Performance of Spread-spectrum Radio Techniques in an Interference-limited Hf Environment

In HF radio communications, the performance is often limited by the large amount of mostly narrowband interfering signals from other HF users. Therefore, when evaluating HF spread-spectrum systems, a statistical model of the interference is necessary. In this work, we perform a comparison between a frequency-hopping (FH) and a direct-sequence (DS) spread-spectrum system, for an interference model based on the HF congestion prediction model by Laycock and Gott. The performance measure used is the error probability for the uncoded bits. The results show that the FH system performs better than the DS system on the interference-limited HF channel. The performance of the FH system can also be further improved by introducing so-called adaptive frequency-hopping, which implies that the system will adaptively use the least interfered channels for the communication.