greater for a larger number of multiplexed users per subcarrier or a larger number of OFDM subcarriers, under which the PAPRs of designs using conventional algorithms are higher. When the total user number, the number of the multiplexed users per subcarrier, and the number of subcarriers are 5, 2, and 16, respectively, the throughputs of the three proposed algorithms are 62.17%, 53.35%, and 67.25% higher than the conventional joint allocation algorithm, while the user fairness is improved by 4.64%, 7.87%, and degraded by 20.71%, respectively. Therefore, the three proposed algorithms can address the requirements in FTB, FF, and TF scenarios, respectively.

Subcarrier and Power Allocation in OFDM-NOMA VLC Systems

We propose a novel subcarrier and power allocation method to improve both the throughput and user fairness in orthogonal frequency division multiplexing non-orthogonal multiple access visible light communication (OFDM-NOMA VLC) systems. The proposed method considers various constraints in practical VLC systems, including bandwidth limitation, non-negative optical signal, peak power for eye safety, and quality of service. The method adopts the log utility function to improve the user fairness and is applicable to cases where the number of multiplexed users on each subcarrier is not equal to the total user number due to the decoding complexity of NOMA. The problem is generalized as a non-convex one and is solved by the genetic algorithm. Monte Carlo simulations show that at a signal to interference noise ratio of 2.5 dB, the throughput of the proposed method is 11%, 22%, and 125% higher than the conventional enhanced power allocation, the fixed power allocation, and the gain ratio power allocation algorithms, while the fairness is improved by 23%, 30%, and 49%, respectively.

Performance enhancement for a non-orthogonal multiple access system using 4 × 4 multiple-input multiple-output visible-light communication

A multi-user visible-light communication (VLC) system based on 4 × 4 multiple-input multiple-output (MIMO) was investigated. The system consists of four light-emitting diodes (as a transmitter) and four photodetectors (as a receiver). The proposed system was simulated for two, three, and four users. The objective of this study is to optimize the system power consumption and to utilize the sum rate on the system coverage area. By expanding the system from a 2 × 2 MIMO-VLC to a 4 × 4 MIMO-VLC, the results demonstrate that the total sum rate of the system can be improved. The findings reveal that the 4 × 4 MIMO-VLC achieves a maximum sum-rate enhancement of 143% compared with the 2 × 2 MIMO-VLC. The results also show that the efficiency of 4 × 4 MIMO-VLC system with non-orthogonal multiple access (NOMA) and gain ratio power allocation (GRPA) was increased by around 181% compared to 2 × 2 MIMO-NOMA-based VLC with GRPA in combination. For the 4 × 4 MIMO-NOMA-VLC device with GRPA, the sum bit rate for two, three, and four users was increased by 40%, 33%, and 24%, respectively. Through this study, it can be concluded that GRPA scheme plays an important role in utilizing MIMO-VLC system sum rate of the MIMO-VLC system.

A low complexity power allocation scheme for NOMA-based indoor VLC systems

The narrow modulation bandwidth of light emitting diode (LED) is a barrier for indoor visible light communication (VLC) systems to achieve high data rate. The non-orthogonal multiple access (NOMA) is considered to be a promising technology to improve spectral efficiency of wireless communication systems. In this paper, we apply the non-orthogonal multiple access (NOMA) to visible light communication (VLC) systems, and propose a low complexity power allocation scheme for NOMA-based indoor VLC systems which is called the simplified gain ratio power allocation (S-GRPA) scheme. In the S-GRPA scheme, the channel state information (CSI) used for power allocation is not complete and obtained through look-up table method rather than calculation, which reduces the complexity of the power allocation scheme. Simulation results are presented to verify the effectiveness of the proposed scheme.

Power Allocation for Downlink Hybrid Power Line and Visible Light Communication System

Light-emitting diode (LED)-based visible light communication (VLC) is a great promising high-speed wireless access solution due to its low power consumption, no electromagnetic interference, large available bandwidth, and no authentication required. However, visible light cannot be used directly as an information source, and must be combined with other communication technologies to avoid becoming an information island. In hybrid power line and visible light communication (HPV) system, power line communication (PLC) can be used to deliver data to VLC transmitters. Multiple users can share the same time and frequency resources to provide higher spectral efficiency using non-orthogonal multiple access (NOMA) method than traditional multiple access method. Therefore, we investigate the power allocation strategy for a downlink of HPV system based on NOMA. Our goal is to maximize achievable sum rate of the HPV system while considering user fairness. To solve this optimization problem, we present an optimal power allocation (OPA) algorithm that finds optimal solution by transforming the non-convexity of the original formulated model into the convex programming. Numerical results show that the proposed OPA algorithm significantly outperforms the gain ratio power allocation (GRPA) and the fixed power allocation (FPA) algorithm in terms of the sum rate, and improves the fairness among users.

Enhancing power allocation efficiency of NOMA aided-MIMO downlink VLC networks

In order to enhance the achievable sum rate of indoor non-orthogonal multiple access (NOMA) aided multiple-input multiple-output (MIMO) visible light communication (VLC) downlink networks, in this paper, an efficient low computational complexity power allocation strategy termed as normalized logarithmic gain ratio power allocation (NLGRPA) is proposed, in which the optical channel information of all transmitter light-emitting diodes (LEDs) are exploited and properly ordered to ensure efficient power allocation Numerical results depict that our proposed NLGRPA method exhibits significant improvement in terms of achievable sum rate of NOMA aided MIMO-VLC networks when compared with other conventional power allocation approaches. Specifically, the proposed NLGRPA algorithm attains an achievable sum rate improvement of more than 55% and 33% compared with the gain ratio power allocation (GRPA) method and normalized gain difference power allocation (NGDPA) method in the 4 × 2 MIMO-VLC networks with nine randomly distributed users.

Channel and Bit Adaptive Power Control Strategy for Uplink NOMA VLC Systems

Non-orthogonal multiple access (NOMA) can be an effective solution to the limited bandwidth of light emitting diodes for visible light communication (VLC) systems to support multiuser communication. The current available works for NOMA VLC systems mainly concentrate on downlinks and the existing power allocation algorithms mainly focus on the channel state information and ignore the influence of transmitted signals. In this paper, we propose a channel and bit adaptive power control strategy for uplink NOMA VLC systems by jointly considering the channel state information and the transmission bit rate. Under this adaptive power control strategy, it is proved that the received signal at the photodiode (PD) receiver constitutes a sizeable pulse amplitude modulation constellation and low-complexity maximum likelihood detection is admitted. The simulation results indicate that our proposed adaptive power control strategy outperforms the gain ratio power allocation scheme, fixed power allocation scheme, and time division multiple access scheme.

Strategy-Based Gain Ratio Power Allocation in Non-Orthogonal Multiple Access for Indoor Visible Light Communication Networks

Visible light communication (VLC) is an evolving green communication technology for indoor wireless communication networks. VLC utilizes light-emitting diodes (LEDs) for both illumination and communication. To achieve economic and energy-efficient communications, non-orthogonal multiple access (NOMA) improves the system throughput by enhancing spectral efficiency. In indoor VLC networks, the gain ratio power allocation (GRPA) of NOMA allocates greater signal power to the users of poor channels to achieve both fairness and high data rate. However, current GRPA strategies developed for radio frequency channels are not necessarily effective in all VLC channel and illumination cases. This study makes the following contributions. First, a GRPA strategy based on VLC channels is proposed that modifies the power counting and channel proportions enhance the NOMA-VLC throughput. Second, owing to difficulties of directly analyzing NOMA-VLC throughput, an alternative lower bound based on a VLC channel model to facilitate throughput comparisons is proposed. It is proved that the proposed alternative lower bound is asymptotic and compact with respect to NOMA-VLC throughput. Third, for the case of LED heights greater than 1 m, a local extremum solution using the proposed strategy is analytically demonstrated based on the alternative bound of VLC network throughput. Then, for the case of LED heights smaller than 1 m, the necessary but not sufficient condition under which the proposed strategy outperforms previous strategies is provided in VLC scenarios. Finally, the experimental results demonstrate the compactness of the proposed alternate lower bound and the advantages of the proposed strategy.

Optimal Power Allocation Scheme Based on Multi-Factor Control in Indoor NOMA-VLC Systems

In order to overcome the limitation of narrow modulation bandwidth on the performance in the visible light communication (VLC) systems, non-orthogonal multiple access (NOMA) is applied to the downlink VLC networks in this paper to improve the sum rate performance effectively. We first propose an optimal power allocation strategy which is based on the multi-factor control (MFOPA), aiming to maximize the total system capacity subject to ensuring all users' quality of service (Qos) and fairness, as well as illumination requirements. The analytical results indicate that the proposed MFOPA could provide higher system sum rate and better user fairness as well as guarantee the Qos and eye safety of each user at the same time when compared with the static power allocation (SPA) and gain ratio power allocation (GRPA) schemes, especially in high demand for signal-to-interference-plus-noise ratio (SINR). What is more, considering the residual interference may exist during the successive interference cancellation (SIC) at the receiver, namely imperfect SIC, the interference cancellation factor is also taken into account in MFOPA strategy. The numerical results are shown to demonstrate the robustness and effectiveness of the MFOPA in NOMA-VLC when the residual interference remains.

Enhanced Power Allocation for Sum Rate Maximization in OFDM-NOMA VLC Systems

This letter investigates the power allocation problem for the downlink of an orthogonal frequency division multiple (OFDM)-based non-orthogonal multiple access visible light communication (NOMA-VLC) system. Unlike the commonly used two-user OFDM-NOMA VLC model, in this letter, an arbitrary number of multiplexed users is considered when formulating the sum rate maximization problem. Moreover, both user-level and subcarrier-level power optimization are taken into account to improve the system performance. The corresponding theoretical analysis is presented, with the consideration of optimal decoding order and each user's required signal-to-interference-plus-noise ratio (SINR). Given a fixed power constraint on each OFDM subcarrier, we derive the optimal power ratio for an arbitrary number of multiplexed users in OFDM-NOMA VLC. Numerical results show that with a required SINR of 3 dB, the proposed enhanced power allocation algorithm has 39.59% and 40.11% sum-rate enhancement when compared to optimized fixed power allocation algorithm and gain ratio power allocation algorithm, respectively.

Performance analysis of gain ratio power allocation strategies for non-orthogonal multiple access in indoor visible light communication networks

Non-orthogonal multiple access (NOMA) is a promising method for enhancing the throughput in visible light communication (VLC) networks. In NOMA, signal power domain control, called gain ratio power allocation (GRPA), can significantly improve the user sum rate with full-time frequency resource utilization. In indoor NOMA-VLC networks, the scenario in which users are covered by VLC illuminants on the ceiling is typical. First, this paper proposes a novel GRPA strategy for a single VLC cell. Second, due to the difficulty of direct comparisons between our and previously reported GRPA strategies, this paper presents an alternative lower bound for comparability. Third, in two- and three- user cases, this paper analytically demonstrates that our NOMA-VLC GRPA strategy outperforms the aforementioned strategy, when successive interference cancellation (SIC) is used. Moreover, in the multi-user case, experimental results show that the average user data rate (AUDR) of multi-user cases under our strategy is better than that under the previous strategy. Finally, our paper provides both analytic and numerical results to prove that VLC single-cell system throughput under our strategy is better than that under the previous strategy. The proposed alternative lower bound is also proved to fit the original NOMA-VLC GRPA target asymptotically based on indoor VLC channels. Furthermore, to achieve the same AUDR, our strategy supports worse received conditions than does the previous strategy.

On the Performance of MIMO-NOMA-Based Visible Light Communication Systems

In this letter, we apply the non-orthogonal multiple access (NOMA) technique to improve the achievable sum rate of multiple-input multiple-output (MIMO)-based multi-user visible light communication (VLC) systems. To ensure efficient and low-complexity power allocation in indoor MIMO-NOMA-based VLC systems, a normalized gain difference power allocation (NGDPA) method is first proposed by exploiting users’ channel conditions. We investigate the performance of an indoor $2\times 2$ MIMO-NOMA-based multi-user VLC system through numerical simulations. The obtained results show that the achievable sum rate of the $2\times 2$ MIMO-VLC system can be significantly improved by employing NOMA with the proposed NGDPA method. It is demonstrated that NOMA with NGDPA achieves a sum rate improvement of up to 29.1% compared with NOMA with the gain ratio power allocation method in the $2\times 2$ MIMO-VLC system with three users.

Non-Orthogonal Multiple Access for Visible Light Communications

The main limitation of visible light communication (VLC) is the narrow modulation bandwidth, which reduces the achievable data rates. In this paper, we apply the non-orthogonal multiple access (NOMA) scheme to enhance the achievable throughput in high-rate VLC downlink networks. We first propose a novel gain ratio power allocation (GRPA) strategy that takes into account the users' channel conditions to ensure efficient and fair power allocation. Our results indicate that GRPA significantly enhances system performance compared to the static power allocation. We also study the effect of tuning the transmission angles of the light emitting diodes (LEDs) and the field of views (FOVs) of the receivers, and demonstrate that these parameters can offer new degrees of freedom to boost NOMA performance. Simulation results reveal that NOMA is a promising multiple access scheme for the downlink of VLC networks.