Suggested improvements to the PICCOLO modulation format

The PICCOLO modulation scheme was originally developed in the early 1960s as a robust modulation scheme for use over the HF band. This modulation scheme is essentially a 32-ary MFSK system employing an orthogonal signal set. The two main disadvantages of this system are lack of adaptability and an unsophisticated symbol synchronisation system. The authors address these two points and describe a modem which includes improvements in both of these areas. They also suggest appropriate coding schemes for the PICCOLO modulation format. These make use of confidence information which is available at no extra complexity in the modem. Coding schemes which also aid synchronisation are discussed