RADIOTELEPHONE SYSTEM EMPLOYING DIGITIZED SPEECH DATA SIGNALLING

摘要

RADIOTELEPHONE SYSTEM EMPLOYING DIGITIZED SPEECH/DATA AND EMBEDDED SIGNALLING A radiotelephone system is disclosed in which the signalling protocol for the system is embedded in the frame synchronization of the digital messages transmitted on the system. Multiple system state control functions are accomplished via a high autocorrelation, low cross correlation bit sequence synchronization signal. System state communication is achieved by utilizing a sequence of normal synchronization words and their ones complement inverses. Reliabilty of the coding is achieved by detecting normal or inverse words as binary levels when fewer than a predetermined number of bit errors exist in the bit sequence. If the predetermined number of bit errors is exceeded, a selected binary one or zero is substituted. This selected sequence of binary levels is decoded and the Hamming distance between a masked decoded sequence and a masked selected sequence is calculated. If the Hamming distance calculation yields a number greater than the error correction capability of the coding function, a new set of substituted binary levels is tried, otherwise the decoded sequence is accepted as correct.