VLC/OCC Hybrid Optical Wireless Systems for Versatile Indoor Applications

Abstract

In this paper, a hybrid scheme for optical wireless communications using LED lamps is proposed. This scheme allows both visible light communication (VLC) using photodetectors and optical camera communication (OCC) using image sensors of a camera to receive light signals from the same transmitter simultaneously. High-frequency signals are received by VLC, while low-frequency signals are received by OCC. This hybrid transmission system enables the provision of versatile indoor services and allows users to receive data regardless of their device. It reduces the deployment cost of an indoor optical wireless system since the proposed system can provide both services using one LED lamp. To use the dimming property of LED lamps, a variable pulse position modulation scheme is used for OCC, while Manchester coding is used in VLC to avoid flickering. The measurement shows that the transmission distance reaches more than 4 m for both services. Performance analysis and experimental results are presented. INDEX TERMS Visible light communications, optical camera communications, variable pulse position modulation, VLC/OCC hybrid.

Data Rate Enhancement in Optical Camera Communications Using an Artificial Neural Network Equaliser

“…The standard IS-based Rx is modelled as a linear shift-invariant (LSI) system, which is composed of two stages as depicted in Figure 1(b). The voltage at a pixel (U , V ), which corresponds to an individual photodiode, is given by [27] where A is the gain (set to unity for simplicity), C PD and R are the equivalent capacitance and responsivity of the PD and x(t) is the received optical signal at the pixel (U , V ) at time t. Note, T exp >= T sym , where T sym is the symbol period [29]. The number of symbols observed at the Rx depends on the resolution of the IS, exposure time, pixel clock, and the size of the region of interest [5].…”

“…The transmitter is comprised of a pseudorandom binary sequence (PRBS) d with a length of 2 14 − 1 is generated in MATLAB, which is then up-sampled and encoded using the non-return to zero (NRZ)-Manchester line code (MLC) in order to avoid flickering and a unity amplitude rectangular pulse shaping filter. The MLC signal, which ensures a uniform distribution of 1 and 0 symbols b and facilitates both decoding and synchronisation processes of the signal [29], is packetized in order to ensure proper detection at the Rx as illustrated in Figure 5 The pattern of header and footer is designed such that (i) it never occurs in the MLC pattern for the payload; and (ii) the transition from one packet to another is smooth, which facilitates the training of the network. The transmitted optical signal over a free space channel is captured using a CMOS IS Rx (i.e., camera).…”

New Construction of OVSF-OZCZ Codes in Multi-Rate Quasi-Synchronous CDMA VLC Systems for IoT Applications

“…VLC utilizing unregulated spectrum, specifically from 428 to 750 THz, can meet multiple rate transmission requirements [12]- [14]. Recently, there are some VLC multi-rate schemes including using photodetectors (PDs) and image sensors simultaneously [15], hybrid OOK (onoff keying) and ACO-OFDM (asymmetrically clipped optical orthogonal frequency division multiplexing) modulation [16], and WDM (wavelength division multiplexing) technology [17], [18], but these schemes may increase the system complexity. It is reported that the VLC scheme combining code division multiple access (CDMA) with orthogonal variable spreading factor (OVSF) can also be a potential and suitable candidate for IoT network to handle multimedia rates [19]- [21].…”

A Novel Neural Network-Based Method for Decoding and Detecting of the DS8-PSK Scheme in an OCC System

“…OWC/OCC utilized cameras to receive modulated light, and photodiodes have been widely employed in the VLC system. Although OCC has a lower data rate compared to VLC since it receives data via an image sensor [4,5], OCC is still preferable in applications where mobility is crucial because of the wider field of view (FoV) of a camera compared to a photodiode, for example, indoor localization using a personal smartphone [6,7] or vehicular OCC system [8][9][10].…”

“…OWC/OCC utilized cameras to receive modulated light, and photodiodes have been widely employed in the VLC system. Although OCC has a lower data rate compared to VLC since it receives data via an image sensor [4,5], OCC is still preferable in applications where mobility is crucial because of the wider field of view (FoV) of a camera compared to a photodiode, for example, indoor localization using a personal smartphone [6,7] or vehicular OCC system [8][9][10].On the basis of the point of view of OCC technologies, internet of vehicles (IoV) is one of the most promising areas where these technologies could be deployed. Compared to using the traditional radio frequency (RF) communication, OWC/OCC and VLC are considered as reliable, safe for human health, and low-cost communication technologies [4,11].…”