Method and apparatus for determining the rate of received data in a variable rate communication system

摘要

In an apparatus (200) for determining the rate of received data in a variable rate communication system, a decoder (230) decodes each frame of encoded data in a received signal at each possible data rate. The decoded data is processed by a cyclic redundancy check (CRC) element (240) to produce CRC bits. The data is reencoded and correlated by a correlator (234) with the received encoded data to produce a set of normalized correlation metrics. The decoded data may also be input to a Yamamoto detector (248) to Yamamoto quality metrics. Each operation is performed for each possible data rate. The normalized correlation metric for each rate is calculated from a correlation value and a constant computer for the rate. The correlation value is determined from a correlation of the demodulated soft frame symbols and the re-encoded frame. The highest normalized correlation metric is selected and the CRC bit for this data rate is checked. If the CRC checks, this data rate is indicated as the received data rate. Otherwise, the next highest normalized correlation metric is selected and the process continues. If no CRC checks, an erasure is indicated.