| 摘要 |
PURPOSE:To measure line equalization and to determine optimum transmission speed by one training by providing a mean square error calculation circuit calculating the mean square error during a TCF(training check) signal period to an equalizer. CONSTITUTION:The number of times of accumulation N is set to '2400' by using the CCITT modem recommendations V29. In accordance with the CCITT recommendations T30 with respect to the facsimile protocol, as the TCF, a consecutive '0s' signal for 1.5sec+ or -10% is sent. Thus, the N is set to '2400', then the square error is accumulated for 1sec. Then an error rate versus S/N curve for a V29 modem is plotted succeedingly to obtain the S/N with respect to the user allowable error rate. Then the mean square error accumulation is obtained by the square error accumulation level QL with respect to the obtained S/N to plot a threshold level TH. When the value QL is larger than the TH, 9600bps is selected as the optimum transmission speed and when larger, 7200bps is selected as the optimum transmission speed. |
