In the rapid development of wireless communications, femtocells provide tremendous improvement in coverage and quality of service for users. Macro-femto based networks are envisioned to be the de-facto solution for providing ultra-high speed communications in next-generation mobile wireless networks. This paper studies two-tier macro-femto networks and proposes a collection of novel technologies to address the interference problems. First, a novel user association scheme is proposed that aims to optimize the load among femto base stations (FBSs). Second, a near-optimal ergodic search algorithm is proposed to regulate the power consumption at macro base stations (MBSs) and improve energy efficiency. Third, a channel access mechanism is proposed for FBSs that aims to minimize inter-tier interference. For the proposed system, CDF of SINR is derived and used for performance investigation. Simulation results show that the proposed system can significantly outperform a popular, conventional cognitive radio-based system for all the considered simulation scenarios.