| CPC H04B 7/2656 (2013.01) [H04L 5/0007 (2013.01); H04L 5/00 (2013.01); H04L 5/0082 (2013.01); H04W 72/04 (2013.01); H04W 72/12 (2013.01)] | 33 Claims |

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1. A method comprising:
storing, in a terminal device of a cellular communication system, definitions for a first radio frame configuration defining a frame structure of a radio frame comprising at least one sub-frame dedicated only for downlink transmission [ , wherein the terminal device stores definitions for a plurality of different radio frame configurations each defining at least one flexible special sub-frame, wherein at least two of the plurality of different radio frame configurations have different sub-frame lengths] ;
storing, in the terminal device, definitions for a second radio frame configuration defining a frame structure of a radio frame comprising [ the ] at least one flexible special sub-frame configurable as either a [ flexible special ] downlink sub-frame or
receiving, from a network element of
selecting, on the basis of the received information element, a radio frame configuration
wherein, among the at least two of the plurality of different radio frame configurations having different sub-frame lengths, either:
a radio frame configuration having a greater sub-frame length has a smaller sub-carrier spacing in sub-frames than another one of the at least two of the plurality of different radio frame configurations, or
a radio frame configuration having a smaller sub-frame length has a larger sub-carrier spacing in sub-frames than another one of the at least two of the plurality of different radio frame configurations] .
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