Patent ID: 11870489
Assignee: NIPPON TELEGRAPH AND TELEPHONE CORPORATION
Field: Telecommunications (Electrical engineering)
Classification: CPC H | IPC H

Claim 0:
1. An SN ratio estimation circuit, comprising:
a tentative decision unit that makes a tentative decision for symbols on the basis of a received signal and a decision threshold, and outputs a tentative decision signal including a sequence of the symbols;
an updating unit that updates a scale value indicating a rate of increase or reduction of the received signal or updates a threshold change rate indicating a degree of change in the decision threshold so that an appearance frequency of each of symbols included in the tentative decision signal output by the tentative decision unit matches an appearance frequency of each of symbols in a reference signal obtained by modulating a transmitted signal with a modulation method used in transmission, the modulation method being shared between a transmitting side and a receiving side, and that outputs an instruction signal indicating an instruction to calculate an SN ratio of the received signal when a degree of agreement between the appearance frequencies is within a predetermined permissible range; and
an SN ratio calculation unit that, when the instruction signal output by the updating unit is received, calculates an SN ratio using the scale value when the instruction signal is received or using the threshold change rate when the instruction signal is received,
wherein when the scale value has been updated by the updating unit, the tentative decision unit makes a tentative decision for the symbols on the basis of the received signal increased or reduced by the scale value that has been updated and the decision threshold, and when the threshold change rate has been updated by the updating unit, the tentative decision unit makes a tentative decision for the symbols on the basis of the received signal and the decision threshold to which the threshold change rate that has been updated is applied.