The Multiple-Input Multiple-Output based Orthogonal Frequency-Division Multiple Access (MIMO-OFDMA) is a promising high rate air interface technology. It is well known that the capacity and coverage of such a system can be significantly enhanced by employing a proper resource allocation (RA) scheme. In this paper, a SVD based precoder and two corresponding adaptive RA algorithms for MIMO-OFDMA networks are proposed. The proposed centralized algorithms are designed to minimize the total required power while meeting each user's transmission rate and bit error rate requirements. Numerical results show that, for modest rate requirements, the proposed algorithms offer performance gain much larger than that of the existing RA algorithms.