Radio communication apparatus, radio communication system and radio communication method

A radio communication system comprising a radio communication apparatus and two or more tag devices, wherein:

• the two or more tag devices each comprise:
• a transmitter that transmits a backscatter signal, and
• the radio communication apparatus comprises:
• one or more reception antennas that receive a mixed signal including two or more backscatter signals respectively transmitted from the two or more tag devices,
• a converter that converts the mixed signal into complex data on a complex plane,
• a calculator that calculates at least phase angles of carrier waves of the two or more backscatter signals in order to approximate the phase angles to a complex data sequence of a predetermined length, the complex data sequence formed of the complex data, wherein the calculator generates a projector matrix formed of a combination of the phase angles of carrier waves of the two or more backscatter signals, and
• a separator that separates the two or more backscatter signals from the mixed signal based on an inverse matrix of the projector matrix and the complex data sequence,
• wherein a number of reception antennas, out of the one or more reception antennas, used in calculating the phase angles of the carrier waves of the two or more backscatter signals, is less than a number of the two or more tag devices.

A radio communication method comprising steps of:

• receiving a mixed signal including two or more backscatter signals respectively transmitted from two or more tag devices by one or more reception antennas,
• converting the mixed signal into complex data on a complex plane,
• calculating at least phase angles of carrier waves of the two or more backscatter signals in order to approximate the phase angles to a complex data sequence of a predetermined length, the complex data sequence formed of the complex data, and generating a projector matrix formed of a combination of the phase angles of carrier waves of the two or more backscatter signals, and
• separating the two or more backscatter signals from the mixed signal based on an inverse matrix of the projector matrix and the complex data sequence,
• wherein a number of reception antennas, out of the one or more reception antennas, used in calculating the phase angles of the carrier waves of the two or more backscatter signals, is less than a number of the two or more tag devices.