Partial response based analog cellular or mobile radio data modem

A simple and robust baseband partial response modem to be used with a narrowband FM, analog cellular carrier frequency is described. The cellular link considered is modeled as a radio link that uses narrowband FM modulation followed by discriminator detection in the cellular base station and finally connection to the telephone network. The system shows fading on the radio link and a narrowband telephone channel. It is shown that 1-D² is the best partial response polynomial for such a channel. In addition, it is found that the group delay of the telephone link provides a dominant source of distortion. A noise-enhancement-free, periodically adapted, phase equalizer is proposed and evaluated. For four-level inputs the partial-response-based modem provides 9600-b/s analog cellular service and a 19200-b/s mobile radio service