Current designs for fast frequency hopping with MFSK

The performance of many existing communications systems can be improved simply by replacing the currently used forward error correction (FEC) code with a modern iteratively decodable FEC code. The potential improvements of adding modern FEC are even more pronounced for systems that do not currently employ any FEC. In this paper, we compare the performance of fast frequency hopping with simple diversity schemes using only symbol repetition and diversity schemes that also employ convolutional codes, short-block-length iteratively decodable codes, and long-block-length iteratively decodable codes. Both partial-band noise and multi-tone jamming channels are considered. The most powerful codes-namely, the long block length iteratively decodable codes-are shown to greatly improve link robustness while at the same time allow larger data rates than the traditional diversity approaches. In addition, it is demonstrated that these codes enable a system to realize the full benefit of independent tone hopping.