| 摘要 |
PURPOSE:To suppress considerably the degradation of a decoded bit error rate at optimum control, by controlling the relation between the demodulated signal level of a reception base band signal and intervals of a soft decision threshold value in accordance with a preliminarily determined rule. CONSTITUTION:In case of multilevel soft decision, the threshold by which the bit error rate is minimized is dependent upon ES/NO where ES is the energy per one symbol of transmission and NO is the noise power density of one side, and the amplitude of the reception base band signal is expressed with a form where noise components are superposed onto signal components. Characteristic of a level measuring circuit 11 is so set that the relation berween the reception signal and intervals T of the threshold satisfy formulas I, II, and III in the system of detection of the level of (signal components + noise components), the system of detection of the level of signal components, and the system of detection of the level of noise signals respectively (in formulas, beta1, beta2, and beta3 are such constants that the degradation of the bit error rate is minimum). |
