A DIGITAL COMMUNICATIONS SYSTEM HAVING AN AUTOMATICALLY SELECTABLE TRANSMISSION RATE

A system and method for maintaining communication between a paging base station (13) and a mobile paging unit (14) when the signal reception is below a level that would otherwise be unacceptable. The system changes from one data transmission rate to another depending upon the quality of the communication channel. In particular, the symbol rate of the transmissions remains the same, but the number of modulation states and bits per symbol is decreased or increased depending upon the bit error rate of the received signal. In some arrangements, the transceiver (13) transmits at the highest bit rate (46) for that particular system. If no response is received from the paging unit or the paging unit sends a response signal back to the transceiver (13) indicating the signal sent is unacceptable (43), the transceiver (13) retransmits at a lower bit rate (45). In other arrangements, the receiver (14) determines the highest data rate within the group of data rates available and transmits a signal representative of that data rate to the base station (13). In response to such a signal, the base station transmits at the requested data rate until a different data rate is requested (51).