# Low Power FPGA Implementation of a Smart Building Free Space Optical Communication System
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Metric of Concer** & **Conventional Wireless Technology (RF)** &
\begin{tabular}{c} **Optical Wireless Communications** \\ **(OWC)** \\ \end{tabular} \\ \hline Signal Type & RF or Microwave Electromagnetic waves in free space & Light modulated signals through free space \\ Cost & Expensive Infrastructure & Low-cost Implementation \\ Noise & Interference and Jamming Threats & Ambient Light \\ Limited Bandwidth according to the & & The accessible OW spectral areas, such as \\  & operating bands & 1 mm–750 nm for infrared, 780 nm–380 nm \\ Bandwidth & (VHF = 30–300 MHz) & for visible light, and 10 nm–400 nm for UV, \\  & (SHF = 3–30 GHz) & provide infinite bandwidth. \\ License & Need for Licensing & No need for Licensing \\ Data Rates & Less than 2 Gbps & Up to 10 Gbps \\ Distance & Up to 80 km & 2–8 km (FSO) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: RF vs. OWC technologies [5; 11; 12]. For algorithms with high computing needs on a portable PC-independent device, FPGAs are the ideal alternative. For IBs to effectively communicate, a standalone established system that has a portable nature and dynamic capability is the optimal feature a smart network should have. FPGAs are low-power devices that may be employed in embedded systems. Instead of having separate circuitry designs that can merely cause noise and delay accumulations, resulting in falsified outputs, FPGAs help assemble the whole system in one stage [4; 5]. Unlike other signal processing kits, FPGAs have high versatility in dealing with complex data types such as video streams, giving them the advantage of being a more reliable system hosting platform, enabling renovation and upgrading of the design to fit the most recent optimization requirements. Different kinds of modulation are used according to the targeted data rate and the application hosting the system. There are a variety of techniques for modulating the source data into the EM wave carrier at any frequency range, including higher-level Intensity Modulation (IM) and On-Off Keying (OOK). In [21], an indoor FPGA-based FSO communication system was developed using an 808 nm Infra-Red (IR) 100 mW laser source in which a Zedboard comprising the Xilinx XC7Z020-1 CLG484C Zynq-7000 All Programmable System on Chip (AP SoC) associated with dual cortex ARM A9 processors. A data rate of 115 kbps was accomplished at a distance of 12 m via On-Off Keying (OOK) modulation to transmit text and audio files. In this paper, an FPGA-based FSO system is used to transfer data at a distance of 12 m at a data rate of 115 kbps via basic OOK and an optimum bit rate of 230 kbps using IM/PWM is represented using an ALTERA Cyclone IV DE2115 Board with a pre-installed RISC-V software processor and a 650 nm Visible Light (VL) 5 mW laser source. The paper is divided into four further sections. Section 2 illustrates the idea of the implemented system. Section 3 clarifies the implementation steps that have been carried out on both software and hardware scales. Section 4 discusses the results obtained and, finally, the conclusion in Section 5 summarizes the work done.