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Despite its potential for high-speed data transmission, visible light communication (VLC) technology faces significant challenges in achieving reliable real-time audio streaming due to interference, signal degradation, and synchronization issues. These limitations hinder the widespread adoption of VLC technology, especially in high-quality audio transmission. This paper introduces a novel VLC transceiver design incorporating advanced interference-resilient protocols, dynamic frame structuring, and robust error correction algorithms to enhance audio streaming performance. The proposed system achieves a signal-to-noise ratio (SNR) of 45 dB, reduces the bit error rate (BER) by up to four orders of magnitude to $1 \times 10^{-6}$ , and lowers the total latency by 50%. Furthermore, synchronization errors are reduced by 66.7%, while the mean opinion score (MOS) reaches 4.8, and the objective difference grade (ODG) improves to -0.5. The comparative analysis demonstrates significant advantages over Wi-Fi (802.11ac), VLC IM/DD, and state-of-the-art VLC systems. These findings establish the proposed system as a reliable solution for real-time, high-fidelity audio applications and a foundation for extending VLC technology to broader domains.

The Sixth Generation (6G) Wireless Communication Network (WCN) is the successive provision to ameliorate the gain with ultra-low latency, and e xtremely high energy efficiency. The 6G WCN enables the specifications of artificial intelligence to optimize the services and capabilities. The vision of the 6G era is expected to address a seamless fusion of communication between the human, physical world, and digital world. The latest 6G WCN standard is a fundamental foundation and requires immense attention in the field of research. This paper presents the framework of 6G WCN with an illustration of its key technologies. The different technologies involved in 6G are well explained with the demonstration of the communication scenario such that the key performance indicators are improved with major differences. The primary contribution of this paper is the explanation of the 6G with the technologies that have a drastic impact on the characteristic aspects of a wireless communication network such as data rate, spectrum efficiency, energy efficiency, connection density, and reliability. All these technologies have the capability to revolutionize the subsequent WCN.

This paper combines the advantages of both cognitive radio (CR) and visible light communication (VLC) for car-to-car applications to achieve a high data rate with minimum (delay, outage probability, bit error rate (BER), and cost). CR technology hops among the existing radio frequency (RF) available channels to increase the RF spectrum usage efficiency and dodge the scarcity limitation. Moreover, using CR as a license-free application will reduce car-to-car communication running costs. However, CRs require a common control channel (CCC) to communicate the spectrum availability map within the CR network and to inform the receiver end about the change in the transmitter-end channel. Therefore, the CCC is the bottleneck in the car-to-car CR network. Then, we explore the types of CCCs and discuss using each of them to solve this bottleneck issue. In the proposed scheme, we adopt using VLC as CCC. A MATLAB simulation for a car-to-car framework is built to demonstrate the capabilities of VLC through the chosen metrics (i.e., data rate, delay, outage probability, cost, and bit error rate). Our results show that VLC achieves up to 90% of the licensed data rate with a small outage probability of 21.2% and moderate BER and delay. In addition, VLC presents the minimum cost, placing second after the licensed type with a score of 84.2% in the combined metric. In conclusion, with the VLC’s bright future of expansion and growth in the car-to-car application, we have proven that VLC is worthy of implementation practically in modern cars.

Orthogonal frequency division multiplexing (OFDM) is critical for high-speed visible light communication (VLC) transmission; however, it suffers from a high peak-to-average power ratio (PAPR) problem. Among PAPR reduction techniques, pre-coding methods have shown promising advantages such as signal independence and no requirement for signaling overhead. This paper introduces a novel pre-coding technique termed quartered composite transform pre-coding (QCTP), which employs four newly developed orthogonal pre-coding matrices applied to four equally divided segments of modulated data, thereby enhancing the PAPR performance of VLC systems utilizing OFDM. This methodology allows the utilization of a single-tap equalizer, achieving over a 6 dB reduction in PAPR compared to conventional DCT pre-coding and surpassing the PAPR performance of DCT-hybridized (DCT & $\mu $ -compounding and DCT & Gaussian matrix) pre-coding techniques. This enhancement is accomplished without compromising bit error rate (BER) performance, all while maintaining reduced complexity.

In visible light communication (VLC) systems based on light emitting diodes (LEDs), the nonlinearity of LEDs often leads to a high bit error rate (BER), which limits the system’s performance. While artificial neural networks (ANNs) have been used as predistorters to mitigate LED nonlinearity, their effectiveness is hampered by overfitting. This paper proposes an adaptive predistorter based on amplitude time-delay twin support vector regression (ATD-TSVR) to address the nonlinearity of LEDs in orthogonal frequency division multiplexing (OFDM)-based VLC systems. The authors demonstrate through experiments that LED nonlinearity is the primary source of signal distortion in nonlinear VLC systems. Simulation results show that the proposed ATD-TSVR predistorter achieves superior BER, Inputs/Outputs curves, power spectral density (PSD), and constellation plots in an 80Mbit/s OFDM nonlinear VLC system. Meanwhile, as compared to the traditional SVR approach, the CPU training time of ATD-TSVR can be reduced by more than four times. The adaptive pre-distortion method herein is generally applicable to broadband VLC systems and also proves the application prospect and effectiveness of TSVR in VLC system.

In this paper, we proposed an unmanned aerial vehicle (UAV) based all optical triple hop mixed free space optical-free space optical-visible light communication (FSO-FSO-VLC) system for broadband internet access in high-speed train applications. The system consists of triple hops from gateway to the UAV, UAV to train and train to the end user. Two decode and forward relays are mounted on the UAV and train respectively to transmit the data between the gateway to the end-users. The first hop between gateway to UAV consist of FSO link which follows M-distribution. The second hop between the UAV to train consists of FSO link and is modelled using Gamma-Gamma distribution which takes into account both atmospheric turbulence and pointing errors due to position/orientation deviation. The third hop between the train and end user is connected using VLC link and it is mathematically modelled using Lambertian emission distribution. The relays map the incoming signal on the FSO links and send it down to the user inside the train via the VLC downlink. We derived the closed form expressions for average bit error rate and outage probability of the proposed system. This paper investigates the effects of atmospheric turbulence, field of view, beam divergence angle, displacement deviation variance, optical concentrator gain, number of access point, and modulation schemes on system performance. First time, we proposed all-optical system which offers high data rate and low transmission delay.

Efficient utilization of the spectrum, increased resilience to inter-symbol interference (ISI) and simpler channel equalization are becoming important considerations in the design of wireless communication systems including visible light communication (VLC) systems. In this regard, orthogonal frequency division multiplexing (OFDM) has become a preferred modulation technique in wireless communication systems design. However, one of its major challenges is the high peak-to-average power ratio that leads to major inefficiencies. Symbol position permutation (SPP) is a distortion-less technique that achieves substantial PAPR reduction without BER degradation. However, the existing works focus on PAPR reduction using SPP for the radio frequency (RF) OFDM and the use of this technique in optical OFDM is not properly investigated. Therefore, in this paper, we present a new PAPR reduction technique based on lexicographical permutations called lexicographical symbol position permutation (LSPP) for PAPR reduction in direct current optical OFDM (DCO-OFDM). The proposed scheme is less complex than the conventional selective mapping (CSLM) scheme since there is no multiplication of the phase sequences with the DCO OFDM symbol to generate the candidate signals. We further introduce a new way of reducing the complexity by introducing a threshold PAPR and demonstrate that the complexity in terms of inverse fast Fourier transform (IFFT) operations can be reduced substantially depending on the selected threshold and the number of candidate signals.

In this paper, a new non-redundant three-layer peak-to-average power ratio (PAPR) reduction technique is proposed for filter bank multicarrier communication based visible light communication (FBMC based VLC) systems. In the proposed technique, the FBMC based VLC data signal is overlapped with two new non-redundant signals. The initial-layer signals are the FBMC modulated signals. For PAPR reduction, the second-layer signals are constructed to decrease initial-layer large-amplitude signals, while the last-layer signals are used to improve the initial-layer small-amplitude signals. The two non-redundant signals do not overlap with the data signals in the frequency domain, because data signals are distributed on odd subcarriers, while even subcarriers are occupied by the constructed signals. To mitigate the effect of large-amplitude signal reduction in the proposed technique, the negative signals are converted into positive, rather than being clipped off as in conventional FBMC based VLC systems. In order to realize a trade-off between PAPR reduction and bit error rate (BER), we introduce a scaling factor in the converted signals. The performance of the proposed technique is calculated in terms of complementary cumulative distribution function (CCDF) and BER. The obtained results indicate that FBMC based VLC systems with the proposed technique can achieve a good trade-off between PAPR reduction and BER and outperforms the corresponding orthogonal frequency division multiplexing (OFDM) based VLC systems.

With the emergence of the fifth generation and beyond mobile networks, both visible light communications (VLC) and radio frequency (RF) or millimetre wave (mmW) systems are expected to maintain the connectivity in various environments. In outdoor environments the link (VLC or RF) availability is paramount, which is affected by channel conditions. In particular, in vehicular communications other vehicles, harsh environment, and road geometry and structure will have the impact on the link connectivity and availability. In such cases, a front-end antenna solution, which benefits both optical and RF communication links, can be seen as an attractive option that can be fitted in future vehicles. In this paper, we present the design and practical implementation of a planar hybrid VLC/mmW antenna operating at 20.8 GHz and show measured results for characterization of RF and VLC links as well as communications performance. We have used the widely adopted on-off keying and quadrature amplitude modulation schemes with different orders to demonstrate data rates of 5 Mb/s and up to 100 Mb/s for the VLC and mmW links, respectively. By measuring the bit error rate and the error vector magnitude for VLC and RF links, respectively for each modulation we have shown that the proposed hybrid planar antenna is suitable for example in a typical vehicle-to-vehicle communications.

A software-defined networking (SDN) architecture is capable of integrating all radio frequency and optical wireless small cell networks (e.g. fifth generation (5G), long-term evolution (LTE) femtocell, wireless fidelity (WiFi), light fidelity (LiFi)) in one network domain. This paper considers a SDN-enabled heterogeneous network (HetNet) comprised of LiFi, LTE femtocell and WiFi access points (APs). The HetNet control plane maintains the state of the network topology and wireless resources, which can support the development of intelligent service provisioning and efficient data communications in x generation (xG) wireless networks. The SDN applications use the network state to provide services in the data plane. However, when the state of network and wireless resources constantly changes, the SDN applications cannot provide reliable and guaranteed services to the wireless user equipments. This paper develops a queuing theoretic framework, which provides a performance evaluation for the SDN-enabled HetNet and applications convergence. A traffic engineering (TE) scheme is developed to support dynamic agnostic downlink flows routing to APs and differentiated granular services across the HetNet. Network and user centric policies are developed to make applications aware of network resource availability on the northbound and southbound interfaces of a SDN controller. Numerical models are introduced to study the impact of the computation and communication resources of northbound and southbound interfaces on the SDN-enabled HetNet scalability and the quality-of-service (QoS) guarantee of applications. Also, simulation scenarios are conducted to evaluate the performance of the TE scheme in provisioning effective and reliable services for subscribers.

While 5G is being commercialized worldwide, research institutions around the world have started to look beyond 5G and 6G is expected to evolve into green networks, which deliver high Quality of Service and energy efficiency. To meet the demands of future applications, significant improvements need to be made in mobile network architecture. We envision 6G undergoing unprecedented breakthrough and integrating traditional terrestrial mobile networks with emerging space, aerial and underwater networks to provide anytime anywhere network access. This paper presents a detailed survey on wireless evolution towards 6G networks. In this survey, the prime focus is on the new architectural changes associated with 6G networks, characterized by ubiquitous 3D coverage, introduction of pervasive AI and enhanced network protocol stack. Along with this, we discuss related potential technologies that are helpful in forming sustainable and socially seamless networks, encompassing terahertz and visible light communication, new communication paradigm, blockchain and symbiotic radio. Our work aims to provide enlightening guidance for subsequent research of green 6G.

The angular diversity aperture (ADA) receiver is a new form of optical wireless receiver which is made up of a number of receiving elements (REs) each consisting of a photodiode (PD) located below an aperture in an opaque screen. Previous work on the use of ADA receivers for visible light communication (VLC) analyzes only REs with round apertures and photodiodes with a limited range of parameters. This paper extends the analysis to calculate the channel gains for REs with for both round and square apertures and PDs and for more parameters. Graphs show how the gain varies as a function of the relative orientation of the transmitter and receiver for ten different designs. It is shown that the directionality of an RE depends on the offset of the PD from the aperture and that the field of view depends on the distance between the aperture and the PD. Detailed theoretical analysis and extensive simulation results demonstrate the bit error rate (BER) performance of receivers based on these ten designs in a multiple-input multiple-output (MIMO) VLC application. The round and square designs are found to have very similar BERs. It is shown that, even with high levels of shot noise, good BER results can be achieved throughout a typical scenario.

Visible light communication (VLC)-based localization is a potential candidate for a wide range of indoor localization applications. In this paper, we propose a VLC architecture based on orthogonal frequency division multiplexing (OFDM) with multiple functionalities integrated into the same system, i.e., the 3-D receiver location, the control of the room illumination intensity, as well as the data transmission capability. In this paper, we propose an original methodology for LED power discrimination applying spatial optical OFDM (SO-OFDM) structure for position estimation. The hybrid locator initially makes a first estimate using a weighted angle-of-arrival (WAoA)-based locator, which is then used as the starting point of the recursive estimator based on the strength of the received signal. Hence, the first stage is deployed to increase the convergence probability, reducing the root-mean-square error (RMSE) and the number of iterations of the second stage. Also, a performance versus computational complexity comparative analysis is carried out with the parameter variations of these estimators. The numerical results indicate a decade improvement in the RMSE for every two decades of decrement of power noise on the receiver photodiode. The best clipping factor is obtained through the analysis of locator accuracy and transmission capacity for each simulated system. Finally, the numerical results also demonstrate effectiveness, robustness, and efficiency of the proposed architecture.

The requirement of a DC-bias is known to make DC-biased optical orthogonal frequency division multiplexing (DCO-OFDM) less energy efficient. This can be improved by asymmetrically clipped optical OFDM (ACO-OFDM), pulse amplitude modulated OFDM (PAM-OFDM) or Flip-OFDM, but these variants use the bandwidth inefficiently. Our trade-off between energy and spectrum efficiency considers a given limited channel bandwidth of the light emitting diode (LED) and then attempts to get the highest throughput per unit of energy. We investigate previous findings that clipped OFDM can be more attractive in a low-SNR regime. More specifically, we consider visible light communication (VLC) in which the average light level, i.e., the bias, is prescribed by illumination requirements, thus comes for free. ACO/PAM/Flip-OFDM can convert the DC-bias into power for communication, but all variants of OFDM, including DCO-OFDM consume extra electrical power. We conclude that in this scenario, advantages attributed to ACO/PAM/Flip-OFDM vanish, as DCO-OFDM outperforms its variants in all SNR conditions, in terms of achieved throughput over a bandlimited channel as a function of extra electrical power required. For hybrid solutions, such as Asymmetrically clipped DC biased Optical OFDM (ADO-OFDM) and Hybrid ACO-OFDM (HACO-OFDM), we optimize a new adaptive power and rate splitting between odd (clipped) and even (biased/clipped) subcarriers to balance power and bandwidth efficiency.

To improve the data rate in a camera-based visible light communication system, multiple LEDs in an LED array are used to transmit multiple bits in one frame. The problem is that LEDs are always captured in the image with some degree of blooming effect. This effect increases the intensity of pixels surrounding the origin LEDs in the image. When multiple LEDs are used, the blooming effect from all LEDs causes the interpixel interference (IPI) problem that greatly degrades the quality of the received signal. This paper analyzes the blooming effect and finds that the IPI problem increases when the number of ``ON”LEDs in the array increases. Through the analysis, this paper proposes a differential coding to minimize the number of ``ON”LEDs in every transmitted frame and thus minimize the IPI effect. The proposed scheme is then verified through simulations. The results show that a lower bit error rate, which indicates a better signal quality, can be achieved by applying the proposed scheme.

Side-effect modulation (SEM) has the potential to be a significant source of interference in future visible light communication (VLC) systems. SEM is a variation in the intensity of the light emitted by a luminaire and is usually a side effect caused by the power supply used to drive the luminaires. For LED luminaires powered by a switched mode power supply, the SEM can be at much higher frequencies than that emitted by conventional incandescent or fluorescent lighting. It has been shown that the SEM caused by commercially available LED luminaires is often periodic and of low power. In this paper, we investigate the impact of typical forms of SEM on the performance of optical OFDM VLC systems; both ACO-OFDM and DCO-OFDM are considered. Our results show that even low levels of SEM power can significantly degrade the bit-error-rate performance. To solve this problem, an SEM mitigation scheme is described. The mitigation scheme is decision-directed and is based on estimating and subtracting the fundamental component of the SEM from the received signal. We describe two forms of the algorithm; one uses blind estimation, while the other uses pilot-assisted estimation based on a training sequence. Decision errors, resulting in decision noise, limit the performance of the blind estimator even when estimation is based on very long signals. However, the pilot system can achieve more accurate estimations, and thus a better performance. Results are first presented for typical SEM waveforms for the case where the fundamental frequency of the SEM is known. The algorithms are then extended to include a frequency estimation step and the mitigation algorithm is shown also to be effective in this case.

Visible light communication (VLC) is regarded as a promising technology for indoor communications due to its safety, availability, and efficiency. By deploying multiple light-emitting diodes (LEDs) at the transmitter, high data rate can be achieved. On the other hand, the dimming control is necessary in VLC systems to meet the lighting requirements, and puts an additional constraint to the system design. Thus, providing required communication quality while preserving the maximum dimming control capability becomes the baseline design philosophy for VLC systems. In this paper, we focus on multi-user multiple-input multiple-output VLC systems and propose a joint beamforming and direct current bias design. The proposed scheme can be formulated as an optimization problem and finds the minimum dimming level subject to the transmission rate requirement as well as the lighting constraints. Semi-definite program method and concave-convex procedure are exploited to solve the optimization problem efficiently. The impacts of locations of LEDs and users to the dimming control are also studied with numerical results.

Indoor visible light communication (VLC) using a light emitting diode (LED) transmitter provides a high-signal-to-noise (SNR) link, which is ideal for video transmission. The LED lights illuminate their own attocells and convey video streams in the downlink to multiple mobile terminals (MTs). Three different transmission schemes are considered, namely: the unity frequency reuse, the higher frequency reuse factor-based transmission, and the novel vectored transmission. We then formulate the optimization problems aiming at minimizing the video distortion. This paper commences by evaluating the performance of the MT at specific positions and continues by characterizing the peak SNR (PSNR) degradation across the room. Finally, we quantify the average performance of multiple MTs randomly walking in the room. By investigating the PSNR degradation, the video rate achieved, the energy consumed, and the effects of buffering delay on the video distortion, we demonstrate that the proposed VLC system is capable of supporting high-quality multimedia transmissions.