Hierarchical macro/femto-cell networks are considered as a promising technology for the improvement of indoor coverage and network capacity. In these emerging networks, handoff procedures for a mobile station moving from a macrocell to a femtocell should be provided to maximize the advantages of femtocells with respect to user satisfaction and system performance. Therefore, we propose an efficient handoff decision algorithm that can be utilized in the situation where a user enters the coverage area of the femtocell. The main idea of the proposed algorithm is to combine the values of received signal strength from a serving macro BS and a target femto BS in the consideration of large asymmetry in their transmit powers. Numerical results show that there is a significant gain in view of the probability that the user will be assigned to the femtocell while keeping the same level of the number of handoffs.

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This paperproposes two interference mitigation strategies that adjust the maximum transmit power offemtocell users to suppress the cross-tier interference at a macrocell base station (BS). The open-loop and the closed-loop control suppress the cross-tier interference less than a fixed threshold and an adaptive threshold based on the noise and interference (NI) level at the macrocell BS, respectively. Simulation results show that both schemes effectively compensate the uplink throughput degradation of the macrocell BS and that the closed-loop control provides better femtocell throughput than the open-loopcontrol at a minimal cost ofmacrocell throughput.

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