Modulation and coding study for the advanced narrowband digital voice terminal

A study was performed of modulation and coding techniques to support development of specifications for an advanced narrowband digital voice terminal. Emphasis was on the development of a signal design for HF radio transmissions. The results indicate that transmission channel effects can be significantly reduced by the application of forward acting error correction coding to the most sensitive bits of the digital voice signal. A recommendation is made to use the Golay (24, 12) code, with soft decision decoding, to protect 44 percent of each frame of data generated by a linear predictive encoder. This would result in a transmission rate of 3466.6 bps for an input of 2400 bps using multi-tone four phase differentially coherent phase shift keying.