A Survey of NOMA for VLC Systems: Research Challenges and Future Trends

Sadat, Hesham; Abaza, Mohamed; Mansour, Ali; Alfalou, Ayman

doi:10.3390/s22041395

Cited by 47 publications

(24 citation statements)

References 121 publications

(140 reference statements)

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“…Photodiodes are inexpensive and provide low complexity implementation for VLC as the modulation techniques are based on light intensity. In this case, achieving higher data rates is constrained to the response time of the photodiode [1][2][3]. On the other side, exploration of other light properties such as color has shown promising results in terms of better data rate, Refs.…”

Section: Introductionmentioning

confidence: 99%

An Optical Camera Communication Using Novel Hybrid Frequency Shift and Pulse Width Modulation Technique for Li-Fi

Salvi

Vasantha

2022

Computation

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With an increase in network-connected devices, the existing Radio Frequency (RF) spectrum is getting highly saturated. Non-RF-based communication systems have recently garnered attention as they can be considered an alternative to RF-based systems for some applications. The availability of efficient and low-cost electronic components like Light Emitting Diode (LED), photodiode, and cameras have been pivotal in building communications systems using visible light. High-speed communication using visible light can be achieved with customized hardware and software. Visible Light Communication (VLC) uses various properties of light to encode digital data, which is then modulated and transmitted over a short distance to the receiver. Photodiodes are inexpensive and provide low complexity implementation, but their adoption requires modifying existing devices to house dedicated sensors. On the other hand, in Optical Camera Communication (OCC), existing camera-based receivers are used to extract encoded data using properties of light like color, blink frequency, intensity, and polarity. In this paper, a novel OCC technique to achieve improved robustness using a Hybrid Frequency Shift Pulse Width Modulation (HFSPDM) is proposed, implemented, and evaluated. The performance of the proposed technique is compared for a short distance with On-Off Keying (OOK) and Binary Frequency Shift-OOK (BFSOOK) due to similar computational requirements. It was observed that the proposed technique used a 17% lesser number of frames than BFSOOK and provided 8% better BER than OOK under a test environment. It also supports longer distance communication than OOK as it is less sensitive to external noise.

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Section: Introductionmentioning

confidence: 99%

An Optical Camera Communication Using Novel Hybrid Frequency Shift and Pulse Width Modulation Technique for Li-Fi

Salvi

Vasantha

2022

Computation

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“…In the two user PD-NOMA a single-level of SIC is used by the strong user to eliminate the signal of the weak user. Due to non-orthogonal nature of PD-NOMA the inter users' interference is maximum and it becomes worst if more numbers of users are involved [15,16]. Proper power allocation strategies can help to reduce such interference.…”

Section: Introductionmentioning

confidence: 99%

Secure PD-NOMA with Multi-User Cooperation and User Clustering in Both Uplink and Downlink PD-NOMA

et al. 2022

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The power domain non-orthogonal multiple access (PD-NOMA) scheme has gained tremendous interest with the multiple access behavior for fifth-generation (5G) wireless communication. Although the overall performance is improved through accurate power distribution among users’ signals, it depends on the user clustering strategy. Moreover, the PD-NOMA communication is not completely secured due to its broadcast nature, which is still a major problem. This paper presents a novel low-complexity short code-based technique utilized by the registered users and the 5G base station (gNodeB) for communication. By doing so, the PD-NOMA scheme is made secure from unregistered users or eavesdroppers. We proposed a three-step user clustering strategy that selects the best cluster among all the possible clusters to improve the overall performance. The proposed clustering strategy achieves a low outage probability in PD-NOMA systems. Moreover, it uses a multi-user decode and forward cooperative relaying scheme with PD-NOMA (Cop-PD-NOMA) to increase the coverage range of the gNodeB. In the multi-user Cop-PD-NOMA, the strong users (near users) are used as relay stations to aid the weak users (far users) by the decode and forward (D&F) technique. The proposed work provides a secure PD-NOMA network and the most effective user clustering approach during validation. The bit-error-rate (BER) comparisons demonstrate that multi-user cooperation outperforms single-user cooperation in Cop-PD-NOMA communication.

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“…It has been found that NOMA can significantly improve spectral efficiency and network capacity in wireless communication systems [ 8 , 9 ]. More recently, various NOMA techniques have been investigated, applying grant-free multiple access [ 3 , 10 ], backscatter communication [ 11 ], reconfigurable intelligent surface (RIS) [ 12 , 13 ], relay-assisted network [ 14 ], unmanned aerial vehicle (UAV)-enabled network [ 15 ], visible light communication (VLC) [ 16 ], etc.…”

Section: Introductionmentioning

confidence: 99%

A Novel Expectation-Maximization-Based Blind Receiver for Low-Complexity Uplink STLC-NOMA Systems

Lee

Jung

2022

Sensors

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In this paper, we revisit a two-user space-time line coded uplink non-orthogonal multiple access (STLC-NOMA) system for Internet-of-things (IoT) networks and propose a novel low-complexity STLC-NOMA system. The basic idea is that both IoT devices (stations: STAs) employ amplitude-shift keying (ASK) modulators and align their modulated symbols to in-phase and quadrature axes, respectively, before the STLC encoding. The phase distortion caused by wireless channels becomes compensated at the receiver side with the STLC, and thus each STA’s signals are still aligned on their axes at the access point (AP) in the proposed uplink STLC-NOMA system. Then, the AP can decode the signals transmitted from STAs via a single-user maximum-likelihood (ML) detector with low-complexity, while the conventional uplink STLC-NOMA system exploits a multi-user joint ML detector with relatively high-complexity. We mathematically analyze the exact BER performance of the proposed uplink STLC-NOMA system. Furthermore, we propose a novel expectation-maximization (EM)-based blind energy estimation (BEE) algorithm to jointly estimate both transmit power and effective channel gain of each STA without the help of pilot signals at the AP. Somewhat interestingly, the proposed BEE algorithm works well even in short-packet transmission scenarios. It is worth noting that the proposed uplink STLC-NOMA architecture outperforms the conventional STLC-NOMA technique in terms of bit-error-rate (BER), especially with high-order modulation schemes, even though it requires lower computation complexity than the conventional technique at the receiver.

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A Survey of NOMA for VLC Systems: Research Challenges and Future Trends

Cited by 47 publications

References 121 publications

An Optical Camera Communication Using Novel Hybrid Frequency Shift and Pulse Width Modulation Technique for Li-Fi

An Optical Camera Communication Using Novel Hybrid Frequency Shift and Pulse Width Modulation Technique for Li-Fi

Secure PD-NOMA with Multi-User Cooperation and User Clustering in Both Uplink and Downlink PD-NOMA

A Novel Expectation-Maximization-Based Blind Receiver for Low-Complexity Uplink STLC-NOMA Systems

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