Uplink Visible Light Communication Research Articles

Optical investigations of Cu2CdSnS[formula omitted] quaternary alloy nanostructure for indoor optical wireless communications

The development of high-performance nano-luminophores based on luminescent nanomaterials, such as Carbon Nanotubes (CNT) and Quantum Dots (QDs), opens the doors for many potential improvements in luminescent systems and notably Optical Wireless Communication (OWC) systems. Other side, Cu2CdSnS4 quaternary alloy nanostructure has attracted attention in solar cell applications owing to the high optical absorption in visible range. This work presents the feasibility of the infrared uplink Visible Light Communication (VLC) system using Near Infrared Light Emitting Diode (NIR-LED) operating at 780 nm. The used NIR-LED-based Cu2CdSnS4 quaternary alloy nanostructure is to investigate the performance of NIR uplink transmission according to Line of Sight (LOS) channel model. In this transmission, the effect of transmitter orientation and transmitted optical power level with respect to Tx–Rx​ uplink distance are taken into consideration. For this purpose, performance evaluation will be achieved in terms of Bit Error Rate (BER) where we demonstrated satisfactory BER performance (BER≥10−9) over the entire typical room configuration. In addition, an optimal semi-angle interval and optimal Tx power level has been selected. We further investigated the performance improvement by using several transceivers, compared with a single one on the center of the ceiling.

Resource matching algorithm under delay QoS constraint for uplink visible light communication based on supermartingale theory

We propose a supermartingale-based resource matching algorithm to guarantee delay quality of service (QoS) for the visible light communication uplink system. A network queuing model with multiple bursty arrivals is established, and multipacket reception technology is considered to alleviate terminal collisions. We introduce the supermartingale theory to evaluate the delay QoS performance, and a tighter delay-violation probability bound is derived. Relying on the supermartingale analysis, we design a search algorithm to achieve resource matching under a delay QoS constraint. The simulation results prove that the proposed algorithm guarantees delay QoS and saves service resources.

Improving the performance of uplink visible light communication in urban streets

Improving the performance of uplink visible light communication in urban streets

Framework of IoT Services over Unidirectional Visible Lights Communication Networks

Visible Light Communication (VLC) has been noted as an emerging technology for communications in wireless local area networks. VLC provides some distinctive features over the conventional wireless access technologies, such as Wi-Fi, Bluetooth, or ZigBee. The most prominent feature of VLC is that it can provide more exact location information, since it is based on a particular light. In addition, VLC can reduce the frequency interferences from numerous wireless channels, since it uses a completely different radio frequency channel from the conventional wireless access technologies. Thus, VLC can be used for Internet-of-Things (IoT) services. Nevertheless, up to now, not enough studies on how to provide IoT services over VLC networks have been conducted. In this paper, we propose a framework to provide IoT services in VLC networks. In particular, we will consider the unidirectional VLC network, in which the downlink channel from the VLC transmitter to the VLC receiver is given by using VLC communication, whereas the uplink channel from the VLC receiver to the VLC transmitter is implemented by using another wireless access technology, such as Wi-Fi. This is because most of the VLC receivers, such as mobile phones, cannot support the uplink VLC communication. Based on the framework of IoT services over unidirectional VLC, in this paper, we also propose the VLC–IoT protocol (VIP) which is an application layer protocol for data transport with the session management functionality that can be used to effectively provide IoT services among IoT servers, VLC transmitters and VLC receivers in the networks. The proposed VIP protocol is implemented by using the Cooja simulator. For performance analysis, the proposed scheme is compared with the existing CoAP-based scheme that does not provide the session management. From a variety of simulation experiments, we see that the proposed scheme can provide lower data transmission and handover delays, compared to the existing scheme.

Experimental demonstration of a real-time multi-channel uplink VLC system

We propose and experimentally demonstrate a multi-channel uplink visible light communication (VLC) system for the first time, which is based on three commercially available white light emitting diodes (LED) and only one photo-diode (PD). By employing independent Xilinx field programmable gate arrays (FPGA), we realize the real-time data transmission. The on–off keying (OOK) modulation and time division multiple access (TDMA) techniques are combined together to offer a reliable multiple uplink access for three users. The electrical idle signal is designed to deal with serious inter-symbol interference (ISI) caused by the overlap of different LED signals at the receiver side, as well as to provide a stable illuminating environment. The experiment results indicate that our scheme has a great potential for the indoor practical VLC system implementation.

The Uplink Visible Light Communication Beacon System for Universal Traffic Management

This paper presents a feasibility study of the uplink visible light communication (VLC) beacon system for the universal traffic management system (UTMS). The UTMS is a traffic management system beneath the National Police Agency of Japan. Currently, 55 000 UTMS infrared beacon systems have been installed, and they provide expressway and ordinary road information to cars. However, the data rate is 1 Mbps, and a faster data rate is necessary to support automotive and smart mobility devices. In this paper, we propose an uplink V2I system for the UTMS. The system is designed to match the current beacon system as closely as possible, so that the system can easily be replaced and still provide sufficient bandwidth for future automotive and smart mobility devices. We adopt a photo diode (PD) as the VLC receiver and a commercially available off-the-shelf LED headlight as a transmitter. Unfortunately, the bandwidth of such an LED is usually small, so we consider applying a bit-loading algorithm to direct-current-biased optical orthogonal frequency division multiplexing. To reduce strong background noise, such as from the sun, we narrow down the field-of-view by applying a lens to the PD, which forms a tiny communication area, smaller than the current infrared beacon system. We then consider multiple PDs with the lens to create a similar communication area as the infrared beacon system. As a result, we achieve 3.1-Mbps throughput.

Investigation on random access in a VLC system with multipacket reception in the presence of hidden devices and obstructions

Due to the directionality of light, the hidden device problem and the obstruction cannot be ignored for carrier sense multiple access with collision avoidance (CSMA/CA)-based uplink visible light communication (VLC). In this paper, we introduce multipacket reception (MPR) to handle the hidden device problem in VLC system. We model the traffic of the device with on/off Markov source. With the unsaturated traffic, we formulate a two dimensional (2D) Markov chain to model the CSMA/CA-based slotted random access procedure to evaluate the effects of hidden devices and obstructions on the performance of MPR-aided VLC system, which are mapped into the transition probabilities of the Markov chain. Then, we analyze the throughput and the reception power efficiency (RE) of MPR-aided VLC system with the obstructed optical channel. Numerical results show that the effect is negative when hidden devices or obstructions appear solely. But when they appear simultaneously, they will interact with each other to mitigate the negative effects.

Optimal ALOHA-Like Random Access With Heterogeneous QoS Guarantees for Multi-Packet Reception Aided Visible Light Communications

There is a paucity of random access protocols designed for alleviating collisions in visible light communication (VLC) systems, where carrier sensing is hard to achieve due to the directionality of light. To resolve the problem of collisions, we adopt the successive interference cancellation (SIC) algorithm to enable the coordinator to simultaneously communicate with multiple devices, which is referred to as the multi-packet reception (MPR) capability. However, the MPR capability could be fully utilized only when random access algorithms are properly designed. Considering the characteristics of the SIC aided random access VLC system, we propose a novel effective capacity (EC)-based ALOHA-like distributed random access algorithm for MPR-aided uplink VLC systems having heterogeneous quality-of-service (QoS) guarantees. First, we model the VLC network as a conflict graph and derive the EC for each device. Then, we formulate the VLC QoS-guaranteed random access problem as a saturation throughput maximization problem subject to multiple statistical QoS constraints. Finally, the resultant non-concave optimization problem is solved by a memetic search algorithm relying on invasive weed optimization and differential evolution. We demonstrate that our derived EC expression matches the Monte Carlo simulation results accurately, and the performance of our proposed algorithms is competitive.

Performance of a wavelength hopping MC-VPPM scheme for vehicle-to-infrastructure(V2I) VLC

Multi-coded variable PPM (MC-VPPM) is a modulation technique for visible light communication (VLC), providing high data rate transmission and processing gain improvement at the receiver side. This paper proposes wavelength hopping MC-VPPM supporting multi-user communications in the vehicle-to-infrastructure (V2I) downlink and uplink scenarios of a metropolitan intelligent transportation system and analyzes its performance. By defining outdoor daylight noise and analyzing the sub-band selection effect for wavelength hopping, the communication capability of multi-user V2I downlink and uplink VLC at the daytime was investigated. The simulation results provide the required VLC transmission power for reliable data communication under the predescribed V2I scenario.