Multilevel adaptive coded modulation waveforms for HF channels

The HF channel is a time and frequency dispersive channel that causes significant problems to radio communication. The propagation effects of the channel can be overcome by the use of equalization and channel coding. The highly variant nature of the channel suggests the need for communication techniques that can adapt to channel conditions. Any such system would require a collection of transmission modes capable of operating effectively in the range of channel conditions supported by the system. There is considerable interest in maximizing the performance of the 3 kHz bandwidth channels; in particular there is a trend towards investigation of techniques capable of achieving transmissions in excess of 10 kilobits per second. With this fact in mind, a suite of multilevel channel coded modulation waveforms are proposed supporting high data rate communication. Different rates are supported from 2 kbit/sec to 12 kbit/sec depending on the channel conditions.