and the vertical axis indicates strength the thermal noise 1010 illustrated in fig1 a becomes noise such as the thermal noise 1020 illustrated in fig1 b due to the analog filter 524 that is due to the frequency response 920 illustrated in fig1 b the thermal noise 1020 becomes noise that is obtained by extracting the component of the merely effective bandwidth 901 see fig1 b the correction unit 130 obtains the thermal noise 1020 on the basis of the thermal noise 1010 that is indicated by the thermal noise power information that is output from the thermal noise power obtaining unit 810 and the frequency response 920 that is indicated by the frequency response information that is output from the frequency response obtaining unit 820 for example the correction unit 130 obtains the thermal noise 1020 by multiplying the strength of the thermal noise 1010 by the permeation rate of the frequency response 920 for each frequency therefore the thermal noise power n that is included in the system bandwidth ndl effective bandwidth 901 is obtained for example the thermal noise power n is calculated by integrating the pieces of strength of the thermal noise 1020 fig1 a is a diagram illustrating an example of an rssi that is measured by the rssi measurement unit in fig1 a the same reference numerals are given to portions that are similar to those of.