Transmitting station and receiving station for operating with a systematic recurrent code

A receiving station comprising a receiver adapted for receiving a sequence of bit trains comprising identifiable continuation bit trains and repetition bit trains, the corresponding transmitted sequence resulting from the coding in a systematic recurrent code of information bits including at least message bits, and the formation of continuation and repetition bit trains, each including a predetermined number of information bits and the parity bits associated therewith, the message bits of a transmitted repetition bit train being identical to the message bits of the previously transmitted bit train;

• said station further comprising:
• a decoding arrangement for decoding the message bits included in the received bit trains, said decoding arrangement having a signal input coupled to said receiver, a control input, a first output for delivering the decoded bits, and a second output for delivering auxiliary signals, each of which is representative of the probability of accurateness of the decoded bit simultaneously appearing at its first output;
• signal generating means for identifying the nature, continuation or repetition, of the received bit trains and applying to said control input of said decoding arrangement, during the decoding of the message bits from a bit train, a control signal which is a first or a second decoding control signal according to whether the message bits being decoded belong to a continuation or a repetition bit train;
• a shift-register having an input coupled to said first output of said decoding arrangement and an output coupled to said decoding arrangement, for supplying thereto, when a message bit is being decoded, the decoded message bit corresponding to the message bit occupying in the bit train previously applied to said signal input of said decoding means the same position number as the message bit being decoded occupies in the bit train to which it belongs;
• storing means having an input coupled to said second output of said decoding arrangement and an output coupled to said decoding arrangement for supplying thereto the auxiliary signal associated with the bit simultaneously delivered by said output of said shift-register;
• said decoding arrangement comprising a decoder adapted to said code, whose input is said input of said decoding arrangement, and computing means coupled to said decoder, for, when a continuation bit train is applied to said input of said decoding arrangement, delivering for each message bit, at its first and second outputs respectively, a decoded bit and an associated auxiliary signal which are wholly determined by this continuation bit train and, when a repetition bit train is applied to said input of said decoding arrangement, delivering, for each message bit, at its first and second outputs respectively, a decoded bit and an associated auxiliary signal which are predetermined functions of the decoded bit and of the auxiliary signal which would be supplied if the message bit belonged to a continuation bit train, of the bit supplied by said output of said shift-register while this message bit is being decoded, and of the auxiliary signal simultaneously supplied by said output of said storing means, the operations performed by the decoding arrangement being respectively referred to as continuation decoding in the first case, and repetition decoding in the second case, and the nature of the decoding performed being determined by that one of said first and second decoding control signals which is applied to said control input.