This disclosure provides methods, devices and systems for improving wireless communications in power spectral density (PSD)-limited frequency bands. A wireless communication device, having a number (NTX) of transmit antennas, parses a physical layer (PHY) protocol data unit (PPDU) into a number (NSS) of spatial streams and modulates the NSS spatial streams on a number (M) of subcarriers. In some implementations, the wireless communication device may transmit the PPDU using a number (N) of the transmit antennas, where NSS≤N