METHOD OF AND SYSTEM FOR COMMUNICATING MESSAGES

摘要

A method of, and system for, communicating messages in an environment which is subject to fading, in which data to be transmitted is encoded and formatted, a checksum is determined for said encoded and formatted data and in which the checksum is added to an address code word which is concatenated with the encoded and formatted message code words to form a message. A receiver is energized for receiving transmissions in its predetermined frame. In response to recognizing its address code word the concatenated code words are decoded and stored. As each code word is stored, substantially simultaneously a checksum is computed for the message assembled so far and is compared to the checksum in the address code word, if and when they are equal it is concluded that a complete message has been received and further analysis of the stored message is terminated. In a variant of the present invention each message is transmitted at least twice and a final version of the message is assembled code word by code word by comparing the corresponding code words in the respective transmissions and selecting the better (or best) version. As the final version is being assembled the checksum is computed and compared to determine the end of the message. In a further variant the detection of an address or idle code word following a message code word is treated as the beginning of a new message and the computed checksum is used when an undecodable code word is received.