Narrowband FM cellular system

The voice and data transmission parameters of a spectrally-efficient analog frequency division multiple access (FDMA) cellular system with 12.5 kHz channel assignments are described. Low-speed 100 bit/s Manchester data is transmitted during voice activity and provides channel control. In addition, 200 bit/s baseband data patterns support channel supervision. The use of this subaudible signaling method has yielded improved system operation. Eliminating the high-frequency supervisory audio tone has reduced adjacent-channel interference and has allowed increased voice deviation. Using the low-speed data for control messages does not require interruption of the voice activity. The handoff and disconnect protocols have improved falsing protection over current systems.<
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