Interference coordination of the downlink control channel under macro-femto deployment in long term evolution system

Abstract

This paper proposes a simple interference coordination method for the downlink control channel in a long term evolution system. The proposed method works well on a heterogeneous network coexisting with macro and closed access femto base stations (BSs). When a user without authorization to access the femto BS comes close to it, the user suffers from serious interference from the femto BS. The user mentioned above is called a "victim user" hereafter. In order to resolve this problem, the proposed method aims to reduce the collision probability in control channel reception at the victim user. The proposed method applied to the femto BS reduces radio resources for the control channel with the aid of transmission power boosting. The system level simulation demonstrates that the proposed method is always superior to conventional resource assignment without interference coordination in the outage probability of the victim user. The outage probability with the proposed method is 1.2% and substantially less than that of the conventional method, which is 8.6%. In addition, when the proposed method is compared with the alternative, which reduces the transmission power by permitting an increase in the collision probability, it is obvious that the proposed method is better for reducing the outage probability of the victim users, especially when the number of users per hotspot is 10 or less. Therefore, the proposed method is more applicable to macro-femto deployment than the alternative method.