| 摘要 |
PURPOSE: A system is provided to determine the data rate of a frame of data at a receiver of a variable rate communications system. CONSTITUTION: A vocoder at a transmitter encodes a frame of data at one of the rates of a predetermined set of rates. The data rate is dependent on the speech activity during the time frame of the data. The data frame is also formatted with overhead bits, including bits for error detection and detection. At the receiver(50), the data rate for the frame is determined based on hypothesis testing. Because the data rate is based on speech activity, a hypothesis test may be designed based on the statistics of speech activity. The received data frame is first decoded by a decoder(34) into information bits at the most probable rate as provided by the hypothesis testing module(36). Data check element(42) generates error metrics for the decoded information bits. If the error metrics indicate that the information bits are of good quality, then the information bits are presented to a vocoder(44) at the receiver to be processed for interface with the user. If the error metrics indicate that the information bits have not been properly decoded, then decoder(34) decodes the received data frame at the other rates of the set of rates until the actual data rate is determined. |
