An apparatus configured for implementation in a user equipment device, the apparatus comprising: one or more processing elements, wherein the one or more processing elements are configured to: receive TDD configuration information, wherein the TDD configuration information includes parameters that define a semi-static TDD configuration for a frame structure, wherein the parameters include: a period specifying a duration of the frame structure; a first length specifying a duration of a downlink portion of the frame structure, wherein the downlink portion occupies an initial position within the frame structure, and wherein said first length is specified in terms of a first number of whole slots and a non-negative number x of symbols; and a second length specifying a duration of an uplink portion of the frame structure, wherein the uplink portion occupies a terminal position within the frame structure, and wherein said second length is specified in terms of a second number of whole slots and a non-negative number z of symbols; wherein an intermediate portion of the frame structure occurs after the downlink portion and before the uplink portion, wherein TDD structure of the intermediate portion is not determined by the TDD configuration information, and wherein symbols of the intermediate portion of the frame structure are flexible symbols; and wherein the one or more processing elements are further configured to: in response to receiving the TDD configuration information, perform TDD operations including: receiving downlink data from within the downlink portion of the frame structure; and transmitting uplink data within the uplink portion of the frame structure. receive TDD configuration information, wherein the TDD configuration information includes parameters that define a semi-static TDD configuration for a frame structure, wherein the parameters include: a period specifying a duration of the frame structure; a first length specifying a duration of a downlink portion of the frame structure, wherein the downlink portion occupies an initial position within the frame structure, and wherein said first length is specified in terms of a first number of whole slots and a non-negative number x of symbols; and a second length specifying a duration of an uplink portion of the frame structure, wherein the uplink portion occupies a terminal position within the frame structure, and wherein said second length is specified in terms of a second number of whole slots and a non-negative number z of symbols; a period specifying a duration of the frame structure; a first length specifying a duration of a downlink portion of the frame structure, wherein the downlink portion occupies an initial position within the frame structure, and wherein said first length is specified in terms of a first number of whole slots and a non-negative number x of symbols; and a second length specifying a duration of an uplink portion of the frame structure, wherein the uplink portion occupies a terminal position within the frame structure, and wherein said second length is specified in terms of a second number of whole slots and a non-negative number z of symbols; wherein an intermediate portion of the frame structure occurs after the downlink portion and before the uplink portion, wherein TDD structure of the intermediate portion is not determined by the TDD configuration information, and wherein symbols of the intermediate portion of the frame structure are flexible symbols; and wherein the one or more processing elements are further configured to: in response to receiving the TDD configuration information, perform TDD operations including: receiving downlink data from within the downlink portion of the frame structure; and transmitting uplink data within the uplink portion of the frame structure. receiving downlink data from within the downlink portion of the frame structure; and transmitting uplink data within the uplink portion of the frame structure.