In this paper, we consider a downlink two-tier network comprising of a multiple-antenna macrocell base station and a single femtocell access point, each serving multiples users with a single antenna. In this scenario, we treat the total transmit power minimization problem and mean-square error balancing problem. In the presence of perfect channel state information (CSI), we formulate the optimization algorithms in a semi-decentralized manner by introducing the signal-to-leakage plus noise ratio criteria. Taking into account imperfect CSI, we also propose robust algorithms tailored by the worst-case design to mitigate the effect of channel uncertainty. Finally, numerical results are presented to validate our proposed algorithms.