Method and device for multistate modulation and demodulation with adjustable protection level
AssigneeThomson-CSF
InventorPierre A. Laurent
Life of this patent
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Abstract
A method and device are provided for multistate modulation and demodulation with adjustable protection level, consisting in separating the binary signals, before demodulation, into critical and non critical signals, in attributing to the non critical signals all the states of the modulation and in attributing to the critical signals a reduced number of states which are, in the modulation diagram, the furthest removed from each other.
Claims8
A method for multistate modulation and demodulation of binary signals using a 4 FSK modulation scheme having four frequency states F0, F1, F2, F3 for conveying dibits of information comprising the steps of:
- separating the dibits to be transmitted into fragile and non-fragile dibits, said fragile dibits being dibits in which errors can be less tolerated;
- attributing to the non-fragile dibits all states of the modulation scheme;
- and
- attributing to the fragile dibits a reduced number of states of said modulation scheme, said reduced number of states being ones of said discrete frequencies having a largest possible difference from each other.
A multistate binary signal modulation device comprising:
- a demultiplier for separating fragile information, for which errors can be less tolerated from non-fragile information,
- a plurality of registers for reforming the fragile and non-fragile information into words of dibits,
- a programmable read only memory for adding to the fragile information redundancy bits for automatic error correction, and
- a modulator coupled to said multiplexer for transmitting alternately the dibits of the fragile and non-fragile information.
Dependencies are inferred from the claim text.