For example, an apparatus may include a segment parser to parse scrambled data bits of a PPDU into a first plurality of data bits and a second plurality of data bits, the PPDU to be transmitted in an OFDM transmission over an aggregated bandwidth comprising a first channel in a first frequency band and a second channel in a second frequency band; a first baseband processing block to encode and modulate the first plurality of data bits according to a first OFDM MCS for transmission over the first channel in the first frequency band; and a second baseband block to encode and modulate the second plurality of data bits according to a second OFDM MCS for transmission over the second channel in the second frequency band.