A network node that serves a cell in a cellular communication system is operated. An air interface of the cellular communication system is divided up into sequentially occurring frames, each of the frames comprising a plurality of sequentially occurring sub-frames, each of the sub-frames comprising a plurality of sequentially occurring symbols. Operation includes receiving and detecting a request signal transmitted by a device within the cell. Based at least in part on a characteristic of the request signal that is indicative of one or more device capabilities of the device, an associated time/frequency position for transmitting a response signal is ascertained. The response signal is transmitted at the ascertained time/frequency position.