James C. Baker

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.<<ETX>>

Digital cellular modem field results

Digital modem field test results applicable to the North American digital cellular system and the Japanese digital cellular system are presented. A modem meeting all specifications of the North American digital cellular system is described. The model is designed to identify channel conditions and to choose the appropriate detector operating with or without an equalizer. Measured bit error rate performance of the modem is presented in Rayleigh-faded and delay spread channels. Statistical data show the amount of time the modem required an equalizer detector during field testing. The speech quality outputs of the equalizer and nonequalizer detectors are compared. Diversity receiver performance in Rayleigh-faded and time-dispersive channels is reported.<<ETX>>