A method, comprising: at a user equipment device, UE: receiving parameters that define a semi-static TDD configuration, wherein the parameters include: a period; a first length specifying a duration of a downlink portion of the period, wherein the downlink portion occupies an initial position within the period, wherein said first length is specified by a first number of whole slots and a second number of symbols, wherein a slot is a specified number of symbols in length; and a second length specifying a duration of an uplink portion of the period, wherein the uplink portion occupies a terminal position within the period, wherein said second length is specified by a third number of whole slots and a fourth number of symbols; wherein symbols within the period but not occurring in the downlink portion or the uplink portion comprise a flexible portion, wherein symbols of the flexible portion comprise flexible symbols useable for an uplink or downlink direction; and receiving a physical layer signaling including downlink control information, DCI, that dynamically indicates an uplink or downlink direction of at least one flexible symbol. at a user equipment device, UE: receiving parameters that define a semi-static TDD configuration, wherein the parameters include: a period; a first length specifying a duration of a downlink portion of the period, wherein the downlink portion occupies an initial position within the period, wherein said first length is specified by a first number of whole slots and a second number of symbols, wherein a slot is a specified number of symbols in length; and a second length specifying a duration of an uplink portion of the period, wherein the uplink portion occupies a terminal position within the period, wherein said second length is specified by a third number of whole slots and a fourth number of symbols; wherein symbols within the period but not occurring in the downlink portion or the uplink portion comprise a flexible portion, wherein symbols of the flexible portion comprise flexible symbols useable for an uplink or downlink direction; and receiving a physical layer signaling including downlink control information, DCI, that dynamically indicates an uplink or downlink direction of at least one flexible symbol. a period; a first length specifying a duration of a downlink portion of the period, wherein the downlink portion occupies an initial position within the period, wherein said first length is specified by a first number of whole slots and a second number of symbols, wherein a slot is a specified number of symbols in length; and a second length specifying a duration of an uplink portion of the period, wherein the uplink portion occupies a terminal position within the period, wherein said second length is specified by a third number of whole slots and a fourth number of symbols; wherein symbols within the period but not occurring in the downlink portion or the uplink portion comprise a flexible portion, wherein symbols of the flexible portion comprise flexible symbols useable for an uplink or downlink direction; and receiving a physical layer signaling including downlink control information, DCI, that dynamically indicates an uplink or downlink direction of at least one flexible symbol.