Junji Otonari

Autonomous downlink interference control for LTE femtocells in residential deployment

An autonomous downlink interference control method for closed subscriber group (CSG) Long Term Evolution (LTE) femtocells is proposed. The proposed method integrates three interference control methods - power control, timing synchronization, and resource partitioning - by leveraging measurement results in various environments. The interferences on physical downlink data channel (PDSCH) and physical downlink control channel (PDCCH) are separated by using the timing synchronization between macrocells and femtocells, and these two interferences are handled independently. The interference on PDCCH is controlled by the transmission power control and that on PDSCH is controlled by the frequency resource partitioning. Moreover, it can deal with both inter-tier and intra-tier interference on the PDSCH and PDCCH. Computer simulations in accordance with 3GPP specifications are conducted in order to evaluate the effect of the proposed method compared with an existing transmission power control method. The results of the simulations show that the proposed method reduced PDCCH outage probability for both macro users and femto users. They also show that the proposed method can reduce downlink femtocell interference for macro users (victim UEs) without reducing femtocell throughput.