Visible light communication (VLC) is a new paradigm that could revolutionise the future of wireless communication. In VLC, information is transmitted through modulating the visible light spectrum (400–700 nm) that is used for illumination. Analytical and experimental work has shown the potential of VLC to provide high-speed data communication with the added advantage of improved energy efficiency and communication security/privacy. VLC is still in the early phase of research. There are fewer review articles published on this topic mostly addressing the physical layer research. Unlike other reviews, this article gives a system prespective of VLC along with the survey on existing literature and potential challenges toward the implementation and integration of VLC.

A low-profile frequency reconfigurable monopole antenna operating in the microwave frequency band is presented in this paper. The proposed structure is printed on Flame Retardant-4 (FR-4) substrate having relative permittivity of 4.3 and tangent loss of 0.025. Four pin diode switches are inserted between radiating patches for switching the various operating modes of an antenna. The proposed antenna operates in five modes, covering nine different bands by operating at single bands of 5 and 3.5 GHz in Mode 1 and Mode 2, dual bands (i.e., 2.6 and 6.5 GHz, 2.1 and 5.6 GHz) in Mode 3 and 4 and triple bands in Mode 5 (i.e., 1.8, 4.8, and 6.4 GHz). The Voltage Standing Waves Ratio (VSWR) of the presented antenna is less than 1.5 for all the operating bands. The efficiency of the designed antenna is 84 % and gain ranges from 1.2 to 3.6 dBi, respectively, at corresponding resonant frequencies. The achieve bandwidths at respective frequencies ranges from 10.5 to 28%. The proposed structure is modeled in Computer Simulation Technology microwave studio (CST MWS) and the simulated results are experimentally validated. Due to its reasonably small size and support for multiple wireless standards, the proposed antenna can be used in modern handheld fifth generation (5G) devices as well as Internet of Things (IoT) enabled systems in smart cities.

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The design of a 4 × 4 MIMO antenna for UWB communication systems is presented in this study. The single antenna element is comprised of a fractal circular ring structure backed by a modified partial ground plane having dimensions of 30 × 30 mm2. The single antenna element has a wide impedance bandwidth of 9.33 GHz and operates from 2.67 GHz to 12 GHz. Furthermore, the gain of a single antenna element increases as the frequency increases, with a peak realized gain and antenna efficiency of 5 dBi and >75%, respectively. For MIMO applications, a 4 × 4 array is designed and analyzed. The antenna elements are positioned in a plus-shaped configuration to provide pattern as well as polarization diversity. It is worth mentioning that good isolation characteristics are achieved without the utilization of any isolation enhancement network. The proposed MIMO antenna was fabricated and tested, and the results show that it provides UWB response from 2.77 GHz to over 12 GHz. The isolation between the antenna elements is more than 15 dB. Based on performance attributes, it can be said that the proposed design is suitable for UWB MIMO applications.

This paper presents a 4 × 4 multi-input multi-output antenna array for ultra-wideband applications. The single element of the array is comprised of a modified co-planar waveguide-fed double overt-leaf shaped patch radiator. The co-planar ground is optimized to achieve maximum impedance matching in the operating frequency band. The results show that the single antenna element offers an impedance bandwidth of 13.2 GHz starting from 3.2 GHz to 16.7 GHz. It is also observed from the results that the antenna offers good radiation characteristics and acceptable gain for the frequency band of interest. Furthermore, a 4 × 4 MIMO array is designed by utilizing the polarization diversity technique. To improve the isolation performance among antenna elements, a fan-shaped decoupler is introduced on the other side of the substrate, which ensures minimum isolation of 20 dB. Moreover, the proposed MIMO array operates in the frequency range of 2.75–16.05 GHz. The proposed MIMO array is fabricated and measured for the validation of simulation results, and it is observed that both the results are well in agreement.