LiFi Access Points Research Articles

Hybrid CSMA/CA and HCCA uplink medium access control protocol for VLC based heterogeneous users

Light fidelity (LiFi) is an emerging wireless networking technology of visible light communication (VLC) paradigm for multiuser communication. This technology enables high data rates due to the availability of large visible light spectrum. While current studies have shown the potential for LiFi technology, they borrow the MAC-layer protocols from traditional WiFi. However, a number of prior studies have shown the challenges faced by the MAC-layer of WiFi in the presence of large number and types of devices. In this work, we show that the hybrid-coordination-function-controlled-access (HCCA) MAC protocol in LiFi provides higher throughput than the traditional CSMA/CA mechanism to user devices. We also show that HCCA has the limitation of higher message overhead in the presence of a large number of devices. We also evaluate the collision probability, busy channel probability, and delay for HCCA and CSMA/CA MAC protocol. We utilize both theoretical analysis and extensive simulations to study these performance tradeoffs and identify a threshold when a LiFi access point should switch to HCCA from CSMA/CA and vice-versa. Finally, based on our findings, we design a hybrid-MAC mechanism that switches between HCCA and CSMA/CA based on the number and type of devices present. Our evaluation shows that this hybrid mechanism can outperform both HCCA and CSMA/CA individually in the presence of different number of devices.

Mobility aware blockage management of a multi-user multi-cell hybrid Li-Fi Wi-Fi system with freeform diversity receiver

In order to accommodate high data traffic, the co-deployment of heterogeneous networks like light fidelity (Li-Fi) and wireless fidelity (Wi-Fi) can offer supplementary small-cell layers of support and bring about a paradigm shift in achievable system throughput and quality of service. However, dense deployment of Li-Fi access points(APs) in an indoor arena often leads to co-channel-interference (CCI) that can be fruitfully diminished by adopting a customized optical front-end called freeform diversity receiver (FDR). With regard to multi-user association, this work judiciously imparts the motivation behind the adoption of FDR in a hybrid Li-Fi Wi-Fi network (HLWNet). Based on different mobility scenarios and blockage conditions the performance of the proposed HLWNet has been evaluated. A Li-Fi channel model with FDR and a rule-based resource allocation algorithm (RBRA) has been proposed for the purpose. Nevertheless, the network data quality of the multi-user system has been estimated in terms of packet loss, latency, and fairness index. Unlike the existing optimal resource allocation (ORA), the RBRA demonstrates superior network performance. Additionally, the execution time in the RBRA is reduced by a factor of 89 compared to the optimal resource allocation algorithm. Simulation results show a satisfactory fairness index of more than 0.85 and latency within 2.1 ms for a 10-user association inside an indoor environment of 25m2 floor area. In the absence of LOS blockage, the system throughput exhibits minimal variation, staying consistent for both methods with less than a 2% difference. However, significant improvement in average user throughput and effective system throughput has been observed compared to the existing studies. Despite line-of-sight (LOS) blockage, the proposed system with RBRA consistently maintains throughput within the range of 2.01 Gbps to 2.55 Gbps. The average user throughput, varying from 182 Mbps to 480 Mbps, is contingent upon the number of associated users, which ranges from 4 to 14.

Reliable and cost effective all-optical wireless architecture for a broadband access network

The conventional fiber-wireless (FiWi) network integrates a fiber-based back-end with a wireless-fidelity (WiFi)-based front-end in passive optical network architecture. Free-space optics (FSO) has recently been explored as a cost-effective alternative to optical fiber. Moreover, light fidelity (LiFi) is also emerging as a complementary technology to WiFi for indoor communication due to its ease of deployment and large unlicensed spectrum. This paper explores the benefits and trade-offs of integrating the FSO-based back-end with the LiFi-based front-end for an active optical network (AON). We have simulated multiple possible integration architectures of the FSO/fiber-based back-end with the LiFi/WiFi-based front-end. Moreover, to further improve system performance, we explore link aggregation, wherein users can receive data concurrently from both WiFi and LiFi access points. We evaluate and compare these proposed architectures in terms of average throughput, deployment cost, cost-per-bit, fairness, and reliability against conventional FiWi architecture. In addition, we present an analytical framework to estimate the outage probability of the hybrid FSO-LiFi architecture in which the FSO-based back-end network in AON architecture is integrated with a LiFi-based front-end. The obtained simulation results demonstrate the potential of this proposed hybrid architecture over conventional FiWi architecture.

Energy-Efficient Coexistence of LiFi Users and Light Enabled IoT Devices

Owing to power limitations and hardware constraints of the Internet of Things (IoT) device, it requires simple, low power, low complex, energy-efficient communication technology. In contrast, LiFi users require high data rates and reliable connectivity. Motivated by the diverse requirements of these heterogeneous users, this paper proposes novel green communication schemes that can be used for the coexistence of LiFi users and light communication (LC) enabled IoT devices under a common LiFi access point. The proposed coexistence schemes utilize the amalgamation of wavelength division multiplexing, OFDMA, Hartley transform based DCO-OFDM (DCO-OFDM <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\mathrm {H}}$ </tex-math></inline-formula> ), null DC element, interleaved subcarrier mapping, modified data sequence to achieve concurrent interference-free, low complex and reliable communication. Additionally, as the multiple access (MA) techniques affect the choice of modulation techniques and overall performance in the system. Therefore, this paper includes an analytical delay and throughput framework to corroborate the decision of an appropriate combination of MA and modulation techniques in the coexistence scheme. This paper presents a comprehensive analysis of the proposed coexistence schemes against conventional DCO-OFDM <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\mathrm {H}}$ </tex-math></inline-formula> coexistence schemes based on various performance metrics. The results suggest that the proposed DL and UL coexistence schemes reduce the complexity and increase the energy efficiency at the user’s and device’s terminals.

An Adaptive Handover Scheme for Hybrid LiFi and WiFi Networks

The hybrid light fidelity (LiFi) and wireless fidelity (WiFi) network (HLWNet) is considered to be a potential component of the next generation indoor wireless networks. However, due to the susceptible line-of-sight propagation of optical signal and the ultra-dense deployment of LiFi access points, the handover problem in the HLWNet becomes challenging and it is hard to design a handover scheme that adapts to complex indoor working scenarios. In this paper, we propose a novel handover scheme, in which the handover events in HLWNet are classified into three categories and a particular strategy for each category is applied to calculate the optimal dwell time in the handover procedure. The proposed handover scheme is adaptive to different working situations, since the information about multiple attributes, such as channel quality, user velocity, and arrivals data rate, is gathered to make the handover decision and to calculate the dwell value. The simulation results show that, compared to the benchmarks, the proposed method is able to increase the user throughput by around 65%, decrease the handover rate by up to 80%, and reduce the packet delay by up to 57%. In addition, the proposed method significantly improves the robustness performance of user throughput and handover rate under different scenarios.

CoMP-JT Scheme for D2D Communication in Industrial LiFi Networks

This paper focuses on the combined technique of device-to-device (D2D) and coordinated multipoint joint transmission (CoMP-JT) to bridge the indoor industrial wireless gap with LiFi-based networks. It also considers the mobility challange of industrial internet-of-things (IIoT) within a realistic scenario. Using the semiangle at half illuminance of the LiFi access point and D2D transmitting IIoT, we derive a coverage model for the communication range. Using stochastic geometry, the analytical expressions for CoMP-JT probability and coverage performance are derived in terms of different parameters, such as transmitter densities and bias factor. The analytical approximations match quite well with the Monte Carlo method-based simulation results.

Optimal frequency reuse scheme based on cuckoo search algorithm in Li‐Fi fifth‐generation bidirectional communication

Huge demand for bandwidth and capacity is exhibited by various wireless users and applications, for that purpose now the light-fidelity (Li-Fi)-based technologies are developing. In visible light communication, the hybrid networks based on Wi-Fi and Li-Fi has emerged recently. It is based on the concept of integrating small cell Li-Fi networks with large coverage radio frequency (RF) communication systems. For bidirectional data communication, the access links use shared bandwidth since the link of wireless backhaul invokes in the visible light spectrum. Due to the RF spectrum shortage, the bandwidth of Wi-Fi access point (AP) and the coverage of Li-Fi AP are limited in the outdoor environment. To tackle this issue, the authors propose a swarm intelligence-based improved cuckoo search into the frequency reuse of a hybrid Wi-Fi–Li-Fi network in the outdoor environment. The proposed approach employed bidirectional visible light propagation with non-orthogonal multiple access (NOMA) which is an effective approach towards fifth-generation wireless networks. The NOMA can help various users at the same time with the same frequency and multiple power levels. The system throughput and spectral efficiency are improved with dynamic frequency reuse scheme. The simulation results are compared with conventional techniques to show its effectiveness.

Optimized joint LiFi coordinated multipoint joint transmission clustering and load balancing for hybrid LiFi and WiFi networks

Hybrid light fidelity (LiFi) and wireless fidelity (WiFi) networks provide a promising solution for future indoor wireless communication. Hybrid networks face the challenge of imbalanced cell load due to the uneven distribution of user equipment (UE), and they need to suppress inter-cell interference induced by the dense deployment of LiFi access points (APs). In this paper, with the aim to efficiently establish UE-AP associations and allocate resources, we propose a potential game (PG) aided design of joint user-centric LiFi coordinated multipoint (CoMP) joint transmission (JT) clustering and load balancing (LB). In our design, we formulate the joint design problem as a mixed-integer nonlinear programming (MINLP) problem, which integrates the requirement for the minimum data rate of each UE. With the aim to maximize the system throughput under proportional fairness constraints, we propose to build a PG model to solve the MINLP problem. Then we derive the Nash equilibrium based on the best-response dynamics, and thus a suboptimal solution is attained. Thanks to the space diversity gain brought by our joint LiFi CoMP-JT clustering and LB design, the signal-to-interference-plus-noise ratio can be improved. Thus, when the physical layer configurations remain the same, hybrid networks can achieve larger capacity and better reliability performances. Simulation results validate that hybrid networks using our presented design would achieve better throughput and satisfaction performances than benchmarks.

Parallel Transmission LiFi

Light fidelity (LiFi) is a relatively new wireless communication technology that exploits the optical spectrum. Compared to wireless fidelity (WiFi), LiFi is densely deployed with each access point (AP) covering an area only a few meters in diameter. Also, LiFi users are susceptible to intermittent light-path blockages. Meanwhile, the user is served by a single AP in conventional LiFi systems. This would cause frequent handovers for LiFi users, resulting in a degradation in quality of service. In this paper, parallel transmission is investigated for LiFi, which is named PT-LiFi. With a delicate design of the transmitter and the receiver, PT-LiFi enables multiple LiFi APs to serve the user simultaneously. Particularly, data transmission continues without interruption when the user is losing connectivity to some of the connected APs. Resource allocation is studied for the PT-LiFi system, and a novel load balancing method is proposed to jointly allocate resource across the APs. Results show PT-LiFi can make efficient use of the densely deployed LiFi APs and provide a flexible way of load balancing. Compared with a conventional LiFi system, the proposed method can increase user throughput by up to 150% and improve user fairness by up to 15%.

Light Fidelity (Li - Fi) Access Point Selection for Heterogeneous Network with Non Overlapping Li - Fi Access Points

Data transmission is a part of our life in today’s scenario. Data communication can be carried out by wired technology and wireless technology. Radio frequency is a part of the electromagnetic spectrum, which is used for wireless communication. Many technologies are used for wireless communication such as Wi-Fi, Blue Tooth, Ad-hoc, and etc. These are all transmitting data through radio spectrum for short distance. New technology called as Li-Fi (Light-Fidelity) is going to be a major wireless communication technology in future. In the proposed system a heterogeneous network has been consider as a system model. Li-Fi technology is having the capacity of low coverage area. So, non movable wireless devices are getting better usage of Li-Fi technology in an indoor environment. For mobile devices need more number of Li-Fi access points. When the user moves from one access point to another access point covering range, the service should be continued without break. System handover is a major issue in the Li-Fi technology. If the user goes out of the range of light emission area, then the user can get the service through Wi-Fi access point. Proposed system focusing on the handover process based on the measured handover efficiency value. Data transmission can be disturbed due to some power failure or LED fault. In this situation immediately the entire load should be handled by the Wi-Fi access point. In such a situation data rate is coming down than the threshold value. So handover process will be handled by the common controller. Data rate is observed when the number of user increased and for variation in channel gain and the simulation results are analysed.

Load Balancing Scheme in Hybrid WiGig/LiFi Network

Recently, Light fidelity (LiFi) is proposed as a high-speed wireless communication technology. A LiFi access point provides the service in an area of a few square meters known as LiFi attocells. Therefore, by utilizing frequency reuse, LiFi networks provide a high spatial spectral efficiency. Unfortunately, beside to uplink and mobility problems, the LiFi networks suffer more difficulties with increasing of the number of mobile devices. As a solution, hybrid LiFi and radio frequency (RF) networks are proposed. In this article, a hybrid network, that combines LiFi with RF Wireless Gigabit Alliance (WiGig) networks, is proposed. The WiGig access points will provide gigabit-per-second data rates as a result of the availability of large bandwidth at the millimeter wave (mmWave) frequency ranges. Such hybrid networks need an efficient load balancing (LB) scheme. In this article, two modified versions of the separate optimization algorithm (SOA) are proposed; Assign WiGig First SOA (AWFS) algorithm and Consecutive Assign WiGig First SOA (CAWFS) algorithm. The simulation results show that the two proposed algorithms offer better achievable data rates and outage probability performances compared with the SOA algorithm.

Reinforcement Learning Based Load Balancing for Hybrid LiFi WiFi Networks

Light fidelity (LiFi) is an emerging communication technology, which utilizes the light-emitting diodes (LEDs) for high-speed wireless communications. Due to its huge unlicensed bandwidth, LiFi is capable of supporting high data rates. The quality of the LiFi channel fluctuates across the room due to interference, reflection from walls or blockage. On the other hand, WiFi is another wireless communication technology that is capable of providing moderate data rates with ubiquitous coverage. As the electromagnetic spectrum of LiFi does not overlap with WiFi, both of them can coexist to form a hybrid LiFi and WiFi network for seamless and high-throughput connectivity. The performance of a hybrid system significantly depends upon the access point (AP) assignment and resource allocation strategies. In this paper, a downlink hybrid system with one WiFi AP and four LiFi APs is considered, and a reinforcement learning (RL) algorithm is implemented in order to determine an optimal AP assignment strategy, which maximizes the long-term system throughput while ensuring the required users fairness and satisfaction. Furthermore, two different scenarios based on the random waypoint model with uniform and non-uniform distribution of users have been studied. The performance of the proposed system is compared against state-of-the-art benchmark approaches e.g., signal strength strategy (SSS), exhaustive search, and an iterative optimization method. The results are reported in terms of the average system throughput, user satisfaction, fairness, and capacity outage probability. It is shown that the proposed RL method performs closer to the exhaustive search scheme at fairly low complexity. The RL method also outperforms the SSS scheme and the iterative algorithm in most scenarios.

Li-Fi: A Revolution in Wireless Networking

In this paper, the concept and theories of LiFi & VLC (Visible Light Communication) are well explained. Visible light being safe to use for wireless access in such affected environments, also provides illumination. In addition with the misconceptions about LiFi are revealed and also the scope of LiFi in industries and technology are illustrated. To minimize the network traffic, Light Fidelity (LiFi) provides an effective solution to the issues of wireless communication. Since working operations are controlled, lights become LiFi attocells resulting in enhanced wireless capacity for the Internet-of-Things (IoT), 5G and beyond. The architecture of LiFi access point that implements OFDM is investigated. Our detailed study on LiFi can show that this technology can be the pervasive network in future and can create a revolution in telecommunication.

An optical backhaul solution for LiFi-based access networks

The light fidelity (Li-Fi) technology is being considered as one of the most promising solutions that can achieve a dramatic increase in communication capacity and a significant reduction in transmission latency especially when it is deployed in the indoor scenario. This technique can enable fully networking capabilities by exploiting the high speed transmission of visible light communication (VLC) technique and supporting massive deployment of LiFi access points to create a network of attocells. In this paper, we investigate the design of an optical backhaul network architecture that can provide efficient interconnection for LiFi access points. Specifically, we propose a LiFi access-point structure implementing orthogonal frequency division multiplexing (OFDM) and optical encoding technique to provide multi-users access and allow all-optical processing and transmission in the backhaul network. A tunable optical encoding/decoding technique based on delaying optical pulses in a vector of optical delay line (ODLs) loops is designed to allow efficient mapping of the OFDM based access and data forwarding in the optical backhaul network. In this encoding scheme, optical codewords can be easily modified by dynamically changing the number of rounds that must be performed by the optical pulse in the ODL. This feature was exploited in the backhaul architecture to enable appropriate mobility management schemes and allow seamless handover between attocells. Performance evaluation using simulation was performed to show that the proposed optical backhaul solution can achieve high transmission capacity with reduced latency.

Dynamic Multiple Access Configuration in Intelligent Lifi Attocellular Access Points

The exponential growth in the global demand for wireless connectivity calls for efficient and reliable management of the available wireless resources. Light fidelity (LiFi) harnesses the vast untapped wireless transmission resources in the infrared spectrum and visible light spectrum to create ultra-dense wireless networks which support user mobility, multiuser access, and handover. Various multiuser access (MA) protocols have been developed to meet the varying system requirements, including orthogonal multiple access (OMA) and non-orthogonal multiple access (NOMA) schemes. While NOMA, on the one hand, allows for significant enhancement in the achievable data rates, its performance may be severely degraded under particular conditions such as a large number of connected users or users existing in highly symmetrical locations. OMA, on the other hand, provides better link reliability in such scenarios but at the expense of decreased spectral efficiency. Therefore, there is a need to enable a degree of intelligence in the LiFi access point (AP) to facilitate real-time configuration of the MA protocol. To this end, this paper develops a novel cross-layer design framework for dynamic multiple access selections (DMAS) in intelligent LiFi APs. The developed framework runs at LiFi attocell system level and can be configured to cater for various system requirements in terms of sum data rate, average outage probability, and fairness. The obtained results show that DMAS introduces an effective solution for multiuser resource allocation by achieving better satisfaction of the system requirements compared to the static configuration of a single MA scheme.

Bidirectional LiFi Attocell Access Point Slicing Scheme

LiFi attocell access networks will be deployed everywhere to support diverse applications and service provisioning to various end-users. The LiFi infrastructure providers will need to offer LiFi access points (APs) resources as a service. This, however, requires a research challenge to be solved to dynamically and effectively allocate resources among service providers (SPs) while guaranteeing performance isolation among them and their respective users. This paper introduces an autonomic resource slicing (virtualization) scheme, which realizes autonomic management and configuration of virtual APs, in a LiFi attocell access network, based on SPs and their users service requirements. The developed scheme comprises of traffic analysis and classification, a local AP controller, downlink and uplink slice resources manager, traffic measurement, and information collection modules. It also contains a hybrid medium access protocol and an extended token bucket fair queueing algorithm to support uplink access virtualization and spectrum slicing. The proposed resource slicing scheme collects and analyzes the traffic statistics of the different applications supported on the slices defined in each LiFi AP and distributes the available resources fairly and proportionally among them. It uses a control algorithm to adjust the minimum contention window of user devices to achieve the target throughput and ensure airtime fairness among SPs and their users. The developed scheme has been extensively evaluated using OMNeT++. The obtained results show various resource slicing capabilities to support differentiated services and performance isolation.

Load Balancing Game With Shadowing Effect for Indoor Hybrid LiFi/RF Networks

Light Fidelity (LiFi) is a recently proposed technology that uses 300 THz visible light spectrum for high speed wireless communications as well as providing illumination. Basically, a LiFi access point (AP) covers only a few square meters, enabling a dense deployment of LiFi APs to improve the network throughput. However, channel blockage and shadowing in conjunction with inter-cell interference compromise the connectivity and system throughput of LiFi networks. In this paper, a network structure that combines LiFi with the conventional radio frequency (RF) system is considered. Users experiencing strong blockages can be switched to the RF system to achieve a higher data rate. In this paper, blockages, random orientation of LiFi receivers, and the user data rate requirement are characterised to model a practical communication scenario. A novel load balancing (LB) scheme based on evolutionary game theory is proposed for hybrid LiFi/RF networks. The performance of the proposed scheme is comprehensively analyzed. Results show that compared to state-of-the-art LB algorithms, the proposed scheme greatly improves user satisfaction levels at reduced computational complexity. Also, an optimal orientation of LiFi receivers and blockage density in hybrid networks would maximize the users quality of service.

Optimization of Load Balancing in Hybrid LiFi/RF Networks

Light fidelity (LiFi) uses light emitting diodes (LEDs) for high-speed wireless communications. Since an LED lamp covers a small area, a LiFi system with multiple access points (APs) can offer a significantly high spatial throughput. However, the spatial distribution of data rates achieved by LiFi fluctuates because users experience inter-cell interference from neighboring LiFi APs. In order to guarantee a quality of service (QoS) for all users in the network, an RF network is considered as an additional wireless networking layer. This hybrid LiFi/RF network enables users with low levels of optical signals to achieve the desired QoS by migrating to the RF network. With regard to moving users, the hybrid LiFi/RF system dynamically allocates either a LiFi AP or an RF AP to users based on their channel state information. In this paper, a dynamic load balancing scheme is proposed, which considers the handover overhead in order to improve the overall system throughput. Joint optimization algorithm (JOA) and separate optimization algorithm (SOA), which jointly and separately optimize the AP assignment and resource allocation, respectively, are proposed. Simulation results show that SOA can offer a better performance/complexity tradeoff than JOA for system load balancing.