Image Number 5 for United States Patent #5838691.
A communication system encodes input data by comparing the data to records in a lossy codebook to determine the closest match. An index corresponding to the record that most closely matches the input data is retrieved from the codebook and transmitted to a receiver. For a predetermined sampling interval, the communication system collects statistics of the frequency of occurrence of each record matching the input data. The records are sorted in descending order by the frequency of occurrence. Using either a predetermined error rate or a predetermined subtable size, the communication system creates a subtable of the records having the greatest frequency of occurrence. To reduce the search time of finding a record matching the input data, the communication system searches only the subtable for records until the error of the match in the subtable exceeds a preselected threshold or until a preselected period of time has elapsed. The communication system again collects statistics of the frequency of occurrence.