Embodiments are provided for supporting variable sub-carrier spacing and symbol duration for transmitting OFDM or other waveform symbols and associated cyclic prefixes. The symbol duration includes the useful symbol length and its associated cyclic prefix length. The variable sub-carrier spacing and symbol duration is determined via parameters indicating the sub-carrier spacing, useful symbol length, and cyclic prefix length. An embodiment method, by a network or a network controller, includes establishing a plurality of multiple access block (MAB) types defining different combinations of sub-carrier spacing and symbol duration for waveform transmissions. The method further includes partitioning a frequency and time plane of a carrier spectrum band into a plurality of MAB regions comprising frequency-time slots for the waveform transmissions. The MAB types are then selected for the MAB regions, wherein one MAB type is assigned to one corresponding MAB region.