## 5 Progress of Data Transmission Protocols for Wireless Communication in Solar PV Monitoring Systems
### ZigBee-Based Module  
The ZigBee technology was developed in alliance with IEEE and ZigBee based on 802.15.4 standards [84]. IEEE is responsible for developing its physical layer, its media storage control layer, and its data link layer while the ZigBee alliance took charge in the development of its logic network, its data transmission encryption mechanism, the application interface specification, and the communication interface between the system protocols. ZigBee modules are driven by low power and can be employed for short-range monitoring in a wireless sensor network [85; 86]. ZigBee is a simple and lightweight wireless network module that uses Radio Frequency (RF) to support the network within sensors. The transmission range of ZigBee may vary from 40 m indoors to 120 m outdoors in the line of sight. ZigBee operates at a 2.4 GHz frequency with a transmission rate of up to 250 kbps [87]. ZigBee uses a ready collision prevention mechanism and a MAC layer to avoid data collisions. The ZigBee module receives the transmitted data and then replies with a confirmation message which greatly increases the reliability of data transmission in a system [88]. [PERSON] et al. [89] presented an overview of ZigBee devices and modules with regard to smart grid infrastructure and the importance of smart metering. The paper discussed four cases of ZigBee technology implementation to detect the interference of the signals at a water treatment plant, a distribution company, a control house of a wind farm, and a home energy system. Although the experiments were performed at several locations to evaluate the performance of ZigBee, the methodology was only limited to the examination of interference of various blockages with no real-time data. Hence, real-time monitoring data should be integrated for further research works. [PERSON] et al. [90] developed a ZigBee-based solar PV monitoring system for a single wire Local Interconnected Network (LIN) bus. The authors also proposed a web-based application to optimize the electrical power output from the solar plant. A three-tier architecture was proposed for the monitoring and characterization systems where the characterization module of the PV solar panel was placed in the first level, the PV cluster gateway was positioned in the second level, and the PV park coordinator and the web-based communication technologies with remote \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & **Arduino Uno** & **Raspberry Pi3** & **PLC (FXIN-14 MR)** & **BeagleBone** & **ATMEGA 16** \\ \hline Communication & 4x SPI, 2x I2C, & 1x SPI, 2x I2C, & & Ladder logic, Ethernet, & 4x UART, 2x SPI, 2x & Serial, 12C, SPI \\ protocol & PCM/IES, 2x UART & PCM/IES, 1x UART & RS-45 modules & & 12C, 2x CAN BUS & - \\ Size of Board & 69 \(\times\) 53 mm & 85 \(\times\) 56 mm & 110 \(\times\) 95 \(\times\) 17 mm & 86 \(\times\) 56 mm & As per Requirement \\ Speed of Clock & 16 MHz & 1.2 GHz & 140–180 MHz & 1.0 GHz & 0–16 MHz \\ RAM & 16 MHz & 1 GB LPDDR2 & - & 512 MB DDR3 & 1 KB SRAM \\ Supply Voltage & 5 V & 5 V & 24 V & 5 V & 2.7–5.5 V \\ GPIO pins & 14 & 26 & 14 & 69 & 32 \\ Storage & 32 KB & Micro SD & 8 MB & 4 GB, micro-SD & 16 KB Flash memory, 512 byte EEPROM \\ Memory & & & & & 512 byte EEPROM \\ USB port & - & 4 \(\times\) USB 2.0 & - & 1 \(\times\) USB & - \\  & & & Broadcom BCM2837, & & AM335x ARM & \\ Processor & ATmega328P & ARM Cortex- A53 & SLC 5/03 CPU & Cortex-A8 & 8 bit processor \\  & & & 64-b Quad Core & & & \\ Power & 98.53 mA @ 9 V & 400 mA @ 5.1 V & 400 mA (Approx) & 500 mA & 1.1 mA @ 3 V \\  & & & & & \\ Weight & 30 g & 45 g & 120 g & 39.68 g & 20 g \\  & & & & & \\ Cost (Approx) & USD 30 & USD 25–35 & USD 45 & USD 30 & USD 3 (Approx) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Comparison for the specification of various data processing modules. monitoring and control computers were located in the final level. The proposed algorithm to monitor the condition of solar panels could further be improved with the addition of environmental parameters such as humidity and temperature.