Optics Communications 473 (2020) 125699 Contents lists available at ScienceDirect Optics Communications journal homepage: www.elsevier.com/locate/optcom A hybrid VLP and VLC system using m-CAP modulation and fingerprinting algorithm Mahdi Nassiri a , Gholamreza Baghersalimi a,∗ , Zabih Ghassemlooy b a Department of Electrical Engineering, University of Guilan, Rasht, Iran b Optical Communications Research Group, Faculty of Engineering and Environment, Northumbria University, Newcastle, UK ARTICLE INFO Keywords: Visible light positioning (VLP) Hybrid VLP and VLC Indoor positioning system (IPS) m-CAP modulation Fingerprinting ABSTRACT A global positioning system (GPS) with high positioning accuracy (PA) is not feasible for challenging environments such as tunnels, underground, complex buildings, etc. For such environments, the alternative technology of visible light positioning (VLP) system has emerged as a viable solution. In this paper, we propose for the first time, a hybrid multi-band carrier-less amplitude and phase (m-CAP) based VLP and visible light communications (VLC) system using the fingerprinting algorithm for determining the position of the receiver, i.e., VLP, and employing the unused sub-bands of m-CAP for VLC. We compare the results for different transmitter configurations and a range of step sizes in terms of the position error (PE) and the bit error rate (BER) performances. Results show that, PE increases with the step size, which is the most critical parameter in fingerprinting-based positioning systems, for a fixed bit energy to noise ratio (  ∕ 0 ). For a fixed   ∕ 0 of 10 dB the PE values are 4.5 and 10.7 cm for the step sizes of 1 and 20 cm, respectively. For a fixed step size, in contrast, PE decreases with increasing   ∕ 0 . Numerical results for a fixed step size of 5 cm show that the PE is reduced from 13.8 to 3.3 cm by 10 dB increase in   ∕ 0 . In addition, by increasing the step size, the quantization error overcomes the noise-induced error. We also show that, configurations I and II outperform configuration III in terms of the PE by about 8 to 6 cm at   ∕ 0 of 5 dB and BER (i.e., 1.56×10 −4 , 2.52×10 −4 and 2.54×10 −3 for configurations I, II and III, respectively at   ∕ 0 of 20 dB), since configuration III is approximately linear with a symmetrical fingerprint map and a lower illumination level. 1. Introduction The 5 th generation (5G) and beyond wireless communications will support a diverse range of methods and techniques for different appli- cations and scenarios delivering high quality services [1]. Despite its low security at the physical layer and relatively low data rates, the radio frequency (RF) wireless technologies are still the most widely used for communications due to its wide coverage area and high mo- bility. However, with the increasing growth of wireless network traffics and the need for more bandwidth, the RF technology is experiencing spectral congestions, which needs to be addressed. Hence, finding and deploying the new spectrum bands can be effective to prevail with this problem [2,3]. There are a number of possible options to address this problem including shifting the transmission carrier frequency to the millimeter (mm)-wave and/or optical frequency band. The latter is attractive since it offers a very high bandwidth, inherent security, lack of susceptibility to the RF electromagnetic interference, and low power usage compared with the RF technologies [3–8]. Optical wire- less communications (OWC) covering all three optical bands of ultra violet (UV), visible, and infrared (IR), is an alternative complementary ∗ Corresponding author. E-mail address: bsalimi@guilan.ac.ir (G. Baghersalimi). technology to RF that could be used in multitude of applications in both indoor and outdoor environments [9]. The OWC technology employing the visible band is known as visible light communications (VLC), which uses solid-state (SS) lights as an optical transmitter (Tx) (i.e., optical antenna) to provide simultaneous data communications, illumination and positioning services [3,5]. The use of VLC is significantly increasing for a number of reasons including high-level security in the physical layer since the light does not pass through walls and other opaque obstacles, high throughput and low latency in urban environments with high density traffic due to the use of pico- and femto-cells, low power base-stations (BSs) and high data rates using massive multiple-input multiple-output (MIMO) [1,3]. Moreover, with the growing interest in smart living, all possible light emitting diodes (LEDs)-based lights in indoor and outdoor environ- ments, traffic lights, etc., could be used for data communications, sensing and positioning [1]. The latter i.e., the visible light positioning (VLP) system is one of the promising applications, which has received the interest of researchers in recent years [4–8,10,11]. For outdoor en- vironments, the global positioning system (GPS) offers a good coverage https://doi.org/10.1016/j.optcom.2020.125699 Received 25 December 2019; Received in revised form 5 March 2020; Accepted 6 March 2020 Available online 7 March 2020 0030-4018/© 2020 Elsevier B.V. All rights reserved.