This paper proposes per-subcarrier transmit antenna subset selection with power balancing for MIMO-OFDM UWB systems to simultaneously improve the system error performance and increase data rates. The deployment of the per-subcarrier antenna subset selection may result in a power unbalance across antennas, which could cause power amplifiers (PAs) to operate in their non-linear regions. To overcome this disadvantage, we formulate a linear optimization problem for the optimal allocation of data subcarriers under a constraint that all antennas have the same number of assigned data symbols. This optimization problem could be applied to systems with an arbitrary number of multiplexed data streams, antennas, and with different selection criteria. The efficacy of the proposed allocation scheme from the PA linearity perspective is validated by analyzing the distribution of the peak amplitude of timedomain signals. Simulation results demonstrate that the proposed system outperforms the system without a balancing constraint.