Fundamentals of wireless communications

Radio Frequency (RF) communications are an important smart grid enabler for functions such as volt/VAR control, recloser control, feeder restorations and isolation, fault detections and sensor alerting in other industrial markets such as cement, mining, and transportation. This paper will give a basic tutorial on the types of radio frequency communications and the benefits and liabilities of each. Specific topics to be explored will be licensed versus unlicensed frequencies, distance between remote devices and base stations, and communication architectures. Radio technology is often referred in numerical ranges or frequencies. The decision on which frequency to employ in a network depends on a few key variables. Prior to deciding which frequency for a network, the application for the radio use will assist with dictation of which frequency range to utilize. Applications such as recloser control and volt/Var control may require a radio device that can provide a high bandwidth/fast speed solution. Other SCADA applications such as sensor monitoring may only require small bandwidth and for data delivery to be at a much slower speed. Besides SCADA applications, wireless communications is now required in other industries such as cement and mining. Another variable when deciding on a radio network is the distance from the main hosts to end remote devices such as RTUs or PLCs in the SCADA environment and sensors and devices for monitoring kiln states in the cement industry. Lower end frequencies (100MHz-900MHz) provide further coverage and greater distance from base stations/Access Points to remote end devices, whereas higher frequencies (2.4GHz-5.8GHz) provide shorter distance coverage, but higher bandwidth and relay data back to SCADA hosts much faster.