An apparatus for use in a cognitive radio system, comprising a circuitry (1001, 1002, 1003) configured to: receive a radio communication signal between apparatuses in another radio communication system; determine, based on the radio communication signal, a feature that can reflect the difference between uplink transmission mode and downlink transmission mode; and judge whether the radio communication signal is for uplink transmission or downlink transmission according to the feature; wherein the circuitry is configured to: estimate an energy value of the radio communication signal in a channel resource of the radio communication signal as the feature; judge whether a predetermined relationship is satisfied between the estimated energy value and a first threshold value, and based on a judgement result of yes, judge that the radio communication signal is for downlink transmission; and acquire information about relative positions between nodes in the cognitive radio communication system in which the apparatus operates and in the other radio communication system; estimate, according to the information about the relative positions, the probability of misjudging whether the radio communication signal is for uplink transmission or downlink transmission; and determine the first threshold value according to the estimated probability value. receive a radio communication signal between apparatuses in another radio communication system; determine, based on the radio communication signal, a feature that can reflect the difference between uplink transmission mode and downlink transmission mode; and judge whether the radio communication signal is for uplink transmission or downlink transmission according to the feature; wherein the circuitry is configured to: estimate an energy value of the radio communication signal in a channel resource of the radio communication signal as the feature; judge whether a predetermined relationship is satisfied between the estimated energy value and a first threshold value, and based on a judgement result of yes, judge that the radio communication signal is for downlink transmission; and acquire information about relative positions between nodes in the cognitive radio communication system in which the apparatus operates and in the other radio communication system; estimate, according to the information about the relative positions, the probability of misjudging whether the radio communication signal is for uplink transmission or downlink transmission; and determine the first threshold value according to the estimated probability value. estimate an energy value of the radio communication signal in a channel resource of the radio communication signal as the feature; judge whether a predetermined relationship is satisfied between the estimated energy value and a first threshold value, and based on a judgement result of yes, judge that the radio communication signal is for downlink transmission; and acquire information about relative positions between nodes in the cognitive radio communication system in which the apparatus operates and in the other radio communication system; estimate, according to the information about the relative positions, the probability of misjudging whether the radio communication signal is for uplink transmission or downlink transmission; and determine the first threshold value according to the estimated probability value.