AbstractOne of the digital modulation methods is wavelet packet modulation (WPM). This modulation method is a multiplex transmission method in which the time and frequency division regions in the transmission frame can be rather flexibly modified. In this paper, a digital communication system is studied that can adaptively carry out transmission by using WPM. Because WPM has a time–frequency resolution, an effective decoding/coding method is proposed for a communication channel in which pulse and tone noise exist in addition to Gaussian noise. Specifically, when a part of the receiving signal sequence is lost due to pulse interference noise, the lost signal is estimated and decoded by repeatedly computing the squared Euclidean distance sum between several degraded signals and decoded signals while spreading of the signal into the time–frequency region by WPM is used. Adaptive decoding is discussed in which the transmission characteristic not influenced by the interference is well maintained in a tone interference noise environment. For each method, the characteristics are evaluated and the effectiveness is confirmed in the fundamental interference noise environment by computer simulation. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 85(11): 20–33, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.10002