A method of operation of a network node of a Long Term Evolution, LTE, cellular communications network, comprising: partitioning a plurality of subframes into at least two sets of subframes, the at least two sets of subframes comprising a first set of subframes for legacy Time Division Duplexing, TDD, transmissions that do not support short Transmit Time Intervals, sTTIs, wherein sTTIs have a duration that is shorter than a duration of LTE Release 8 Transmit Time Intervals, TTIs, and a second set of subframes for sTTI TDD transmissions that do support sTTIs; and performing one or more telecommunications functions according to the at least two sets of subframes, wherein partitioning the plurality of subframes into the at least two sets of subframes comprises: selecting at least one downlink subframe index, selecting all mandatory uplink subframe indices that are predefined as being mandatory uplink subframe indices corresponding to the at least one downlink subframe index, selecting zero, one, or two or more optional uplink subframe indices that are predefined as being optional uplink subframe indices corresponding to the at least one downlink subframe index, forming the first set of subframes for legacy TDD transmissions using the at least one downlink subframe index, the mandatory uplink subframe indices, and the zero, one, or two or more optional uplink subframe indices, and forming the second set of subframes for sTTI TDD transmissions using a complement of the first set of subframes within a radio frame. partitioning a plurality of subframes into at least two sets of subframes, the at least two sets of subframes comprising a first set of subframes for legacy Time Division Duplexing, TDD, transmissions that do not support short Transmit Time Intervals, sTTIs, wherein sTTIs have a duration that is shorter than a duration of LTE Release 8 Transmit Time Intervals, TTIs, and a second set of subframes for sTTI TDD transmissions that do support sTTIs; and performing one or more telecommunications functions according to the at least two sets of subframes, wherein partitioning the plurality of subframes into the at least two sets of subframes comprises: selecting at least one downlink subframe index, selecting all mandatory uplink subframe indices that are predefined as being mandatory uplink subframe indices corresponding to the at least one downlink subframe index, selecting zero, one, or two or more optional uplink subframe indices that are predefined as being optional uplink subframe indices corresponding to the at least one downlink subframe index, forming the first set of subframes for legacy TDD transmissions using the at least one downlink subframe index, the mandatory uplink subframe indices, and the zero, one, or two or more optional uplink subframe indices, and forming the second set of subframes for sTTI TDD transmissions using a complement of the first set of subframes within a radio frame. selecting at least one downlink subframe index, selecting all mandatory uplink subframe indices that are predefined as being mandatory uplink subframe indices corresponding to the at least one downlink subframe index, selecting zero, one, or two or more optional uplink subframe indices that are predefined as being optional uplink subframe indices corresponding to the at least one downlink subframe index, forming the first set of subframes for legacy TDD transmissions using the at least one downlink subframe index, the mandatory uplink subframe indices, and the zero, one, or two or more optional uplink subframe indices, and forming the second set of subframes for sTTI TDD transmissions using a complement of the first set of subframes within a radio frame.