A parameter obtaining method, wherein the method comprises: receiving multiple signals over a communications link on a network, characterized in that each of the received signals is corresponding to a point on a complex plane; performing decision on each of the received signals, so as to obtain a decision signal; determining, for each of the received signals, an error signal between the received signal and a corresponding decision signal; and determining, according to all the determined error signals, a complex-plane distribution feature parameter used to indicate a distribution feature, on the complex plane, of the signals received over the communications link; wherein the determining a complex-plane distribution feature parameter comprises: collecting statistics about amplitudes, real parts, or imaginary parts of all the error signals, so as to generate a first statistical value; and using the generated first statistical value as the complex-plane distribution feature parameter; and determining a second statistical value used to indicate a relationship between all the error signals and their respective received signals, and using the second statistical value as the complex-plane distribution feature parameter; or determining a third statistical value used to indicate a relationship between all the error signals and their respective decision signals, and using the third statistical value as the complex-plane distribution feature parameter. receiving multiple signals over a communications link on a network, characterized in that each of the received signals is corresponding to a point on a complex plane; performing decision on each of the received signals, so as to obtain a decision signal; determining, for each of the received signals, an error signal between the received signal and a corresponding decision signal; and determining, according to all the determined error signals, a complex-plane distribution feature parameter used to indicate a distribution feature, on the complex plane, of the signals received over the communications link; wherein the determining a complex-plane distribution feature parameter comprises: collecting statistics about amplitudes, real parts, or imaginary parts of all the error signals, so as to generate a first statistical value; and using the generated first statistical value as the complex-plane distribution feature parameter; and determining a second statistical value used to indicate a relationship between all the error signals and their respective received signals, and using the second statistical value as the complex-plane distribution feature parameter; or determining a third statistical value used to indicate a relationship between all the error signals and their respective decision signals, and using the third statistical value as the complex-plane distribution feature parameter. collecting statistics about amplitudes, real parts, or imaginary parts of all the error signals, so as to generate a first statistical value; and using the generated first statistical value as the complex-plane distribution feature parameter; and determining a second statistical value used to indicate a relationship between all the error signals and their respective received signals, and using the second statistical value as the complex-plane distribution feature parameter; or determining a third statistical value used to indicate a relationship between all the error signals and their respective decision signals, and using the third statistical value as the complex-plane distribution feature parameter.