Method and system for increasing the reliability of multiple frequency

Abstract

The inherent structure of redundant information fields contained in the message format of a multifrequency communication system is utilized to determine if the information on the individual hops has been degraded due to interference. By detecting bit errors in the received data sequence and identifying the frequencies on which signals representing the bits in error were transmitted, one can block out data from those frequencies on a dynamic basis. The received data sequence is correlated against the possible code words that might have been transmitted. The result of this correlation is a decision by the receiver that a particular code word was transmitted. Then, the code word that the receiver decides was transmitted is compared against the received data sequence and bit errors are identified. Finally, by knowing the relationship between the transmission frequencies and the order of the received bits, the receiver can identify the frequencies on which signals representing the bits in error were transmitted. A sum of the errors associated with each frequency is maintained. When the sum exceeds some predetermined threshold, which will vary depending upon experience with each communication link, present and future data associated with the interfered frequency will be discarded from the decision process. Thus, the accuracy of the receiver's decisions will be improved; hence the reliability of the entire communication system will also be improved.