| 摘要 |
PURPOSE: A forward error correction method is provided to improve an error correction performance by adjusting an interleaving depth according to an error number. CONSTITUTION: In a forward error correction method, when a signal is sent to a terminal from a base station, an RS encoder of a transmitter adds 2N parities every RS block. In a case where an error number generated at an RS decoder of a reception side is below N, an error correction is performed, and the error corrected data is sent to a convolution de-interleaver(46). To a micro processor unit of the terminal is inputted a zero as an error number value which indicates that the data is not corrected. A comparator of the micro processor unit(49) compares an output(a zero value) of the RS decoder(47) with a threshold value from a threshold value generator, and outputs a select control signal for selecting an 'OK' message when the error number generated from the RS decoder is below N. A multiplexer outputs either one of an 'OK' message and an 'NO' message according to the select control signal. A micro processor unit(40) of a head end side receiving an output of the multiplexer maintains a present depth of a convolution interleaver(43). In a case where the error number generated from the RS decoder(47) of a reception side exceeds a predetermined generation frequency and thus exists between (N+1) and 2N, the micro processor unit(49) of the terminal selects the 'NO' message. In a case where a generation frequency of the 'NO' message exceeds a predetermined limit, the micro processor unit(40) of the head end increases an interleaving depth of the convolution interleaver(43) by a predetermined amount.
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