Method and apparatus for determining data rate of transmitted variable rate data in a communications receiver

A system for determining the rate at which data has been encoded in the receiver of a variable-rate communications system. The data is received in frames having a fixed number of symbols. Multiple copies of symbols fill the frame when data is encoded at less than the full rate. At an encoding rate of one fourth the full rate, for example, each symbol in the frame is repeated four times. The incoming symbols are provided to multiple paths for decoding. Each path decodes the symbols at one of the possible rates. Error metrics, which describe the quality of the decoded symbols, are extracted and provided to a processor. The error metrics may include Cyclic Redundancy Check (CRC) results, Yamamoto Quality Metrics, and Symbol Error Rates. The processor analyzes the error metrics and determines the most probable rate at which the incoming symbols were encoded.