Unlicensed radio communications in a changing regulatory environment

The wireless revolution is having a major impact on how we set up and communicate between nodes in a supervisory control and data acquisition system (SCADA). Normally, customers requiring wireless communication systems would require FCC licensing. These licensed applications were difficult or impossible to obtain. The result was that systems were being tested using technologies that did not suit the application. This led to increased costs, poor system performance and poor system reliability. The solution in wireless technology today is the emergence of Spread Spectrum Technology (SS). The new digital technology provides most of the capabilities and performance of a licensed radio system with a license free approach. For long distance data communications in a control or data gathering application, frequency hopping spread spectrum radios provides the most robust solution. Spread Spectrum uses the frequency band of 902 to 928 MHz. The new digital radio of today provides frequency hopping within this range to ensure maximum performance and maximum reliability for SCADA communications. Sophisticated hopping sequences and forward error correction reduces interference from unwanted sources. These enhancements to the radios provide very low bit error rates and greater range of use. In addition, use of Digital Signal Processing (DSP) technology allows systems to communicate at speeds of up to 19.2 KBPS and higher in the presence of weak signals and interfering sources. The added intelligence created by the use of microprocessors in the radio allows for improved diagnostic facilities. These facilities allow for the monitoring and control of radio parameters, locally at the radio, as well as via the master base station. This paper will briefly discuss the historical background of spread spectrum radio, FCC rules and regulations, as well as the definition and application of direct sequence and frequency hopping techniques. Furthermore, system architecture options, design and installation considerations will be given in a brief discussion.