Radio base station capable of distinguishing between interference due to collisions of outgoing call signals and an external interference noise

A method of detecting interference in at least one control channel arranged between a plurality of mobile stations and a radio base station, a control signal being transferred, between said mobile stations and a radio exchange station via said radio base station and the control channel, said method comprising the steps of:

• (a) detecting, in said radio base station, the interference in the control channel;
• (b) initializing, in said radio base station, a continuous interference occurrence number to zero when the interference is detected at the step (a);
• (c) initializing, in said radio base station, an intermittent interference occurrence number to zero after the step (b);
• (d) setting, in said radio base station, a first timer interval in a first timer after the step (c);
• (e) incrementing, in said radio base station, the continuous interference occurrence number by one after the step (d);
• (f) putting said radio base station into a waiting state after the step (e);
• (g) stopping, in said radio base station, the first timer and a second timer when the interference is detected in the waiting state;
• (h) incrementing, in said radio base station, the continuous interference occurrence number by one after the step (g);
• (i) comparing, in said radio base station, the continuous interference occurrence number with a first predetermined number after the step (h);
• (j) delivering from said radio base station to said radio exchange station an interference information signal indicative of the continuous interference noise when the continuous interference occurrence number is not less than the first predetermined number;
• (k) setting, in said radio base station, the first timer interval in the first timer again when the continuous interference occurrence number is less than the first predetermined number;
• (l) turning back to the step (f) from the step (k) thereby making said radio base station put into the waiting state again;
• (m) comparing, in,said radio base station, the continuous interference occurrence number with a second predetermined number when the first timer interval expires in the first timer in the waiting state;
• (n) incrementing, in said radio base station, the intermittent interference occurrence number by one when the continuous interference occurrence number is not less than the second predetermined number;
• (o) comparing, in said radio base station, the intermittent interference occurrence number with a third predetermined number after the step (n)
• (p) delivering from said radio base station to said radio exchange station the interference information signal indicative of the intermittent interference noise when the intermittent interference occurrence number is not less than the third predetermined number;
• (q) initializing, in said radio base station, the continuous interference occurrence number to zero again when the intermittent interference occurrence number is less than the third predetermined number;
• (r) setting, in said radio base station, a second timer interval in the second timer after the step (q);
• (s) turning back to the step (f) from the step (r) thereby making said radio base station put into the waiting state again;
• (t) deciding, in said radio base station, on an interference signal due to collisions of outgoing call signals by the mobile stations when the continuous interference occurrence number is less than the second predetermined number at the step (m) and thereby carrying out the subsequent interference detection operation without delivery of the interference information signal to said radio exchange station;
• and
• (u) deciding, in said radio base station, on the interference signal due to collisions of the outgoing call signals by the mobile stations when the second timer interval expires in the second timer in the waiting state and thereby carrying out the subsequent interference detection operation without delivery of the interference information signal to said radio exchange station.